Publications by authors named "Simon D Rundle"

27 Publications

  • Page 1 of 1

Both maternal and embryonic exposure to mild hypoxia influence embryonic development of the intertidal gastropod .

J Exp Biol 2020 10 26;223(Pt 20). Epub 2020 Oct 26.

Marine Biology and Ecology Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.

There is growing evidence that maternal exposure to environmental stressors can alter offspring phenotype and increase fitness. Here, we investigate the relative and combined effects of maternal and developmental exposure to mild hypoxia (65 and 74% air saturation, respectively) on the growth and development of embryos of the marine gastropod Differences in embryo morphological traits were driven by the developmental environment, whereas the maternal environment and interactive effects of maternal and developmental environment were the main driver of differences in the timing of developmental events. While developmental exposure to mild hypoxia significantly increased the area of an important respiratory organ, the velum, it significantly delayed hatching of veliger larvae and reduced their size at hatching and overall survival. Maternal exposure had a significant effect on these traits, and interacted with developmental exposure to influence the time of appearance of morphological characters, suggesting that both are important in affecting developmental trajectories. A comparison between embryos that successfully hatched and those that died in mild hypoxia revealed that survivors exhibited hypertrophy in the velum and associated pre-oral cilia, suggesting that these traits are linked with survival in low-oxygen environments. We conclude that both maternal and developmental environments shape offspring phenotype in a species with a complex developmental life history, and that plasticity in embryo morphology arising from exposure to even small reductions in oxygen tensions affects the hatching success of these embryos.
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http://dx.doi.org/10.1242/jeb.221895DOI Listing
October 2020

A high-throughput and open-source platform for embryo phenomics.

PLoS Biol 2018 12 13;16(12):e3000074. Epub 2018 Dec 13.

Marine Biology and Ecology Research Centre, School of Biological and Marine Sciences, University of Plymouth, Plymouth, Devon, United Kingdom.

Phenomics has the potential to facilitate significant advances in biology but requires the development of high-throughput technologies capable of generating and analysing high-dimensional data. There are significant challenges associated with building such technologies, not least those required for investigating dynamic processes such as embryonic development, during which high rates of temporal, spatial, and functional change are inherently difficult to capture. Here, we present EmbryoPhenomics, an accessible high-throughput platform for phenomics in aquatic embryos comprising an Open-source Video Microscope (OpenVIM) that produces high-resolution videos of multiple embryos under tightly controlled environmental conditions. These videos are then analysed by the Python package Embryo Computer Vision (EmbryoCV), which extracts phenomic data for morphological, physiological, behavioural, and proxy traits during the process of embryonic development. We demonstrate the broad-scale applicability of EmbryoPhenomics in a series of experiments assessing chronic, acute, and multistressor responses to environmental change (temperature and salinity) in >30 million images of >600 embryos of two species with markedly different patterns of development-the pond snail Radix balthica and the marine amphipod Orchestia gammarellus. The challenge of phenomics is significant but so too are the rewards, and it is particularly relevant to the urgent task of assessing complex organismal responses to current rates of environmental change. EmbryoPhenomics can acquire and process data capturing functional, temporal, and spatial responses in the earliest, most dynamic life stages and is potentially game changing for those interested in studying development and phenomics more widely.
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http://dx.doi.org/10.1371/journal.pbio.3000074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6292576PMC
December 2018

Transcriptomic responses to predator kairomones in embryos of the aquatic snail .

Ecol Evol 2018 Nov 17;8(22):11071-11082. Epub 2018 Oct 17.

Marine Biology and Ecology Research Centre University of Plymouth, Drake Circus Plymouth UK.

The ability of organisms to respond to predation threat by exhibiting induced defenses is well documented, but studies on the potential mechanistic basis for such responses are scarce. Here, we examine the transcriptomic response to predator kairomones of two functionally distinct developmental stages in embryos of the aquatic snail : E8-the stage at which a range-finding trial indicated that kairomone-induced accelerated growth and development first occurred; and E9-the stage at which embryos switched from ciliary- to crawling-driven locomotion. We tested whether expression profiles were influenced by kairomones and whether this influence varied between stages. We also identified potential candidate genes for investigating mechanisms underpinning induced responses. There were 6,741 differentially expressed transcripts between developmental stages, compared to just five in response to predator kairomones. However, on examination of functional enrichment in the transcripts responding to predator kairomones and adopting a less stringent significance threshold, 206 transcripts were identified relating to muscle function, growth, and development, with this response being greater at the later E9 stage. Furthermore, these transcripts included putative annotations for genes identified as responding to predator kairomones in other taxa, including C1q, lectin, and actin domains. Globally, transcript expression appeared reduced in response to predator kairomones and we hypothesize that this might be a result of metabolic suppression, as has been reported in other taxa in response to predation threat.
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http://dx.doi.org/10.1002/ece3.4574DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6262742PMC
November 2018

Thermal strategies vary with life history stage.

J Exp Biol 2018 04 20;221(Pt 8). Epub 2018 Apr 20.

Departamento de Ecología, Center of Applied Ecology and Sustainability, Facultad de Ciencias Biológicas, Universidad Católica de Chile, Santiago 6513677, Chile.

With both global surface temperatures and the incidence and intensity of extreme temperature events projected to increase, the assessment of species' sensitivity to chronic and acute changes in temperature has become crucial. Sensitivity predictions are based predominantly on adult responses, despite the fact that early life stages may be more vulnerable to thermal challenge. Here, we compared the sensitivity of different life history stages of the intertidal gastropod using thermal death time curves, which incorporate the intensity and duration of heat stress, and used these to calculate upper critical thermal limits (CT) and sensitivity to temperature change (). Early (larval) life stages had both a lower CT and a lower than adults, suggesting they are less good at withstanding short-term extreme thermal challenges but better able to survive moderate temperatures in the long term. This result supports the predicted trade-off between acute and chronic tolerance to thermal stress, and is consistent with the different thermal challenges that these stages encounter in the intertidal zone. We conclude that different life history stages employ different thermal strategies that may be adaptive. Our findings caution against the use of predictions of the impact of global warming that are based on only adult responses and, hence, which may underestimate vulnerability.
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http://dx.doi.org/10.1242/jeb.171629DOI Listing
April 2018

An annotated draft genome for Radix auricularia (Gastropoda, Mollusca).

Genome Biol Evol 2017 Feb 15. Epub 2017 Feb 15.

Department of Botany and Molecular Evolution, Senckenberg Research Institute, Frankfurt am Main, Germany.

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http://dx.doi.org/10.1093/gbe/evx032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5381561PMC
February 2017

Regional adaptation defines sensitivity to future ocean acidification.

Nat Commun 2017 01 9;8:13994. Epub 2017 Jan 9.

Marine Biology &Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Drake Circus, Plymouth, Devon PL4 8AA, UK.

Physiological responses to temperature are known to be a major determinant of species distributions and can dictate the sensitivity of populations to global warming. In contrast, little is known about how other major global change drivers, such as ocean acidification (OA), will shape species distributions in the future. Here, by integrating population genetics with experimental data for growth and mineralization, physiology and metabolomics, we demonstrate that the sensitivity of populations of the gastropod Littorina littorea to future OA is shaped by regional adaptation. Individuals from populations towards the edges of the natural latitudinal range in the Northeast Atlantic exhibit greater shell dissolution and the inability to upregulate their metabolism when exposed to low pH, thus appearing most sensitive to low seawater pH. Our results suggest that future levels of OA could mediate temperature-driven shifts in species distributions, thereby influencing future biogeography and the functioning of marine ecosystems.
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http://dx.doi.org/10.1038/ncomms13994DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5227702PMC
January 2017

Differences in the timing of cardio-respiratory development determine whether marine gastropod embryos survive or die in hypoxia.

J Exp Biol 2016 Apr 19;219(Pt 7):1076-85. Epub 2016 Feb 19.

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Plymouth PL4 8AA, UK

Physiological plasticity of early developmental stages is a key way by which organisms can survive and adapt to environmental change. We investigated developmental plasticity of aspects of the cardio-respiratory physiology of encapsulated embryos of a marine gastropod, Littorina obtusata, surviving exposure to moderate hypoxia (PO2 =8 kPa) and compared the development of these survivors with that of individuals that died before hatching. Individuals surviving hypoxia exhibited a slower rate of development and altered ontogeny of cardio-respiratory structure and function compared with normoxic controls (PO2 >20 kPa). The onset and development of the larval and adult hearts were delayed in chronological time in hypoxia, but both organs appeared earlier in developmental time and cardiac activity rates were greater. The velum, a transient, 'larval' organ thought to play a role in gas exchange, was larger in hypoxia but developed more slowly (in chronological time), and velar cilia-driven, rotational activity was lower. Despite these effects of hypoxia, 38% of individuals survived to hatching. Compared with those embryos that died during development, these surviving embryos had advanced expression of adult structures, i.e. a significantly earlier occurrence and greater activity of their adult heart and larger shells. In contrast, embryos that died retained larval cardio-respiratory features (the velum and larval heart) for longer in chronological time. Surviving embryos came from eggs with significantly higher albumen provisioning than those that died, suggesting an energetic component for advanced development of adult traits.
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http://dx.doi.org/10.1242/jeb.134411DOI Listing
April 2016

Home advantage? Decomposition across the freshwater-estuarine transition zone varies with litter origin and local salinity.

Mar Environ Res 2015 Sep 29;110:1-7. Epub 2015 Jul 29.

Marine Biology and Ecology Research Centre, Plymouth University, PL4 8AA Plymouth, Devon, United Kingdom.

Expected increases in the frequency and intensity of storm surges and river flooding may greatly affect the relative salinity of estuarine environments over the coming decades. In this experiment we used detritus from three contrasting environments (marine Fucus vesiculosus; estuarine Spartina anglica; terrestrial Quercus robur) to test the prediction that the decomposition of the different types of litter would be highest in the environment with which they are associated. Patterns of decomposition broadly fitted our prediction: Quercus detritus decomposed more rapidly in freshwater compared with saline conditions while Fucus showed the opposite trend; Spartina showed an intermediate response. Variation in macro-invertebrate assemblages was detected along the salinity gradient but with different patterns between estuaries, suggesting that breakdown rates may be linked in part to local invertebrate assemblages. Nonetheless, our results suggest that perturbation of salinity gradients through climate change could affect the process of litter decomposition and thus alter nutrient cycling in estuarine transition zones. Understanding the vulnerability of estuaries to changes in local abiotic conditions is important given the need to better integrate coastal proceses into a wider management framework at a time when coastlines are increasingly threatened by human activities.
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http://dx.doi.org/10.1016/j.marenvres.2015.07.012DOI Listing
September 2015

Combining motion analysis and microfluidics--a novel approach for detecting whole-animal responses to test substances.

PLoS One 2014 2;9(12):e113235. Epub 2014 Dec 2.

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth, United Kingdom.

Small, early life stages, such as zebrafish embryos are increasingly used to assess the biological effects of chemical compounds in vivo. However, behavioural screens of such organisms are challenging in terms of both data collection (culture techniques, drug delivery and imaging) and data evaluation (very large data sets), restricting the use of high throughput systems compared to in vitro assays. Here, we combine the use of a microfluidic flow-through culture system, or BioWell plate, with a novel motion analysis technique, (sparse optic flow - SOF) followed by spectral analysis (discrete Fourier transformation - DFT), as a first step towards automating data extraction and analysis for such screenings. Replicate zebrafish embryos housed in a BioWell plate within a custom-built imaging system were subject to a chemical exposure (1.5% ethanol). Embryo movement was videoed before (30 min), during (60 min) and after (60 min) exposure and SOF was then used to extract data on movement (angles of rotation and angular changes to the centre of mass of embryos). DFT was subsequently used to quantify the movement patterns exhibited during these periods and Multidimensional Scaling and ANOSIM were used to test for differences. Motion analysis revealed that zebrafish had significantly altered movements during both the second half of the alcohol exposure period and also the second half of the recovery period compared to their pre-treatment movements. Manual quantification of tail flicking revealed the same differences between exposure-periods as detected using the automated approach. However, the automated approach also incorporates other movements visible in the organism such as blood flow and heart beat, and has greater power to discern environmentally-driven changes in the behaviour and physiology of organisms. We suggest that combining these technologies could provide a highly efficient, high throughput assay, for assessing whole embryo responses to various drugs and chemicals.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0113235PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4251981PMC
July 2015

Parent--offspring similarity in the timing of developmental events: an origin of heterochrony?

Proc Biol Sci 2013 Oct 21;280(1769):20131479. Epub 2013 Aug 21.

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Davy Building, Drake Circus, Plymouth PL4 8AA, UK.

Understanding the link between ontogeny (development) and phylogeny (evolution) remains a key aim of biology. Heterochrony, the altered timing of developmental events between ancestors and descendants, could be such a link although the processes responsible for producing heterochrony, widely viewed as an interspecific phenomenon, are still unclear. However, intraspecific variation in developmental event timing, if heritable, could provide the raw material from which heterochronies originate. To date, however, heritable developmental event timing has not been demonstrated, although recent work did suggest a genetic basis for intraspecific differences in event timing in the embryonic development of the pond snail, Radix balthica. Consequently, here we used high-resolution (temporal and spatial) imaging of the entire embryonic development of R. balthica to perform a parent-offspring comparison of the timing of twelve, physiological and morphological developmental events. Between-parent differences in the timing of all events were good predictors of such timing differences between their offspring, and heritability was demonstrated for two of these events (foot attachment and crawling). Such heritable intraspecific variation in developmental event timing could be the raw material for speciation events, providing a fundamental link between ontogeny and phylogeny, via heterochrony.
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http://dx.doi.org/10.1098/rspb.2013.1479DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768304PMC
October 2013

A genetic basis for intraspecific differences in developmental timing?

Evol Dev 2011 Nov-Dec;13(6):542-8

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Drake Circus, Plymouth, UK.

Heterochrony, altered developmental timing between ancestors and their descendents, has been proposed as a pervasive evolutionary feature and recent analytical approaches have confirmed its existence as an evolutionary pattern. Yet, the mechanistic basis for heterochrony remains unclear and, in particular, whether intraspecific variation in the timing of developmental events generates, or has the potential to generate, future between-species differences. Here we make a key step in linking heterochrony at the inter- and intraspecific level by reporting an association between interindividual variation in both the absolute and relative timing (position within the sequence of developmental events) of key embryonic developmental events and genetic distance for the pond snail, Radix balthica. We report significant differences in the genetic distance of individuals exhibiting different levels of dissimilarity in their absolute and relative timing of developmental events such as spinning activity, eyespot formation, heart ontogeny, and hatching. This relationship between genetic and developmental dissimilarity is consistent with there being a genetic basis for variation in developmental timing and so suggests that intraspecific heterochrony could provide the raw material for natural selection to produce speciation.
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http://dx.doi.org/10.1111/j.1525-142X.2011.00510.xDOI Listing
January 2013

Development of cardiovascular function in the marine gastropod Littorina obtusata (Linnaeus).

J Exp Biol 2012 Jul;215(Pt 13):2327-33

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.

The molluscan cardiovascular system typically incorporates a transient extracardiac structure, the larval heart, early in development, but the functional importance of this structure is unclear. We documented the ontogeny and regulatory ability of the larval heart in relation to two other circulatory structures, the true heart and the velum, in the intertidal gastropod Littorina obtusata. There was a mismatch between the appearance of the larval heart and the velum. Velar lobes appeared early in development (day 4), but the larval heart did not begin beating until day 13. The beating of the larval heart reached a maximum on day 17 and then decreased until the structure itself disappeared (day 24). The true heart began to beat on day 17. Its rate of beating increased as that of the larval heart decreased, possibly suggesting a gradual shift from a larval heart-driven to a true heart-driven circulation. The true heart was not sensitive to acutely declining P(O(2)) shortly after it began to beat, but increased in activity in response to acutely declining P(O(2)) by day 21. Larval heart responses were similar to those of the true heart, with early insensitivity to declining P(O(2)) (day 13) followed by a response by day 15. Increased velum-driven rotational activity under acutely declining P(O(2)) was greatest in early developmental stages. Together, these findings point to cardiovascular function in L. obtusata larvae being the result of a complex interaction between velum, larval and true heart activities, with the functions of the three structures coinciding but their relative importance changing throughout larval development.
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http://dx.doi.org/10.1242/jeb.067967DOI Listing
July 2012

Exposure to elevated temperature and Pco(2) reduces respiration rate and energy status in the periwinkle Littorina littorea.

Physiol Biochem Zool 2011 Nov-Dec;84(6):583-94. Epub 2011 Oct 14.

Marine Biology and Ecology Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.

In the future, marine organisms will face the challenge of coping with multiple environmental changes associated with increased levels of atmospheric Pco(2), such as ocean warming and acidification. To predict how organisms may or may not meet these challenges, an in-depth understanding of the physiological and biochemical mechanisms underpinning organismal responses to climate change is needed. Here, we investigate the effects of elevated Pco(2) and temperature on the whole-organism and cellular physiology of the periwinkle Littorina littorea. Metabolic rates (measured as respiration rates), adenylate energy nucleotide concentrations and indexes, and end-product metabolite concentrations were measured. Compared with values for control conditions, snails decreased their respiration rate by 31% in response to elevated Pco(2) and by 15% in response to a combination of increased Pco(2) and temperature. Decreased respiration rates were associated with metabolic reduction and an increase in end-product metabolites in acidified treatments, indicating an increased reliance on anaerobic metabolism. There was also an interactive effect of elevated Pco(2) and temperature on total adenylate nucleotides, which was apparently compensated for by the maintenance of adenylate energy charge via AMP deaminase activity. Our findings suggest that marine intertidal organisms are likely to exhibit complex physiological responses to future environmental drivers, with likely negative effects on growth, population dynamics, and, ultimately, ecosystem processes.
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http://dx.doi.org/10.1086/662680DOI Listing
May 2012

Susceptibility to predation affects trait-mediated indirect interactions by reversing interspecific competition.

PLoS One 2011 17;6(8):e23068. Epub 2011 Aug 17.

Marine Biology and Ecology Research Centre, The University of Plymouth, Plymouth, United Kingdom.

Numerous studies indicate that the behavioral responses of prey to the presence of predators can have an important role in structuring assemblages through trait-mediated indirect interactions. Few studies, however, have addressed how relative susceptibility to predation influences such interactions. Here we examine the effect of chemical cues from the common shore crab Carcinus maenas on the foraging behavior of two common intertidal gastropod molluscs. Of the two model consumers studied, Littorina littorea is morphologically more vulnerable to crab predation than Gibbula umbilicalis, and it exhibited greater competitive ability in the absence of predation threat. However, Littorina demonstrated a greater anti-predator response when experimentally exposed to predation cues, resulting in a lower level of foraging. This reversed the competitive interaction, allowing Gibbula substantially increased access to shared resources. Our results demonstrate that the susceptibility of consumers to predation can influence species interactions, and suggest that inter-specific differences in trait-mediated indirect interactions are another mechanism through which non-consumptive predator effects may influence trophic interactions.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0023068PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3157367PMC
February 2012

Studying the altered timing of physiological events during development: it's about time…or is it?

Respir Physiol Neurobiol 2011 Aug 15;178(1):3-12. Epub 2011 Jun 15.

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, University of Plymouth, Plymouth, UK.

The investigation of the altered timing of developmental events is key to understanding evolution. Most empirical investigations of event timing are biased towards studying morphological variation. Recent reviews, however, have attempted to marshal the evidence for the importance of altered timing of physiological events, focusing on such timing shifts between species (physiological heterochrony) and within species (physiological heterokairy). Here we update these reviews. We firstly take a comparative developmental physiology approach to explore how recent studies have furthered our understanding of the links between physiological event timing shifts at different levels of biological organisation (i.e. individual, population and species). The alternative strategy of concentrating effort on one model system is then considered, in particular focussing on substantial recent advances in our understanding of fetal haemoglobin expression in humans. We conclude that, while the fetal haemoglobin model may be appropriate as a model for some questions, it can never be the model study system. We also discuss the different quantitative analyses available for investigating event timing alterations. We consider the efficacy of the terms heterochrony and heterokairy.
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http://dx.doi.org/10.1016/j.resp.2011.06.005DOI Listing
August 2011

Predator cues alter the timing of developmental events in gastropod embryos.

Biol Lett 2011 Apr 29;7(2):285-7. Epub 2010 Sep 29.

Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, University of Plymouth, Plymouth, UK.

Heterochrony, differences in the timing of developmental events between descendent species and their ancestors, is a pervasive evolutionary pattern. However, the origins of such timing changes are still not resolved. Here we show, using sequence analysis, that exposure to predator cues altered the timing of onset of several developmental events in embryos of two closely related gastropod species: Radix balthica and Radix auricularia. These timing alterations were limited to certain events and were species-specific. Compared with controls, over half (62%) of exposed R. auricularia embryos had a later onset of body flexing and an earlier occurrence of the eyes and the heart; in R. balthica, 67 per cent of exposed embryos showed a later occurrence of mantle muscle flexing and an earlier attachment to, and crawling on, the egg capsule wall. The resultant developmental sequences in treated embryos converged, and were more similar to one another than were the sequences of the controls for both species. We conclude that biotic agents can elicit altered event timing in developing gastropod embryos. These changes were species-specific, but did not occur in all individuals. Such developmental plasticity in the timing of developmental events could be an important step in generating interspecific heterochrony.
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http://dx.doi.org/10.1098/rsbl.2010.0658DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3061156PMC
April 2011

Experimental determination of a Viviparus contectus thermometry equation.

Rapid Commun Mass Spectrom 2009 Sep;23(18):2939-51

School of Earth, Ocean & Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.

Experimental measurements of the (18)O/(16)O isotope fractionation between the biogenic aragonite of Viviparus contectus (Gastropoda) and its host freshwater were undertaken to generate a species-specific thermometry equation. The temperature dependence of the fractionation factor and the relationship between Deltadelta(18)O (delta(18)O(carb.) - delta(18)O(water)) and temperature were calculated from specimens maintained under laboratory and field (collection and cage) conditions. The field specimens were grown (Somerset, UK) between August 2007 and August 2008, with water samples and temperature measurements taken monthly. Specimens grown in the laboratory experiment were maintained under constant temperatures (15 degrees C, 20 degrees C and 25 degrees C) with water samples collected weekly. Application of a linear regression to the datasets indicated that the gradients of all three experiments were within experimental error of each other (+/-2 times the standard error); therefore, a combined (laboratory and field data) correlation could be applied. The relationship between Deltadelta(18)O (delta(18)O(carb.) - delta(18)O(water)) and temperature (T) for this combined dataset is given by: T = - 7.43( + 0.87, - 1.13)*Deltadelta18O + 22.89(+/- 2.09) (T is in degrees C, delta(18)O(carb.) is with respect to Vienna Pee Dee Belemnite (VPDB) and delta(18)O(water) is with respect to Vienna Standard Mean Ocean Water (VSMOW). Quoted errors are 2 times standard error).Comparisons made with existing aragonitic thermometry equations reveal that the linear regression for the combined Viviparus contectus equation is within 2 times the standard error of previously reported aragonitic thermometry equations. This suggests there are no species-specific vital effects for Viviparus contectus. Seasonal delta(18)O(carb.) profiles from specimens retrieved from the field cage experiment indicate that during shell secretion the delta(18)O(carb.) of the shell carbonate is not influenced by size, sex or whether females contained eggs or juveniles.
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http://dx.doi.org/10.1002/rcm.4203DOI Listing
September 2009

Embryonic rotational behaviour in the pond snail Lymnaea stagnalis: influences of environmental oxygen and development stage.

Zoology (Jena) 2009 27;112(6):471-7. Epub 2009 Jun 27.

Department of Biology, State University of New York at Fredonia, 122 Jewett Hall, Fredonia, NY 14063, USA.

Responses of freshwater organisms to environmental oxygen tensions (PO(2)) have focused on adult (i.e. late developmental) stages, yet responses of embryonic stages to changes in environmental PO(2) must also have implications for organismal biology. Here we assess how the rotational behaviour of the freshwater snail Lymnaea stagnalis changes during development in response to conditions of hypoxia and hyperoxia. As rotation rate is linked to gas mixing in the fluid surrounding the embryo, we predicted that it would increase under hypoxic conditions but decrease under hyperoxia. Contrary to predictions, early, veliger stage embryos showed no change in their rotation rate under hyperoxia, and later, hippo stage embryos showed only a marginally significant increase in rotation under these conditions. Predictions for hypoxia were broadly supported, however, with both veliger and hippo stages showing a marked hypoxia-related increase in their rotation rates. There were also subtle differences between developmental stages, with hippos responding at PO(2)s (50% air saturation) greater than those required to elicit a similar response in veligers (20% air saturation). Differences between developmental stages also occurred on return to normoxic conditions following hypoxia: rotation in veligers returned to pre-exposure levels, whereas there was a virtual cessation in embryos at the hippo stage, likely the result of overstimulation of oxygen sensors driving ciliary movement in later, more developed embryos. Together, these findings suggest that the spinning activity of L. stagnalis embryos varies depending on environmental PO(2)s and developmental stage, increasing during hypoxia to mix capsular contents and maintain a diffusive gradient for oxygen entry into the capsule from the external environment ("stir-bar" theory of embryonic rotational behaviour).
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http://dx.doi.org/10.1016/j.zool.2009.03.001DOI Listing
January 2010

The effect of CO2 acidified sea water and reduced salinity on aspects of the embryonic development of the amphipod Echinogammarus marinus (Leach).

Mar Pollut Bull 2009 Aug 21;58(8):1187-1191. Epub 2009 Jun 21.

Marine Biology and Ecology Research Centre, School of Biological Sciences, University of Plymouth, Plymouth PL4 8AA, UK.

We investigated the effect of CO(2) acidified sea water (S=35, 22 and 10(PSU)) on embryonic development of the intertidal amphipod Echinogammarus marinus (Leach). Low pH, but not low salinity (22(PSU)), resulted in a more protracted embryonic development in situ although the effect was only evident at low salinity. However reduced salinity, not pH, exerted a strong significant effect, on numbers and calcium content of hatchlings. Females exposed to low salinity (10(PSU)) did not carry eggs through to hatching. There was no significant difference in the number of viable hatchlings between females cultured in 22 and 35(PSU) but the exoskeleton of the juveniles at 22(PSU) contained significantly less calcium. Ocean acidification may affect aspects of E. marinus development but exposure to realistic low salinities appear, in the short term, to be more important in impacting development than exposure to CO(2) acidified sea water at levels predicted for 300 years time.
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http://dx.doi.org/10.1016/j.marpolbul.2009.03.017DOI Listing
August 2009

Comparing the strength of behavioural plasticity and consistency across situations: animal personalities in the hermit crab Pagurus bernhardus.

Proc Biol Sci 2008 Jun;275(1640):1305-11

Marine Biology and Ecology Research Centre, School of Biological Sciences, The University of Plymouth, Drake Circus, Plymouth, UK.

Many phenotypic traits show plasticity but behaviour is often considered the 'most plastic' aspect of phenotype as it is likely to show the quickest response to temporal changes in conditions or 'situation'. However, it has also been noted that constraints on sensory acuity, cognitive structure and physiological capacities place limits on behavioural plasticity. Such limits to plasticity may generate consistent differences in behaviour between individuals from the same population. It has recently been suggested that these consistent differences in individual behaviour may be adaptive and the term 'animal personalities' has been used to describe them. In many cases, however, a degree of both behavioural plasticity and relative consistency is probable. To understand the possible functions of animal personalities, it is necessary to determine the relative strength of each tendency and this may be achieved by comparison of statistical effect sizes for tests of difference and concordance. Here, we describe a new statistical framework for making such comparisons and investigate cross-situational plasticity and consistency in the duration of startle responses in the European hermit crab Pagurus bernhardus, in the field and the laboratory. The effect sizes of tests for behavioural consistency were greater than for tests of behavioural plasticity, indicating for the first time the presence of animal personalities in a crustacean model.
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http://dx.doi.org/10.1098/rspb.2008.0025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2602678PMC
June 2008

Phylogenetic relatedness and ecological interactions determine antipredator behavior.

Ecology 2007 Oct;88(10):2462-7

Marine Biology and Ecology Research Centre, School of Biological Sciences, University of Plymouth, Plymouth PL4 8AA, United Kingdom.

Interspecific recognition of alarm cues among guild members through "eavesdropping" may allow prey to fine-tune antipredator responses. This process may be linked to taxonomic relatedness but might also be influenced by local adaptation to recognize alarm cues from sympatric species. We tested this hypothesis using antipredator responses of a freshwater gastropod Lymnaea stagnalis (L.) to alarm cues from damaged conspecific and 10 heterospecific gastropod species. As predicted, the magnitude of antipredator response decreased significantly with increasing phylogenetic distance, but increased when species were naturally sympatric (defined as species cohabiting in the same water body) with the source population of L. stagnalis. The responses to sympatric species were higher overall, and the relationship between genetic distance and alarm cue response was stronger when tested with sympatric species. This is the first study to demonstrate that population sympatry influences innate antipredator responses to alarm cues from intraguild members and suggests that responses based on phylogenetic relationships can be modified through local adaptation. Such adaptation to heterospecific alarm cues suggests that species could be at a disadvantage when they encounter novel intraguild members resulting from species invasion or range expansion due to a reduction in the presence of reliable information about predation risk.
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http://dx.doi.org/10.1890/07-0403.1DOI Listing
October 2007

Plasticity in the timing of physiological development: physiological heterokairy--what is it, how frequent is it, and does it matter?

Comp Biochem Physiol A Mol Integr Physiol 2007 Dec 12;148(4):712-9. Epub 2007 Jun 12.

Marine Biology and Ecology and Research Centre, School of Biological Sciences, University of Plymouth, Plymouth PL4 8AA, UK.

The study of developmental sequences of physiological traits could be an important way of placing comparative developmental physiology (CDP) within the research agenda being forged by work on developmental plasticity. Here we focus on the concept of heterokairy defined by Spicer & Burggren in 2003 as changes in the timing of physiological development in an individual. The role of this concept in the future of the CDP is discussed. First we provide an historical perspective of the ideas that have led to the investigation of sequences in CDP. This is followed by a re-examination and clarification of the definition of physiological heterokairy before empirical case studies that (explicitly or implicitly) demonstrate physiological heterokairy are reviewed. We suggest that physiological heterokairy can be demonstrated through a wide range of invertebrate and vertebrate examples. However, care must be taken when inferring that heterokairy as a pattern is always the result of heterokairic processes as there is evidence that physiological heterokairy could result from the altered timing of both homologous or analogous physiological mechanisms. We conclude by discussing the potential link between heterokairy and heterochrony and suggest that the investigation of this link should be a major goal for workers in both CDP and developmental plasticity.
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http://dx.doi.org/10.1016/j.cbpa.2007.05.027DOI Listing
December 2007

Do developmental mode and dispersal shape abundance-occupancy relationships in marine macroinvertebrates?

J Anim Ecol 2007 Jul;76(4):695-702

Marine Biology and Ecology Research Centre, School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.

1. Dispersal is a crucial process in maintaining population structures in many organisms, and is hypothesized as a process underlying the interspecific relationship between abundance and distribution. Here we examined whether there was a link between the dispersal and developmental modes of marine macroinvertebrates and the slopes and elevations of interspecific abundance-occupancy relationships. We predicted that if within-site retention of larvae ranks in the order brooders > lecithotrophs > planktotrophs, for any given level of mean abundance, occupancy should increase in the order brooders < lecithotrophs < planktotrophs. We also predicted that propensity to form metapopulations should be greater for planktonic dispersers (i.e. lecithotrophs and planktotrophs combined) than for non-planktonic (i.e. brooders), resulting in steeper abundance-occupancy relationships for the former. 2. Predictions were tested using a data set for 362 subtidal marine macroinvertebrates occurring across 446 1-km(2) grid squares around the British Isles; analyses were performed on the data set as a whole and for separate phyla. 3. The total data set had a Z-transformed effect size of 0.79, within the confidence intervals described by Blackburn et al. (2006; Journal of Animal Ecology, 75, 1426-1439), and was consistently present with relatively homogeneous effect size in separate analyses of polychaetes, crustaceans, molluscs and echinoderms. 4. In all cases, planktonic dispersing organisms showed an abundance-occupancy relationship with greater elevation than that for non-planktonic organisms; in polychaetes the elevation of slopes was in the rank order planktotrophs > lecithotrophs > brooders. No differences between the slopes of the abundance-occupancy relationship were apparent for different dispersal modes either within, or across phyla. 5. We conclude that dispersal capacity may play an important part in determining the elevation of the abundance-occupancy relationship, the corollary of low dispersal in the marine realm being greater local retention of larvae and greater local population abundance at low extents of geographical distribution.
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http://dx.doi.org/10.1111/j.1365-2656.2007.01245.xDOI Listing
July 2007

An integrative approach identifies developmental sequence heterochronies in freshwater basommatophoran snails.

Evol Dev 2007 Mar-Apr;9(2):122-30

Marine Biology and Ecology Research Centre, University of Plymouth, Drakes Circus, Plymouth PL4 8AA, UK.

Adopting an integrative approach to the study of sequence heterochrony, we compared the timing of developmental events encompassing a mixture of developmental stages and functional traits in the embryos of 12 species of basommatophoran snails in an explicit phylogenetic framework. PARSIMOV analysis demonstrated clear functional heterochronies associated both with basal branches within the phylogeny and with terminal speciation events. A consensus of changes inferred under both accelerated transformation and delayed transformation optimizations identified four heterochronies where the direction of movement was known plus six twin heterochronies where the relative movements of the two events could not be assigned. On average, 0.5 and 0.58 events were inferred to have changed their position in the developmental sequence on internal and terminal branches of the phylogeny, respectively; these values are comparable with frequencies of sequence heterochrony reported in mammals. Directional heterochronies such as the early occurrence of body flexing in relation to the ontogeny of the eye spots, heart beat, and free swimming events occurred convergently and/or at different levels (i.e., familial, generic, and species) within the phylogeny. Such a functional approach to the study of developmental sequences has highlighted the possibility that heterochrony may have played a prominent role in the evolution of this group of invertebrates.
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http://dx.doi.org/10.1111/j.1525-142X.2007.00143.xDOI Listing
October 2007

A microplate freshwater copepod bioassay for evaluating acute and chronic effects of chemicals.

Environ Toxicol Chem 2005 Jun;24(6):1528-31

AstraZeneca Global Safety, Health and Environment, Brixham Environmental Laboratory, Freshwater Quarry, Brixham, Devon TQ5 8BA, United Kingdom.

Toxicity test protocols for establishing the effect of zinc on the freshwater copepod Bryocamptus zschokkei are reported. In the absence of food, larval life-history stages were more sensitive than adult females to acute zinc exposure with a 96-h median lethal concentration of 0.62 mg Zn/L (0.52-0.73 mg Zn/L, 95% confidence intervals) for copepodids. The acute toxicity of zinc to adult females was also significantly reduced in the presence of food (a leaf disc). The main toxic effect of zinc in a life-cycle test was a reduction in the number of offspring per brood at 0.48 mg Zn/L. As this endpoint corresponded with zinc concentrations causing reduced juvenile survival, prolonged embryonic development times, and mortality during hatching, it appears that zinc had a direct toxic effect on the current brood rather than an indirect effect on egg production via maternal reallocation of resources. The lowest-observed-effect concentration for reproduction of measured zinc concentrations of 0.48 mg Zn/L corresponded with environmental concentrations of zinc causing reduced population densities of this copepod in the field. It is proposed that B. zschokkei is an ecologically relevant test species for evaluating the potential effects of contaminants on freshwater invertebrates and for giving insight into the mode of action of a test chemical.
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http://dx.doi.org/10.1897/04-111r.1DOI Listing
June 2005

Environmental calcium modifies induced defences in snails.

Proc Biol Sci 2004 Feb;271 Suppl 3:S67-70

School of Biological Sciences, University of Plymouth, Plymouth PL4 8AA, UK.

Inducible defences are adaptive phenotypes that arise in response to predation threats. Such plasticity incurs costs to individuals, but there has been little interest in how such induced traits in animals may be constrained by environmental factors. Here, we demonstrate that calcium availability interacts with predation cues to modify snail shell growth and form. Small snails increased their growth and were heavier when exposed to fish chemical cues, but this response was calcium limited. There was also an interactive effect of fish cues and calcium on the shell growth of larger snails, but shell strength and aperture narrowness were affected by calcium alone. For small snails, behavioural avoidance was greatest for snails exhibiting least morphological plasticity, suggesting a trade-off. There was no trade-off of somatic growth with plasticity. We suggest that the expression of defensive traits in molluscs can be constrained by calcium availability, which has implications for molluscan ecology and evolution.
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http://dx.doi.org/10.1098/rsbl.2003.0106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1809991PMC
February 2004

Interactions between freshwater snails and tadpoles: competition and facilitation.

Oecologia 1991 Jun;87(1):8-18

Department of Ecology, University of Lund, Helgonavägen 5, S-223 62, Lund, Sweden.

Freshwater snails and anuran tadpoles have been suggested to have their highest population densities in ponds of intermediate size where abiotic disturbance (e.g. desiccation) is low and large predators absent. Both snails and tadpoles feed on periphytic algae and, thus, there should be a large potential for competitive interactions to occur between these two distantly related taxa. In a field experiment we examined the relative strength of competition between two closely related snail species, Lymnaea stagnalis and L. peregra, and between L. stagnalis and tadpoles of the common frog, Rana temporaria. Snail growth and egg production and tadpole size at and time to metamorphosis were determined. Effects on the common food source, periphyton, were monitored with the aid of artificial substrates. Periphyton dry weight was dramatically reduced in the presence of snails and/or tadpoles. There were no competitive effects on growth or egg production of the two snail species when they were coexisting. Mortality of L. peregra was high (95%) after reproduction, but independent of treatment. Growth of L. stagnalis was reduced only at the highest tadpole densities, whereas egg production was reduced both by intraspecific competition and by competition with tadpoles. Differences in egg production were retained after tadpole metamorphosis. Tadpole larval period increased, weight of metamorphosing frogs decreased and growth rate was reduced as a function of increasing tadpole density. However, contrary to expectation, snails had a positive effect on tadpole larval period, weight and growth rate. Further, in experimental containers without snails there was a dense growth of the filamentous green alga Cladophora sp. We suggest that the facilitative effects of snails on tadpoles are due to an "indirect mutualistic" mechanism, involving competition between food sources of different quality (microalgae and Cladophora sp.) and tadpoles being competitively dominant over snails for the preferred food source (microalgae). In the presence of tadpoles snails will be forced to feed on low-quality Cladophora, increasing nutrient turnover rates, which results in enhanced productivity of microalgae, increasing tadpole food resources. Thus, tadpoles have a negative effect on snails through resource depression, while snails facilitate tadpole growth through an indirect enhancement of food availability.
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http://dx.doi.org/10.1007/BF00323774DOI Listing
June 1991