Marine Invertebrate Populations Research Articles

Long term environmental variability modulates the epigenetics of maternal traits of kelp crabs in the coast of Chile

The methylation of DNA is an environmentally inducible epigenetic mechanism reflecting the short‐term ecological and environmental background of populations. Marine invertebrate populations, which spread along a latitudinal cline, are particularly suitable for profiling DNA methylation, due to the heterogenous environmental conditions experienced. We used the MSAP (Methylation Sensitive Amplified Polymorphism) technique to investigate the natural variation in DNA methylation of different female’s tissues (muscle, gonads, and gills) and early-stage eggs from five populations of the kelp crab Taliepus dentatus, distributed along a latitudinal cline in the coast of Chile. We assessed whether, (1) the distribution of DNA methylation profiles can be associated with the temporal variability of long term (18 years) climatologies (sea surface temperature, turbidity and productivity) and (2) the epigenetic diversity of eggs is related to the population-level phenotypic variability of several maternal investment traits (egg volume, egg weight, egg lipids and fecundity). The DNA methylation of eggs correlated positively and negatively with the long term variability in productivity and sea surface temperature, respectively. Furthermore, the diversity of DNA methylation of eggs correlated positively with the population-level phenotypic variability of several maternal investment traits, suggesting a key role of epigenetic mechanisms in generating phenotypic variability at population level for this species. We provide evidence of a strong link between the temporal variability of long term climatologies with the epigenetic profiles of key early ontogenetic traits associated with the maternal investment of kelp crabs. These modulating mechanisms can hence contribute early to phenotypic variability at population levels in response to local and past environmental fluctuation.

On the Spread of Microbes That Manipulate Reproduction in Marine Invertebrates.

AbstractBacterial symbionts are functionally integral to animal reproduction and development, some of which have evolved additional mechanisms to override these host programs. One habitat that is increasingly recognized to contain phylogenetically related lineages of reproductive manipulators is the ocean. The reproduction of marine invertebrates often occurs by free spawning instead of by the physical contact of copulation in terrestrial systems. We developed an integrated model to understand whether and when microbes that manipulate host reproduction by cytoplasmic incompatibility, feminization, and male killing spread within populations of free-spawning marine invertebrates. Our model supports three primary findings. First, sex ratio distortion leads to suboptimal fertilization and zygote production in planktotrophs (feeding larvae) but enhance these processes in lecithotrophs (nonfeeding larvae). Second, feminization and a combination of male killing plus enhanced growth are effective at spreading reproductive manipulators while also inducing a female-biased sex ratio. Third, the majority of free-spawning marine invertebrates could be infected across a range of life history combinations, with infections harming species with smaller eggs and longer pelagic durations while benefiting species with larger eggs and shorter pelagic durations. Together, this supports the general premise that microbes may manipulate the reproduction of free-spawning marine invertebrates (e.g., by inducing changes in developmental life history) and that these types of manipulations overlap considerably with terrestrial systems.

Ocean temperature and density dependence as key drivers of the population dynamics of an intertidal crab at the Brazilian oceanic islands

AbstractUnderstanding how climatic and density‐dependent processes affect demography is crucial for predicting population responses to climate change. For marine invertebrates with complex life cycle such as decapod crustaceans, increasing temperatures might affect survival and development of early pelagic stages, whereas high density can increase competition and thus reduce growth and fecundity of older life stages. In this study, we investigate the effects of warm ocean events, body size and density on the population dynamics of the intertidal Sally lightfoot crab (Grapsus grapsus) at the Brazilian oceanic islands. Firstly, we assessed the trends of marine heatwaves (MHW) and positive temperature anomalies (ΔSST+) at the equatorial St Peter and St Paul (SPSP) Archipelago and Rocas Atoll and the subtropical Trindade Island. We then jointly analyzed short‐term count, capture‐recapture and fecundity data, and long‐term population monitoring data (2003–2019) using an integrated population model. Warm ocean events have become more frequent and intense only at the equatorial islands. Increasing MHW frequency positively influenced recruitment in the high‐density SPSP population, while MHW intensity and ΔSST+ frequency had negative impacts. Conversely, no climatic effects were observed for the low‐density Rocas population, which has the largest crabs. Despite a lack of warming in Trindade, this subtropical population with intermediate density and body size was negatively affected by ΔSST+. Our findings revealed population‐specific responses to climate change when accounting for local life history and ecology. Thus, environmental and density‐dependent effects should be broadly considered in future conservation studies regarding ocean warming impacts on marine invertebrate populations.

Assessments of 15 Exploited Fish Stocks in Chinese, South Korean and Japanese Waters Using the CMSY and BSM Methods

The status of fifteen marine fish and invertebrate populations exploited by Chinese, South Korean or Japanese fishing fleets were assessed, using two newly developed computer-intensive methods, CMSY and BSM. The results show that among these fifteen populations in question, 2 have collapsed, 3 are grossly over-fished and 9 are overfished. Also, we compared results of the CMSY and BSM methods, and it shows that, while the CPUE data for use with the BSM method lead to narrower confidence intervals and may modify the shape of the biomass trajectory, they do not lead to over- or underestimates of terminal B/BMSY values. These results, although still tentative because the methods used to generate them are relatively new, generally match what is known of the status and exploitation of the populations in question, which makes CMSY and BSM to be promising stock assessment approaches in data-sparse situations. Based on our results, a consistent signal is obtained, thus suggesting that a reduction in fishing pressure would be necessary to restore the abundance status of these fifteen populations.

Historical translocations and stocking alter the genetic structure of a Mediterranean lobster fishery.

Stocking is often used to supplement wild populations that are overexploited or have collapsed, yet it is unclear how this affects the genetic diversity of marine invertebrate populations. During the 1970s, a lobster stock enhancement program was carried out around the island of Corsica in the Mediterranean using individuals translocated from the Atlantic coast of France. This included the release of thousands of hatchery‐reared postlarval lobsters and several adult individuals, but no monitoring plan was established to assess whether these animals survived and recruited to the population. In this study, we sampled European lobster (Homarus gammarus) individuals caught around Corsica and tested whether they showed Atlantic ancestry. Due to a natural marked phylogeographic break between Atlantic and Mediterranean lobsters, we hypothesized that lobsters with dominant (>0.50) Atlantic ancestry were descended from historical stocking releases. Twenty Corsican lobsters were genotyped at 79 single nucleotide polymorphisms, and assignment analysis showed that the majority (13) had dominant Atlantic ancestry. This suggests that the hatchery stocking program carried out in Corsica during the 1970s, using individuals translocated from the Atlantic coast of France, has likely augmented local recruitment but at a cost of altering the genetic structure of the Corsican lobster population.

Monospecific Biofilms of Pseudoalteromonas Promote Larval Settlement and Metamorphosis of Mytilus coruscus

As a stage of life cycle, larval settlement and metamorphosis are critical processes for persistence of many marine invertebrate populations. Bacterial biofilms (BFs) could induce larval settlement and metamorphosis. Pseudoalteromonas, a widely distributed genus of marine bacteria, showed inductive effects on several invertebrates. However, how Pseudoalteromonas BFs induce settlement and metamorphosis of Mytilus coruscus remains unclear. Pseudoalteromonas marina BFs with the highest inducing activity were further investigated to define inductive cues. Surface-bound products of P. marina BFs could induce larval settlement and metamorphosis. P. marina BFs treated with formalin, antibiotics, ultraviolet irradiation, heat and ethanol significantly reduced inductive effects and cell survival rates. The confocal laser scanning microscopy and the biovolume analysis showed the dominance of α-polysaccharides on P. marina BFs. Treatment of BFs with amylases, proteases and lipase led to the decrease of inducing activity, suggesting that inductive cues of P. marina BFs may comprise of molecular domains of polysaccharides, proteins, and lipids. Finding inductive cues of BFs could put forward further studies about the mechanism of larval settlement and metamorphosis of marine invertebrates.

Applications and Future Directions for Population Transcriptomics in Marine Invertebrates

RNA-sequencing has provided a new way to study transcriptomic population differences of non-model organisms such as marine invertebrates. Importantly, population transcriptomics can provide insight regarding the genetic mechanisms that allow some populations to tolerate various environmental stressors in this era of climate change. Such studies can help us predict future population dynamics and species survival for marine invertebrates of ecological and economic value. Here, I review practical considerations for marine invertebrate researchers using RNA-sequencing, recent applications of population transcriptomics in marine invertebrates, current limitations of this approach, and future areas of study. Recent marine invertebrate studies have examined population-specific responses to abiotic stressors including temperature, salinity, pH, and water quality. Populations tolerant of environmental stressors generally show high constitutive gene expression before stress exposure and a muted overall transcriptional response following stress exposure. Evidence for molecular signatures of selection on several genes including ATP synthase and aquaporins has been identified in marine invertebrate populations exposed to broad temperature regimes. At present, the genetic mechanisms underlying individual variation within a population and the transcriptome response to multiple environmental stressors remain poorly understood. Complete assessment of marine invertebrate population responses to climate change will require pairing RNA-sequencing approaches with complementary phenotype studies. Improvements in transcriptome annotation and future work investigating gene expression regulation will lead to an increased understanding of the genes responsible for population-level tolerance to environmental stressors.

Pesticide drugs used against sea lice cause transcriptome changes in the early stages of the non-target species Choromytilus chorus

Increasing evidence suggests that long non-coding RNAs (lncRNAs) play diverse roles in cellular processes, including in the regulation of embryogenesis and growth. However, little is known about the role of lncRNAs in marine invertebrates inhabiting changing environments. Therefore, the aim of this study was to present the first characterization of lncRNAs in an intertidal marine gastropod. Specifically, Tegula atra individuals were sampled in four sites of the central-northern Chilean coastline (28–31°) during summer and winter. A pipeline was constructed, and 3524 putative lncRNAs were identified from transcriptome databases specific to T. atra. These lncRNAs exhibited characteristics common to known lncRNAs, including a length shorter than coding sequences, low GC-content, and low sequence conservation. Expression analyses revealed that lncRNAs varied more in the summer. Furthermore, a majority of the differentially expressed lncRNAs were found in the southernmost population, the seasonal temperatures of which varied the greatest among all groups. Additionally, co-expression analysis found some lncRNAs strongly correlated with coding genes involved in the environmental stress response, such as heat shock proteins and metalloproteins. In contrast, other lncRNA expressions were strongly uncorrelated with genes involved in lipid/carbohydrates metabolism and cell-cell communication. This study provides the first large-scale characterization of lncRNAs in a marine gastropod, with results suggesting a putative role of lncRNAs in thermal tolerance, as well as an association with molecular mechanisms involved in the local adaptations of marine invertebrate populations.

Comparison of the Polychaetous Annelids Populations on Suspended Test Panels in Los Angeles Harbor in 1950-1951 with the Populations in 2013-2014

A 14-month study was conducted of the polychaetous annelids present on attached wooden blocks at nine stations in Los Angeles Harbor in 2013-2014. The results were compared to a similar study conducted at the same stations in 1950-1951. The primary objective in both studies was to determine the location and occurrence of marine borers in the harbor. Since fouling organisms, including polychaetes, attached to the wooden blocks, it also provided an opportunity to study the polychaetes that settled on the blocks. The number of polychaete species in these two studies increased from 22 to 71. The serpulid Hydroides elegans was a dominate species in both studies but the pollution indicator Capitella capitata, common in the earlier study, was rare in the recent study. There was a seasonal occurrence in both the number of species and specimens with highs in the warmer months and lows from December through March in both studies. Many environmental changes have occurred in the Los Angeles Harbor complex over the past 63 years. New harbor piers constructed that extend into the Outer Harbor, channels have been dredged deeper and pollution abatement programs initiated. The water quality has been improved especially in the Inner Harbor as a result of these changes where the dissolved oxygen in the water was low or absent in 1950-1951 but higher (over 6.0 mg/L) in 2013-2014. This study is unusual since long-term, seasonal comparisons of marine invertebrate populations are uncommon.

Does pre-exposure to warming conditions increase Mytilus galloprovincialis tolerance to Hg contamination?

The degree to which marine invertebrate populations can tolerate extreme weather events, such as short-term exposure to high temperatures, and the underlying biochemical response mechanisms are not yet fully understood. Furthermore, scarce information is available on how marine organisms respond to the presence of pollutants after exposure to heat stress conditions. Therefore, the present study aimed to understand how the mussel Mytilus galloprovincialis responds to Hg pollution after pre-exposure to warming conditions. Mussels were exposed to control (17°C) and warming (21°C) conditions during 14days, followed by Hg contamination during 28days under different temperature regimes (17 and 21°C). The results obtained demonstrated significantly higher Hg concentrations in mussels under 17°C during the entire experiment than in organisms exposed to 21°C during the same period, which resulted in higher oxidative stress in mussels under control temperature. Significantly higher Hg concentrations were also observed in mussels pre-exposed to 21°C followed by a 17°C exposure comparing with organisms maintained the entire experiment at 21°C. These results may be explained by higher metabolic capacity in organisms exposed to 17°C after pre-exposure to 21°C that although induced antioxidant defences were not enough to prevent oxidative stress. No significant differences in terms of Hg concentration were found between mussels exposed to 17°C during the entire experiment and organisms pre-exposed to 21°C followed by a 17°C exposure, leading to similar oxidative stress levels in mussels exposed to both conditions. Therefore, our findings demonstrated that pre-exposure to warming conditions did not change mussels' accumulation and tolerance to Hg in comparison to Hg contaminated mussels maintained at control temperature. Furthermore, the present study indicate that organisms maintained under warming conditions for long periods may prevent the accumulation of pollutants by decreasing their metabolism which will limit cellular injuries. CapsuleMussels under warming conditions presented reduced metabolic capacity, resulting in lower Hg accumulation, which in turn prevented higher damages and, consequently, physiological impairments.

Demographic inference and genetic diversity of Octopus mimus (Cephalopoda: Octopodidae) throughout the Humboldt Current System

Climatic and oceanographic events occurring during the last glacial cycle in the Humboldt Current System (HCS) have left genetic footprints in marine invertebrate populations. The objective of this study was to evaluate the effect of the glacial period on Octopus mimus populations found throughout the HCS. This species lays a large number of small eggs which hatch into planktonic paralarvae with the potential to undergo wide dispersal. We sequenced the COIII gene to perform phylogeographic analyses of 197 octopuses sampled from seven localities. The genetic diversity of Octopus mimus was low and decreased towards the southern end of the distribution range, which comprises a single population. The haplotype genealogy and Bayesian Skyride plot suggest that O. mimus underwent a demographic expansion after the last glacial maximum (LGM). This would imply a contraction of the range of this organism toward northern latitudes during the LGM followed by southward expansion and recolonization once the contemporary interglacial period began.

Epigenetic signatures of invasive status in populations of marine invertebrates

Epigenetics, as a DNA signature that affects gene expression and enables rapid reaction of an organism to environmental changes, is likely involved in the process of biological invasions. DNA methylation is an epigenetic mechanism common to plants and animals for regulating gene expression. In this study we show, for the first time in any marine species, significant reduction of global methylation levels during the expansive phase of a pygmy mussel (Xenostrobus securis) recent invasion in Europe (two-year old), while in older introductions such epigenetic signature of invasion was progressively reduced. Decreased methylation was interpreted as a rapid way of increasing phenotypic plasticity that would help invasive populations to thrive. This epigenetic signature of early invasion was stronger than the expected environmental signature of environmental stress in younger populations sampled from ports, otherwise detected in a much older population (>90 year old) of the also invasive tubeworm Ficopomatus enigmaticus established in similar locations. Higher epigenetic than genetic diversity found in X. securis was confirmed from F. enigmaticus samples. As reported for introduced plants and vertebrates, epigenetic variation could compensate for relatively lower genetic variation caused by founder effects. These phenomena were compared with epigenetic mechanisms involved in metastasis, as parallel processes of community (biological invasion) and organism (cancer) invasions.

Conceptual and methodological advances for holobiont research.

Conceptual and methodological advances for holobiont research.

Long non-coding RNAs are associated with spatiotemporal gene expression profiles in the marine gastropod Tegula atra

Increasing evidence suggests that long non-coding RNAs (lncRNAs) play diverse roles in cellular processes, including in the regulation of embryogenesis and growth. However, little is known about the role of lncRNAs in marine invertebrates inhabiting changing environments. Therefore, the aim of this study was to present the first characterization of lncRNAs in an intertidal marine gastropod. Specifically, Tegula atra individuals were sampled in four sites of the central-northern Chilean coastline (28–31°) during summer and winter. A pipeline was constructed, and 3524 putative lncRNAs were identified from transcriptome databases specific to T. atra. These lncRNAs exhibited characteristics common to known lncRNAs, including a length shorter than coding sequences, low GC-content, and low sequence conservation. Expression analyses revealed that lncRNAs varied more in the summer. Furthermore, a majority of the differentially expressed lncRNAs were found in the southernmost population, the seasonal temperatures of which varied the greatest among all groups. Additionally, co-expression analysis found some lncRNAs strongly correlated with coding genes involved in the environmental stress response, such as heat shock proteins and metalloproteins. In contrast, other lncRNA expressions were strongly uncorrelated with genes involved in lipid/carbohydrates metabolism and cell-cell communication. This study provides the first large-scale characterization of lncRNAs in a marine gastropod, with results suggesting a putative role of lncRNAs in thermal tolerance, as well as an association with molecular mechanisms involved in the local adaptations of marine invertebrate populations.

Large-scale, multidirectional larval connectivity among coral reef fish populations in the Great Barrier Reef Marine Park.

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no-take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers (Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60-220km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P.maculatus and 17 juvenile P.leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short-distance larval dispersal within regions (200m to 50km) and long-distance, multidirectional dispersal of up to ~250km among regions. Dispersal strength declined significantly with distance, with best-fit dispersal kernels estimating median dispersal distances of ~110km for P.maculatus and ~190km for P.leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long-distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations.

Effects of coal contamination on early life history processes of a reef-building coral, Acropora tenuis

Successful reproduction and larval dispersal are important for the persistence of marine invertebrate populations, and these early life history processes can be sensitive to marine pollution. Coal is emerging as a contaminant of interest due to the proximity of ports and shipping lanes to coral reefs. To assess the potential hazard of this contaminant, gametes, newly developed embryos, larvae and juveniles of the coral Acropora tenuis were exposed to a range of coal leachate, suspended coal, and coal smothering treatments. Fertilisation was the most sensitive reproductive process tested. Embryo survivorship decreased with increasing suspended coal concentrations and exposure duration, effects on larval settlement varied between treatments, while effects on juvenile survivorship were minimal. Leachate exposures had negligible effects on fertilisation and larval settlement. These results indicate that coral recruitment could be affected by spills that produce plumes of suspended coal particles which interact with gametes and embryos soon after spawning.

Novel enemies – previously unknown predators of the bearded fireworm

Novel enemies – previously unknown predators of the bearded fireworm

Using a length-based stock assessment model to evaluate population structure hypotheses of nylon shrimp Heterocarpus reedi (Decapoda, Caridea) exploited off central Chile

Spatial processes are rarely considered explicitly in the evaluation and management of marine invertebrate populations. This is particularly true when larval drift acts as one of the main mechanisms of population expansion. The ecological concept metapopulation is widely used and accepted for understanding low-mobility marine populations. This study uses a length-based dynamic analysis model for nylon shrimp (Heterocarpus reedi) exploited off central Chile (25°–37°S) to contrast various hypotheses of population structure and spatial connectivity. The two subpopulations studied are located to the north and south of 32°S. The model is fitted to the historical fishery data (from the mid-1940s to the present), the results of monitoring of fishing activities (1970s-present), and research surveys (1990s-present). Statistically, several hypotheses can explain the data. The most likely hypothesis is that of a metapopulation in which the south zone acts as a source population (reproductive refuge) and determines, partially or totally, the recruits in the north zone, thereby explaining the population increase over the last decade. Empirical evidence will strengthen the hypothesis of spatial connectivity and special attention should be paid to the biological-fishery conditions recorded south of 32°S given the implications for managing the fishery for this resource.

Strong association between parasitism and phenotypic variation in a supralittoral amphipod

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 553:111-123 (2016) - DOI: https://doi.org/10.3354/meps11752 Strong association between parasitism and phenotypic variation in a supralittoral amphipod C. Lagrue, K. Heaphy, B. Presswell, R. Poulin* Department of Zoology, University of Otago, Dunedin 9054, New Zealand *Corresponding author: robert.poulin@otago.ac.nz ABSTRACT: Phenotypic variation is common among conspecifics from the same population, but its causes are not always clear. Parasites may often play a role, as their ability to induce phenotypic changes in their hosts is well established, though not widely acknowledged among marine ecologists. Here, we tested for a possible role of parasites as determinants of marked colour polymorphism, as well as variation in several distinct behavioural traits in the supralittoral amphipod Transorchestia chiliensis (Talitridae). Our results indicate that the juvenile stages of 2 parasites, the acanthocephalan Plagiorhynchus allisonae and a dilepidid cestode, are disproportionately common in certain colour morphs (i.e. green and dark grey in the case of acanthocephalans and green and blue in the case of cestodes) relative to other colour morphs. In addition, amphipods preferring light over dark background substrate were more likely to harbour acanthocephalans, whereas amphipods that either stayed at the surface or did not burrow very deeply harboured more cestodes than those that burrowed deep into the sediment. Our findings also indicate that later developmental stages of P. allisonae are associated with more pronounced host phenotypic variation, suggesting that phenotypic changes escalate in parallel with parasite growth within the host. Furthermore, the 2 parasite species tend not to co-occur in the same individual hosts; thus, their distinct phenotypic effects apply to different subsets of the host population. We suggest that the role of parasitism in inducing and maintaining phenotypic variation within populations of marine invertebrates is probably more important than currently recognised. KEY WORDS: Behavioural changes · Colour polymorphism · Host manipulation · Phenotypic variation · Talitridae · Acanthocephalans · Cestodes · Transorchestia chiliensis Full text in pdf format PreviousNextCite this article as: Lagrue C, Heaphy K, Presswell B, Poulin R (2016) Strong association between parasitism and phenotypic variation in a supralittoral amphipod. Mar Ecol Prog Ser 553:111-123. https://doi.org/10.3354/meps11752 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 553. Online publication date: July 14, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Geographic patterns of genetic diversity in two species complexes of Canadian marine bivalves

Larval development has strong impacts on dispersal potential and gene flow among populations of marine invertebrates. However, Pleistocene glaciations have also played an important role in shaping population structure in benthic taxa in the Northern Hemisphere, even those with planktotrophic larvae. Each glacial advance tended to fragment species distributions, often separating populations for long periods and setting the stage for their differentiation. This study examines patterns of sequence divergence of the mitochondrial cytochrome c oxidase subunit I gene in North American populations of two bivalve species complexes, Hiatella arctica s. l. and Macoma balthica s. l., with complementary data from the nuclear internal transcribed spacer-2 (ITS2) gene for the latter. Our results confirm the presence of two known species from the M. balthica complex in Canada, but also provide evidence for a third clade in Atlantic Canada. Our study confirms that the H. arctica complex in Canada contains at least four species, with support for a novel clade (Hiatella N) in the northeastern Pacific. Our results extend the range of a previously identified Hiatella clade (K) to include the northwestern Atlantic. Both M. balthica s. l. and H. arctica s. l. have broad Holarctic distributions and planktotrophic larvae, but this work reveals differences in phylogeographic structure and genetic diversity.