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Microscopic plastic items (microplastics) are ubiquitously present in aquatic ecosystems. With decreasing size their availability and potential to accumulate throughout food webs increase. However, little is known on the uptake of microplastics by freshwater invertebrates. To address this, we exposed species with different feeding strategies to 1, 10 and 90 µm fluorescent polystyrene spheres (3–3 000 particles mL −1 ). Additionally, we investigated how developmental stages and a co-exposure to natural particles (e.g., food) modulate microplastic ingestion. All species ingested microplastics in a concentration-dependent manner with Daphnia magna consuming up to 6 180 particles h −1 , followed by Chironomus riparius (226 particles h −1 ), Physella acuta (118 particles h −1 ), Gammarus pulex (10 particles h −1 ) and Lumbriculus variegatus (8 particles h −1 ). D. magna did not ingest 90 µm microplastics whereas the other species preferred larger microplastics over 1 µm in size. In C. riparius and D. magna , size preference depended on the life stage with larger specimens ingesting more and larger microplastics. The presence of natural particles generally reduced the microplastics uptake. Our results demonstrate that freshwater invertebrates have the capacity to ingest microplastics. However, the quantity of uptake depends on their feeding type and morphology as well as on the availability of microplastics.

Adaptive radiations are bursts of evolutionary species diversification that have contributed to much of the species diversity on Earth. An exception is modern Europe, where descendants of ancient adaptive radiations went extinct, and extant adaptive radiations are small, recent and narrowly confined. However, not all legacy of old radiations has been lost. Subterranean environments, which are dark and food-deprived, yet buffered from climate change, have preserved ancient lineages. Here we provide evidence of an entirely subterranean adaptive radiation of the amphipod genus Niphargus , counting hundreds of species. Our modelling of lineage diversification and evolution of morphological and ecological traits using a time-calibrated multilocus phylogeny suggests a major adaptive radiation, comprised of multiple subordinate adaptive radiations. Their spatio-temporal origin coincides with the uplift of carbonate massifs in South-Eastern Europe 15 million years ago. Emerging subterranean environments likely provided unoccupied, predator-free space, constituting ecological opportunity, a key trigger of adaptive radiation. This discovery sheds new light on the biodiversity of Europe. There are relatively few known extant adaptive radiations in Europe that predate the Pleistocene. Here, Borko et al. characterize the diversity and diversification of the subterranean amphipod genus Niphargus , showing evidence for a large adaptive radiation associated with massif uplift 15 million years ago.

Regenerating animals have the ability to reproduce body parts that were originally made in the embryo and subsequently lost due to injury. Understanding whether regeneration mirrors development is an open question in most regenerative species. Here, we take a transcriptomics approach to examine whether leg regeneration shows similar temporal patterns of gene expression as leg development in the embryo, in the crustacean Parhyale hawaiensis. We find that leg development in the embryo shows stereotypic temporal patterns of gene expression. In contrast, the dynamics of gene expression during leg regeneration show a higher degree of variation related to the physiology of individual animals. A major driver of this variation is the molting cycle. We dissect the transcriptional signals of individual physiology and regeneration to obtain clearer temporal signals marking distinct phases of leg regeneration. Comparing the transcriptional dynamics of development and regeneration we find that, although the two processes use similar sets of genes, the temporal patterns in which these genes are deployed are different and cannot be systematically aligned.

The amphipod crustacean Parhyale hawaiensis is a blossoming model system for studies of developmental mechanisms and more recently regeneration. We have sequenced the genome allowing annotation of all key signaling pathways, transcription factors, and non-coding RNAs that will enhance ongoing functional studies. Parhyale is a member of the Malacostraca clade, which includes crustacean food crop species. We analysed the immunity related genes of Parhyale as an important comparative system for these species, where immunity related aquaculture problems have increased as farming has intensified. We also find that Parhyale and other species within Multicrustacea contain the enzyme sets necessary to perform lignocellulose digestion ('wood eating'), suggesting this ability may predate the diversification of this lineage. Our data provide an essential resource for further development of Parhyale as an experimental model. The first malacostracan genome will underpin ongoing comparative work in food crop species and research investigating lignocellulose as an energy source. The marine crustacean known as Parhyale hawaiensis is related to prawns, shrimps and crabs and is found at tropical coastlines around the world. This species has recently attracted scientific interest as a possible new model to study how animal embryos develop before birth and, because Parhyale can rapidly regrow lost limbs, how tissues and organs regenerate. Indeed, Parhyale has many characteristics that make it a good model organism, being small, fast-growing and easy to keep and care for in the laboratory. Several research tools have already been developed to make it easier to study Parhyale. This includes the creation of a system for using the popular gene editing technology, CRISPR, in this animal. However, one critical resource that is available for most model organisms was missing; the complete sequence of all the genetic information of this crustacean, also known as its genome, was not available. Kao, Lai, Stamataki et al. have now compiled the Parhyale genome – which is slightly larger than the human genome – and studied its genetics. Analysis revealed that Parhyale has genes that allow it to fully digest plant material. This is unusual because most animals that do this rely upon the help of bacteria. Kao, Lai, Stamataki et al. also identified genes that provide some of the first insights into the immune system of crustaceans, which protects these creatures from diseases. Kao, Lai, Stamataki et al. have provided a resource and findings that could help to establish Parhyale as a popular model organism for studying several ideas in biology, including organ regeneration and embryonic development. Understanding how Parhyale digests plant matter, for example, could progress the biofuel industry towards efficient production of greener energy. Insights from its immune system could also be adapted to make farmed shrimp and prawns more resistant to infections, boosting seafood production.

Research on the uptake and effects of bioplastics by aquatic organisms is still in its infancy. Here, we aim to advance the field by comparing uptake and effects of microplastic particles (MPP) of a biodegradable bioMPP (polyhydroxybutyrate (PHB)) and petroleum-based MPP (polymethylmethacrylate (PMMA)) in the freshwater amphipod Gammarus fossarum. Ingestion of both MPP in different particle sizes (32–250 µm) occurred after 24 h, with highest ingestion of particles in the range 32–63 µm and almost complete egestion after 64 h. A four-week effect-experiment showed a significant decrease of the assimilation efficiency in amphipods exposed to the petroleum-based MPP from week two onwards. The petroleum-based PMMA affected assimilation efficiency significantly in contrast to the biodegradable PHB, but overall differences in direct comparison of MPP types were small. Both MPP types led to a significantly lower wet weight gain relative to the control treatments. After four weeks, differences between both MPP types and silica, used as a natural particle control, were detected. In summary, these results suggest that both MPP types provoke digestive constraints on the amphipods, which go beyond those of natural non-palatable particles. This highlights the need for more detailed research comparing environmental effects of biodegradable and petroleum-based MPP and testing those against naturally occurring particle loads.

It has been suggested that giant Antarctic marine invertebrates will be particularly vulnerable to declining O 2 levels as our ocean warms in line with current climate change predictions. Our study provides some support for this oxygen limitation hypothesis, with larger body sizes being generally more sensitive to O 2 reductions than smaller body sizes. However, it also suggests that the overall picture is a little more complex. We tested predictions from three different, but overlapping, O 2 -related hypotheses accounting for gigantism, using four Antarctic amphipod species encompassing a wide range of body sizes. We found a significant effect of body size, but also of species, in their respiratory responses to acutely declining O 2 tensions. The more active lifestyle of intermediate-sized Prostebbingia brevicornis was supported by a better respiratory performance than predicted by the oxygen limitation hypothesis alone, but consistent with the symmorphosis hypothesis. We suggest that giant polar amphipods are likely to be some of the first to fare badly in an O 2 -poor ocean. However, the products of past evolutionary innovation, such as respiratory pigments that enhance O 2 -transport and novel gas exchange structures, may in some species offset any respiratory disadvantages of either large or small body size. This article is part of the theme issue ‘Physiological diversity, biodiversity patterns and global climate change: testing key hypotheses involving temperature and oxygen’.

We explore the delayed consequences of parental exposure to environmentally relevant cadmium concentrations on the life-history traits throughout generations of the freshwater crustacean Gammarus fossarum. We report the preliminary results obtained during a challenging one-year laboratory experiment in this environmental species and propose the use of population modeling to interpret the changes in offspring life-history traits regarding their potential demographic impacts. The main outcome of this first long-term transgenerational assay is that the exposure of spawners during a single gametogenesis cycle (3 weeks) could result in severe cascading effects on the life-history traits along three unexposed offspring generations (one year). Indeed, we observed a decrease in F1 reproductive success, an early onset of F2 offspring puberty with reduced investment in egg yolk reserves, and finally a decrease in the growth rate of F3 juveniles. However, the analysis of these major transgenerational effects by means of a Lefkovitch matrix population model revealed only weak demographic impacts. Population compensatory processes mitigating the demographic consequences of parental exposure seem to drive the modification of life-history traits in offspring generations. This exploratory study sheds light on the role of population mechanisms involved in the demographic regulation of the delayed effects of environmental toxicity in wild populations.

Artificial light at night (ALAN) is proliferating at an alarming rate across the globe, particularly around aquatic habitats. Natural and predictable light cycles dictate much of an individual organism’s life by acting as a major signal for their circadian clock, driving rhythmic behaviours and physiological changes throughout the body. Light cycles also help populations coordinate group behaviour and greatly impact the interspecies dynamics of a community. Research into the ecological impacts of ALAN has highlighted numerous effects on these biological processes, including higher predation rates, impaired growth and development, and diminished reproductive success. Invertebrates play an undeniable role in ecosystem functioning and show robust daily rhythms. As such, it is vital to understand how ALAN may disrupt their behavioural patterns. The aim of this study was to monitor the impacts of increasing levels of light at night (0 lux – 80 lux), as well as constant light and constant darkness, on the behavioural rhythms of the intertidal amphipod, Marinogammarus marinus , and the freshwater species, Gammarus pulex . Gammarus pulex activity was not strongly synchronised to any of the light at night treatments . Marinogammarus marinus , however, exhibited strong behavioural rhythmicity in diurnal cycles with dark night periods. All the ALAN treatments resulted in a significant decrease in M. marinus rhythmicity and overall activity. Moreover, ALAN between 1–50 lux disrupted nocturnality in this species. These results indicate that while some amphipods show some adaptive plasticity when it comes to light pollution, others may experience strong direct impacts on their activity. This may be relevant to individual and population level fitness of vulnerable species in more heavily urbanised areas.

Amphipods have elicited interest for use as a live feed to culture marine species. However few studies have been conducted to determine optimal conditions necessary for large scale culture. The amphipod, Parhyale hawaiensis is a tropical species that has been considered for use in warm water marine culture. A 30 days study examined the effects of culture system and diet on amphipod production. Two culture systems (biofloc, clearwater) and three diets (fresh and dried Ulva lactuca , commercial shrimp diet) were compared. Water quality, and total adult, juvenile and hatchling densities were evaluated. Water quality was not significantly different between treatments, although a trend towards lower ammonia and nitrite levels were seen in biofloc systems. After 30 days, 50% of the population was comprised of juveniles, with adults and hatchlings each comprising 25% of the population. Total amphipod density differed significantly between treatments with highest density in the biofloc + fresh U. lactuca treatment and lowest density in the clear water + fresh U. lactuca treatment. Significant differences were seen in adult and juvenile populations, with higher densities noted in biofloc systems. Although no significant differences were seen with regards to diet, amphipods fed the U. lactuca diets showed more variation in density than those fed the commercial shrimp diet. Results of this study suggest that utilization of a biofloc culture system may both improve water quality and increase P. hawaiensis production. It is further suggested that more consistent production may been seen if amphipods are fed a commercial shrimp diet rather than a U. lactuca diet.

Amphipods are known as umbrella species in conservation biology that their protection indirectly protects other species. Recent hypotheses suggest a bimodal latitudinal global species richness pattern for amphipods, irrespective of species’ depth or habitat type. Phylogeographic hypotheses suggested two distinct procedures for amphipod diversification: ecological radiation and Pangea fragmentation. This study aimed to revisit the bimodal latitudinal pattern of species richness for amphipods, investigate similarities in species composition and main environmental amphipod distribution drivers regarding their depth and habitat variations. The comprehensive database was collected from open-access data and a personal sampling database from the Persian Gulf and the Gulf of Oman. After rigorous data quality controls, the final dataset comprised 1,142,416 distribution records of 6,424 accepted marine amphipod species distributed from 0 to 10,900 m depth. All the species were grouped into pelagic and benthic, shallow-water (> 200 m), and deep-sea (< 200 m). Alpha and gamma species richness and the expected number of species per 50 random samples (ES50) were calculated. Our findings showed that species richness patterns in amphipods are shaped not only by habitat types but also by depth, and they are not significantly bimodal in all groups. Also, the Beta diversity of benthic species revealed distinct diversification patterns between benthic and pelagic species. The species similarity clusters revealed a fragmentation between Gondwana and Laurasia for shallow benthic species. However, the similarity between pelagic amphipod communities is more compatible with ecological parameters. Generalized Additive Models (GAMs) highlighted that environmental variables play a significant role in species distributions, for example, temperature and chlorophyll levels were the main predictors of species richness in shallow waters. However, a complete effect of multiple environmental variables is responsible for deep-sea species gradients. These findings are crucial information to be considered when managing the species richness and establishing conservation priorities for their habitats.