Estuarine Fauna Research Articles

Unexpected stability in faunal population abundances following an estuary‐wide collapse of oysters

AbstractLive oyster reefs are considered a critical recruitment habitat for estuarine faunal populations as localized in situ or mesocosm studies have demonstrated many faunal species prefer live oyster habitat. It has therefore been assumed that the loss of live oyster habitat would precipitate faunal population declines, but this has been largely untested at large (estuary) scales. Here, we assessed how estuary‐wide faunal populations were affected by a 95% loss of live oyster habitat following the 2012 oyster collapse of Apalachicola Bay, FL, which previously supported one of the largest oyster fisheries in the United States. We standardized long‐term fisheries‐independent monitoring seine and trawl data to create relative indices of resident, associated, and transient faunal species' overall abundance and recruit abundance (restrictive to sizes between 15% and 35% of ). We expected that both relative abundance indices would decrease following the oyster collapse, particularly among species that reside on or recruit to oyster reefs. However, analyses via a series of one‐sided Bayesian t tests did not indicate that faunal recruitment or overall abundance significantly declined in 2012 post‐collapse. As the response of the faunal population could be lagged relative to the 2012 collapse, we also conducted change point analyses to search for lagged declines. Of the 24 relative abundance time series, only two had significant change points post‐collapse, and only black sea bass overall relative abundance declined with an associated change point at the end of the time series. The surprising paucity of faunal decline following oyster loss may be due to the use of alternative habitat types, exceptionally lagged faunal responses, or, perhaps most compelling, a disconnect between preferred and required habitats. Our failure to detect faunal consequences following an oyster population collapse suggests that assumptions of habitat loss (or restoration) effects on estuarine fauna at ecosystem scales are not straightforward and the extrapolation of sub‐estuary‐scale studies may result in poor predictions of future outcomes.

Life is like a reservoir into which a scientist who is completely devoted to his work plunges

The article is devoted to the description of the pages of the life and scientific activity of the outstanding Ukrainian scientist N. I. Zagubizhenko, who made a great contribution to the formation of the theoretical base on the enrichment of natural and artificial water bodies with fodder resources in the conditions of the Steppe zone of Ukraine. Being a student of the doctor of biological sciences, professor P. O. Zhuravel [1,2], who believed that the enrichment of the benthic fauna of the Steppe zone of Ukraine can be carried out by introducing animal organisms that are absent in these reservoirs, which are characterized by wide plasticity and high vitality [9,12,15], Nadezhda Ivanovna Zagubizhenko was engaged in the study of the reconstruction of the benthic fauna of the reservoirs of southeastern Ukraine. In connection with the instability of the fodder base of water bodies in the Steppe zone of Ukraine, the question of the introduction of representatives of the estuarine fauna, their habituation and inclusion in the food rations of a number of commercial fish was and remains relevant in the current period of time. According to the nature of nutrition, most acclimatizers are biofilters [9], for which there is a sufficient amount of food in the form of detritus, the remains of higher aquatic vegetation, in most reservoirs of the Steppe zone of Ukraine. The conduct and substantiation of these research works were of a positive nature and have a significant contribution to the scientific base, theory, and practice of enriching water bodies with fodder resources and preserving the environment. The quality of water at all times has been and is one of the main indicators of the standard of living, therefore, all developed societies make every effort to provide the population and economy with a sufficient amount of water of a quality that is adequate to the requirements of the consumer. Most of the water comes from natural sources – rivers, lakes, reservoirs, the water quality of which must not only be assessed, but also predicted. Two main components are responsible for the quality of water in nature – the catchment basin and the ecological system of the water body [6, p. 36]. Each of them is located in certain conditions of geography and climate, characteristic of the region under study, in our research – the Steppe zone of Ukraine.

Trends in the decapod crustacean community at the southernmost estuary of the Atlantic coast of Europe

Climate change may enhance the establishment of introduced species, as well as the poleward shift in distribution of numerous species over decades. Long-term research and monitoring of an ecosystem at the southernmost point of the Atlantic coast of Europe should be an important priority in order to detect and understand trends in species composition and the related environmental changes. The Guadalquivir estuary (South West Spain) is more likely to suffer the exacerbated effects of climate change due to its location in the Mediterranean-climate zone. The long-term data set between 1997 and 2006 has allowed us to analyse the variability of the natural and anthropogenic stressors. The mean interannual dissimilarity of the estuarine fauna (Bray–Curtis dissimilarity index) has showed important differences throughout the years, and the species that most contributed to these differences were the exotic species capable of completing their life cycles. This long-term monitoring of the estuarine community has allowed us to anticipate future events and ecological risk assessment in European waters.

EXTENSIÓN EN LA DISTRIBUCIÓN DEL CAMARÓN ALFEIDEO Potamalpheops tyrymembe SOLEDADE, SANTOS & ALMEIDA, 2014 (DECAPODA: ALPHEIDAE)

TThe occurrence of the alpheid mangrove shrimp Potamalpheops tyrymembe Soledade, Santos and Almeida, 2014, is here e extended from 8°41’S (Rio Ariquindá, state of Pernambuco) to 7°01’S (Rio Paraíba do Norte, state of Paraíba) in northeastern Brazil, enlarging the northern known range of this shrimp. Moreover, we provide additional locality records for this tiny and poorly known shrimp which has been observed in burrows of the mangrove crab Ucides cordatus (Linnaeus, 1763). Keywords: Caridea, estuarine fauna, mangrove fauna, new records, western Atlantic.

Eco-engineered mangroves provide complex but functionally divergent niches for estuarine species compared to natural mangroves

There is growing demand for novel coastal protection approaches that also provide co-benefits such as enhanced biodiversity. Rock-fillets, which are used to stabilise eroding banks in estuaries, can be colonised by mangroves, and may provide habitat for estuarine fauna. However, it is unknown whether hybrid mangrove/rock-fillet habitats are functionally equivalent to natural mangroves, for estuarine fauna. To determine whether hybrid mangrove habitats are functionally equivalent to natural mangroves, we used δ13C and δ15N stable isotope analyses to describe the isotopic niche space and overlap of estuarine species in these two habitats across three estuaries in NSW, Australia. Using a Bayesian standard ellipse analysis of isotopic niche area, over half the 12 species observed had larger isotopic niche areas in natural mangroves compared to hybrid habitats, however there were no clear patterns for species between habitats. Natural mangroves and hybrid rock-fillet habitats were isotopically distinct for all species sampled (low proportional overlap, 0–19%) suggesting they are not, at present, wholistically functionally equivalent. Estuarine communities from the two habitat types, however, had similar isotopic niches. Hybrid communities displayed a broader range of δ13C values compared to natural mangroves, suggesting mangrove/rock-fillet habitats have a more diverse range of basal food sources. These findings demonstrate the potential for defence solutions to provide unique co-benefits by supporting food webs, but also that natural habitats provide unique ecosystem services that should be protected and rehabilitated where possible. Future modelling and monitoring of habitat utilisation and species performance could provide further insight into the co-benefits and trade-offs of hybrid habitats.

Surprising Pseudogobius: Molecular systematics of benthic gobies reveals new insights into estuarine biodiversity (Teleostei: Gobiiformes)

Snubnose gobies (genus Pseudogobius: Gobionellinae) are ubiquitous to, and important components of, estuarine ecosystems of the Indo-west Pacific. These small benthic fishes occur in freshwater, brackish and marine habitats such as mangroves, sheltered tide pools and lowland streams, and represent a model group for understanding the biodiversity and biogeography of estuarine fauna. To develop the species-level framework required for a concurrent morphological taxonomic appraisal, we undertook thorough sampling around the extensive Australian coastline, referenced to international locations, as part of a molecular systematic review using both nuclear and mitochondrial markers. The results indicate that while there are currently eight recognised species, the true diversity is close to double this, with a hotspot of endemism located in Australia. Complicated patterns were observed in southern Australia owing to two differing zones of introgression/admixture. Key drivers of diversity in the group appear to include plate tectonics, latitude, and historic barriers under glacial maxima, where an interplay between ready dispersal and habitat specialisation has led to regional panmixia but frequent geographic compartmentalisation within past and present landscapes. The findings have significant implications for biodiversity conservation, coastal and estuarine development, the basic foundations of field ecology, and for applied use such as in biomonitoring.

Availability and assessment of microplastic ingestion by marsh birds in Mississippi Gulf Coast tidal marshes

Millions of tons of plastic enter the environment every year, where much of it concentrates in environmental sinks such as tidal marshes. With prior studies documenting harm to marine fauna caused by this plastic pollution, the need to understand how this novel type of pollution affects estuarine fauna is great. Yet, research on the fate and uptake of plastic pollutants in estuarine ecosystems is sparse. Therefore, we quantified plastic prevalence and ingestion by two species of resident marsh bird, Clapper Rails (Rallus crepitans) and Seaside Sparrows (Ammospiza maritima), in coastal marsh ecosystems within Mississippi. We detected microplastics (plastics smaller than 5 mm) in 64% of marsh sediment samples, 83% of Clapper Rail and 69% of Seaside Sparrow proventriculus samples. Dominant types of microplastics detected in sediment and bird samples were fibers. This study provides the first evidence of microplastic ingestion by marsh birds and its distribution in coastal marshes within Mississippi.

Juvenile fish assemblage recruitment dynamics in a mid-Atlantic estuary: before and after Hurricane Sandy

Hurricanes can have long-term effects on estuarine fauna. Understanding these effects is important as climate change may influence the severity and frequency of these storms. On 29 October 2012, Hurricane Sandy, a large storm spanning roughly 1850 km in diameter, made landfall in Brigantine, New Jersey (USA), approximately 20 km south of Barnegat Bay, during an ongoing study of the bay’s ichthyofauna, providing an opportunity to observe fish recruitment dynamics coincident with hurricane passage. The objective of this study was to measure variance in the Barnegat Bay pre-Sandy fish assemblage relative to that of 1 and 2 yr after the storm. Barnegat Bay fishes were surveyed with an extensive otter trawl study in April, June, August, and October of 2012 (pre-Sandy), 2013 (1 yr post-Sandy), and 2014 (2 yr post-Sandy). Species composition of the fish assemblage was similar across years. Analyzed structural characteristics (abundance, diversity, richness) of the fish assemblage were occasionally more likely to occur or were larger pre-Sandy and 2 yr post-Sandy relative to 1 yr post-Sandy, but this trend was inconsistent across seasons and between structural characteristics. Furthermore, odds of occurrence and length frequency distributions for many resident species and sentinel fall/winter spawners did not indicate that variance could be definitively explained as a hurricane effect. The capability of fish to relocate from areas of temporarily unsuitable habitat and annual new recruitment of larvae and juveniles to the bay likely contributed to the observed stability in the fish assemblage.

The influence of prolonged drought and anthropogenic impact reversal on fish community structure and ecosystem state cycling of Lake St Lucia, Africa’s largest estuarine lake

Historically, the St Lucia Estuarine Lake System and uMfolozi River joined via an estuarine bay before exiting to the sea. In 1952, separate mouths were created, because of sediment problems originating from the uMfolozi River. During the 2004 drought, the mouth of the 525 km2 St Lucia System closed and has remained so to date, except for a single opening in 2007, lasting six months. From 2008, management actions have been implemented to 'reconnect' St Lucia to uMfolozi. This study assessed the effects of a new channel between the two on the St Lucia fish community and its effectiveness for recruitment of marine species. Twelve marine species previously absent and a 67% increase in abundance in the Lower Narrows were recorded after channel opening, which allowed for limited recruitment of marine species. This paper reviews the effects of a permanent connection between St Lucia and uMfolozi, via the uMfolozi Spillway, established in 2012, which has pushed the system into a prolonged freshwater state severely reducing the estuarine fish fauna. This, the lack of a connection to the sea for 15 years and issues potentially associated with increased sedimentation in the lower reaches are reviewed in relation to management decisions that have been implemented.

Abundance/occupancy/patchiness relations in estuarine seagrass macrobenthos

Using >1800 macrobenthic samples from 25 representative intertidal seagrass sites in the Knysna estuarine bay (warm-temperate South Africa), abundance/occupancy relations were examined in the light of Foggo et al.'s (2003) earlier work concerning British estuarine faunas. In addition, the relationship of degree of variation in macrobenthic abundance across unit area, 'patchiness', to this macroecological picture was investigated. Across the group of 30 dominant faunal components as a whole, the most widely and abundantly distributed species had (a) the highest mean abundances and (b) the least spatially-patchy densities in each of Knysna's diverse regions and at all spatial scales from landscape to local; however no significant relationship was observed between mean abundance and degree of patchiness. Individual dominant species displayed considerable variation; some showing positive occupancy/patchiness correlations, and several displaying significant positive and others negative abundance/patchiness ones. As expected along the estuarine gradient, positive and negative correlations of both abundance and occupancy with distance upstream were found in different species (both metrics in a given species always responding in the same manner), although significant upstream relationships with patchiness were found in only two. Local patchiness clearly contributes macroecological information additional to that provided by abundance or occupancy.

Propagule risk in a marine foundation species: Seascape effects on Zostera marina seed predation

Abstract Both biotic and abiotic factors can affect whether seagrass meadows establish as large, continuous features or as a mosaic of smaller patches, and these processes act across multiple spatial scales. Of these processes, sexual recruitment is considered vital for the recovery and resilience of seagrass meadows. Because numerous estuarine fauna can impact sexual recruitment by consuming seeds, it is important to understand variation in seed consumption throughout the seascape. We sought to determine how cross‐scale processes affected seed consumption of Zostera marina, a widely distributed seagrass species. We deployed seed predation units (SPU) within patches ranging in size from 0.28 to 28.48 m2, and on unvegetated, sandy bottom. Seed consumption was analysed across patch sizes, at patch centres and edges and within the context of total seagrass cover within buffer zones surrounding SPU locations. Using structural equation modelling, we found that measured seascape parameters explained 34% of the observed variation in seed consumption. Specifically, we found that seagrass presence had the strongest effect on seed predation followed by a negative effect of patch size on seed consumption. Although there was no direct effect of percent seagrass cover (within a 4‐m buffer of the SPU) on seed predation, percent seagrass cover had a negative indirect effect through its positive correlation with patch size. However, we found that once variation due to patch size and areal cover were accounted for, seeds placed at patch interiors actually experienced greater consumption rates. We did not find similar relationships with our potential seed consumers, although our snapshot sampling likely obscured transient effects. We argue that seagrass recruitment could be affected by seed predation, which is influenced by multiple processes, including predator dispersal, behaviour and aggregation. Since seed‐based restoration is becoming more common, and the role of sexual recruitment in meadow maintenance appears to be increasingly important for seagrass resilience, our results demonstrate that for current management strategies to be successful, there is a need to better understand seed predation in seagrass‐dominated seascapes. Synthesis. Factors that influence propagule supply and recruitment success of seagrass operate and interact across multiple spatial scales, which can have implications for management.

DISTRIBUIÇÃO DE MERCÚRIO NA FAUNA ESTUARINA DO RIO JAGUARIBE - CE

Modificações na paisagem natural aliadas às mudanças climáticas globais, alteram a hidrodinâmica da Bacia Inferior do rio Jaguaribe, possibilitando maior biodisponibilidade de contaminantes, entre eles o mercúrio (Hg). Análise das concentrações de Hg na fauna estuarina (13 espécies de peixes e 5 de invertebrados) mostraram variações nas concentrações de Hg relacionadas aos hábitos alimentares das espécies. Tanto entre invertebrados quanto nos peixes, as maiores concentrações foram encontradas nas espécies carnívoras. Entretanto, não foram encontradas diferenças significativas entre as concentrações médias entre peixes carnívoros e onívoros, e entre invertebrados carnívoros e filtradores, o que pode estar relacionado as características biológicas específicas, como tamanho, estado de maturação e composição da dieta.

Mangrove forests may serve as stable environments for the meiobenthic Echinoderes komatsui (Kinorhyncha: Cyclorhagida): distribution patterns and population dynamics in a subtropical estuary

ABSTRACTEchinoderes komatsui (Kinorhyncha: Cyclorhagida) is a meiobenthic animal inhabiting the interstitial spaces of the sediment on a subtropical tidal flat along the Oura River, Japan. This species mostly occurred within 0–10 mm from the surface of the sediment, and the dispersion pattern was significantly patchy. The population dynamics of E. komatsui were investigated by monthly surveys from January 2014 to May 2016 at four sites along the river, and from April 2015 to May 2016 at one site in the mangrove forest. Echinoderes komatsui occurred all year round; however, the population density showed different patterns among the sampling sites in response to seasonal changes. On the tidal flat, the population density was high in winter, but very low in summer. In the mangrove forest, the density was high (or not low) throughout the year. As was shown in laboratory experiments, E. komatsui survived in 1–44 salinity seawater but died at 0 (salinity experiments), and died within 4.5 days at 40°C (temperature experiments). Therefore, the low population density recorded in summer on the tidal flat was likely caused by high temperature and fresh water. The shade offered by the mangrove forest suppressed the increase in temperature of the sediment in the summer, probably resulting in the higher population density at this site relative to the tidal flat population. Mangrove forests may also mitigate the disturbance of the sediment by summer typhoons and serve as stable environments that are fundamental in the sustainability of estuarine meiobenthic fauna.

Mangrove clearing impacts on macrofaunal assemblages and benthic food webs in a tropical estuary

Despite over 21,000ha of mangrove forests being removed per year in Brazil, ecological changes following mangrove deforestation have been overlooked. Here we evaluated changes in benthic macrofaunal assemblages and food-webs at a mangrove removal and natural sites in a tropical estuary in Eastern Brazil. The impacted site had coarser sediment particle sizes suggesting significant changes in sedimentation processes after forest clearing. Spatial differences in macrofaunal abundance, biomass and diversity were not directly associated with the removal of mangrove forests, supporting recolonization of impacted areas by estuarine fauna. However, benthic assemblage composition, infaunal δ13C signatures and food-web diversity markedly differed at the impacted site being strongly related to sedimentary changes. The loss of infaunal trophic diversity that followed mangrove removal suggests that large-scale forest clearing may impact estuarine food webs, with potential consequences to nearby coastal ecosystems given the high clearing rate of mangrove forests in Brazil.

Comparative Analysis of Distribution of Intertidal Fish Assemblages in Different Estuarine Systems on Northern Coast of Brazil

The northern coast of Brazil has more than 30 estuaries distributed along 650 km of coastline. These conditions favor the presence of relatively large fish communities in estuarine environments, but published information on the fish fauna in tidal creeks in northern Brazil is only available for some mangrove systems, and comparative studies between fish estuarine communities in different tidal creeks are less common. The choice of the study area was based on the fact that it has been poorly investigated with regard to estuarine fish fauna in comparison in mangrove tidal creeks using the same fishing gear. The objective of the present study was to compare the composition of the relative biomass of taxonomic, functional and ecological guilds of fish assemblages occurring in estuarine systems along the northern coast of Brazil. The study area of the present comparative analysis extended from the southeastern edge of the Marajoara Gulf to the western edge of the Maranhense Gulf. A comparative analysis among different estuarine systems was performed using data from other studies. The abundance of juveniles was greater in the Caeté, Curuçá and Cururuca estuaries than other estuaries. Cluster analysis separated the estuaries into two distinct groups and significant differences between these groups only exist in relation to geographical proximity. The present investigation indicates that the coastal region between the states of Pará and Maranhão is characterized by high dynamics and environmental heterogeneity, particularly with regard to changes in river discharge and tidal fluctuations. The present results underscore the importance of ecological information on ichthyofauna in tropical estuaries in order to include appropriate descriptors in conservation or restoration processes of marine communities and habitats.

Linking the Abundance of Estuarine Fish and Crustaceans in Nearshore Waters to Shoreline Hardening and Land Cover

Human alteration of land cover (e.g., urban and agricultural land use) and shoreline hardening (e.g., bulkheading and rip rap revetment) are intensifying due to increasing human populations and sea level rise. Fishes and crustaceans that are ecologically and economically valuable to coastal systems may be affected by these changes, but direct links between these stressors and faunal populations have been elusive at large spatial scales. We examined nearshore abundance patterns of 15 common taxa across gradients of urban and agricultural land cover as well as wetland and hardened shoreline in tributary subestuaries of the Chesapeake Bay and Delaware Coastal Bays. We used a comprehensive landscape-scale study design that included 587 sites in 39 subestuaries. Our analyses indicate shoreline hardening has predominantly negative effects on estuarine fauna in water directly adjacent to the hardened shoreline and at the larger system-scale as cumulative hardened shoreline increased in the subestuary. In contrast, abundances of 12 of 15 species increased with the proportion of shoreline comprised of wetlands. Abundances of several species were also significantly related to watershed cropland cover, submerged aquatic vegetation, and total nitrogen, suggesting land-use-mediated effects on prey and refuge habitat. Specifically, abundances of four bottom-oriented species were negatively related to cropland cover, which is correlated with elevated nitrogen and reduced submerged and wetland vegetation in the receiving subestuary. These empirical relationships raise important considerations for conservation and management strategies in coastal environments.

Effects of Clam Aquaculture on Nektonic and Benthic Assemblages in Two Shallow-Water Estuaries

ABSTRACT Aquaculture of the northern quahog (=hard clam) Mercenaria mercenaria (Linnaeus, 1758) is widespread in shallow waters of the United States from Cape Cod to the eastern Gulf of Mexico. Grow-out practices generally involve bottom planting and the use of predator exclusion mesh. Both the extent and scale of clam farms have increased in recent decades resulting in concerns regarding the impacts of these practices on estuarine fauna. Seasonal distribution, abundance, biomass, species richness, and community composition of nektonic, demersal, epibenthic, and infaunal organisms were examined in cultivated and uncultivated shallow-water habitats in Virginia and New Jersey. The results reveal that clam aquaculture, as practiced in both Virginia and New Jersey, has remarkably few quantifiable impacts on estuarine fauna. Seasonal variations were observed in the biota, but of the 39 population and community metrics tested, mean values associated with 26 did not differ between cultivated and uncultivated are...

Assessment of Mg/Ca in Saccostrea glomerata (the Sydney rock oyster) shell as a potential temperature record

Bivalve shell Mg/Ca records can be important potential tracers of paleo-temperature, but evidence has shown that the temperature dependence of trace metal incorporation rates can vary significantly between different species and even within the same species. This study assesses one such bivalve specimen as a potential temperature proxy for the east coast of Australia. Specimens of the Sydney rock oyster (Saccostrea glomerata) were cultured for approximately one year at two locations on the east coast of Australia: Moreton Bay, Queensland, a semi-enclosed bay with consistently marine conditions, and Pambula Lake, New South Wales, a tidal lake which can undergo significant variations in salinity as a result of rainfall and river discharge. Transects of the oysters' growth axis were analysed via LA-ICP-MS. Mg/Ca-temperature relationships for the oysters show a robust temperature dependence but there is also a clear discrepancy between the two sites. However, this discrepancy was not evident when the temperature dependence of Mg partition coefficients (DMg) was determined, indicating that the difference seen in the direct Mg/Cashell-temperature relationships can be accounted for by variation in salinity at the estuarine site of Pambula Lake. This has implications for the use of Mg/Ca as a paleo-temperature tracer within estuarine fauna as knowledge of the water chemistry is required to determine DMg values. However, S. glomerata Mg/Ca remains a promising paleo-temperature tracer as the direct Mg/Ca-temperature relationships can still be applied to samples from environments that experienced little variation in salinity. Combined analysis of Mg/Ca coupled with δ18Oshell records has the potential to enable the deconvolution of the combined salinity/temperature signal in the δ18Oshell and Mg/Cashell records.

Coastal evacuations by fish during extreme weather events

An increase in the intensity and frequency of extreme events is predicted to occur as a result of climate change. In coastal ecosystems, hurricanes and flooding can cause dramatic changes in water quality resulting in large mortality events in estuarine fauna. Facultative migration behaviors represent a key adaptation by which animals can evacuate ecological catastrophes, but remain poorly studied in marine systems. Here we identify coastal evacuations by otherwise resident riverine striped bass in the Hudson River Estuary, New York, USA, caused by an intense period of tropical storms in autumn 2011. These storms produced record rainfall and high water discharges into the Hudson River Estuary that increased the water level and reduced the water temperature, salinity and dissolved oxygen levels. Striped bass moved out of the estuary, exhibiting novel migration behaviours, that may have been in response to the strong flow and unsuitable conditions. In the months following the storms, some fish demonstrated exploratory trips back to the estuary, which may have been to assess the conditions before returning for the remainder of the winter. Behavioural adaptions to weather events by striped bass and other coastal fishes will depend on maintenance of key population segments and unimpeded evacuation routes.

The first fossil record of larval stages of parasitic isopods: cryptoniscus larvae preserved in Miocene amber

Fossil parasites represent rarities. In many cases, only trace fossils are preserved while body fossils are often lacking. We report here the first find of larval stages of parasitic isopods, identified as cryptoniscus larvae, from Chiapas Amber, Mexico (Lower Miocene). Different crustacean groups, including free-living isopods, have already been reported from the estuarine fauna presented in this type of amber. The seven specimens described here are interpreted as cryptoniscus larvae due to the following characters: 1) The general body organisation in combination with the appendage morphology. 2) A body length between 450 mu m and 695 mu m, which is known from larval stages of Bopyroidea and Cryptoniscoidea (Epicaridea). 3) The morphology of the uropods and the elongated and thin dactyli of the posterior thoracopods (pereiopods) are very similar to the condition in extant cryptoniscus larvae. Although parasitic behaviour can only rarely be directly identified in the fossil record, we can here clearly identify a specialised life stage, the cryptoniscus, which occurs only in a specific monophyletic group, of which all extant representatives are parasitic. These fossils not only represent rare cases of fossil parasites but also the first case of fossil peracarid larvae and the first body fossils of epicarid isopods.