Nancy Fockedey

Feeding of the hyperbenthic mysid Neomysis integer in the maximum turbidity zone of the Elbe, Westerschelde and Gironde estuaries

The diet of the mysid Neomysis integer in the maximum turbidity zone (MTZ) of three European estuaries (Elbe, Westerschelde and Gironde) was investigated in spring 1993. The quality and quantity of the diet were assessed through measurement of the stomach fullness and microscopical analysis of the stomach content combined with image analyses. N. integer was found to be an omnivore which mainly utilizes mesozooplankton and detritus carbon pools. The quality of the diet did not differ between the sexes or between different developmental stages, although smaller individuals consumed fewer items. In all three estuaries the diet was dominated by Copepoda Calanoida (5–10 Eurytemora affinis ind−1 for adults; 2–5 ind−1 and 2–3 ind−1 for subadults and juveniles, respectively) and was supplemented with Rotifera and Cladocera. Phytoplankton and benthic organisms, though present in the stomachs, were negligible. Macrophytal detritus and amorphous material, the latter unidentifiable under the light microscope, were very abundant food items. The amorphous detritus was found to originate from the suspended sediment flocs which are characteristic for the MTZ and mainly consist of clay minerals. The energetic value of the flocs for N. integer remains unclear.

Comparative study of the hyperbenthos of three European estuaries

The hyperbenthic fauna of the subtidal channels of the Eems (N. Netherlands), Westerschelde (S.W. Netherlands), and Gironde (S.W. France) estuaries was sampled within a 15-day period in summer 1991. In each estuary, quantitative samples were taken at regularly spaced stations covering the entire salinity gradient from marine conditions at the mouth to nearly freshwater conditions upstream. The diversity of the samples and the distribution of the species along the main estuarine gradients were assessed. Hyperbenthic communities were identified using different multivariate statistical techniques. The species composition and the density and biomass of the dominant species of each community were compared among communities.

Mysid crustaceans as potential test organisms for the evaluation of environmental endocrine disruption: a review

Anthropogenic chemicals that disrupt the hormonal systems (endocrine disruptors) of wildlife species recently have become a widely investigated and politically charged issue. Invertebrates account for roughly 95% of all animals, yet surprisingly little effort has been made to understand their value in signaling potential environmental endocrine disruption. This omission largely can be attributed to the high diversity of invertebrates and the shortage of fundamental knowledge of their endocrine systems. Insects and crustaceans are exceptions and, as such, appear to be excellent candidates for evaluating the environmental consequences of chemically induced endocrine disruption. Mysid shrimp (Crustacea: Mysidacea) may serve as a viable surrogate for many crustaceans and have been put forward as suitable test organisms for the evaluation of endocrine disruption by several researchers and regulatory bodies (e.g., the U.S. Environmental Protection Agency). Despite the long-standing use of mysids in toxicity testing, little information exists on their endocrinology, and few studies have focused on the potential of these animals for evaluating the effects of hormone-disrupting compounds. Therefore, the question remains as to whether the current standardized mysid endpoints can be used or adapted to detect endocrine disruption, or if new procedures must be developed, specifically directed at evaluating hormone-regulated endpoints in these animals. This review summarizes the ecological importance of mysids in estuarine and marine ecosystems, their use in toxicity testing and environmental monitoring, and their endocrinology and important hormone-regulated processes to highlight their potential use in assessing environmental endocrine disruption.

Spatial patterns of the surf zone hyperbenthic fauna of Valdivia Bay (Ecuador)

AbstractThe present research is a first attempt to study the hyperbenthic fauna of the surf zone of Valdivia Bay (South East Pacific--Ecuador), an exposed low tide terrace--rip beach. The aims of the study were to contribute to the inventory of the surf zone fauna of the tropical southeast Pacific coast, to investigate spatial distribution patterns along the bay and to search for possible tidal effects on the hyperbenthic composition. Samples were taken during daylight with a hyperbenthic sledge on 6 consecutive days in August 1999 at high tide, low tide and mid tide. The hyperbenthic community was characterized by quantifying the higher taxa, their density and the relative composition of the dominant groups. No tidal effect could be observed, but two main geographically distinct hyperbenthic assemblages were distinguished along the bay, related to hydrodynamic factors (local current velocity, intertidal beach slope and suspended particulate matter). In the turbulent northern part of the bay the highest densities were encountered and hyperbenthos was, next to the dominant mysid Metamysidopsissp., mainly composed of planktonic organisms (calanoid copepods, chaetognaths and fish eggs). In the calmer southern part of the bay Metamysidopsissp. dominated as well, but the community was completed with other mysid species, and early life stages of Brachyura and fish. Most striking was the general dominance of the mysid Metamysidopsis sp. in all the samples (97%, max. density of 62000 ind. 100 m-2) and the high amount of unknown species. Penaeid shrimp larvae, important for the local shrimp industry, were only found in very low densities during the sampling period (≈1%). Compared to other studies on the whole surf zone hyperbenthic community of sandy beaches, the average densities encountered in Valdivia Bay can be considered to be relatively high (2500--6000 ind. 100 m-2). Although limited in time and performed with a limited taxonomic resolution, the results indicate a high contribution of early life stages of invertebrate and fish species to the biodiversity of the intertidal hyperbenthic community in comparison with temperate regions.

Aberrant individuals of Neomysis integer and other Mysidacea: intersexuality and variable telson morphology

Intersexuality in the mysidNeomysis integer is described from samples collected in the Elbe (north Germany), Eems-Dollard (north Netherlands), Westerschelde (south-west Netherlands) and Gironde (southwest France) estuaries. Individuals which had an irregularly shaped or nearly symmetrically rounded telson, rather than a typically truncated one, were also recorded from the four populations studied. A culture experiment with damaged specimens revealed that all types of abnormal telson morphology found in the field can result from regeneration of damaged parts. It is concluded that both intersexuality and aberrant telson morphology are widespread phenomena among estuarineN. integer populations. Both abnormalities seem to be rare in the other common mysid species in the study area: only one intersexualGastrosaccus spinifer and oneSchistomysis kervillei with an aberrant telson were recorded.

First record of Synidotea laevidorsalis (Miers, 1881) (Crustacea: Isopoda) in Europe (Gironde estuary, France)

This note reports on the presence of a well established population of the isopod Synidotea laevidorsalis (Miers) in the Gironde estuary (southwestern France). This species is new for the European fauna. S. laevidorsalis is a nonendemic cool-temperate to subtropical, shallow-water species which was probably introduced into the study area from Asia. In the salinity range of 1 to 10 g 1-1 of the Gironde the species constitutes an important component of the brackish-water hyperbenthic community. The population was already present in 1975 when it was misidentified as the native species Idotea emarginata (Fabricius).