Coping with the "dirt": brown shrimp and the microplastic threat.

Microplastic pollution is an emerging threat to marine biota. Uptake of microplastics can impair nutrition and affect the performance of organisms. However, the vulnerability to microplastics seems to vary between species for yet widely unexplored reasons. We investigated the stomach content of the brown shrimp, Crangon crangon, from the southern North Sea and performed feeding experiments and anatomical studies of the digestive organs to comprehend the distribution of fluorescent microparticles within the shrimp. Shrimp collected in their natural environment contained between 51 and more than 3,000 sand grains and fragments of bivalve shells in their stomachs. Sand grains may have been ingested to exploit the associated biofilm or to support maceration of food. Bivalve shell fragments were particularly abundant in summer when shrimp fed on freshly settled mussels. Shrimps' stomach can be cleaned from ingested particles by regurgitation. In an experimental approach, we administered fluorescent microbeads of 0.1, 2.1, and 9.9 µm diameter. Only the smallest particles (0.1 µm) entered the midgut gland, which is the principal site of nutrient resorption in crustaceans. A fine-meshed chitinous filter system in the stomach of the shrimp prevents the passage of particles larger than about 1 µm. C. crangon appears well adapted to handle natural microscopic particles. This trait might also be advantageous in coping with microplastic pollution.

Predictive framework for codend size selection of brown shrimp (Crangon crangon) in the North Sea beam-trawl fishery.

The brown shrimp (Crangon crangon) fishery is of great socio-economic importance to coastal communities on the North Sea. The fishery is exploited by beam trawlers often using codends with very small mesh sizes, leading to concerns about catch rates of undersized shrimp. However, little information is available on codend size selection, making it difficult to provide scientifically based advice on alternative codend designs. Therefore, this study establishes a predictive framework for codend size selection of brown shrimp, based on a large selectivity dataset from 33 different codend designs tested during four experimental fishing cruises, during which more than 350,000 brown shrimp were length measured. Predictions by the framework confirm concerns about the exploitation pattern in the fishery, because the retention probability of undersized shrimp reaches 95% with the currently applied designs. The framework predictions allow the exploration of obtainable exploitation patterns depending on codend design. For example, increasing codend mesh size to 25-29 mm would reduce the retention rate of undersized shrimp to a maximum of 50%, depending on codend mesh type.

Insights on the biology and ecology of the deep-water shrimp Parapontophilus occidentalis (Faxon, 1893) (Crustacea: Caridea: Crangonidae) in the eastern Pacific with notes on its morphology.

The deep-water crangonid Parapontophilus occidentalis (Faxon, 1893) is endemic to the eastern Pacific and has been reported from Mexico to Chile, in depths of 837-4082 m. Material collected off the west coast of the Baja California Peninsula (BCP) during the TALUD XV, XVI and XVI-B cruises consists of a series of 136 specimens (M:F = 1:3.6) with 30 % of ovigerous females. The material examined was captured in depths of 1296-2093 m. Size ranged from 8.4 to 16.1 mm CL, with females being significantly larger than males. Number of eggs carried by ovigerous females ranged from 7 to 998, without a significant relationship between female size and number of eggs. Using only data of females carrying at least 100 eggs, egg mass weight varied from 0.036 to 0.181 g. Size of oval-shaped eggs also varied considerably (0.515 to 0.922 mm). Larger densities of P. occidentalis were observed between 1700 and 2100 m, where larger individuals were collected, and sex proportions differed across all depth strata. At the northern BCP, P. occidentalis was collected at dissolved oxygen concentrations from 0.76 to 1.83 ml l(-1), at temperature from 2.1 to 3.4°C, and salinity from 34.54 to 34.63 kg g(-1). Density of P. occidentalis was positively correlated with dissolved oxygen, salinity, and silt contribution to sediments, and negatively correlated with temperature and primary productivity five months before sampling.

Systematic position of Neocrangon communis (Decapoda, Crangonidae) based on the features of larval morphology.

The present article deals with morphological comparison of four species of shrimp larvae, such as Neocrangon communis and Mesocrangon intermedia, Crangon dalli and C. septemspinosa, inhabiting the Okhotsk Sea and north-western part of the Pacific Ocean. Morphological comparison of I-V zoeal stages is discussed. The main morphological differences of the appropriate larval stages are detected. Most features of C. dalli and C. septemspinosa are similar and differ from M. intermedia and N. communis. It is shown that M. intermedia and N. communis more similar species by their origin than it is accepted to think. It is assumed that these two species should be included into one genus-Mesocrangon. The figures of I, III-V zoeal stages are presented.

Two new species and two new records of deep-water caridean shrimps from Brazil (Decapoda: Pandalidae, Palaemonidae, Crangonidae).

The present study deals with four species of benthic deep-water caridean shrimps collected on the continental slope off southeastern Brazil, between 360 m and 900 m. The deepwater pandalid Bitias stocki Fransen, 1990, previously known only from a few localities in the eastern Atlantic, is reported for the first time from the western Atlantic (Brazil). The Brazilian material of B. stocki also represents the first record of the genus Bitias Fransen, 1990 in the western Atlantic. The palaemonid Periclimenes tenellus (Smith, 1882), previously known only from South Carolina and New Jersey, USA, is reported for the first time from Brazil, representing a considerable range extension of this uncommon species into the southwestern Atlantic. Another deepwater palaemonid shrimp is described as new: Periclimenes bathyalis sp. nov. The new species is morphologically closest to the echinoid associates Periclimenes milleri Bruce, 1986 and Periclimenes ingressicolumbi Berggren & Svane, 1989. Finally, the bizarre deepwater crangonid genus Prionocrangon Wood-Mason in Wood-Mason & Alcock, 1891 is reported for the first time from Brazil and the southwestern Atlantic, where it is represented by a new species, Prionocrangon brasiliensis sp. nov.

Syncrangon, a new crangonid genus, with redescriptions of S. angusticauda (De Haan) and S. dentata (Balss) (Crustacea, Decapoda, Caridea) from East Asian waters.

A new genus of the crangonid shrimps, Syncrangon, is proposed for Crangon angusticauda De Haan, 1849 and C. (Sclerocrangon) angusticauda var. dentata Balss, 1914, both from East Asian waters. The new genus is readily distinguished from all known genera of the Crangonidae by the flattened middorsal carina and the deep groove on each lateral side of the middorsal carina on the third to sixth abdominal somites. Syncrangon angusticauda new combination has previously been assigned to the genus Metacrangon, while S. dentata new combination has not been reported since the original description. These two species are easily distinguished from each other by many characters, especially the rostral and abdominal features. They are redescribed and illustrated in detail.