Volume 9, Issue 1 - Topical Issue: Water ecosystems and ecology

This review aimed to place crustacean research on in vivo protein synthesis into a broader context, assess its potential for providing further insights into crustacean nutrition and physiology, and recommend future directions relevant to crustacean aquaculture. In crustaceans the flooding dose measurement of protein synthesis is the only method that has been used, it is relatively complex, time consuming and uses radioactive labels. Protein synthesis provides a subtle approach to assessing imbalances and deficiencies in dietary amino acid and energy. In addition, the calculation of protein synthesis retention efficiency (SRE) is recommended in order to understand and optimize parameters such as feeding regime and diet composition. For prawns, SRE was highest at optimum dietary protein content and quality. Similarly the most efficient feeding regimes in juvenile lobsters were demonstrated by the highest efficiency of retaining synthesized protein. Understanding how various abiotic and biotic factors influence protein synthesis has great potential for improving different aspects of crustacean aquaculture but very few studies have done this; better knowledge of how abiotic and biotic factors affect crustacean protein synthesis will contribute to optimising growth of crustaceans in culture.

Indigenous freshwater crayfish species (ICS) are important biodiversity components and desirable fishery targets. However, ICS populations are increasingly threatened by various anthropogenic stressors. Moreover, established populations of non-indigenous freshwater crayfish species (NICS) and new ‘waves’ of NICS introductions exert significant pressure on ICS populations at a pan-European level. These effects include direct competition for space and resources as well as crayfish ‘plague’ transmission from introduced North American species. Given low public knowledge of this problematic, considerable risk of future introductions exist as a result of conventional and internet-based aquarium trade, which often lead to deliberate and/or accidental releases of NICS into the wild. In 2011, we conducted a survey of freshwater crayfish species in eleven large-size pet shops located in three major cities and in three large internet-based aquarium companies in Greece. Overall, eight species belonging to three genera (Procambarus, Cherax and Cambarellus) were recorded, originating from the USA, Australia, New Guinea and Mexico. The invasion potential of the three most popular species was assessed using the Freshwater Invertebrate Invasiveness Scoring Kit (FI-ISK). Two species were determined to constitute a ‘very high risk’ of invasion. As such, regulatory measures need to be implemented to monitor the ornamental trade of NICS in Greece and a national framework developed for protecting ICS.

Carbon utilization and allocation were examined between two populations of shrimp (Palaemonetes pugio) to determine the possible effects of living in an area of high anthropogenic impact. Carbon assimilation has been studied in P. pugio, but no study has looked at how assimilation might be influenced by contaminants. Anthropogenic effects on carbon assimilation in grass shrimp represent a major unmeasured impact on the carbon budget of multi-cellular organisms in estuaries and near shore environments. The influence of anthropogenic contamination on carbon assimilation has implications for predicting the environmental impact of contaminants, for models of estuarine function, and trophic transfer from the dominant macroscopic detritus processor to species of direct economic importance. Shrimp budgets were compared between two populations, one from a highly polluted marsh creek system in Northern New Jersey, and one from a clean reference site in Southern New Jersey. All components of the carbon budgets were measured directly including carbon allocated to reproduction. Carbon lost to respiration was lower in shrimp from the polluted system allowing them to have increased reproductive output. This is examined in the context of previous studies that show lowered predation by a piscine predator at the polluted site, resulting in a trophic cascade and changes in ecosystem function due to anthropogenic impacts.

For crab larvae, swimming behaviors coupled with the movement of tides suggests that larvae can normally move upstream within estuaries by avoiding ebb tides and actively swimming during flood tides (i.e., flood-tide transport [FTT]). Recently, a 1-D transport model incorporating larval behavior predicted that opposing forces of river discharge and tidal amplitude in the Pee Dee River/Winyah Bay system of South Carolina, USA, could limit dispersal within a single estuary for downstream transport as well as become a dispersal barrier to recruitment of late stage larvae to the freshwater adult habitats of Uca minax (LeConte 1855). We sequenced 394-bp of the mitochondrial cytochrome apoenzyme b for 226 adult U. minax, from four locales along a 49-km stretch of the Pee Dee River/Winyah Bay estuary, above and below the boundary of salt intrusion. Results of an analysis of molecular variance (AMOVA) and an exact test of population differentiation showed a small, but statistically significant (α=0.05) population subdivision among adults of the 4 subpopulations, as well as all subpopulations being significantly differentiated (α=0.05). This pattern fitted with model predictions, which implies that larval transport within the tidally influenced river system is limited.

The reproductive organs of both male and female European lobsters (Homarus gammarus) are H-shaped gonads that lie dorsal to the gut on the large hepatopancreas. The ovary consists of a pair of tubular, parallel lobules with a connecting bridge. The germarium of the ovary containing oogonia is concentrated in the center of the ovarian lobe. As oogonesis proceeds, the oocytes move to the peripheral regions of the ovary. The follicle cells begin to surround the oocytes in the previtellogenic stage, and the mature oocytes are completely surrounded by the follicle cells. Carbohydrates exist in both early and late vitellogenic oocytes that give PAS positive reaction. However, their rising protein content in late vitellogenic oocytes makes them stain with Bromophenol blue. Testes show convoluted lobules with a germinal epithelium and a central collecting duct, and the paired vasa deferentia have three distinct parts. Spermatophores are nonpedunculate and tubular, which extrude as a continuous column and consist of a sperm mass covered with primary and secondary layers. The primary layer stains with Bromophenol Blue and gives a PAS positive reaction. But the secondary layer only weakly stains with Bromophenol Blue. The histochemical results may indicate that the function of the two layers is different.

The blue crab (Callinectes sapidus) is native to the western Atlantic, but is an invasive species in the Mediterranean. This study examined the dynamics of growth in an invasive population of blue crab in the Yumurtalık Cove, Turkey (North Eastern Mediterranean). Growth was quantified using a discontinuous growth model, a molt process model. Crab growth histories were observed for individual crabs held in field enclosures in summer 2010 and 2011. Carapace widths ranged from 14.13 to 80.07 mm. A mean growth per molt of 120.6% increase in carapace width was observed. Chronological inter-molt periods ranging between 3 days and 67 days were observed. The average IMP was 16 days in Yumurtalık Cove. The mean physiological IMP was 270±163 degree-days, ranging from 72–781 degree-days.

The composition of the diet of the invasive spiny-cheek crayfish Orconectes limosus was studied using qualitative and quantitative analyses of stomach contents. A total of 368 specimens collected in 2003–2005 and 2008 in Czech localities were examined, predominantly from the Labe (Elbe) and Vltava River basins. Food components were compared for three size classes of crayfish and both sexes. The following conclusions were reached: (1) the spiny-cheek crayfish is an omnivorous species consuming plants, animals and detritus; (2) quantitatively, the main food component of O. limosus is detritus, while the plant component was second; (3) O. limosus may swallow whole food particles up to 4 mm in size, and the bodies of small animals may sometimes be found undamaged in their stomachs.

This study investigated the seasonal variation in the structure and secretory activity of the androgenic gland (AG) in the freshwater crab: Travancoriana schirnerae. The androgenic gland is an elongate structure, attached to one side on the wall of the ejaculatory duct. Histological studies showed the presence of three cell types, which differ in size, shape of nuclei, and presence or absence of secretory vesicles. Type I cells are small with large nuclei whereas type II cells are large with small nuclei. Type III cells are intermediate in size and exhibited streak-like nuclei and transparent cytoplasm. Seasonal changes were discerned in the morphology, histology and secretory activity of the gland. March-June appeared to be the active season with type II cells containing secretory vesicles. The mode of release of secretion found to be holocrine. The secretory activity almost completed by July-August (the mating season) with vacuolization of type II cells. The gland remained inactive from September-December with abundance of vacuoles, scattered pycnotic nuclei, indistinct cell membranes and total cellular degeneration. January-February was the revival period with type I cell proliferation. The present study revealed that the secretory activity of the gland is in tune with the male reproductive cycle.

A study was performed on the microhabitat distribution and some aspects of behaviour of the ectosymbiotic branchiobdellidan Holtodrilus truncatus (Annelida, Clitellata) found on the freshwater shrimp that inhabit the Sugo River, Hyogo Prefecture, western Japan. Observations on shrimp that were collected from the Sugo River (2003 to 2011) confirmed that the host shrimp is Neocaridina spp. (Atyidae). The attachment location on the host shrimp was predominately between the 1st pleopod and the 5th pereopod (55.3%). The reproductive method of H. truncatus is hemaphroditism. The cocoon was found only inside the carapace of the host shrimp. The cocoon was transparent and contained a maximum of 14 juvenile worms (developing embryos). When hatching approached, H. truncatus’s worms became elongated and slender, and only one worm hatched out at a time. When Holtodrilus truncatus was removed from its host and was maintained in river water without any food, it survived for a maximum of 46 days. In a host exchange experiment, where we provided several other freshwater shrimp species, Palaemonidae fed on H. truncatus. Moreover, Palaemon paucidens and Macrobrachium nipponense from Lake Biwa also preyed upon H. truncatus. The possible symbiotic relationship between H. truncatus and Neocaridina spp. (family Atyidae) is further discussed.

The metabolic response of the freshwater prawn, Macrobrachium nipponense to nitrite toxicity was evaluated. The prawns were exposed to 0, 1, 2, 3 and 4 mg L−1 NO2-N concentrations for 48 h. The metabolic parameters in muscle were measured after 12, 24 and 48 h. Glucose level significantly increased after 24 h. Exposure to lower nitrite concentrations (1 and 2 mg L−1) resulted in significant increases in alanine aminotransferase (ALT) activities after 24 and 48 h. Aspartate aminotransferase (AST) activities treated with 2 and 3 mg L−1 nitrite-N at 48 h were significantly higher than those at 12 and 24 h. Intermediate sublethal nitrite concentrations produced significant elevations in lactate dehydrogenase (LDH) activities from 12 h up to 48 h. No significant changes were detected in any of the groups for triglycerides and creatine kinase (CK). To satisfy the increased energy demands caused by acute nitrite exposure, mobilization of lipids is not the main reason while utilization of amino acids seems to play a more important role. The results would be helpful for aquaculture farmers to prevent a potential depression of productivity caused by elevated nitrite levels.

Distribution of squat lobsters of the genera Gastropthychus (one species), Uroptychus (1), Janetogalathea (1), Galacantha (1), Munidopsis (8), and Munida (7) in the Gulf of California, Mexico, was plotted vs. the localization of the Oxygen Minimum Zone (OMZ) using bottom projections of the 0.50, 0.25, 0.10, and 0.05 ml l−1 oxylines. Four fringes where oxygen concentrations were equal or lower than these concentrations were obtained, extending from the southern Gulf to about 28°–28°30′N. A total of 172 sampling locations with squat lobsters were plotted on four maps, one for each fringe, noting that with decreasing values of bottom oxygen (i.e., from 0.50 to 0.05 ml l−1) the number of locations with species included between the upper and lower boundaries of these fringes decreases as follows: 34% for 0.50, 25% for 0.25, 12% for 0.10, and 5% for 0.05 ml l−1. The upper and lower limits of the 0.05 ml l−1 fringe are recognised as threshold frontiers, acting as barriers between shallow and deep communities of squat lobsters in the area. The distribution of the localities where species have been collected with respect to the upper and lower boundaries of the 0.05 ml l−1 fringe clearly indicates a segregation pattern. Eight species of Munida (except M. perlata), and one each of Janetogalathea and Gastropthychus inhabit the shallow area, just above the OMZ core, with species of Munida generally found a rather long distance from this fringe. By contrast, species of Munidopsis, G. diomedeae and U. pubescens correspond to the deep area, i.e., below the OMZ core. It is suggested that the core of the OMZ in the Gulf of California serves as a vertical and latitudinal distribution filter, preventing species from freely migrating up and down or south and north.

Bristle crabs of the genus Pilumnus (Brachyura: Heterotremata: Pilumnidae) are common inhabitants of European waters. They are easily identifiable as a genus, but with the exception of P. inermis, intrageneric classification turns out to be quite complex. There is no general agreement on the number and distinction of species. Therefore, this genus is well-suited for comparative molecular studies. Specimens of the Pilumnus hirtellus complex, here defined as including Pilumnus hirtellus, P. villosissimus, P. spinifer, P. aestuarii, and an undescribed species, were gathered from throughout the Mediterranean Sea and the eastern Atlantic Ocean. DNA sequence data were obtained from the barcoding region of the cytochrome oxidase 1 mitochondrial gene and used for reconstruction of a phylogenetic tree and a haplotype network. The morphology of the gastric ossicles was compared in the search of separating characters. Our results give evidence for five genetic clusters within the P. hirtellus complex. There is negligible geographic variation within these clusters. Unambiguous mtDNA sequences within morphologically variable local populations argue against possible hybridization. The here encountered evolutionary units are relatively young and possibly allow to study ongoing processes of morphological, genetic, and ecological differentiation, leading to speciation and radiations in the coastal marine environment.

In the current study, we redescribe and revalidate a freshwater crab species of the genus Potamon Savigny, 1816, from northern Iran. Potamon elbursi Pretzmann, 1962, differs from the species it has been synonymised with, Potamon persicum Pretzmann, 1962, mainly by the shape of the first gonopods in males. Consistent and marked genetic divergence was also recognised in the mitochondrial 16S rRNA and cytochrome oxidase subunit I genes. This study elevates P. elbursi to species rank and therefore increases the number of valid species of the genus Potamon to a total of twenty-two.