Osmotic and ionic regulation in Callianassa kraussi Stebbing (Crustacea: Decapoda: Thalassinidea)

Callianassa kraussi Stebbing in southern Africa has been recorded in salinities down to 1‰ Experiments suggest that because of the burrowing activities of the prawns, the substratum is unlikely to provide insulation against transient low surface salinities. Investigation of osmotic and ionic regulation in this species has shown that hyper-osmoregulation occurs in salinities below $\text{\$}\text{?}$20 ‰: hyper-osmoregulatory ability decreases in salinities below $\text{\$}\text{?}$3.5 ‰ Previous work on the genus Callianassa suggested that there was no osmo-regulatory ability in this group and a possible reason for the development of this faculty in the southern African species is discussed.     

Comparative studies of the branchial morphology, gill area and gill ultrastructure of some thalassinidean mud-shrimps (Crustacea: Decapoda: Thalassinidea)

The morphology, gill area and branchial formulae of six thalassinidean decapods ( Calocaris macandreae, Jaxea nocturna, Callianassa subterranea, Upogebia stellata, U. deltaura and U. pusilla ) are reported. Additionally, the rarely-encountered Axius stirhynchus receives brief attention. Gill formulae are presented; the simplest arrangements are found in the Callianassidae and Upogebiidae. The deeper-burrowing, deposit-feeding species that are regularly exposed to prolonged periods of hypoxia, i.e. Callianassa subterranea and Jaxea nocturna , had significantly larger gill areas than thalassinideans that occupied more oxygenated burrows ( Upogebia spp., Calocaris macandreae ). The increase in gill area was a result of flattening of the trichobranchiate gill filaments giving rise to a phylloid gill form. It is suggested that the efficiency of gas transfer, and hence diffusing capacity, was enhanced in the phylloid gill by the larger gill area and, because of the reduced cuticle thickness, by the shorter water-haemolymph diffusion distance. The increased diffusion capacity of the phylloid gill is interpreted as a functional adaptation to the more severe physicochemical burrow water conditions experienced by Callianassa subterranea and Jaxea nocturna .     

Phylogeny of Thalassinidea (Crustacea, Decapoda) inferred from three rDNA sequences: implications for morphological evolution and superfamily classification

The infraorder Thalassinidea is a group of cryptic marine burrowing decapods of which the higher taxonomy is often contentious. The present analysis attempts to reconstruct phylogenetic relationship among 12 of the 13 currently recognized families using partial nuclear 18S, 28S rDNA and mitochondrial 16S rDNA sequences. The infraorder is divided into two distinct clades, with the first clade consisting of Thalassinidae, Laomediidae, Axianassidae and Upogebiidae, and the second clade including Axiidae, Calocarididae, Eiconaxiidae, Callianassidae, Ctenochelidae, Micheleidae, Strahlaxiidae and Callianideidae. Within the first clade, the Upogebiidae is the basal family. The Axianassidae shows low affinity to other laomediid genera indicating that it is a valid family. The interfamilial relationships are less well resolved in the second clade. The Axiidae is paraphyletic with respect to Calocarididae and Eiconaxiidae. Thus, the status of these two latter families is not supported if the currently defined Axiidae is maintained. All three families appear to be basal in the thalassinidean clade. The Micheleidae is closely related to the Callianideidae and they form a sister group to the Strahlaxiidae. The monophyletic Callianassidae aligns with the Micheleidae + Callianideidae + Strahlaxiidae clade. The relationship among the Axiidae + Calocarididae + Eiconaxiidae clade, Callianassidae + Micheleidae + Callianideidae + Strahlaxiidae clade and the Ctenochelidae cannot be resolved which might be due to a rapid radiation of the three lineages. Our results do not support the generally used classification scheme of Thalassinidea and suggest that the infraorder might be divided into two superfamilies instead of three as suggested based on larval morphology, second pereiopod morphology in adults and gastric mill structure. The two superfamilies are Thalassinoidea (i.e. Thalassinidae, Laomediidae, Upogebiidae and Axianassidae) and Callianassoidea (i.e. Axioidea + Callianassoidea, as defined in Martin and Davis (2001) but excluding Laomediidae and Upogebiidae). It also appears that gill‐cleaning adaptations are important in thalassinidean evolution while the presence of linea thalassinica is a result of parallel evolution.     

Dead Shrimp Blues: A Global Assessment of Extinction Risk in Freshwater Shrimps (Crustacea: Decapoda: Caridea)

We present the first global assessment of extinction risk for a major group of freshwater invertebrates, caridean shrimps. The risk of extinction for all 763 species was assessed using the IUCN Red List criteria that include geographic ranges, habitats, ecology and past and present threats. The Indo-Malayan region holds over half of global species diversity, with a peak in Indo-China and southern China. Shrimps primarily inhabit flowing water; however, a significant subterranean component is present, which is more threatened than the surface fauna. Two species are extinct with a further 10 possibly extinct, and almost one third of species are either threatened or Near Threatened (NT). Threats to freshwater shrimps include agricultural and urban pollution impact over two-thirds of threatened and NT species. Invasive species and climate change have the greatest overall impact of all threats (based on combined timing, scope and severity of threats).     

Characteristics of palinurids (Decapoda; Crustacea) in larval culture

Complete development of phyllosomas wasaccomplished in Palinurus elephas, Panulirus japonicus, Jasus edwardsii and J. verreauxi. Larval development differsbetween species in duration and moult frequency aswell as morphology. The highest percent survival was obtained during the phyllosoma stage forJ. verreauxi. Phyllosomas of P. elephas were the mostdifficult to cultureregardless of the fact that they hatch at arelatively advanced stage. Culture experiments werecarried out to improve the percent survival of P. elephas. First instars of P. elephasexhibited vigorous predation upon the larvae ofJapanese sandfish Arctoscopus japonicus.Duration of the first instar was shorter at 12.8days when reared at 18 °C and percent survival wasapproximately 30%. Better results were obtainedfor first instars cultured in water inoculated withChaetoceros sp. and fed enriched Artemianauplii. Phyllosomas of J. edwardsii and P. japonicus were cultured without particulardifficulty. Most distinguishing features of P. elephasis the heavily setose six or seven longspines on the distal edges of the scaphognathite ofthe second maxillae while only four long spines arefound in other species. These facts suggest thatphyllosomas of P. elephas are initiallyplankton feeders and from first instar becomerapacious predators.     

Austinogebia, a new genus in the Upogebiidae and rediagnosis of its close relative, Gebiacantha Ngoc-Ho, 1989 (Crustacea: Decapoda: Thalassinidea)

New material described recently permits the separation of six upogebiid species into the new genus Austinogebia, for which the diagnostic characters and a key are presented. The new taxon is compared to its close relative, Gebiacantha Ngoc-Ho, 1989, and the opportunity is taken to rediagnose the latter.     

Fishery of the Deep-water Rose Shrimp Parapenaeus longirostris (Lucas, 1846) (Crustacea: Decapoda) in the Northern Tyrrhenian Sea (Western Mediterranean)

The aim of this study is to provide information on the fishing pattern of Parapenaeus longirostris in the northern Tyrrhenian Sea (western Mediterranean), in order to improve the management of the resource in the area. Data were obtained from commercial fishery, covering the period 1991–2002. Catch rates revealed notable inter-annual fluctuation of the P. longirostris landing, probably due to the life cycle of the species. The highest yields (kg per hour of trawl) of the commercial fishery were obtained at depths ranging between 180 and 300 m, the lower ones at depths between 100 and 180 m, where small specimens are more abundant. Commercial catches were characterised by a very low presence of specimens smaller than 20 mm carapace length (CL), mainly due to the deeper localisation of the fishing grounds when compared to the recruitment areas of the species. The size at which 50% of the specimens were discarded by the fishermen was 15 mm CL, while the estimated size at first capture of the individuals caught by the commercial net was 12.4 mm CL.     

Molecular systematics of the Kakaducarididae (Crustacea: Decapoda: Caridea)

The systematic relationships of the freshwater shrimp family, Kakaducarididae, were examined using mitochondrial and nuclear DNA sequences. Combined nuclear (18S rDNA, 28S rDNA, Histone) and mitochondrial (16S rDNA) analyses placed the kakaducaridid genera, Kakaducaris and Leptopalaemon, as a strongly supported clade within the Palaemonidae, in a close relationship with the genus Macrobrachium. Monophyly of the Australian Kakaducarididae was strongly supported by the molecular data. Estimated net divergence times between Kakaducaris and Leptopalaemon using mitochondrial 16S rDNA equate to a late Miocene/Pliocene split. Within Leptopalaemon, each locality was distinct for mitochondrial COI haplotypes, suggesting long-term isolation or recent genetic bottlenecks, a lack of contemporary gene flow amongst sites and a small Ne. Mitochondrial groupings within Leptopalaemon were largely congruent with several previously recognised morphotypes. Estimated net divergence times between L. gagadjui and the new Leptopalaemon morphotypes equate to a split in the late Pliocene/early Pleistocene. The hypothesis that the Kakaducarididae is comprised of relict species in specialised ecological niches is not supported by the molecular data, which instead suggest a relatively recent origin for the group in northern Australia, sometime in the late Miocene or Pliocene.     

Ageing and longevity in the Decapoda (Crustacea): A review

Ageing and longevity is a neglected field of crustacean biology. Information on longevity is available for less than 2% of the extant species of the Decapoda. Maximum ages reliably determined range from 40 days to 72 years corresponding to a life span difference of a factor of 650. The shortest-lived decapods are planktonic dendrobranchiate shrimps, and particularly long-lived species with life spans of decades are found in the Astacidea. Most decapods seem to live for 1-10 years. High geographical latitude, the deep sea and freshwater caves promote longevity. The majority of the Decapoda is indeterminately growing and presumably characterized by negligible senescence. The adults of the determinately growing decapods like some brachyuran crabs suffer from mechanical senescence and are unable to regenerate lost appendages. The decapod crustaceans have developed many effective anti-ageing mechanisms including moulting, detoxification of free radicals, removal of cellular waste, renewal of tissues by life-long stem cell activity, regeneration of appendages, detoxification of environmental pollutants and isolation of pathogens and diseased tissue areas by melanisation and encapsulation. Age related diseases including cancer are virtually unknown. The present compilation of data on longevity and senescence in decapods is the first one that covers the whole spectrum of a higher invertebrate taxon. It is hoped to provide an interesting source of information for carcinologists and biogerontologists. Further improvement of knowledge on ageing and longevity in the Decapoda would be beneficial for crustacean aquaculture, fisheries and ecological modelling. Some decapods even have good potential to become models for general ageing research.     

Descriptions of some planktonic larvae of the Calappidae (Crustacea: Decapoda; Brachyura)

Some unidentified planktonic larval stages have been assignedto the Calappidae using Rice's key of Brachyura families. Zoeastage I from the eastern region of the Algerian coast (westernMediterranean Sea) has been attributed, according to Manningand Holthuis (1980), to Calappa granulata (L.), the only recordedrepresentative of the family from the Mediterranean Sea. Zoealstages 1-lV from the Jordanian coast of the Gulf of Aqaba, NorthernRed Sea, have been reported to the subfamily Matutinae. Comparisonsof larvae of Calappa and of Hepatus and then, of larvae of Hepatusand of Matuta, show that Hepatus larvae are more closely relatedto those of Calappa, while those of Matuta are clearly distinct.It s suggested to place the genus Hepatus with the Calappinae.Guinot (1966. 1978) placed some genera, including Hepatus. ina 'unit parthenoxystomienne, lea Aethrinae'. Larval developmentis unknown for Aethra, Actaeomorpha. Hepatella andOsachila.However, comparison of Hepatus larvae with those of Parthenopidaeshows that larval characters, particularly the setation of theendopod of the first maxilliped, are not conclusive for supportingsuch a regrouping. Moreover, the Calappidae have a combinationof primitive and advanced features which suggest that theirgrouping in the Oxystomata seems more likely to be an adaptationto a similar way of life. The morphotypal taxon Oxystornatahas been definitively rejected by Guinot (1978).     

The mouth apparatus of Lithodes maja (Crustacea: Decapoda) – form,function and biological role

Being able to utilize many different food resources is probably an important aspect of the success of decapod crustaceans which fill a wide range of various ecological niches worldwide. The phenomenon is facilitated by the complex mouth apparatus found in this group, whose representatives possess six pairs of mouthparts– mandibles, maxillae 1, and maxillae 2 and three maxillipeds, the first three pairs of thoracic appendages which are also specialized to food manipulation. These six pairs are able to perform a number of movements for transporting, aligning, crushing and cutting. Studies into the functional morphology of mouthparts have already been carried out in some decapod species. This study focuses on Lithodes maja, a species of the hitherto understudied king crabs (Lithodidae), chosen on the grounds of their remarkable evolutionary history as ‘derived hermit crabs’. Individuals were filmed while being presented with different kinds of food. To obtain structural information on the individual mouthpart elements as naturally arranged in relation to one another, the shape of the mouthparts was 3D‐reconstructed from micro‐CT scans. These data were complemented by scanning electron microscopy, to analyse the surface structures in detail. There is evidence that the various elements of the mouthparts of L. maja can be sorted into six functional groups: (i) transporting mouthpart elements, (ii) aligning/sorting mouthpart elements, (iii) clutching/holding mouthpart elements, (iv) tearing/cutting/crushing mouthpart elements, (v) current‐generating mouthpart elements and (vi) grooming mouthpart elements. According to our 3D reconstruction, there only seem to be minor differences in morphology and relative position between the mouthparts of L. maja and those of the closely related species, Pagurus bernhardus.     

Global diversity of shrimps (Crustacea: Decapoda: Caridea) in freshwater

Freshwater caridean shrimps account for approximately a quarter of all described Caridea, numerically dominated by the Atyidae and Palaemonidae. With the exception of Antarctica, freshwater shrimp are present in all biogeographical regions. However, the Oriental region harbours the majority of species, whilst the Nearctic and western Palaearctic are very species-poor. Many species are important components of subsistence fisheries, whilst the Giant River Prawn forms the basis of an extensive aquaculture industry. A total of 13 species are threatened or endangered, with one species formally extinct. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Kinetic incorporation of mercury in Emerita portoricensis (Crustacea: Decapoda)

Benthic test species used in toxicity assays are the best indicators of sediment toxicity because they live in direct contact with sediments and the water column. Mercury chloride is one the most toxic metallic salts. Its strong affinity for particles explains the high Hg content found in benthic populations. The genus Emerita is abundantly found in Venezuelan coasts and is a good bioaccumulator of pollutants, but the toxicological assays performend on this genus are scarce. The present experimental test reports on the distribution of mercury in the water column and sediment, using static bioassay in short term (24 hr) and the ability of Emerita portoricensis to bioconcentrate mercury under experimental conditions. Our results suggest that the Hg transference from water to sediment is enhanced in the presence of Emerita. The kinetic uptake of Hg in Emerita portoricensis shows a mechanism of rapid absorption reaching high metal concentrations in short exposure times.     

Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater

An assessment of the global freshwater crab diversity is presented. A total of 1,476 species in 14 families are currently known from all zoogeographical regions (except Antarctica), including 1,306 species in eight exclusively freshwater families (Pseudothelphusidae, Trichodactylidae, Potamonautidae, Deckeniidae, Platythelphusidae, Potamidae, Gecarcinucidae and Parathelphusidae). Estimates of true freshwater crab diversity including likely numbers of undescribed taxa suggest that the field remains largely in a “discovery” phase. Main ideas on the origins, diversification, and phylogeny of true freshwater crabs are briefly discussed. The economic importance of freshwater crabs is also highlighted. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Morphology and ultrastructure of the adult ovarian cycle in Mithracidae (Crustacea,Decapoda, Brachyura,Majoidea)

The ultrastructure of the ovary during development and yolk production is poorly known in Brachyura and Majoidea in particular. Here, we describe the histology, histochemistry and ultrastructure of the adult ovarian cycle in four Mithracidae species from three different genera: Mithrax hispidus, Mithrax tortugae, Mithraculus forceps and Omalacantha bicornuta. All species showed a similar pattern of ovarian development and vitellogenesis. Macroscopically, we detected three stages of ovarian development: rudimentary (RUD), developing (DE) and mature (MAT); however, in histological and ultrastructural analyses, we identified four stages of development. The oocytes of the RUD stage, during endogenous vitellogenesis, have basophilic cytoplasm filled with dilated rough endoplasmic reticulum. The reticulum lumen showed many granular to electron-dense materials among the different stages of development. The Golgi complexes were only observed in the RUD stage and are responsible for releasing vesicles that merge to the endogenous or immature yolk vesicles. At the early DE stage, the oolemma showed many coated and endocytic vesicles at the cortex. The endocytic vesicles merge with the endogenous yolk to form the exogenous or mature yolk vesicles, always surrounded by a membrane, characterizing exogenous vitellogenesis. The exogenous yolk vesicles comprise glycoproteins, showing only neutral polysaccharides. At the late DE stage, endocytosis still occurs, but the amount of endogenous yolk decreases while the exogenous yolk increases. The late DE stage is characterized by the beginning of chorion production among the microvilli. The MAT stage is similar to the late DE, but the endogenous yolk is restricted to a few cytoplasmic areas, the ooplasma is filled with exogenous yolk, and the oolemma has very few coated vesicles. In the MAT stage, the chorion is fully formed and shows two electron-dense layers. The ovarian development of the species studied has many similarities with the very little known Majoidea in terms of the composition, arrangement and increment of the yolk vesicles during oocyte maturation. The main differences are in the vitellogenesis process, where immature yolk formation occurs without the direct participation of the mitochondria but with the participation of the rough endoplasmic reticulum in the endogenous phase.     

Carotenoids and carotenoid metabolism in Carcinus maenas (Crustacea: Decapoda)

The carotenoid pigments of the hepatopancreas, ovaries and epidermis of Carcinus maenas were investigated. The following pigments were identified: β-carotene, δ-carotene, echinenone, isocryptoxanthin, canthaxanthin, lutein, zeaxanthin, flavoxanthin and astacene.
The relative abundance of these pigments in the three tissues and the presence of possible hydroxy and keto intermediates suggest the metabolism of astaxanthin from β-carotene. The metabolic pathway in Carcinus is discussed in relation to recent studies on other invertebrates.     

Carotenoids and carotenoid metabolism in Carcinus maenas (Crustacea: Decapoda)

The carotenoid pigments of the hepatopancreas, ovaries and epidermis of Carcinus maenas were investigated. The following pigments were identified: β-carotene, δ-carotene, echinenone, isocryptoxanthin, canthaxanthin, lutein, zeaxanthin, flavoxanthin and astacene.
The relative abundance of these pigments in the three tissues and the presence of possible hydroxy and keto intermediates suggest the metabolism of astaxanthin from β-carotene. The metabolic pathway in Carcinus is discussed in relation to recent studies on other invertebrates.     

Lecithin essay in the diet of young Penaeus vannamei (Crustacea: Decapoda)

The effect of different lecithin sources and presentations on growth, food conversion ratio and survival of P. vannamei (290 mg +/- 0.02) was studied. The bioassay was designed in order to compare different dietary levels and different quality of lecithin. Squid lecithin, crude soybean (7%), deoiled soybean lecithin (3.48%) in combination with fish oil or squid neutral lipids, in a partially dilapidate formula. The isoenergetic diets were fed ad libitum to four replicate groups (tanks) of 15 shrimps each (5 x 4 x 15), during 28 days. The result of the bioassay with the partially dilapidate formulas was; the best growth rate (191%) and FCR (1.69 +/- 0.041) were obtained with the diet containing 7% of soybean crude lecithin as the unique lipid source. Followed by the diet countering 3.94% deoiled lecithin and 2.42% Menhaden oil (172% and 2.03 +/- 0.054 respectively). As expected, the worst results were obtained without the dietary lecithin 121% and 2.42 +/- 0.129). Crude soybean lecithin alone covered the phospholipid and neutral lipids requirements as well as the combination of deoiled soybean lecithin with fish or squid oil.