Symbiont Community Composition in Rimicaris kairei Shrimps from Indian Ocean Vents with Notes on Mineralogy.

Hydrothermal vent ecosystems are home to a wide array of symbioses between animals and chemosynthetic microbes, among which shrimps in the genus Rimicaris is one of the most iconic. So far, studies of Rimicaris symbioses have been restricted to Atlantic species, including Rimicaris exoculata, which is totally reliant on the symbionts for nutrition, and the mixotrophic species Rimicaris chacei. Here, we expand this by investigating and characterizing the symbiosis of the Indian Ocean species Rimicaris kairei using specimens from two vent fields, Kairei and Edmond. We also aimed to evaluate the differences in mineralogy and microbial communities between two cephalothorax color morphs, black and brown, through a combination of 16S metabarcoding, scanning electron microscopy, fluorescent in situ hybridization, energy-dispersive X-ray spectroscopy, and synchrotron near-edge X-ray absorption structure analyses. Overall, our results highlight that R. kairei exhibits similar symbiont lineages to those of its Atlantic congeners, although with a few differences, such as the lack of Zetaproteobacteria. We found distinct mineralization processes behind the two color morphs that were linked to differences in the vent fluid composition, but the symbiotic community composition was surprisingly similar. In R. exoculata, such mineralogical differences have been shown to stem from disparity in the microbial communities, but our results indicate that in R. kairei this is instead due to the shift of dominant metabolisms by the same symbiotic partners. We suggest that a combination of local environmental factors and biogeographic barriers likely contribute to the differences between Atlantic and Indian Ocean Rimicaris symbioses. IMPORTANCE Hydrothermal vent shrimps in the genus Rimicaris are among the most charismatic deep-sea animals of Atlantic and Indian Oceans, often occurring on towering black smokers in dense aggregates of thousands of individuals. Although this dominance is only possible because of symbiosis, no study on the symbiosis of Indian Ocean Rimicaris species has been conducted. Here, we characterize the Rimicaris kairei symbiosis by combining molecular, microscopic, and elemental analyses, making comparisons with those of the Atlantic species possible for the first time. Although most symbiotic partners remained consistent across the two oceans, some differences were recognized in symbiont lineages, as well as in the mechanisms behind the formation of two color morphs with distinct mineralogies. Our results shed new light on relationships among mineralogy, environmental factors, and microbial communities that are useful for understanding other deep-sea symbioses in the future.

A Tale of Two Lobsters-Transcriptomic Analysis Reveals a Potential Gap in the RNA Interference Pathway in the Tropical Rock Lobster Panulirus ornatus.

RNA interference (RNAi) has been widely utilised in many invertebrate models since its discovery, and in a majority of instances presents as a highly efficient and potent gene silencing mechanism. This is emphasized in crustaceans with almost all taxa having the capacity to trigger effective silencing, with a notable exception in the spiny lobsters where repeated attempts at dsRNA induced RNAi have demonstrated extremely ineffective gene knockdown. A comparison of the core RNAi machinery in transcriptomic data from spiny lobsters (Panulirus ornatus) and the closely related slipper lobsters (Thenus australiensis, where silencing is highly effective) revealed that both lobsters possess all proteins involved in the small interfering and microRNA pathways, and that there was little difference at both the sequence and domain architecture level. Comparing the expression of these genes however demonstrated that T. australiensis had significantly higher expression in the transcripts encoding proteins which directly interact with dsRNA when compared to P. ornatus, validated via qPCR. These results suggest that low expression of the core RNAi genes may be hindering the silencing response in P. ornatus, and suggest that it may be critical to enhance the expression of these genes to induce efficient silencing in spiny lobsters.

Double-Stranded RNA Binding Proteins in Serum Contribute to Systemic RNAi Across Phyla-Towards Finding the Missing Link in Achelata.

RNA interference (RNAi) has become a widely utilized method for studying gene function, yet despite this many of the mechanisms surrounding RNAi remain elusive. The core RNAi machinery is relatively well understood, however many of the systemic mechanisms, particularly double-stranded RNA (dsRNA) transport, are not. Here, we demonstrate that dsRNA binding proteins in the serum contribute to systemic RNAi and may be the limiting factor in RNAi capacity for species such as spiny lobsters, where gene silencing is not functional. Incubating sera from a variety of species across phyla with dsRNA led to a gel mobility shift in species in which systemic RNAi has been observed, with this response being absent in species in which systemic RNAi has never been observed. Proteomic analysis suggested lipoproteins may be responsible for this phenomenon and may transport dsRNA to spread the RNAi signal systemically. Following this, we identified the same gel shift in the slipper lobster Thenus australiensis and subsequently silenced the insulin androgenic gland hormone, marking the first time RNAi has been performed in any lobster species. These results pave the way for inducing RNAi in spiny lobsters and for a better understanding of the mechanisms of systemic RNAi in Crustacea, as well as across phyla.

Characterization of G-protein coupled receptors from the blackback land crab Gecarcinus lateralis Y organ transcriptome over the molt cycle.

BACKGROUND: G-protein coupled receptors (GPCRs) are ancient, ubiquitous, constitute the largest family of transducing cell surface proteins, and are integral to cell communication via an array of ligands/neuropeptides. Molt inhibiting hormone (MIH) is a key neuropeptide that controls growth and reproduction in crustaceans by regulating the molt cycle. It inhibits ecdysone biosynthesis by a pair of endocrine glands (Y-organs; YOs) through binding a yet uncharacterized GPCR, which triggers a signalling cascade, leading to inhibition of the ecdysis sequence. When MIH release stops, ecdysone is synthesized and released to the hemolymph. A peak in ecdysone titer is followed by a molting event. A transcriptome of the blackback land crab Gecarcinus lateralis YOs across molt was utilized in this study to curate the list of GPCRs and their expression in order to better assess which GPCRs are involved in the molt process. RESULTS: Ninety-nine G. lateralis putative GPCRs were obtained by screening the YO transcriptome against the Pfam database. Phylogenetic analysis classified 49 as class A (Rhodopsin-like receptor), 35 as class B (Secretin receptor), and 9 as class C (metabotropic glutamate). Further phylogenetic analysis of class A GPCRs identified neuropeptide GPCRs, including those for Allatostatin A, Allatostatin B, Bursicon, CCHamide, FMRFamide, Proctolin, Corazonin, Relaxin, and the biogenic amine Serotonin. Three GPCRs clustered with recently identified putative CHH receptors (CHHRs), and differential expression over the molt cycle suggests that they are associated with ecdysteroidogenesis regulation. Two putative Corazonin receptors showed much higher expression in the YOs compared with all other GPCRs, suggesting an important role in molt regulation. CONCLUSIONS: Molting requires an orchestrated regulation of YO ecdysteroid synthesis by multiple neuropeptides. In this study, we curated a comprehensive list of GPCRs expressed in the YO and followed their expression across the molt cycle. Three putative CHH receptors were identified and could include an MIH receptor whose activation negatively regulates molting. Orthologs of receptors that were found to be involved in molt regulation in insects were also identified, including LGR3 and Corazonin receptor, the latter of which was expressed at much higher level than all other receptors, suggesting a key role in YO regulation.

Molecular characterization of a cDNA encoding Na+/K+/2Cl- cotransporter in the gill of mud crab (Scylla paramamosain) during the molt cycle: Implication of its function in osmoregulation.

Although iono-regulatory processes are critical for survival of crustaceans during the molt cycle, the mechanisms involved are still not clear. The Na+/K+/2Cl- cotransporter (NKCC), a SLC12A family protein that transports Na+, K+ and 2Cl- into cells, is essential for cell ionic and osmotic regulation. To better understand the role of NKCC in the molt osmoregulation, we cloned and characterized a NKCC gene from the mud crab, Scylla paramamosain (designated as SpNKCC). The predicted SpNKCC protein is well conserved, and phylogenetic analysis revealed that this protein was clustered with crustacean NKCC. Expression of SpNKCC was detected in all the tissues examined but was highest in the posterior gills. Transmission electron microscopy revealed that posterior gills had a thick type of epithelium for ion regulation while the anterior gills possessed a thin phenotype related to gas exchange. During the molting cycle, hemolymph osmolality and ion concentrations (Na+ and Cl-) increased significantly over the postmolt period, remained stable in the intermolt and premolt stages and then decreased at ecdysis. Meanwhile, the expression of SpNKCC mRNA was significantly elevated (26.7 to 338.8-fold) at the ion re-establishing stages (postmolt) as compared with baseline molt level. This pattern was consistent with the coordinated regulation of Na+/K+-ATPase α-subunit (NKA α), carbonic anhydrase cytoplasmic (CAc) isoform and Na+/H+ exchanger (NHE) genes in the posterior gills. These data suggest that SpNKCC may be important in mediating branchial ion uptake during the molt cycle, especially at the postmolt stages.

De novo assembly and analysis of changes in the protein-coding transcriptome of the freshwater shrimp Paratya australiensis (Decapoda: Atyidae) in response to acid sulfate drainage water.

BACKGROUND: The atyid shrimp Paratya australiensis occurs in surface freshwater habitats throughout eastern Australia and has been used to study the ecotoxicology of contaminants such as pesticides and metals. The acidification of surface water that can occur after acid sulfate material in soils and sediments is oxidised and subsequently re-wetted is a serious environmental issue in coastal regions and inland riverine floodplains worldwide. Solubilisation of soil-associated minerals can result in high waterborne concentrations of mineral salts and dissolved metals, which together with low pH represent a potential threat to aquatic ecosystems in affected regions. The aims of the present study were to gain insight into stress responses induced by exposure to acid drainage water (ADW) in P. australiensis by determining changes in the abundance of protein-coding transcripts and to generate a comprehensive transcriptomic resource to facilitate further research into gene regulation or protein structure and function in this species. Adult P. australiensis were exposed for 24 h to undiluted ADW, 50 % ADW diluted in river water, or to river water as control, and high-throughput mRNA sequencing (RNA-Seq) conducted on whole-body tissues. A reference transcriptome was generated using de novo assembly and putative protein-coding regions were identified and annotated. Changes in transcript abundance in response to ADW exposure were determined by aligning reads to the reference transcriptome and quantifying coverage. RESULTS: A high proportion of arthropod benchmarking universal single-copy orthologues were present in the reference transcriptome. Functions associated with cuticle biosynthesis and oxidative stress were significantly enriched in the lists of transcripts exhibiting differential abundance in either direction after exposure to 50 % or 100 % ADW. Transcripts involved in osmoregulation exhibited decreased abundance following exposure to ADW. The transcriptome contained full-length coding sequences for numerous proteins known to be involved in environmental response pathways, including two putative metallothioneins, four glutathione peroxidases and 19 nuclear receptors. CONCLUSIONS: The results of the present study provide insight into stress response pathways induced in crustaceans by short-term exposure to multiple stressors present in ADW such as low pH, high salinity and dissolved metals, and represent a resource for future toxicogenomics and protein functional studies in P. australiensis.

Spectral sensitivity, spatial resolution and temporal resolution and their implications for conspecific signalling in cleaner shrimp.

Cleaner shrimp (Decapoda) regularly interact with conspecifics and client reef fish, both of which appear colourful and finely patterned to human observers. However, whether cleaner shrimp can perceive the colour patterns of conspecifics and clients is unknown, because cleaner shrimp visual capabilities are unstudied. We quantified spectral sensitivity and temporal resolution using electroretinography (ERG), and spatial resolution using both morphological (inter-ommatidial angle) and behavioural (optomotor) methods in three cleaner shrimp species: Lysmata amboinensis, Ancylomenes pedersoni and Urocaridella antonbruunii. In all three species, we found strong evidence for only a single spectral sensitivity peak of (mean ± s.e.m.) 518 ± 5, 518 ± 2 and 533 ± 3 nm, respectively. Temporal resolution in dark-adapted eyes was 39 ± 1.3, 36 ± 0.6 and 34 ± 1.3 Hz. Spatial resolution was 9.9 ± 0.3, 8.3 ± 0.1 and 11 ± 0.5 deg, respectively, which is low compared with other compound eyes of similar size. Assuming monochromacy, we present approximations of cleaner shrimp perception of both conspecifics and clients, and show that cleaner shrimp visual capabilities are sufficient to detect the outlines of large stimuli, but not to detect the colour patterns of conspecifics or clients, even over short distances. Thus, conspecific viewers have probably not played a role in the evolution of cleaner shrimp appearance; rather, further studies should investigate whether cleaner shrimp colour patterns have evolved to be viewed by client reef fish, many of which possess tri- and tetra-chromatic colour vision and relatively high spatial acuity.

Diversity and distribution patterns of the Oligocene and Miocene decapod crustaceans (Crustacea: Malacostraca) of the Western and Central Paratethys.

Decapod associations have been significant components of marine habitats throughout the Cenozoic when the major diversification of the group occurred. In this respect, the circum-Mediterranean area is of particular interest due to its complex palaeogeographic history. During the Oligo-Miocene, it was divided in two major areas, Mediterranean and Paratethys. Decapod crustaceans from the Paratethys Sea have been reported in the literature since the 19th century, but only recent research advances allow evaluation of the diversity and distribution patterns of the group. Altogether 176 species-level taxa have been identified from the Oligocene and Miocene of the Western and Central Paratethys. Using the three-dimensional NMDS analysis, the composition of decapod crustacean faunas of the Paratethys shows significant differences through time. The Ottnangian and Karpatian decapod associations were similar to each other both taxonomically and in the mode of preservation, and they differed taxonomically from the Badenian ones. The Early Badenian assemblages also differed taxonomically from the Late Badenian ones. The time factor, including speciation, immigration from other provinces and/or (local or global) extinction, can explain temporal differences among assemblages within the same environment. High decapod diversity during the Badenian was correlated with the presence of reefal settings. The Badenian was the time with the highest decapod diversity, which can, however, be a consequence of undersampling of other time slices. Whereas the Ottnangian and Karpatian decapod assemblages are preserved virtually exclusively in the siliciclastic "Schlier"-type facies that originated in non-reefal offshore environments, carbonate sedimentation and the presence of reefal environments during the Badenian in the Central Paratethys promoted thriving of more diverse reef-associated assemblages. In general, Paratethyan decapods exhibited homogeneous distribution during the Oligo-Miocene among the basins in the Paratethys. Based on the co-occurrence of certain decapod species, migration between the Paratethys and the North Sea during the Early Miocene probably occurred via the Rhine Graben. At larger spatial scales, our results suggest that the circum-Mediterranean marine decapod taxa migrated in an easterly direction during the Oligocene and/or Miocene, establishing present-day decapod communities in the Indo-West Pacific.

Parasitization of juvenile edible crabs (Cancer pagurus) by the dinoflagellate, Hematodinium sp.: pathobiology, seasonality and its potential effects on commercial fisheries.

This study reports on the prevalence and severity of infections caused by the parasitic dinoflagellate, Hematodinium in juvenile edible crabs (Cancer pagurus) found in 2 intertidal survey sites (Mumbles Head and Oxwich Bay) in the Bristol Channel, UK. Crabs were assessed for the presence and severity of Hematodinium infections by the histological examination of infected tissues. Such infections were found to exhibit a seasonal trend in the 2 study areas with high numbers of animals (ca. 30%) infected in the spring to summer but with low severity. Conversely, in November only ca. 10% of crabs were infected but these animals had large numbers of parasites in their haemolymph and other tissues. At this time, the carapace and underlying tissues of infected crabs had the chalky, pinkish-orange appearance that is characteristic of this disease. Hematodinium-infected crabs ranged in size from 12 to 74 mm carapace width. Overall, it is concluded that the high prevalence of infection of juvenile crabs in this area may have implications for the sustainability of the edible crab fishery in the Bristol Channel.

On the occurrence of Ctenocheles (Decapoda, Axiidea, Ctenochelidae) in the Bohemian Cretaceous Basin.

Because of close morphological affinities, fossil cheliped fragments of the ghost shrimp Ctenocheles (Decapoda, Axiidea, Ctenochelidae) can be easily misidentified as remains of different decapod crustacean taxa. Re-examination of the Cretaceous decapods deposited in the National Museum in Prague revealed that all supposed specimens of the lobster genus Oncopareia found in the Middle Coniacian calcareous claystones of the Brezno Formation, including one of the Fritsch's original specimens of Stenocheles parvulus, actually belong to Ctenocheles. This material together with newly collected specimens from the same locality, allowed for erection of a new species, Ctenocheles fritschi. Its major chela possesses a serrated ischium and ovoid, unarmed merus; therefore, it is considered a close relative of the extant C. collini and C. maorianus. Ctenocheles fritschi sp. nov. represents the first report on the occurrence of the genus from the Bohemian Cretaceous Basin. It is one of the oldest records of Ctenocheles and simultaneously one of the best preserved fossils of the genus reported to date. Confusing taxonomy of S. parvulus is reviewed and shortly discussed.

The complete mitochondrial genome of the sand bubbler crab Scopimera longidactyla Shen 1932 (Decapoda: Dotillidae) and its phylogenetic analysis.

The sand bubbler crab, Scopimera longidactyla Shen, 1932 (Arthropoda: Malacostraca: Decapoda: Thoracotremata: Dotillidae), is commonly found along tropical and subtropical sandy shores of China, Korea, and Taiwan. Ecologically, it plays an important role in the productivity of sandy shores through their feeding and burrowing activities. In this study, the first complete mitochondrial genome (mitogenome) of S. longidactyla was analyzed using next-generation sequencer. Its mitogenome, circular in structure, spans 15,965 bp with a GC content of 29.97%, consisting of 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and one putative control region. Its mitogenome arrangement and composition are identical to its two congeners, S. globosa and S. intermedia. Phylogenetic analysis fully supports for the monophyly of the genus Scopimera and the sister relationship between S. longidactyla and S. globosa. The complete mitogenome of S. longidactyla and its phylogenetic implications will provide valuable insights for further studies in phylogenetic and evolutionary biology.

Infection of Norway lobster (Nephrops norvegicus) by the parasite Hematodinium sp.: insights from 30 years of field observations.

The Norway lobster, Nephrops norvegicus, is an important representative of the benthos and also supports valuable fisheries across Europe. Nephrops are susceptible to infection by Hematodinium sp., an endoparasitic dinoflagellate that causes morbidity and mortality. From an epizootiological perspective, the Clyde Sea Area (CSA; west of Scotland) is the best-studied Hematodinium-Nephrops pathosystem, with historical data available between 1988 and 2008. We have revisited this pathosystem by curating and updating prevalence values, differentiating host traits associated with disease exposure and progression, and comparing Hematodinium sp. disease dynamics in the CSA to other locations and to other decapod hosts (Cancer pagurus, Carcinus maenas). Prevalence from a 2018/2019 survey (involving 1739 lobsters) revealed Hematodinium sp. still mounts a synchronized patent infection in the CSA; hence this pathogen can be considered as enzootic in this location. We highlight for the first time that Nephrops size is associated with high severity infection, while females are more exposed to Hematodinium sp. More generally, regardless of the host (Norway lobster, brown and shore crabs) or the geographical area (Ireland, Wales, Scotland), Hematodinium sp. patent infections peak in spring/summer and reach their nadir during autumn. We contend that Hematodinium must be considered one of the most important pathogens of decapod crustaceans in temperate waters.

Rapid re-establishment of top-down control at a no-take artificial reef.

Establishment of artificial reefs and no-take areas are management measures available for restoring deteriorated marine ecosystems, compensating for habitat loss and strengthening harvested populations. Following the establishment of no-take artificial reefs in western Sweden to compensate for hard bottoms lost to a shipping lane, we detected rapid positive effects on crustaceans and demersal fish compared to fished reference areas. The relative abundance and size structure of European lobster (Homarus gammarus) increased strongly in the no-take area indicating more than doubled and tripled egg production in 5 and 10 years, respectively. For benthic fish and crustacean communities, the abundances of gadoids and wrasses increased and the abundances of small decapod crustaceans decreased in the no-take area, likely indicating cascading effects of increased predation. The study demonstrates that relatively small no-take areas, enhanced by artificial reefs, can rapidly invigorate populations of lobster and fish that in turn may re-initiate local top-down control.

Microplastic distribution among estuarine sedimentary habitats utilized by intertidal crabs.

The high accumulation potential of estuaries for plastics, particularly microplastics, poses a threat to the high societal value and biodiversity they provide. To support a spatially refined evaluation of the risk that microplastic pollution poses to fauna utilizing estuarine sedimentary habitats, we investigated the distribution of microplastics (lower limit of quantification, LOQ = 62 µm) at the sediment surface of two dominant habitats, and subsequently compared microplastic burdens between two crabs species utilizing these habitats. Microplastics were dominated by low density polyolefins (45-50 %), comparable to the polymer composition of macroplastics. The vast majority (99 %) of microplastics were ≤1 mm, and increased exponentially (with an exponent of 2.7) in abundance at smaller sizes, hinting at three-dimensional fragmentation. Our results suggest that the presence of vegetation needs to be accounted for in risk assessments with small microplastics (≥62 µm and ≤1 mm) on average 2.6 times more prevalent within reed beds compared to mudflats. Additionally, sediment properties also play a role with an exponential decrease in small microplastic abundance at coarser sediments, increased organic matter content, and decreased water content. These results suggest that at specific locations, such as the study area, local sources can provide a substantial contribution to microplastic contamination. To translate these habitat- and site-specific differences into a risk assessment relevant for macroinvertebrates, ecological traits such as differences in feeding modes should be accounted for, as we found substantial differences in both size and abundance of microplastics in gastrointestinal tracts of two crab species, Chiromantes dehaani and Chasmagnathus convexus, with different feeding modes.

Genomic divergence and differential gene expression between crustacean ecotypes across a marine thermal gradient.

Environmental gradients between marine biogeographical provinces separate distinct faunal communities. However, the absence of absolute dispersal barriers allows numerous species to occur on both sides of such boundaries. While the regional populations of such widespread species are often morphologically indistinguishable from each other, genetic evidence suggests that they represent unique ecotypes, and likely even cryptic species, that may be uniquely adapted to their local environment. Here, we explored genomic divergence in four sympatric southern African decapod crustaceans whose ranges span the boundary between the cool-temperate west coast (south-eastern Atlantic) and the warm-temperate south coast (south-western Indian Ocean) near the southern tip of the African continent. Using genome-wide data, we found that all four species comprise distinct west coast and south coast ecotypes, with molecular dating suggesting divergence during the Pleistocene. Transcriptomic data from the hepatopancreas of twelve specimens of one of these species, the mudprawn Upogebia africana, which were exposed to either 10 °C or 20 °C, showed a clear difference in gene expression profiles between the west- and south coast ecotypes. This difference was particularly clear at 10 °C, where individuals from the south coast experienced a 'transcriptomic shock'. This low temperature is more typical of the west coast during upwelling events, and the physiological stress experienced by the south coast ecotype under such conditions may explain its absence from that coastline. Our results shed new light on the processes involved in driving genomic divergence and incipient speciation along coastlines with porous dispersal barriers.

A remarkable burrow-dwelling alpheid shrimp, new genus and new species, from the tropical eastern Pacific (Malacostraca: Decapoda: Caridea).

A new alpheid shrimp genus, Pachelpheus gen. nov., is established to accommodate Pachelpheus pachyacanthus sp. nov., described based on two specimens from the Las Perlas Archipelago, Pacific coast of Panama. Pachelpheus pachyacanthus sp. nov. appears to be an obligate symbiont dwelling in burrows of yet unknown infaunal hosts, on shallow near-shore subtidal sand flats. The main morphological characters of Pachelpheus gen. nov. are: (1) frontal margin of carapace with broadly rounded rostral projection, without orbital teeth; (2) sixth pleonite with articulated plate; (3) telson with two pairs of cuspidate setae dorsally, without anal tubercles; (4) eyes concealed in dorsal view, partly visible in lateral view; (5) chelipeds equal in size, symmetrical in shape, moderately enlarged, stout, carried extended; (6) cheliped carpus without rows of setae mesially; (7) cheliped fingers without snapping mechanism, each finger armed with one stout tooth; (8) second pereiopod carpus with five sub-articles; (9) third, fourth and fifth pereiopods with ischia armed with single robust cuspidate seta, meri armed with one to several unusually robust cuspidate setae; (10) second pleopod with appendix masculina in males only; (11) uropodal exopod and endopod with rows of slender spiniform setae on their distal margins; (12) uropodal diaeresis unusually thickened laterally, with two very stout spiniform setae; and (13) lateral lobe of the uropodal protopod rounded. The new genus appears to be morphologically most similar to Jengalpheops Anker Dworschak, 2007 and Leslibetaeus Anker, Poddoubtchenko Wehrtmann, 2006.

Multi-Tissue Transcriptome Analysis Identifies Key Sexual Development-Related Genes of the Ornate Spiny Lobster (Panulirus ornatus).

Sexual development involves the successive and overlapping processes of sex determination, sexual differentiation, and ultimately sexual maturation, enabling animals to reproduce. This provides a mechanism for enriched genetic variation which enables populations to withstand ever-changing environments, selecting for adapted individuals and driving speciation. The molecular mechanisms of sexual development display a bewildering diversity, even in closely related taxa. Many sex determination mechanisms across animals include the key family of "doublesex- and male abnormal3-related transcription factors" (Dmrts). In a few exceptional species, a single Dmrt residing on a sex chromosome acts as the master sex regulator. In this study, we provide compelling evidence for this model of sex determination in the ornate spiny lobster Panulius ornatus, concurrent with recent reports in the eastern spiny lobster Sagmariasus verreauxi. Using a multi-tissue transcriptomic database established for P. ornatus, we screened for the key factors associated with sexual development (by homology search and using previous knowledge of these factors from related species), providing an in-depth understanding of sexual development in decapods. Further research has the potential to close significant gaps in our understanding of reproductive development in this ecologically and commercially significant order.

On three symbiotic species of the alpheid shrimp genus Salmoneus Holthuis, 1955 from the Indo-West Pacific, including one new to science (Malacostraca: Decapoda: Caridea).

Three species of the alpheid shrimp genus Salmoneus Holthuis, 1955 associated with burrows of other decapod crustaceans are reported from various Indo-West Pacific localities. Salmoneus venustus sp. nov. is described based on material collected at two distant localities, Nha Trang Bay, southern Vietnam, the type locality of the new species, and the Yiti-Sifah region east of Muscat, northern Oman. Both specimens were collected with the aid of a suction pump applied to burrow entrances or mounds in muddy sand; the holotype was possibly associated with burrows of the callianassid ghost shrimp, Glypturus sp. Salmoneus venustus sp. nov. shares many characteristics with S. latirostris (Coutière, 1897), including the red banding of the pleon, but can be distinguished from S. latirostris and all other species of the genus by a unique combination of morphological characters. The large-sized Salmoneus brucei Komai, 2009 is reported from Sumba, central Indonesia, representing a significant southward extension of the species' previously known distribution range and the first record since its original description. The callianassid ghost shrimp Lepidophthalmus cf. rosae (Nobili, 1904) is recorded as a new host of S. brucei. Finally, Salmoneus colinorum De Grave, 2004, associated with burrows of larger snapping shrimps from the Alpheus malabaricus Fabricius, 1798 species complex, is reported for the first time from Madang, Papua New Guinea, representing an eastward extension of the species' previously known distribution range.

Checklist of species of Stratiodrilus Haswell, 1900 (Annelida: Histriobdellidae), and new host records from Southern Brazil.

Species of Stratiodrilus are ectocommensals of freshwater decapod crustaceans, and the genus is also the most speciose within the family Histriobdellidae. However, a global review of the species of Stratiodrilus and their hosts has not been performed in nearly two decades. Based new field collections in Brazil and a literature search, we present a list of Stratiodrilus species and their hosts. We searched for host and occurrence records in papers of species descriptions, review papers and specialized databases. Forty-one host records were summarized worldwide. All host taxa were freshwater decapod crustaceans belonging to Aegla, Astacoides, Astacopsis, Cherax, Parastacus, Samastacus, and Trichodactylus. In addition, we report four new host records for Stratiodrilus circensis, and found Aegla lata as the northernmost host record for this polychaete species. Stratiodrilus circensis also had the largest number of different host species. The greatest species richness of Stratiodrilus is found in the Neotropical region, although members of this genus are also found in Australia and Madagascar associated with crayfishes. Aegla was the most reported host genus associated with species of Stratiodrilus. We provide an updated list to the known species of Stratiodrilus and also discuss the distribution of these histriobdellids.

Checklists of Crustacea Decapoda from the Canary and Cape Verde Islands, with an assessment of Macaronesian and Cape Verde biogeographic marine ecoregions.

The complete list of Canarian marine decapods (last update by González Quiles 2003, popular book) currently comprises 374 species/subspecies, grouped in 198 genera and 82 families; whereas the Cape Verdean marine decapods (now fully listed for the first time) are represented by 343 species/subspecies with 201 genera and 80 families. Due to changing environmental conditions, in the last decades many subtropical/tropical taxa have reached the coasts of the Canary Islands. Comparing the carcinofaunal composition and their biogeographic components between the Canary and Cape Verde archipelagos would aid in: validating the appropriateness in separating both archipelagos into different ecoregions (Spalding et al. 2007), and understanding faunal movements between areas of benthic habitat. The consistency of both ecoregions is here compared and validated by assembling their decapod crustacean checklists, analysing their taxa composition, gathering their bathymetric data, and comparing their biogeographic patterns. Four main evidences (i.e. different taxa; divergent taxa composition; different composition of biogeographic patterns; different endemicity rates) support that separation, especially in coastal benthic decapods; and these parametres combined would be used as a valuable tool at comparing biotas from oceanic archipelagos. To understand/predict south-north faunal movements in a scenario of regional tropicalization, special attention is paid to species having at the Canaries their southernmost occurrence, and also to tropical African warm-affinity species.