Global distribution patterns and geographic range of Cymothoa Fabricius, 1793 (Isopoda: Cymothoidae) associated with host fish.

Over recent years, fish parasites of the genus Cymothoa Fabricius, 1793, have received increased attention due to both their ecological and their economic importance to aquaculture and fishery. As the studies about Cymothoa have increased this improve our understanding on the host specificity and distribution of these parasites. The aim of this paper was to review the current global geographic distribution, distribution patterns and parasite-host interactions patterns of Cymothoa spp. associated with fish from marine and brackish water bodies around the world. A total of 144 samples were analyzed, from which 23 species of Cymothoa were found parasitizing 84 teleost fish species of 35 families and 20 orders. Most of these parasites were found in the mouth of the host fish, including in wild fish. The highest occurrence of parasites was found in host species belonging to the families Carangidae and Lutjanidae. Host specificity was an important factor in the geographic distribution of Cymothoa species as also environmental temperature. Cymothoa indica, Cymothoa exigua and Cymothoa excisa were the species with lowest specificity for host family and widest geographic distribution.

Description of Sandythoa gen. nov., a fish parasitic branchial cymothoid (Crustacea: Isopoda: Cymothoidae) from the Indian Ocean, with five species including one new species.

The comparative analysis of records of Elthusa samariscii (Shiino, 1951) from Japan and India, alongside corresponding illustrations, indicates that the records of E. samariscii from Samaris cristatus Gray in India represent a distinct and previously undescribed species. This study introduces Sandythoa tiranga gen. and sp. nov., providing comprehensive descriptions of various lifecycle stages, including the female, male, transitional, premanca, and manca larvae. The following combinations of characters identify the genus: cephalon anterior margin with acute rostrum; pleonite 1 is distinctly narrow, not extending laterally; presence of a narrow gap between pleonites; antenna with more than 10 articles; maxilliped with oostegital lobe. Sandythoa tiranga sp. nov. is specifically identified along the southwest coast of India. Furthermore, we propose transferring the following species from Elthusa: Sandythoa arnoglossi (Trilles and Justine 2006) comb. nov.; Sandythoa parabothi (Trilles and Justine, 2004) comb. nov.; Sandythoa samariscii (Shiino, 1951) comb. nov.; Sandythoa moritakii (Saito and Yamauchi, 2016) comb. nov. A revised key to the global marine branchial cymothoid genera is provided.

Evolutionary history of inversions in directional mutational pressures in crustacean mitochondrial genomes: Implications for evolutionary studies.

Inversions of the origin of replication (ORI) in mitochondrial genomes produce asymmetrical mutational pressures that can cause strong base composition skews. Due to skews often being overlooked, the total number of crustacean lineages that underwent ORI events remains unknown. We analysed skews, cumulative skew plots, conserved sequence motifs, and mitochondrial architecture of all 965 available crustacean mitogenomes (699 unique species). We found indications of an ORI in 159 (22.7%) species, and mapped these to 23 ORI events: 16 identified with confidence and 7 putative (13 newly proposed, and for 5 we improved the resolution). Two ORIs occurred at or above the order level: Isopoda and Copepoda. Shifts in skew plots are not a precise tool for identifying the replication mechanism. We discuss how ORIs can produce mutational bursts in mitogenomes and show how these can interfere with various types of evolutionary studies. Phylogenetic analyses were plagued by artefactual clustering, and ORI lineages exhibited longer branches, a higher number of synonymous substitutions, higher mutational saturation, and higher compositional heterogeneity. ORI events also affected codon usage and protein properties. We discuss how this may have caused erroneous interpretation of data in previous studies that did not account for skew patterns.

Parasitism-Induced Intersexuality in a Sexually Dimorphic Varunid Crab, Ptychognathus ishii (Decapoda: Varunidae).

Although many animals that perform sexual reproduction exhibit sexual dimorphism, individuals with intersex traits between the traits of males and females appear in some species, depending on environmental factors. Ptychognathus ishii, a varunid crab, exhibits distinctive sexual dimorphism in the morphology of its abdomen, chelipeds and setal tufts on the chelipeds. In this study, however, we report for the first time that intersex individuals with intermediate characters between those of males and females were occasionally found in wild populations. Morphological features of intersex individuals are described. Their taxonomic positions are identified based on DNA sequences of part of the mitochondrial cytochrome c oxidase I (COI) gene. It was shown that the intersexuality was induced by entoniscid parasites, because all intersex individuals were parasitized by entoniscid isopods, identified as Entionella sp. The apparent correlation between parasitism and morphological anomalies suggests that the parasitic isopods affect physiological conditions, leading to the feminization of male hosts.

Two new species and a new record of Bopyrinae (Isopoda: Bopyridae) infesting Alpheidae and Hippolytidae, with comments on the genus Bopyrina Kossmann, 1881.

Two new bopyrids, Bopyrinina articulata n. sp. and Bopyrinella asymmetrica n. sp. are described from French Polynesia, the Red Sea, and the Philippines. Bopyrinina articulata n.sp. infests Salmoneus cf. gracilipes Miya, and is distinguishable from other species of this genus by the structure of the maxilliped, pleopods and oostegite 1. Bopyrinella asymmetrica n. sp. is most similar to Bopyrinella albida Shiino, 1958, but females differ from that species because all pereomeres on the short side have round dorsolateral bosses and its pleotelson is greatly distorted. Bopyrina ocellata (Czerniavsky, 1868) is newly recorded from the Western Atlantic, from Florida, USA. Review of the species of Bopyrina revealed that B. choprai Nierstrasz & Brender à Brandis, 1929 and B. sewelli Chopra, 1930 are intermediate in morphology between Bopyrina and Schizobopyrina, the taxonomic assignment of these two species needs further evaluation. Keys to Bopyrinella Nierstrasz & Brender à Brandis, 1925 and Bopyrina Kossmann, 1881 are presented. Hosts and distributions of the seven species of Bopyrinella are summarized.

Disrupted architecture and fast evolution of the mitochondrial genome of Argeia pugettensis (Isopoda): implications for speciation and fitness.

BACKGROUND: Argeia pugettensis is an isopod species that parasitizes other crustaceans. Its huge native geographic range spans the Pacific from China to California, but molecular data are available only for a handful of specimens from North-American populations. We sequenced and characterised the complete mitogenome of a specimen collected in the Yellow Sea. RESULTS: It exhibited a barcode (cox1) similarity level of only 87-89% with North-American populations, which is unusually low for conspecifics. Its mitogenome is among the largest in isopods (≈16.5 Kbp), mostly due to a large duplicated palindromic genomic segment (2 Kbp) comprising three genes. However, it lost a segment comprising three genes, nad4L-trnP-nad6, and many genes exhibited highly divergent sequences in comparison to isopod orthologues, including numerous mutations, deletions and insertions. Phylogenetic and selection analyses corroborated that this is one of the handful of most rapidly evolving available isopod mitogenomes, and that it evolves under highly relaxed selection constraints (as opposed to positive selection). However, its nuclear 18S gene is highly conserved, which suggests that rapid evolution is limited to its mitochondrial genome. The cox1 sequence analysis indicates that elevated mitogenomic evolutionary rates are not shared by North-American conspecifics, which suggests a breakdown of cox1 barcoding in this species. CONCLUSIONS: A highly architecturally disrupted mitogenome and decoupling of mitochondrial and nuclear rates would normally be expected to have strong negative impacts on the fitness of the organism, so the existence of this lineage is a puzzling evolutionary question. Additional studies are needed to assess the phylogenetic breadth of this disrupted mitochondrial architecture and its impact on fitness.

Less effective selection leads to larger genomes.

The evolutionary origin of the striking genome size variations found in eukaryotes remains enigmatic. The effective size of populations, by controlling selection efficacy, is expected to be a key parameter underlying genome size evolution. However, this hypothesis has proved difficult to investigate using empirical data sets. Here, we tested this hypothesis using 22 de novo transcriptomes and low-coverage genomes of asellid isopods, which represent 11 independent habitat shifts from surface water to resource-poor groundwater. We show that these habitat shifts are associated with higher transcriptome-wide [Formula: see text] After ruling out the role of positive selection and pseudogenization, we show that these transcriptome-wide [Formula: see text] increases are the consequence of a reduction in selection efficacy imposed by the smaller effective population size of subterranean species. This reduction is paralleled by an important increase in genome size (25% increase on average), an increase also confirmed in subterranean decapods and mollusks. We also control for an adaptive impact of genome size on life history traits but find no correlation between body size, or growth rate, and genome size. We show instead that the independent increases in genome size measured in subterranean isopods are the direct consequence of increasing invasion rates by repeat elements, which are less efficiently purged out by purifying selection. Contrary to selection efficacy, polymorphism is not correlated to genome size. We propose that recent demographic fluctuations and the difficulty of observing polymorphism variation in polymorphism-poor species can obfuscate the link between effective population size and genome size when polymorphism data are used alone.

Infestation of the Parasitic Isopod Mothocya parvostis on Juveniles of the Black Sea Bream Acanthopagrus schlegelii as an Optional Intermediate Host in Hiroshima Bay.

In Hiroshima Bay, parasitic isopods of the genus Mothocya infest the black sea bream Acanthopagrus schlegelii (Bleeker, 1854) and the Japanese halfbeak Hyporhamphus sajori (Temminck and Schlegel, 1846), two fish species that are abundant and commercially important in the Seto Inland Sea of Japan. Immature and mature Mothocya individuals can infect both juveniles and adults of H. sajori, while immature Mothocya are known to parasitize juveniles of A. schlegelii; i.e., no Mothocya parasites are found in adult A. schlegelii. The identification of the immature Mothocya parasitizing juveniles of A. schlegelii remains uncertain, because Mothocya species are morphologically identifiable only based on adult females. Also, the biological/ecological relationship between the hosts and parasites has not been studied. Here, we identified the parasites on A. schlegelii as Mothocya parvostis Bruce, 1986 by molecular sequence analyses along with other parasites obtained from H. sajori, the latter being morphologically confirmed by comparison with paratype materials of M. parvostis as well as the similar congener Mothocya sajori Bruce, 1986. The growth rates of the infected A. schlegelii juveniles from June to September in the years 2013-2015 and 2018 were significantly lower than those of the uninfected ones, suggesting a negative effect of the infection on the hosts. Our data on the prevalence and duration of the infection, as well as the body size gain of the hosts and parasites, corroborate a hypothesis that M. parvostis would utilize A. schlegelii as an optional intermediate host before it reaches the final host, H. sajori.

A new species of Crinoniscus Pérez, 1900 (Crustacea: Isopoda: Crinoniscidae) parasitising the pedunculate barnacle Heteralepas newmani Buhl-Mortensen & Mifsud (Cirripedia: Heteralepadidae) with notes on its ecology and a review of the genus.

The new species Crinoniscus stroembergi n. sp. belonging to the parasitic isopod family Crinoniscidae Bonnier, 1900, is described from a pedunculate barnacle host collected in the Mediterranean Sea. This is the first species of Crinoniscus Pérez, 1900 described from a host in the genus Heteralepas Pilsbry. The male cryptoniscus larva is distinguished from congeneric species by having a dorsoventrally flattened body with the posterolateral margins of the cephalon scarcely extending beyond the anterior margin of pereomere 1 (in contrast to C. cephalatus Hosie, 2008 with extended margins); articles 1 and 2 of the antennule being subequal in width and the anterodistal angle of antennule article being low and rounded; propodus of pereopods 6 and 7 having a sinuous dorsal margin that is distally narrowing and the posterior margin of the pleotelson being short and rounded. The mature females of species in Crinoniscus are of two basic forms: those with ventrolateral lobes on the pereomeres (C. alepadis (Gruvel, 1901) n. comb., and C. politosummus Hosie, 2008) and those lacking such lobes (C. cephalatus and C. stroembergi n. sp.). The mature females of C. stroembergi n. sp. can be distinguished from other species of Crininiscus based on their lacking lobes on the anterior end. The material examined includes the male and three female developmental stages of the parasite in the host, Heteralepas newmani Buhl-Mortensen & Mifsud. The mouthparts of the immature female are described and the feeding biology and effects on the host are discussed along with a review of feeding modes in species of the Cryptoniscoidea. Leponiscus alepadis is transferred to Crinoniscus; the latter genus now contains five species. A modified diagnosis of Crinoniscus is provided.

Hooked on you: shape of attachment structures in cymothoid isopods reflects parasitic strategy.

BACKGROUND: Parasite attachment structures are critical traits that influence effective host exploitation and survival. Morphology of attachment structures can reinforce host specificity and niche specialisation, or even enable host switching. Therefore, it is important to understand the determinants of variation in attachment structures. Cymothoid isopods are striking ectoparasites of fishes that include the infamous 'tongue-biters.' They are known to parasitise hosts in one of four qualitatively distinct anatomical regions. Here, we quantify variation in cymothoid attachment structures - hook-like appendages called dactyli - and test whether differences in dactylus shape are correlated with parasite mode (where they attach), allometry, or both, using multivariate ordinary least squares regression. We also assess the influence of shared ancestry on shape using a molecular phylogeny to weight our models using phylogenetic generalised least squares regression. RESULTS: We find clear differences in shape between externally-attaching and internally-attaching cymothoids but also between anterior and posterior dactyli across various species with the same attachment mode. Allometric effects are significant for anterior but not posterior dactyli. Mouth-attaching species show greater shape variability than gill- and mouth-attaching species. We find no evidence that there are clade-specific patterns of association between parasite mode and dactylus shape. CONCLUSIONS: Parasite mode appears to be the main driver of attachment morphology. This likely reflects several components of parasite ecology including feeding and functional demands of attachment in different microhabitats. Geometric morphometric approaches to the quantification of shape variation of simple structures is an effective tool that provides new insights into the evolvability of parasite attachment.

Genetic and morphological divergence at a biogeographic break in the beach-dwelling brooder Excirolana hirsuticauda Menzies (Crustacea, Peracarida).

BACKGROUND: There is a biogeographic break located at 30°S in the southeast Pacific, in a coastal area of strong environmental discontinuities. Several marine benthic taxa with restricted dispersal have a coincident phylogeographic break at 30°S, indicating that genetic structure is moulded by life history traits that limit gene flow and thereby promote divergence and speciation. In order to evaluate intraspecific divergence at this biogeographic break, we investigated the genetic and morphological variation of the directly developing beach isopod Excirolana hirsuticauda along 1900 km of the southeast Pacific coast, across 30°S. RESULTS: The COI sequences and microsatellite data both identified a strong discontinuity between populations of E. hirsuticauda to the north and south of 30°S, and a second weaker phylogeographic break at approximately 35°S. The three genetic groups were evidenced by different past demographic and genetic diversity signatures, and were also clearly distinguished with microsatellite data clustering. The COI sequences established that the genetic divergence of E. hirsuticauda at 30°S started earlier than divergence at 35°. Additionally, the three groups have different past demographic signatures, with probable demographic expansion occurring earlier in the southern group (south of 35°S), associated with Pleistocene interglacial periods. Interestingly, body length, multivariate morphometric analyses, and the morphology of a fertilization-related morphological character in males, the appendix masculina, reinforced the three genetic groups detected with genetic data. CONCLUSIONS: The degree of divergence of COI sequences, microsatellite data, and morphology was concordant and showed two geographic areas in which divergence was promoted at differing historical periods. Variation in the appendix masculina of males has probably promoted reproductive isolation. This variation together with gene flow restrictions promoted by life history traits, small body size, oceanographic discontinuities and sandy-beach habitat continuity, likely influenced species divergence at 30°S in the southeast Pacific coast. The degree of genetic and morphological differentiation of populations to the north and south of 30°S suggests that E. hirsuticauda harbours intraspecific divergence consistent with reproductive isolation and an advanced stage of speciation. The speciation process within E. hirsuticauda has been shaped by both restrictions to gene flow and a prezygotic reproductive barrier.

Deep segregation in the open ocean: Macaronesia as an evolutionary hotspot for low dispersal marine invertebrates.

Diversification and speciation of terrestrial organisms are anticipated in oceanic islands such as Macaronesia, a group of Atlantic islands that have remained unconnected to continental landmasses. Hitherto, the diversification of marine organisms in oceanic islands, especially those with low vagility, has received little direct empirical analysis using molecular markers. Here, we focus on such a case study, through applying a multilocus molecular approach to investigate the diversity and evolution of a group that lacks a planktonic larval stage, the isopod genus Dynamene, in Macaronesia and Northeast Atlantic. Sequences of two mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and two nuclear (18S rRNA and 28S rRNA) loci were obtained from specimens of Dynamene edwardsi (Lucas, 1849), Dynamene magnitorata Holdich, 1968 and Dynamene bidentata (Adams, 1800) collected along the Northeast Atlantic and Macaronesia. Although no major phylogeographic structure was detected in D. bidentata and D. magnitorata, from five to nine deeply divergent lineages were evident within D. edwardsi. The divergent lineages displayed genetic distances comparable to those found among established species of peracarids. D. edwardsi exhibits a long, rich and complex phylogeographic history in Macaronesia, where the geodynamics of the islands possibly associated with founder effects and subsequent lack of gene flow among populations confounds patterns based on geographic proximity of targeted populations. Our findings collectively suggest a much larger role of oceanic islands in the diversification of marine invertebrates than previously anticipated. The work provides insights into the origins and dynamics of ongoing geographic segregation and associated deep divergence among sister evolutionary lineages in Macaronesia.

The first complete mitochondrial genome of a parasitic isopod supports Epicaridea Latreille, 1825 as a suborder and reveals the less conservative genome of isopods.

The complete mitochondrial genome sequence of the holoparasitic isopod Gyge ovalis (Shiino, 1939) has been determined. The mitogenome is 14,268 bp in length and contains 34 genes: 13 protein-coding genes, two ribosomal RNA, 19 tRNA and a control region. Three tRNA genes (trnE, trnI and trnS1) are missing. Most of the tRNA genes show secondary structures which derive from the usual cloverleaf pattern except for trnC which is characterised by the loss of the DHU-arm. Compared to the isopod ground pattern and Eurydice pulchra Leach, 1815 (suborder Cymothoida Wägele, 1989), the genome of G. ovalis shows few differences, with changes only around the control region. However, the genome of G. ovalis is very different from that of non-cymothoidan isopods and reveals that the gene order evolution in isopods is less conservative compared to other crustaceans. Phylogenic trees were constructed using maxiumum likelihood and Bayesian inference analyses based on 13 protein-coding genes. The results do not support the placement of G. ovalis with E. pulchra and Bathynomus sp. in the same suborder; rather, G. ovalis appears to have a closer relationship to Ligia oceanica (Linnaeus, 1767), but this result suggests a need for more data and further analysis. Nevertheless, these results cast doubt that Epicaridea Latreille, 1825 can be placed as an infraorder within the suborder Cymothoida, and Epicaridea appears to also deserve subordinal rank. Further development of robust phylogenetic relationships across Isopoda Latreille, 1817 will require more genetic data from a greater diversity of taxa belonging to all isopod suborders.

168 million years old "marine lice" and the evolution of parasitism within isopods.

BACKGROUND: Isopods (woodlice, slaters and their relatives) are common crustaceans and abundant in numerous habitats. They employ a variety of lifestyles including free-living scavengers and predators but also obligate parasites. This modern-day variability of lifestyles is not reflected in isopod fossils so far, mostly as the life habits of many fossil isopods are still unclear. A rather common group of fossil isopods is Urda (190-100 million years). Although some of the specimens of different species of Urda are considered well preserved, crucial characters for the interpretation of their lifestyle (and also of their phylogenetic position), have so far not been accessible. RESULTS: Using up-to-date imaging methods, we here present morphological details of the mouthparts and the thoracopods of 168 million years old specimens of Urda rostrata. Mouthparts are of a sucking-piercing-type morphology, similar to the mouthparts of representatives of ectoparasitic isopods in groups such as Aegidae or Cymothoidae. The thoracopods bear strong, curved dactyli most likely for attaching to a host. Therefore, mouthpart and thoracopod morphology indicate a parasitic lifestyle of Urda rostrata. Based on morphological details, Urda seems deeply nested within the parasitic isopods of the group Cymothoida. CONCLUSIONS: Similarities to Aegidae and Cymothoidae are interpreted as ancestral characters; Urda is more closely related to Gnathiidae, which is therefore also interpreted as an ingroup of Cymothoida. With this position Urda provides crucial information for our understanding of the evolution of parasitism within isopods. Finally, the specimens reported herein represent the oldest parasitic isopods known to date.

Molecular systematics and biodiversity of oniscidean isopods in the groundwater calcretes of central Western Australia.

Groundwater calcrete aquifers of central Western Australia have been shown to contain a high diversity of stygobiont (subterranean aquatic) invertebrates, with each species confined to an individual calcrete and the entire system resembling a 'subterranean archipelago' containing hundreds of isolated calcretes. Here, we utilised alternative sampling techniques above the water table and uncovered a significant fauna of subterranean terrestrial oniscidean isopods from the calcretes. We explored the diversity and evolution of this fauna using molecular analyses based on one mitochondrial gene, Cytochrome C Oxidase Subunit I (COI), two Ribosomal RNA genes (28S and 18S), and one protein coding nuclear gene, Lysyl-tRNA Synthetase (LysRS). The results from 12 calcretes showed the existence of 36 divergent DNA lineages belonging to four oniscidean families (Paraplatyarthridae, Armadillidae, Stenoniscidae and Philosciidae). Using a combination of phylogenetic and species delimitation methods, we hypothesized the occurrence of at least 27 putative new species of subterranean oniscideans, of which 24 taxa appeared to be restricted to an individual calcrete, lending further support to the "subterranean island hypothesis". Three paraplatyarthrid species were present on adjacent calcretes and these exceptions possessed more ommatidia and body pigments compared with the calcrete-restricted taxa, and are likely to represent troglophiles. The occurrence of stenoniscid isopods in the calcretes of central Western Australia, a group previously only known from the marine littoral zone, suggests a link to the marine inundation of the Eucla basin during the Late Eocene. The current oniscidean subterranean fauna consists of groups known to be subtropical, littoral and benthic, reflecting different historical events that have shaped the evolution of the fauna in the calcretes.

Influence of season and site location on European cultured sea bass parasites in Corsican fish farms using indicator species analysis (IndVal).

The parasites of 536 European sea bass, Dicentrarchus labrax, were studied between January 2012 and December 2013 in six Corsican fish farms. The indicator value (IndVal) method, which combines measures of fidelity and specificity, has been used in this study. Because of its resilience to changes in abundance, IndVal is a particularly effective tool for ecological bioindicator. The IndVal method showed how season can influence the occurrence of parasite species in cultured sea bass and also identified parasites as bioindicators relative to fish farm location. The combination of specificity and fidelity highlighted several parasite species as significant indicators. A randomization test identified five parasite species as having a significant indicator value for season (the monogenean Diplectanum aequans; the copepods Lernanthropus kroyeri and Caligus minimus; the isopod Ceratothoa oestroides, and the myxosporidian Ceratomyxa labracis). If gills parasites are compared, they can be seen to be indicator species for two different seasons. The only Monogenea species D. aequans had fidelity and specificity more pronounced in winter, whereas both copepod species and the Isopoda revealed highest rates of infestation corresponding with an increase of water temperature. Four species have a significant indicator value for site location (D. aequans, L. kroyeri, C. minimus, and C. oestroides). The fact that the farm 6 was isolated on the east coast of Corsica may not have allowed the parasite to infect other farms. The presence of copepods on a single farm can also be explained according to salinity variations. Data for species composition and infection levels should help to improve the monitoring and management of parasitism in cultured sea bass populations.

Mothocya renardi (Bleeker, 1857) (Crustacea: Isopoda: Cymothoidae) parasitising Strongylura leiura (Bleeker) (Belonidae) off the Malabar coast of India: Redescription, occurrence and life-cycle.

Mothocya renardi (Bleeker, 1857), a protandrically hermaphroditic cymothoid, parasitising the banded needle fish Strongylura leiura (Bleeker) from the Malabar Coast, India is redescribed and morphological data for different life-cycle stages [male, transitional and ovigerous female, larvae (pre-manca and manca) and juvenile] are provided. Mothocya renardi exhibited strict oligoxenous host specificity by infesting only S. leiura and showed high prevalence levels (reaching up to 92%). The life-cycle of M. renardi comprises three major phases (marsupial phase, free living phase and infestive phase). The marsupial phase comprised one zygotic, three embryonic and two larval stages, all of which remained in the marsupium until the final staged manca is released into the surrounding water. After having led a short free- swimming life, the manca infested the branchial cavity of the host fish, S. leiura. Subsequently it was transformed successively into juvenile, male, transitional and finally functional female through biphasic moult which occurs in between each stage. Based on the presence (or absence) of a brood pouch and/or marsupiumites, six successive stages of the female population were also identified. These data will help precise identification of the female M. renardi irrespective of their stage. The present paper also discusses the host-parasite interactions between S. leiura and M. renardi.

Pigmentation patterns are useful for species identification of third-stage larvae of gnathiids (Crustacea: Isopoda) parasitising coastal elasmobranchs in southern Japan.

Previous studies from southern Japan reported larval stages of eight gnathiid isopod species parasitising coastal elasmobranchs. Since gnathiid larvae of these different species closely resembled each other, it was necessary to obtain specimens of free-living adult males for identification to the species level. This was achieved by allowing larvae of the final stage to moult into adult males. From these males, specimens of a species new to science were discovered and described here as Gnathia rufescens n. sp. The main differentiating characteristics of G. rufescens n. sp. are: (i) the apex of pleotelson is oval shaped; (ii) the dorsal sulcus is wide in the posterior part; and (iii) the article 3 of the pylopod is not reduced in the male. Additionally, this paper summarises the specific pigmentation patterns of third-stage larvae of the new species and eight previously described species. Furthermore, host records and host use by the gnathiids were summarised based on data from 158 hosts and over 4,500 gnathiid samples; these are discussed with a focus on host-specificity of the nine gnathiid species studied.

A new genus for Entophilus mirabiledictu Markham & Dworschak, 2005 (Crustacea: Isopoda: Cryptoniscoidea: Entophilidae) with remarks on morphological support for epicaridean superfamilies based on larval characters.

A detailed reexamination of male and female Entophilus mirabiledictu Markham & Dworschak, 2005 (an endoparasite of callianassid shrimp), resulted in recognition of seven female and five male characters that separate the species from its sole congener, E. omnitectus Richardson, 1903 (an endoparasite of munidid squat lobsters). These characters show that the two species are so different as to warrant E. mirabiledictu being placed in its own genus within the Entophilidae. Additionally, a review of the morphological features of entophilid cryptoniscus larvae led to the finding that the number of flagellar segments on the second antenna offers morphological support for a recent molecular phylogeny of epicaridean taxa that rearranged the component families within the two recognised superfamilies. This work highlights the power of using larval characters in testing hypotheses on the evolutionary relationships of epicaridean taxa.

Review of the buccal-attaching fish parasite genus Glossobius Schioedte & Meinert, 1883 (Crustacea: Isopoda: Cymothoidae).

Two species of Glossobius Schioedte & Meinert, 1883 are known from Australia: Glossobius anctus Bruce & Bowman, 1989 and Glossobius impressus (Say, 1818), the latter recorded here for the first time from Australia and southern Africa. Glossobius ogasawarensis Nunomura, 1994 is here placed in synonymy with Glossobius auritus Bovallius, 1885; whereas Glossobius crassa (Dana, 1853) is removed from synonymy with G. auritus and placed into nomen dubium. Glossobius arimae Nunomura, 2001 is transferred to the genus Ceratothoa Dana, 1852. A key to the species of Glossobius is presented.