Low diversity, high dominance, and high host prevalence of parasitic isopods of the family Cymothoidae in Chilika lagoon, India: a comparative study between a semi-enclosed ecosystem and its adjoining open region.

Patterns in parasite diversity are shaped by their environmental and ecological settings, and to better understand their interactions with hosts and the corresponding biology, it is crucial to understand these context-dependent patterns. To achieve this, we use cymothoid isopods, an important group of fish parasites, to test a long-standing hypothesis about parasite diversity and prevalence pattern: whether semi-enclosed water bodies allow low diversity and high prevalence of parasitic isopods. Specifically, we compare these patterns between Chilika lagoon (Odisha, India), a semi-enclosed water body, and the adjoining Odisha coast (India). Our finding reveals that the semi-enclosed Chilika lagoon has a considerably lower diversity of parasitic isopods than its adjoining open sea along the Odisha coast. Additionally, the parasitic isopod infection levels in Chilika lagoon are noticeably higher, and isopod assemblage is less even than those in coastal waters along the Odisha coast. Our results support the hypothesised association between enclosed water bodies, parasite diversity, and host prevalence and contribute to an enhanced comprehension of the ecology of parasitic isopods in distinct marine environments.

Finding Nemo! Description of a New Species of Branchial Fish Parasitic Cymothoid, Elthusa Schioedte and Meinert, 1884 (Crustacea: Isopoda), infesting Callionymus filamentosus Valenciennes, 1837 from the Northern Indian Ocean.

PURPOSE: Specimens of Elthusa from trashfish of the Indian SW coast were described as a new parasitic cymothoid, Elthusa nemo sp. nov., (Crustacea: Isopoda). Later, the branchial cavity of the Blotchfin dragonet Callionymus filamentosus Valenciennes, 1837 were documented as its micro- and macro-habitat (host). METHODS: Fresh/live specimens of unidentified cymothoid samples were collected from the trash fishes obtained from Neendakara (08°30.0' N 76°53.30' E) fish landing centre, Kollam district, Kerala state, southwest coast of India. After a long search for the host species, we recovered the isopod from the branchial cavity of the deep-sea fish Callionymus filamentosus Valenciennes, 1837 (Callionymiformes: Callionymidae). The new species is described and illustrated based on ovigerous females. RESULTS: Elthusa nemo sp. nov., has the following sets of combinations of characters: body slightly twisted, elongated, dorsal surfaces smooth, nearly twice as long as greatest width; pleon short, ~ 14% body length, 0.8 times as wide as pereon maximum width; widest at pleonite 2 and narrowest at pleonite 1; only pleonite 1, laterally overlapped by pereonite 7 posterolateral expansion and coxa 7; presence of appendix masculina on pleopod 2; uropods 0.8 times as the length of pleotelson; antenna with two plumose setae on article 4. CONCLUSION: Elthusa nemo sp. nov., is the sixth species of the genus known from Indian waters.

Morphological Description and Molecular Characterisation of Glyptothoa gen. nov., a Fish Parasitic Deep-sea Cymothoid (Crustacea: Isopoda) from the Indian Ocean, with Four Species, Including One New Species.

Glyptothoa sagara gen. and sp. nov. is described from the host fish Glyptophidium macropus Alcock, 1894 (Ophidiidae), at depths 300 to 650 metres from the southwest coast of India. The mitochondrial cytochrome c oxidase subunit I (COI) gene of the species was sequenced and compared with other closely related branchial cymothoid genera. Both morphological and molecular data corroborate the inclusion of this parasitic isopod as a new genus, and we describe Glyptothoa sagara gen. and sp. nov. The following combinations of characters characterise the genus: cephalon immersed in pereonite 1; dorsum vaulted; all coxae visible in dorsal view; coxae shorter than or as long as pereonites; pereonites 4-7 slightly decrease in width towards one side, slightly asymmetrical, lateral margins slightly constricted, in hunched side; relatively wide pleon, with large lateral gaps between pleonites; antennula narrowly separated by rostrum, slender, shorter than antenna; antenna with 13 articles, buccal cone obscuring antennal bases; brood pouch arising from coxae 1-4, 6; oostegite 1 bilobed; pleopods rami all simple, without proximomedial lamellar lobe, without folds or thickened ridges. The adult life stages, such as females (ovigerous and non-ovigerous), males and transitional stage of the new species are described. The species is currently known only from the type locality and the type host. The ecological remarks of the newly described taxon are also provided. The following species are transferred from Elthusa Schioedte and Meinert, 1884: Glyptothoa myripristae (Bruce, 1990) comb. nov., Glyptothoa propinqua (Richardson, 1904) comb. nov. and Glyptothoa caudata (Schioedte and Meinert, 1884) comb. nov.

Functional and sex-specific dynamics of ectoparasite size evolution in marine isopod-fish interactions: Harrison's rule and increasing variance.

Harrison's rule, a pattern predicting that the body size of parasites correlates positively with the size of their hosts, is well-supported. However, its interaction with highly distinct "guilds" of closely related parasites warrants further exploration. The increasing variance hypothesis predicts that the variance in parasite size should also increase with the size of their hosts. Though untested, in parasite taxa with differential sex-dependent pressures on body size, this relationship should also be divergent across sexes due to differential size-fecundity relationships. We compiled global data on sequentially hermaphroditic isopods (Isopoda: Cymothoidae) parasitic on fish from published literature. With a data set comprising of 204 marine cymothoid species and their hosts, we used Bayesian hierarchical models to primarily test (1) Harrison's rule and its scaling across three functionally distinct guilds (mouth, gill, external); (2) the increasing variance hypothesis and sex-specific patterns. Our results revealed a strong positive association between parasite and host body sizes, but with uniform scaling across guilds. Host size exerted divergent, sex-specific effects on the relative intraspecific variation in parasite size, where this association was positive in males and absent in females. Here, we show that Harrison's rule is independent of guild, suggesting body size evolution across all cymothoids is equally underpinned by the size of their hosts. The sex-specificity of the increasing variance hypothesis can be explained by female fecundity being tightly bound to body size, whereas the dependency of reproductive success on size is inherently more relaxed in males.

Truly a hyperparasite, or simply an epibiont on a parasite? The case of Cyclocotyla bellones (Monogenea, Diclidophoridae).

Cyclocotyla bellones Otto, 1823 (Monogenea, Diclidophoridae) is one of the few monogenean species reported as hyperparasitic: the worms dwell on cymothoid isopods, themselves parasites of the buccal cavity of fishes. We present here observations based on newly collected monogenean specimens from Ceratothoa parallela (Otto, 1828), an isopod parasite of Boops boops off Algeria and also investigated its diet to address whether Cy. bellones is indeed a hyperparasite, i.e., whether it feeds on the isopod. We also compared the body shape of various monogeneans belonging to the same family as Cy. bellones, the Diclidophoridae, including Choricotyle cf. chrysophryi Van Beneden & Hesse, 1863, collected from Pagellus acarne off Algeria. No morphological character of the anterior organs suggested any special adaptation in Cy. bellones to the perforation of the crustacean cuticle. The wall of the oesophagus and of the intestine of Cy. bellones was lined with a dark pigment similar to what is usually observed in haematophagous polyopisthocotyleans, and which is derived from ingested fish blood. We noticed that an anterior elongate stem exists only in diclidophorids dwelling on parasitic isopods and never in those attached to the gills. We hypothesize that the anterior stem of the body of Cy. bellones is an anatomical adaptation for the monogenean to feed on the fish while dwelling on the isopod. We thus consider that Cy. bellones is an epibiont of the parasitic crustacean, as it uses it merely as an attachment substrate, and is not a true hyperparasite.

Title: Vraiment un hyperparasite, ou simplement un épibionte sur un parasite ? Le cas de Cyclocotyla bellones (Monogenea, Diclidophoridae). Abstract: Cyclocotyla bellones Otto, 1823 (Monogenea, Diclidophoridae) est l'une des rares espèces de monogènes signalées comme hyperparasites : les vers vivent sur des isopodes cymothoïdes, eux-mêmes parasites de la cavité buccale des poissons. Nous présentons ici des observations basées sur des spécimens de monogènes nouvellement collectés de Ceratothoa parallela (Otto, 1828), un isopode parasite de Boops boops au large de l'Algérie et avons également étudié son régime alimentaire pour déterminer si Cy. bellones est bien un hyperparasite (c'est-à-dire, se nourrit-il de l'isopode ?). Nous avons également comparé la morphologie de divers monogènes appartenant à la même famille que Cy. bellones, les Diclidophoridae, dont Choricotyle cf. chrysophryi Van Beneden & Hesse, 1863, collecté sur Pagellus acarne au large de l'Algérie. Aucun caractère morphologique des organes antérieurs ne suggérait d'adaptation particulière à la perforation de la cuticule des crustacés chez Cy. bellones. La paroi de l'œsophage et de l'intestin de Cy. bellones était tapissée d'un pigment foncé semblable à ce que l'on observe habituellement chez les Polyopisthocotylea hématophages, et qui est issu du sang de poisson ingéré. Nous avons remarqué qu'une partie allongée antérieure n'existe que chez les Diclidophoridae vivant sur des isopodes parasites et jamais chez ceux attachés aux branchies. Nous émettons l'hypothèse que la partie antérieure du corps de Cy. bellones est une adaptation anatomique permettant au monogène de se nourrir du poisson tout en vivant sur l'isopode. Nous considérons donc que Cy. bellones est un épibionte du crustacé parasite, puisqu'il ne l'utilise que comme substrat pour son attachement, et n'est pas un véritable hyperparasite.

Renocila richardsonae Williams & Bunkley-Williams, 1992 (Isopoda: Cymothoidae), a parasite of Japanese goatfish, Upeneus japonicus off Sarawak, South China Sea

@#Renocila richardsonae Williams & Bunkley-Williams, 1992 is recorded for the first time from Sarawak coastal waters. During a survey of marine fishes at depth of 200 metres in South China Sea, off the coast of Sarawak from 3° to 5°N and 110° to 111°E, five specimens of Renocila richardsonae were collected from Japanese goatfish, Upeneus japonicus (Houttuyn, 1782) (Mullidae) with average prevalence of 17% and mean intensity of one isopod per fish from examination of 64 fish. The isopod was observed to cause tissue damage on the site of attachment to the host.

Description and ontogeny of a 40-million-year-old parasitic isopodan crustacean: Parvucymoides dvorakorum gen. et sp. nov.

A collection of exceptionally well-preserved fossil specimens of crustaceans, clearly representatives of Isopoda, is presented here. Excavated from the late Eocene (approximately 40 million years ago) freshwater sediments of the Trupelník hill field site near Kuclín, Czech Republic, these specimens are preserved with many details of the appendages. The morphological characteristics of the fossils were documented using macro-photography with polarised light, as well as stereo imaging. These characteristics, especially including the trunk appendage morphology, were compared to those of related extant groups from different ontogenetic stages. All specimens are conspecific, representing a single species Parvucymoides dvorakorum gen. et sp. nov. Morphometric analysis of body shapes and sizes of the reconstructed fossils and related extant species were performed. These analyses provided insight into the ontogenetic stages of each reconstructed fossil specimen. In combination with the morphological assessment, the results indicate that the fossils represent at least two (possibly three) developmental stages, including immatures. The morphology of the appendages suggests that these fossils were parasites. The fossils are interpreted as either representatives of Cymothoidae or at least closely related to this group.

First record of Lobothorax typus from Odisha coast, India, with molecular characterization and observation of its biphasic moulting.

Two distinct morphologies of Cymothoidae isopod, Lobothorax typus were collected from the marine water of Bay of Bengal, Goapalpur-on-Sea as the first record of this parasite from coastal water of Odisha, India. All specimens were found attached to the buccal region of different individuals of the same host fish Trichiurus lepturus. With the aid of COI gene sequencing and morphological analysis, the individuals were found to be conspecific. The most prominent variation among the two morphologies includes the size of 5th pereonite and pleon length to total body length ratio. These variations are as a result of the biphasic moulting process. Maximum Likelihood tree analysis based on COI gene sequences concluded the monophyletic taxonomy of different buccal attaching genera under the family Cymothoidae which is in congruence with their morphological divergence.

A Taxonomic Review of the Buccal-attaching Fish Parasite genus Lobothorax Bleeker, 1857 (Crustacea: Isopoda: Cymothoidae) with Description of a New Species from Southwestern India.

The genus Lobothorax Bleeker, 1857 is revised with the description of a new species collected from the gempylidaen fish Promethichthys prometheus (Cuvier, 1832) from the southwestern coast of India. A revised generic diagnosis is provided based on the redescription of the type species. Lobothorax aurita (Schioedte and Meinert, 1883) is here synonymised with Lobothorax typus Bleeker, 1857 based on the original description. Lobothorax nicosmiti Aneesh, Bruce and Kumar sp. nov. is described from the female stage and it is characterized by: pereonite 1 anterolateral expansion not extending to the anterior margin of cephalon; coarsely pitted pereonites dorsal surfaces; pereonites without dorsal median longitudinal ridges; anteriorly truncate cephalon; pleotelson about 0.6 times as long as wide, posterior margin weakly emarginate, broadly sub-truncate, lateral margins convex; maxilliped palp article 3 with three RS; pereopods basis much wider with prominent carina. A key to the species of Lobothorax Bleeker, 1857 is presented.

First record of Mothocya renardi and Mothocya collettei (Isopoda: Cymothoidae) from northern part of East Coast of India and new host record of Mothocya collettei.

The present record of different developmental stages of the parasite Mothocya renardi (Bleeker, 1857) and gravid female of Mothocya collettei Bruce, 1986 from different individuals of same host Strongylura leiura (Bleeker, 1850) collected from Bay of Bengal, Gopalpur-on-Sea, Odisha, India are the first record of these parasites from the northern part of east coast of India. The record of Mothocya collettei from the host Strongylura leiura is the first host record for this parasite.

Occurrence of ectoparasitic isopod Norileca indica (H. Milne Edwards, 1840) on bigeye scad Selar crumenophthalmus (Bloch, 1793) from Great Nicobar Island, India.

Present study records the occurrence and range extension of an ectoparasitic isopod, Norileca indica (H. Milne Edwards, 1840) from the branchial cavity of bigeye scad Selar crumenophthalmus (Bloch, 1793) collected from Pilobah, Great Nicobar Islands. Detailed morphological characteristic of the parasite were presented along with prevalence, mean intensity and abundance. Out of the 130 specimens of S. crumenophthalmus examined, 32 were found to be infested with N. indica. The sizes of the female specimens were in the ranges 14.0 to 20.1 mm and the male specimens were 13-14 mm.

First Record of the Cymothoid Isopod Nerocila exocoeti Pillai, 1954 (Crustacea, Isopoda) in the South-West Indian Ocean and First Record of a Perciform Host, Echeneis naucrates, for this Species.

PURPOSE: Cymothoid isopods of the genus Nerocila are generally poorly known. The aim of this work was to document the first record of cymothoid isopod Nerocila exocoeti for the South-West Indian Ocean, representing a significant westward range extension for this species. METHODS: A single adult, female N. exocoeti and 38 mancae specimens were collected from a live sharksucker Echeneis naucrates at D'Arros Island, Seychelles. The female isopod specimen was examined using a stereo microscope and described based on distinct morphological traits. Observations of novel behaviour were also made for E. naucrates. RESULTS: The examined female isopod specimen measured 26 mm long by 10 mm wide. It possessed short coxae with the postero-lateral angles of pereonites 1-5 not produced and those of 6 and 7 reduced. The first antenna was composed of eight articles and the endopod of the uropod was half the length of the exopod. These traits confirm the specimen as N. exocoeti. Observations of novel behaviour in the wild host specimen showed the individual to deliberately and repeatedly swim ashore before thrashing in the substrate, returning to the water only once the isopod was removed. CONCLUSION: To date, N. exocoeti is known from India, Indonesia, Papua New Guinea and Taiwan. The present study represents the first record of N. exocoeti from the South-West Indian Ocean region and the first record of E. naucrates as a host of any cymothoid isopod. Additionally, N. exocoeti has previously only been recorded as parasitising beloniform fish hosts and these data present the first evidence of a perciform host for this species. The novel behaviour observed in E. naucrates likely represents a means to remove external parasites.

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.

Seasonal variation of the prevalence of cymothoid isopod Norileca indica (Crustacea, Isopoda), parasitizing on the host fish Rastrelliger kanagurta collected from the Southwest coast of India.

Parasitological investigations on the occurrence of isopod parasites in fishes collected from off Cochin coast along Southwest India was carried out for a period of 1 year from January 2018 to December 2018. Altogether 20 species of fishes were analysed from 12 families including Scombridae, Carangidae, Clupeidae, Nemipteridae, Hemiramphidae, Belonidae, Menidae, Priacanthidae, Sphyraenidae, Stromateidae, Coryphaenidae. Infestation of Norileca indica was noticed only in the host fish Rastelliger kanagurta. Totally 619 specimens of R. kanagurta were examined for the presence of isopod parasite, N. indica. Among those, one hundred and seventy five specimens were found to be infested by N. indica. Overall prevalence, mean intensity and abundance were found to be 28.27%, 1.21, and 0.342 respectively. Highest prevalence of infestation, mean intensity and abundance were recorded in the month of August 2018.

Shape of attachment structures in parasitic isopodan crustaceans: the influence of attachment site and ontogeny.

Many fields of modern systematic biology are adult-centred. This is unfortunately also the case for Cymothoidae, an ingroup of parasitic forms of Isopoda, with fishes as hosts. Different ingroups of Cymothoidae have specialised appendages that enable their fish associated lifestyles, attaching to different sites on the body of the host. The extent to which these structures vary among species and in relation different sites of attachment, and between different ontogenetic stages, is explored here. This study presents the detailed descriptions, illustrations, comparisons, and analysis of a variety of attachment structures of 13 adult and immature specimens representing three major groups Ceratothoa, Elthusa and Anilocra, along with full focus, detailed photographs of all the examined life stages. The three groups exhibit different strategies attaching to mouth, gill and externally, respectively. A statistical representation of the morphology of the dactyli, used for attaching to the host, was performed. This included a critical comparison of 10 additional species documented in literature. This is the first comprehensive description and photographs of specialised appendage morphology of immatures of Ceratothoa, as well as the first detailed micrographs of embryonic stages of Cymothoidae, and the first lateral and ventral views of immature stages of the examined species. Immature specimens possess morphological characters that can be used to distinguish between different species, but cannot be accurately identified based on diagnostic characters of adults. Quantitative analysis indicates that ontogeny plays a major role in the shape of the attachment structures (e.g. dactyli).

Isopods Cymothoidae ectoparasites of fish from the Amazon / Isópodes Cymothoidae ectoparasitos de peixes da Amazônia

Abstract Most freshwater species of Cymothoidae are distributed in South America. They have mainly been recorded in the eastern and western regions of the Amazon River basin. However, in this ecosystem, the biodiversity of this group may be greater if the entire Amazon basin is considered. In this regard, the aim of the present study was to provide an updated list of isopod species of the family Cymothoidae that are found in fish in the Brazilian Amazon region and to report on new fish host occurrences and expanded geographical distributions for cymothoid isopods that parasitize fish in the southwestern Brazilian Amazon region. The parasites found in fish specimens were collected, fixed and identified later. We found eight species of Cymothoidae parasitizing different host fish species in the southwestern Amazon region. However, we found 14 species of Cymothoidae throughout the Brazilian Amazon region. Three additional species are thus reported here, which increases the number of species of Cymothoidae in this region to 17. These additional species are also new records for Brazil. Therefore, this study has contribute to expand the knowledge about the distribution and diversity of Cymothoidae in the Amazon basin.

Resumo A maioria das espécies de água doce de Cymothoidae está distribuída na Sul e foi registrada principalmente nas regiões Leste e Oeste da bacia do Rio Amazonas. Entretanto, nesse ecossistema, a biodiversidade desse grupo pode ser maior se toda a bacia amazônica for considerada. Nesse sentido, o objetivo do presente estudo foi fornecer uma lista atualizada de espécies de isópodes da família Cymothoidae que são encontrados em peixes na Região Amazônica brasileira e relatar novas ocorrências de peixes hospedeiros, ampliando as distribuições geográficas para isópodes cimotoides que parasitam peixes na região Sudoeste da Amazônia brasileira. Os parasitos encontrados em espécimes de peixes coletados foram analisados e posteriormente identificados. Foram encontradas oito espécies de Cymothoidae parasitando diferentes espécies de peixes hospedeiros na região Sudoeste da Amazônia. No entanto, foram encontradas 14 espécies de Cymothoidae em toda a Região Amazônica brasileira. Três novos relatos de espécies foram observados, o que aumenta o número de espécies de Cymothoidae nessa região para 17. Essas espécies relatadas, também são novos registros para o Brasil. Portanto, este estudo ajudou a expandir o conhecimento sobre a distribuição e diversidade de Cymothoidae na bacia amazônica.

A taxonomic review of the fish parasitic isopod family Cymothoidae Leach, 1818 (Crustacea: Isopoda: Cymothooidea) of India.

The parasitic isopod family Cymothoidae Leach, 1818 of the India exclusive economic zone is reviewed. A total of 56 nominal species corresponding to 48 valid species belonging to sixteen genera are reviewed from 73 host species belonging to 35 families. Mothocya plagulophora (Haller, 1880), Nerocila depressa Milne Edwards, 1840, Nerocila loveni Bovallius, 1887, Nerocila trichiura (Miers, 1877), Norileca triangulata (Richardson, 1910) and Ryukyua globosa Williams Bunkley-Williams, 1994 are redescribed. Indusa pustulosa Pillai, 1954 is synonymised with Agarna malayi Tiwari, 1952; Cymothoa krishnai Jayadev Babu Sanjeeva Raj, 1984 is synonymised with Cymothoa eremita (Brünnich, 1783) and Nerocila priacanthusi Kumari, Rao Shyamasundari, 1987 is synonymised with Nerocila arres Bowman Tareen, 1983. Ourozeuktes bopyroides (Lesueur, 1814) is revised and excluded from the Indian fauna. The Indian cymothoid species Agarna bengalensis Kumari, Rao Shaymasundari, 1990, Cymothoa asymmetrica Pillai, 1954 and Nerocila hemirhamphusi Shyamasundari, Rao Kumari, 1990 are regarded here as species inquirenda. A key to the Indian genera of the family Cymothoidae and keys to the Indian species of the genera Cymothoa, Joryma, Mothocya, and Nerocila are presented. A checklist of the valid Cymothoidae species until now reported from Indian marine fishes are compiled. Host preferences, morphological variability and distribution are discussed.

Redescription and neotype designation for the poorly known fish parasitic cymothoid Joryma brachysoma (Pillai, 1964) (Crustacea: Isopoda) from India.

A neotype is designated for Joryma brachysoma (Pillai, 1964). The general morphology and appendages of the female and male stages are illustrated and re-described based on the neotype and several additional fresh specimens collected from the type host Pellona brachysoma Bleeker (=Sardinella brachysoma Bleeker) from nearby the type locality. The present redescription and neotype designation further resolves the taxonomic ambiguity regarding the species identification and conserves the name of J. brachysoma.

A comparison of body condition of the yellowstriped butterfish Labracoglossa argenteiventris in relation to parasitism by the cymothoid isopod Ceratothoa arimae.

Isopods of the genus Ceratothoa (Cymothoidae) are one of the largest invertebrates parasitic on a variety of fishes, which include commercially important species. Nevertheless, the parasitic effects on fish body condition have been studied only in a few Ceratothoa species, particularly those living in the Mediterranean and Australian waters. Findings from these previous studies suggest the hypothesis that effects of parasitism by Ceratothoa species are benign on native host condition in the wild. In this study, to test this hypothesis on another Ceratothoa-fish relationship in different region, we examined the effects of Ceratothoa arimae on the body condition of the yellowstriped butterfish, Labracoglossa argenteiventris, a commercial fish important to local fisheries particularly in the remote islands of Tokyo, Japan. Ceratothoa arimae was found in 8 out of 23 fish examined (prevalence: 34.8%). Although infected and uninfected fish were similar in standard length, the body condition index (relative weight) of infected fish was significantly lower than that of uninfected fish. The observed weight of infected fish was an average of 89.2% of the expected weight. These results are inconsistent with the hypothesis and suggest that the potential effects of Ceratothoa parasites need to be considered carefully in fishery management plan of host fish.

The parasitic isopod Mothocya nana drives dietary shifts and poorer condition of Brazilian silversides Atherinella brasiliensis.

Cymothoids are ectoparasites that may attach to various parts of the fish for molting and reproductive purposes, thus increasing the energetic costs of the host. This study investigated the influence of the parasitic isopod Mothocya nana on the physiological condition and diet of adult Brazilian silversides Atherinella brasiliensis at a sandy beach in southeastern Brazil. We collected 268 A. brasiliensis individuals, of which 230 fish were non-parasitized (mean ± SE total weight [TW] = 16.92 ± 0.38 g; total length [TL] = 127 ± 0.88 mm) and 38 were parasitized by up to 2 isopods (TW = 15.89 ± 0.79 g; TL = 126 ± 1.96 mm). Parasitic prevalence (P) and intensity (I) reached highest values in June 2015 (P = 20.88%; I = 1.31) and were slightly higher on males (P = 17.39%; I = 1.33) than on females (P = 13.07%; I = 1.27). Parasitized fish revealed poorer condition than non-parasitized ones, among which male hosts were especially burdened by M. nana's attachment. The condition factor, the eviscerated condition factor and the fullness index each showed a decreasing trend according to the parasite's development and offspring weight (i.e. increase in egg and larval weight). Parasitized and non-parasitized Brazilian silversides fed mainly on microcrustaceans, but the first group showed reduced phytoplankton intake and was associated with fewer trophic categories in comparison to non-parasitized fish. These dietary shifts revealed correlation with the poorer physiological condition reported for infected A. brasiliensis, whose decreased feeding efficiency is likely related to potential impairment of the filter-feeding mechanism and/or altered behaviour due to pressure atrophy and the increased energetic costs imposed by M. nana's development.