Two New Genera and Species of the Parasitic Copepod Family Chondracanthidae Milne Edwards, 1840 (Copepoda: Cyclopoida) from Deep-Sea Fishes Off Suruga Bay, Japan.

PURPOSE: The present paper describes two new genera and species of the parasitic copepod family Chondracanthidae Milne Edwards, 1840 based on specimens collected from two species of deep-sea fishes at a depth of 212 m off Suruga Bay, Japan. Avatar nishidai gen. et sp. nov. is described from the host fish Chaunax abei Le Danois, 1978 (Chaunacidae). Kokeshioides surugaensis gen. et sp. nov. is described from the host fish Setarches longimanus (Alcock, 1894) (Setarchidae). METHODS: Fresh specimens of chondracanthids were collected from the buccal cavity of two species of deep-sea fishes (fish hosts were frozen), Chaunax abei Le Danois, 1978 (Lophiiformes: Chaunacidae) and Setarches longimanus (Alcock, 1894) (Perciformes: Setarchidae), caught at a depth of 212 m in Suruga Bay, Japan (34° 37'48.87″ N, 138° 43'2.958″ E). Both the species are described and illustrated based on ovigerous females. RESULTS: The genus Avatar gen. nov. can readily be distinguished from all other chondracanthid genera by the following combination of features: cephalothorax slightly wider than long with anterior pair of large and posterior pair of small lateral lobes, and two pairs of ventro-lateral processes; the very posteriormost part of the first pedigerous somite contributes to the neck; cylindrical trunk with two pairs of blunt proximal fusiform processes; antennule with small knob terminally; antenna bearing distal endopodal segment; labrum protruding ventrally; two pairs of biramous legs each with 2-segmented rami. Kokeshioides gen. nov. has the following combinations of features that distinguish it from other chondracanthid genera: body flattened, without lateral processes; cephalothorax much wider than long, with paired anterolateral and posterolateral lobes, folded ventrally; the very posteriormost part of the first pedigerous somite contributes to the neck; mandible elongate; legs unique, heavily sclerotized, represented by two pairs of acutely pointed processes. CONCLUSION: With the addition of two new genera presently reported, the family Chondracanthidae currently includes 52 valid genera. Among the described genera Avatar gen. nov. seems to be very primitive, while Kokeshioides gen. nov. is highly advanced. The deduced evolutionary history of chondracanthid genera is also discussed.

A new species of branchial fish parasitic deep-sea isopod, Brucethoa Aneesh, Hadfield, Smit & Kumar, 2020 (Isopoda: Cymothoidae) from the Indian Ocean, with the transfer of two Elthusa Schioedte & Meinert, 1884 species.

Brucethoa isro n. sp., a new species of deep-sea cymothoid is described and illustrated from the host fish Spinyjaw greeneye, Chlorophthalmus corniger Alcock, 1894, at depths of 265 to 458 metres from the southwest coast of India. Brucethoa isro n. sp. is recovered from the base of the gill cavity, facing the head towards the anterior, and the dorsal body closely adpressed against the gill, while the ventral brood presses against the inner wall of the operculum. Brucethoa isro n. sp., the second species of the genus, is characterized by: head weakly immersed in pereonite 1, very elongated body (3.15 times as long as wide); body dorsum not vaulted, almost flat; all coxae short, 0.5 times as the length of corresponding pereonites; sternite 7 with prominent posterior lobes. All adult life stages of the new species are described [including females (ovigerous and non-ovigerous), males, transitional, and juvenile. The species is currently known from the southwest coast of India and is the type locality. Additionally, this research provides valuable ecological insights into Brucethoa isro n. sp. and its habitat. As part of the taxonomic contributions, two species, Brucethoa alvaradoensis (Rocha-Ramírez, Chávez-López & Bruce, 2005) comb. n. and Brucethoa epinepheli (Trilles & Justine, 2010) comb. n., are transferred from the Elthusa genus to the Brucethoa genus.

Habitat shift of adult Caligus undulatus (Copepoda: Siphonostomatoida: Caligidae) from host fish to plankton in response to host behavior.

Before 2019, adults of the sea louse Caligus undulatus were reported exclusively in plankton from ocean samples worldwide and were not known to parasitize fish hosts. In 2019, the first instance of this caligid parasitizing a fish host, Japanese sardinella Sardinella zunasi, was reported in the Seto Inland Sea, Japan. The presently reported study aimed to investigate the biology and ecology of adult C. undulatus in plankton communities in the Seto Inland Sea and surrounding waters from March 2020 to November 2021. The occurrence of sea lice in plankton communities was restricted to the period of August-January, mainly between October and December with maximum plankton abundance (10.5 ind. per 1000 m3) recorded on 30 November 2020. All post-naupliar stages of C. undulatus were found on the host fish, and they represented a typical life cycle pattern known for Caligus species. The sex ratios in both planktonic and parasitic adults were not significantly different. The frequency of occurrence of planktonic and parasitic adult females with egg strings was 68 and 46%, respectively. The number of eggs per string was significantly higher in parasitic adult females (mean ± SD: 16.9 ± 8.6) than in planktonic females (10.4 ± 10.8). These data suggest that adult females were detached from their hosts and continued to produce eggs without feeding. Seasonal migration of S. zunasi to brackish water for spawning may result in the detachment of mature caligids from the host and may be effective in protecting the offspring, which are less tolerant of less brackish water.

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.

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.

Redescription and molecular characterization of Mothocya parvostis Bruce, 1986 (Crustacea: Isopoda: Cymothoidae) parasitic on Japanese halfbeak, Hyporhamphus sajori (Temminck & Schlegel, 1846) (Hemiramphidae) with Mothocya sajori Bruce, 1986 placed into synonymy.

Two species of Mothocya have previously been recorded from Hyporhamphus sajori: M. parvostis Bruce, 1986 and M. sajori Bruce, 1986. Mothocya parvostis is re-described based on the ovigerous female type and additional materials collected from the host from in and around the type locality. Morphological re-examination of fresh specimens and the type materials together with genetic data show that the M. sajori and M. parvostis are the same species, differing primarily in size, therefore we have placed Mothocya sajori Bruce, 1986 into a junior synonym of Mothocya parvostis Bruce, 1986. Mothocya parvostis is characterized by the following combinations of characters: 1) body slightly to moderately twisted to one side; 2) pereonite 7 posterior margin moderately to deeply recessed; 3) uropodal rami extending to pleotelson posterior margin; and 4) uropod rami bluntly rounded, exopod 1.5 times as long as peduncle. The differences of four morphological features for M. parvostis and M. sajori was quantified. Furthermore, a total of 635 isopods infesting H. sajori were collected from all over Japan to conduct quantitative morphological and molecular sequence analyses (mitochondrial cytochrome c oxidase subunit I and 16S rRNA). Although the four quantitative features did not overlap between the two species in type specimens, all quantitative morphological values of newly collected specimens in this study did not display a bimodal distribution. In addition, our molecular analyses found only a single clade for our newly collected specimens in neighbor-joining tree.

A new species of Cardiodectes Wilson C.B., 1917 (Copepoda: Siphonostomatoida: Pennellidae) from Spinyjaw greeneye, Chlorophthalmus corniger Alcock, 1894 off the Indian Ocean.

A new species of flesh penetrating parasitic copepod of the genus CardiodectesWilson C.B., 1917 (Siphonostomatoida: Pennellidae) parasitizing the fish Spinyjaw greeneye, Chlorophthalmus cornigerAlcock, 1894 (Chlorophthalmidae), inhabiting at depths of 265 to 458 meters from the south-west coast of India is described and illustrated. The new species, Cardiodectes vampire sp. nov., can be distinguished from its other 16 congeners by the following features: (i) trunk 3.15 times as long as wide; (ii) extremely long (3.5 times as long as total body length) and uncoiled egg sacs; (iii) difference in the armature of legs 13; (iv) comparatively longer trunk (0.7 times as long as total body length). A checklist of valid global species of Cardiodecteswith its host and distribution is also provided.

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.

Morphological description and molecular characterisation of a new species of Anilocra Leach, 1818 (Crustacea: Isopoda: Cymothoidae) from India.

A fish parasitic isopod recently reported from India as Anilocra leptosoma Bleeker, 1857, was re-examined and morphologically compared to five closely related species: A. capensis Leach, 1818, A. clupei Williams and Bunkley-Williams, 1986, A. leptosoma Bleeker, 1857, A. paulsikkeli Welicky and Smit, 2019 and A. pilchardi Bariche and Trilles, 2006. This species was sequenced and compared to other known Anilocra species based on mitochondrial cytochrome c oxidase subunit I (COI) gene fragments. Both morphological and molecular data corroborate that the Anilocra species parasitising the clupeid fish Tenualosa toli (Valenciennes, 1847) from India should be recognised as a new species, and we describe Anilocra grandmaae n. sp. based on the holotype and paratype females. The key characters of A. grandmaae n. sp. include the body being less than 4.0 times as long as wide; antennula article 3 anterodistal margin expanded, 1.2-1.4 times as wide as long; pleonite 1 concealed by pereonite 7 and lateral margin posteriorly produced; pereopods 1-4 with three nodules on dactylus; endopod of pleopods 3-5 with a proximomedial lobe and folding; and pleotelson ovate, with lateral margins converging smoothly to a caudomedial point.

Protandrous Hermaphroditic Reproductive System in the Adult Phases of Mothocya renardi (Bleeker, 1857) (Cymothoidae: Isopoda: Crustacea) -Light and Electron Microscopy Study.

The reproductive system of Mothocya renardi (Bleeker, 1857), a protandrous hermaphroditic cymothoid that infects the belonid fish Strongylura leiura Bleeker, 1850, is characterized using light and electron microscopy. Three protandrous hermaphroditic adult phases are identified: male, transitional and female. Each phase includes a paired reproductive system, one on either side of the gut. Each consists of three lobed testes, followed by an ovary, then a vas deferens that opens into a penis on the same side. During the male phase, all testis lobes are filled with germ cells at various stages of spermatogenesis and spermeogenesis. Primary and secondary spermatogonial cells are confined to the peripheral side of the testis lobe. The ovary shows peripheral germarium and a large number of yolkless oocytes encircled by follicle cells. The oviduct emerged from the ovary mid laterally and its distal end was found to be sealed. The exceptionally elongated spermatozoon consists of a head and a long filamentous tail. The spermatozoa are found organized into characteristic bundles to form spermatophores, and these are also packed in the vas deferens during the male phase. During the transitional phase, on the other hand, testes appear to be withered, but the vas deferens contains spermatophores. The ovary shows yolky oocytes encircled by follicle cells. During the female phase, the testis lobes appear as thin, empty, and sac like, and the extremity of the vas deferens is closed. Ovaries contain yolky oocytes and more prominent oviducts than male and transitional phases. The present paper also discusses the pattern of correlation between 1) the ovarian and brood cycles and 2) the ovarian and molt cycles.

Redescription of Lernaeenicus stromatei Gnanamuthu, 1953 (Copepoda: Siphonostomatoida: Pennellidae) infesting the Black Pomfret Parastromateus niger (Bloch) from Indian waters.

The parasitic copepod Lernaeenicus stromatei Gnanamuthu, 1953 infecting black pomfret, Parastromateus niger (Bloch) (Carangidae) is redescribed based on a neotype and additional fresh material obtained from hosts collected at different fish landing centers on the Chennai Coast (Tamil Nadu), Malabar Coast (Kerala), and from West Bengal, India. A female L. stromatei obtained from the Chennai Coast has been designated as a neotype and deposited in the National Zoological Collections of Zoological Survey of India (NZC-ZSI). Lernaeenicus stromatei can be identified based on the following features: A long and slender body; head anteriorly rounded, dorso-ventrally flattened and slightly longer than broad; presence of three posterior horns on the head, one median and two lateral, all sub-similar and apically rounded; and an anterior neck with an indistinct partition on the dorsal side, indicating thoracic segments, and a three-jointed antennule.

Agarna malayi Tiwari 1952 (Crustacea: Isopoda: Cymothoidae) Parasitising the Marine Fish, Tenualosa toli (Clupeidae) from India: Re-description/description of Parasite Life Cycle and Patterns of Occurrence.

Panakkool Thamban Aneesh, Kappalli Sudha, Ameri Kottarathil Helna, and Gopinathan Anilkumar (2018) This paper re-describes the female stage of Agarna malayi Tiwari 1952, a protandrically hermaphroditic parasitic cymothoid, and describes the remaining life cycle stages for the first time. The re-description (female phase) of A. malayi was made based on the type specimens deposited by Tiwari (1952) in the National Zoological Collections of the Zoological Survey of India (NZC-ZSI) and data obtained from several live specimens collected from Ayyikkara Fish Landing Centre (11°51'N, 75°22'E, of Malabar Coast, India) and Marina Beach (13.0500°N, 80.2824°E, Bay of Bengal, India). General morphology, mouthparts and appendages of the species' life cycle stages such as larvae, juveniles, male and transitional stages are also reported for the first time. We closely observed 80 marine fish species belonging to 35 different families to identify the potential host of A. malayi, and only recovered the parasite from one fish, Tenualosa toli, signifying A. malayi's oligoxenous host specificity; the prevalence and intensity of parasitisation is 17.3 and 1.86%, respectively. The present paper also discusses sequential life cycle stages of the species.

Redescription of Nerocila exocoeti Pillai, 1954 (Crustacea: Isopoda: Cymothoidae) parasitic on beloniform (Exocoetidae and Hemiramphidae) hosts with Nerocila madrasensis Ramakrishna Ramaniah, 1978 placed into synonymy.

Nerocila exocoeti Pillai, 1954 is re-described based on the neotype and additional material from exocoetid hosts. Nerocila madrasensis Ramakrishna Ramaniah, 1978 (from Madras) is placed into synonymy with N. exocoeti. Nerocila exocoeti is characterized by the presence of short coxae, postero-lateral angles of the first five pereonites not backwardly produced, pereonites 6-7 are reduced, cephalon sub-quadrate with anterior border straight; first antenna composed of eight articles and endopod of uropod half the size of exopod. Nerocila exocoeti is only known from beloniform hosts; Parexocoetus brachypterus and Exocoetus volitans (Exocoetidae); Hemiramphus sp. and Rhynchorhamphus malabaricus (Hemiramphidae) are the identified hosts for the species.

A case of persisting massive infection of Scomberomorus commerson, a commercially exploited scombrid fish, with Cybicola armatus (Copepoda: Siphonostomatoida: Pseudocycnidae).

During an extensive survey of fish parasites along the Malabar coast of India we observed exceptionally high or even massive infection of the narrow-barred Spanish mackerel, Scomberomorus commerson (Scombridae), with parasitic copepods Cybicola armatus. Such infection has not hitherto been reported. The copepods occurred on the gills of its host and the infection persisted for many years (the survey lasted from January 2010 to July 2014). The overall prevalence was very high (95%); out of a total of 981 fish studied, 933 were infected, and the maximum intensity reached 42. The highest rate of infection (prevalence 99.2%) was observed in medium sized fish (36.0-79.9 cm). We found this parasite only on S. commerson even though we examined 81 fish species, including five of the family Scombridae. Interestingly, the parasite exhibits strict site specificity and microhabitat preference. A significant proportion of them was seen attached to pseudobranchs rather than to main gill arches. Significantly, the body size of the parasite was positively correlated with that of the host fish. Our SEM micrographs contributed new facts to this copepod's morphology by illustrating for the first time the ventral part of its cephalothorax, illustrating the nature of attachment, and by finding a new structure - a premaxillary pad. We demonstrated the haematophagous nature of C. armatus by finding and documenting the host's blood cells in the parasite's intestine.

Multiple parasitic crustacean infestation on belonid fish Strongylurastrongylura.

Simultaneous multiple infestation of parasitic crustacean species involving a cymothoid isopod, Cymothoafrontalis Milne Edward, 1840 and four species of copepods such as Lernanthropustylosuri Richiardi, 1880, Caligodeslacinatus Kroyer, 1863, Bomolochusbellones Burmeister, 1833 and Dermoergasiluscoleus Cressey & Collette, 1970 was frequently noticed on spot-tail needlefish, Strongylurastrongylura (Belonidae) captured from the Malabar coast (Kerala, India) during the period from April 2011 to March 2012. All the 43 fishes (Strongylurastrongylura) collected, were under the hyper-infection with parasitic crustaceans; a total of 388 parasitic crustaceans including 57 Cymothoafrontalis, 252 Lernanthropustylosuri, 31 Caligodeslacinatus, 24 Bomolochusbellones and 32 Dermoergasiluscoleus were recovered from the host fish. 4 members (9.30%) of host fish were under quadruple parasitism, in two different combinations. Seventeen (39.53%) host fishes showed triple parasitism and 20 (46.51%) members exhibited double parasitism, with four and five parasitic combinations respectively. Remaining two (4.65%) fishes were parasitized only by the copepod, Lernanthropustylosuri. The infestations by all recovered parasitic crustaceans were highly site specific. The damage caused by the parasitic crustaceans was also discussed.

Seasonal fluctuation of the prevalence of cymothoids representing the genus Nerocila (Crustacea, Isopoda), parasitizing commercially exploited marine fishes from the Malabar Coast, India.

The presently reported study investigated seasonal fluctuations in the prevalence in four species of Nerocila infesting commercially exploited marine fishes representing the families Engraulidae, Clupeidae and Ambassidae, from the Malabar coast (Kerala, India). Seven of 56 fish species belonging to 23 families were infested by either one or two species of Nerocila. All the collected Nerocila species showed significant seasonal fluctuations in the prevalence of infestation, reaching maximum from October through April and minimum (or total absence of the parasites) from May through September. Such fluctuations were analyzed based on environmental parameters. Body surface, postero-ventral side of the head and the lateral line of the host fish form the major infestation site for the recovered Nerocila species. Skin lesion and hemorrhages were observed on the fish parasitized with these cymothoids.