Infection of the Parasitic Isopods on Commercial Fishes of the Northern Part of the East Coast of India

The present study report the parasitic isopod infection on commercial fishes of the northern part of the east coast of India collected during the period 2010-2015 from the marine water of Odisha and West Bengal. During the study, 394 isopods were collected after examining 2668 fishes. These include 14 species of isopods, out of which 13 belong to 5 genera under the family Cymothoidae, and a single species Alitropus typus belongs to the family: Aegidae. Of theses, 03 species viz., Catoessa boscii, Cymothoa eremita and Nerocila loveni are first record to the northern part of east coast of India. Out of the 2668 fishes examined, 326 examples belonging to 34 species under 19 different families were infected by different isopods. Member of the host fish family Carangidae was more parasitized by isopods, followed by Clupeidae, Scoberidae, and Leiognathidae. The dominant isopods were Nerocila phaiopleura and Catoessa boschii. The total prevalence was 12.21. The prevalence was high on the host fish Alepes djedaba and lowest on Lutjanus johnii. The total infection caused by genus Alitropus was 1.52%, Anilocra was 5.07%, Catoessa was 24.87%, Cymothoa was 0.25%, Nerocila was 65.73%, and Norileca was 2.55%. The isopod prevention was high during the post-monsoon and low during the monsoon period.

New record of two isopods Alitropus Typus and Tachaea Spongillicola from riverine freshwater fishes in western India

The present paper deals with the infestation of freshwater fishes Labeo boggut, Oreochromis niloticus, Systomus sarana, and Xenentodon cancila by the parasitic isopods Alitropus typus and Tachaea spongillicola in Tapti, a westward freshwater flowing river of India. It is the first record of the infestation of parasitic isopods Alitropus typus, and Tachaea spongillicola in the freshwater fishes of river Tapti with new hosts’ species Labeo boggut, Oreochromis niloticus, and Systomus sarana.

Parasitic isopods on some marine fishes caught from the coasts of Sinop in the Black Sea, Turkey

Marine fish species such as grey wrasse Symphodus cinereus, common sole Solea solea, knout goby Mesogobius batrachocephalus and rusty blenny Parablennius sanguinolentus were studied for their parasitic isopods on the Sinop coast of the Black Sea. Two cymothoid species (Nerocila bivittata and Nerocila orbignyi) were identified. Nerocila bivittata was found on the body surface and fins of grey wrasse, common sole, knout goby, and N. orbignyi on the dorsal fin of rusty blenny. The prevalence and mean intensity values of each parasite species on fishes were calculated. Fish species mentioned above were all new hosts for N. bivittata and N. orbignyi in the Turkish coast of the Black sea.

The morphology of the parasitic isopod Tachaea chinensis (Isopoda, Cymothoida) revealed through scanning electron microscopy and histological analysis

Parasitic isopods have negative effects on several commercially important fishes and crustaceans. However, studies on these parasites, especially on their morphology, are limited. In the present study, scanning electron microscopy and simultaneous histological analysis were carried out to examine the external structure and composition of the internal organs of Tachaea chinensis (Isopoda, Corallanidae). Seven pairs of pereopods are sharp and hook-like, which are used for attaching to the host. Four pairs of the paddle-shaped pleopods indicate that it has the ability to swim freely. Analysis of the mouth appendages revealed that T. chinensis mainly feeds on the host’s blood. Moreover, we found numerous glands, including the salivary glands and hepatopancreas, in the coelom; loose connective tissue was also found in the ventral body cavity, which appeared to be a vestigial gonad. In addition, the description of the gland also provides valuable empirical data for future research.

New Records of Fish Parasitic Isopods (Crustacea: Isopoda) from the Gulf of Thailand

From a total of 4140 marine fishes examined, eight species of parasitic isopods were reported from marine fishes in the Gulf of Thailand. These isopods were identified in two families, Corallanidae (Argathona macronema and Argathona rhinoceros) and Cymothoidae (Cymothoa eremita, Cymothoa elegans, Smenispa irregularis, Nerocila sundaica, Norileca indica and Norileca triangulata). Most of these parasitic isopods were found in the buccal cavity of their fish hosts with one host recorded as follows: C. eremita was found from Nemipterus hexodon, C. elegans was found from Scatophagus argus, N. sundaica was found from Saurida tumbil. The majority of the isopod specimens recorded in this study was S. irregularis, which was found in the buccal cavities of five host fish, Pampus argentius, Alepes melanoptera, Caranx hippos, Parastromateus niger and Terapon jarbua, with a prevalence of 11.67%, 10.43%, 9.78%, 6.10% and 4.21%, respectively. Argathona rhinoceros was found in the nasal cavity and branchial cavity of Epinephelus coioides, whereas A. macronema and N. triangulata were found on the skin of Epinephelus coioides and Seriolina nigrofasciata, respectively. The highest species diversity was found in E. coioides, which harbored two species of parasitic isopods, A. macronema and A. rhinoceros. Cymothoa eremita, C. elegans, S. irregularis and N. triangulata were recorded for the first time in the Gulf of Thailand. The reported discovery of C. eremita, S. irregularis, N. sundaica and N. triangulata in their fish hosts were new recorded hosts. Moreover, A. macronema and N. triangulata were found for the first time in the central Indo-Pacific region.

A new genus and species of parasitic isopod (Bopyroidea: Entoniscidae) infesting pinnotherid crabs (Brachyura: Pinnotheridae) on the Atlantic coast of the USA, with notes on the life cycle of entoniscids

Pinnixion sexdecennia n. gen., n. sp. is described from three pinnotherid hosts: Austinixa gorei (Manning & Felder, 1989), Pinnixa chaetopterana Stimpson, 1860, and Zaops ostreus (Say, 1817). Females of the new species are distinguished from all other entoniscids by possessing two transverse lobes on oostegite 1 and fused oostegites 2–5; males have a pair of lateral expansions on each of the first two pleomeres. The epicaridium larvae of the new species also have a unique elongated, cylindrical terminal process on the pereopod 6 dactylus. Pinnixion sexdecennian. gen., n. sp. exhibited highest prevalence (> 40%) in North Carolina and Florida. Examination of live specimens of P. chaetopterana infested with mature female isopods showed that larvae are liberated via a pore produced in the wall of the host’s branchial chamber. Mature females of P. sexdecennian. gen., n. sp. occupied nearly all available space within the host crab’s hemocoel. Female P. chaetopterana had higher prevalence than males, and intensities of infestations were also greater in females. Evidence from all locations showed that mature parasites do not inhibit breeding or molting in the host. Our report is one of the few studies on the ecology and biology of entoniscids, a cryptic but ecologically important group of parasitic isopods. We also resolve long-standing nomenclatural issues involving Entione Kossmann, 1881 and Entioninae Codreanu, Codreanu & Pike, 1960, the subfamily to which the new genus and species belongs, by synonymizing Grapsion Giard & Bonnier, 1886 with Entione.

Biphasic moult cycle of the parasitic isopod Norileca indica (H. Milne Edwards, 1840) (Isopoda: Cymothoidea): stage-wise characterisation and haemolymph ecdysteroids titre

Norileca indica (H. Milne Edwards, 1840) is a protandrous hermaphroditic and obligatory parasitic isopod of scombrid fishes. The posterior and anterior biphasic moult cycles in the adult phases (male, transitional, and female) of this species are characterised based on the microscopic changes reflected in the uropod exopodite and maxillule, respectively. Biphasic parturial moult as well as the moult removing the old brood pouch characteristic of ovigerous females was recorded. Assay of haemolymph ecdysteroids titre with respect to different biphasic moult cycle stages appears to be first report of its kind among aquatic and/or parasitic isopods. The ecdysteroids titre showed significant fluctuation in relation to the moult cycle stages, while the parasite was at a biphasically intermoult stage, titre was estimated to be 13.64 ± 2.09 ng ml–1. By the onset of the premoult at the posterior body region, titre showed a gradual increase and reached a maximum level (328.54 ± 70.17 ng ml–1; P = 0.0060) when the parasite was at late premoult at the posterior body part and mid premoult stage at the anterior body part. There was a subsequent sharp decline (92.8 ± 12.95 ng ml–1; P = 0.002) soon after the ecdysis of the posterior part by the time premoult changes in the anterior part advanced as late premoult and about to moult. The level of ecdysteroids titre was 55.56 ± 14.47 ng ml–1 when the parasite completed anterior ecdysis and reached postmoult. Data on the monthly occurrence of biphasic moult cycles revealed that a mean average of 23.26% of the adult population undergoes premoult/ecdysis/postmoult activities throughout the year. The rate of moulting showed a decline (16.12 ± 0.60%) during the monsoon months (June-August) when compared to pre-summer/summer (February-May) (24.83 ± 2.42%) and post-monsoon/winter (September-January) (26.28 ± 1.75; P = 0.005).