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.

A new snake eel species of the genus Ophichthus (Anguilliformes: Ophichthidae) from the southeast coast of India, Bay of Bengal, with the taxonomic account of Ophichthus chilkensis.

A new species of the ophichthid eel of the family Ophichthidae is described based on five specimens collected from the Mudasalodai fish landing center, off Cuddalore coast, southeast coast of India, Bay of Bengal. Ophichthus naevius sp. nov. is distinguished from its congeners by having a unique color pattern: dorsal body with numerous dense dark spots or patches, ventral body pale yellowish green, dorsal-fin origin just before pectoral-fin tip, vertebral formula: 12-14/52-53/134-138, and teeth on jaw uniserial and pointed. The study also reports the range extension and molecular evidence of Ophichthus chilkensis from South India. Molecular analyses were performed for both species, and their phylogenetic relationship suggests that the new species exhibits 10.2% genetic divergence with its congener Ophichthus sangjuensis, followed by Ophichthus brevicaudatus (10.4%), and Ophichthus sp. 1 (11.8%) also forms the closest clade in both Bayesian inference and maximum likelihood (ML) tree. Similarly, according to the topology of the ML tree, the species O. chilkensis forms a clade with Ophichthus sp. 5, Ophichthus remiger, Ophichthus frontalis, Ophichthus sp. 6, and Ophichthus rex, suggesting that it would be the genetically closest congener.

Description of a new species of the genus Awaous Valenciennes, 1837 (Gobiiformes: Oxudercidae) from the middle stretch of the Mahanadi River, Odisha, India, with comments on the Awaous species from India.

A new species of the genus Awaous (Oxudercidae), Awaous motla sp. nov., is described based on 18 specimens collected from the Mahanadi River near Sonepur, Subarnapur District, and 3 specimens from the same river near Boudh bridge, Boudh District of Odisha, India. This species is distinct from its congeners by having a combination of characteristics: relatively small eyes, diameter of 6.6-8.4 in head length (LH); robust and long snout, 2.0-2.6 in LH; eye diameter 2.7-4.1 in snout length; cephalic sensory pore system interrupted with eight pores; predorsal scales 13-15; longitudinal scale series 55-58; gill rakers 2 + 1 + (6-7) on the first gill arch; teeth small, conical, and in a single row on the upper jaw and multiserial (2-3) on the lower jaw. This species is also differentiated from some of its congeners in the nucleotide composition of the cytochrome c oxidase I gene by 8.3%-13.8% Kimura two-parameter (K2P) distance and belongs to a separate cluster in the maximum likelihood tree analysis. This finding is also supported by the species delimitation analysis based on Assemble Species by Automatic Partitioning. The new species holds high commercial value in its locality and needs special conservation attention for sustainable utilization.

A new species of cirri-bearing eel of the genus Cirrhimuraena (Anguilliformes: Ophichthidae) from the coastal Bay of Bengal, India.

A new species of cirri-bearing ophichthidae eel Cirrhimuraena odishaensis sp. nov. is described here, on the basis of two specimens collected from the Palur canal and Talasari fish landing centre in Odisha, India. The distinguishing characters of Cirrhimuraena odishaensis sp. nov. that separate it from its congeners include the presence of a single row of mandibular teeth, origin of the dorsal fin directly above the midpoint of pectoral fin, vertebral counts (pre-dorsal 10, pre-anal 46-47, and total 160-162), and number of cirri (13) on the upper jaw. Morphologically Cirrhimuraena odishaensis shows close affinity with Cirrhimuraena yuanding and Cirrhimuraena orientalis. The new species differs from C. yuanding by origin of dorsal fin, number of intermaxillary and maxillary teeth, and length of head. The new species differs from C. orientalis with relatively higher vertebrae.

A new deep-water conger eel of the genus Rhynchoconger (Anguilliformes: Congridae) from the south-west coast of India, Arabian Sea.

A new species of deep-water conger eel, Rhynchoconger bicoloratus sp. nov., is described herein based on three specimens collected from the deep-sea trawlers landing at Kalamukku fishing harbour, off Kochi, Arabian Sea, from a depth beyond 200 m. The new species is distinguished from its congeners by having the following combination of characters: head larger than trunk, rictus at posterior margin of pupil, dorsal fin origin slightly before the pectoral fin insertion, eye diameter 1.7-1.9 times in snout length, ethmovomerine teeth patch broader than long with 41-44 recurved pointed teeth in six or seven rows, vomerine teeth patch pentagonal shaped with single tooth on posterior end, 35 pre-anal vertebrae, body bicoloured, peritoneum and stomach black. Genetically, the new species differs from its congeners with a divergence of 12.9%-20.1% in the mitochondrial COI gene.

A new congrid eel, Rhynchoconger randalli sp. nov. (Congridae: Anguilliformes), with a pentagonal pattern of vomer dentition from the Bay of Bengal, Indian waters.

A new species Rhynchoconger randalli sp. nov. is described herein on the basis of 2 specimens collected from Paradeep fishing harbor, Odisha, India along the Bay of Bengal from a depth of about 3640 meters. The pentagonal vomerine teeth pattern is unique among all the Rhynchoconger species described to date. The new species is characterized by predorsal vertebrae 78 and preanal vertebrae 2931. The new species closely resembles the recently described Rhynchoconger smithi, but differs in having a larger eye diameter (12.512.9% HL vs. 9.59.7% in R. smithi), smaller interorbital space (13.113.5% HL vs. 15.018.1 in R. smithi), lower dorsal-fin ray count before vent 4447 vs. 5458 in R. smithi, and unique pentagonal vomerine teeth pattern.

A new species of conger eel, Ariosoma (Congridae: Bathymyrinae), from the Bay of Bengal, India.

Ariosoma bengalense sp. nov. is described on the basis of two specimens having total length (TL) 216304 mm, collected from the northern part of the Bay of Bengal, India. The new species is characterized by the dorsal-fin origin positioned above the gill-opening margin and above the 9th lateral-line pores, supratemporal pore absent, 910 predorsal vertebrae; 4649 preanal vertebrae and 146149 total vertebrae. The new species most closely resembles the Indian species Ariosoma gnanadossi, the new species differs from A. gnanadossi having the snout length (SL) longer than eye diameter (snout length 1.42.0 in eye diameter) vs. snout length almost equal to the eye diameter in A. gnanadossi. Further, the new species has translucent pectoral fins vs. black pectoral fins in Ariosoma gnanadossi. The new species differs from four of the seven species reported from India: Ariosoma majus, A. melanospilos, A. maurostigma and A. indicum with absence of supratemporal pores vs. three in all the species mentioned.

Infection of the parasitic isopods on commercial fishes of the northern part of the east coast of India.

The present study reports 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 waters 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. Members of the host fish family Carangidae were 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  prevalence was high during post-monsoon than pre-monsoon and monsoon. Supplementary Information: The online version contains supplementary material available at 10.1007/s12639-021-01463-1.

First report of parasitic isopod Nerocila orbignyi (Cymothoidae) from India with its molecular characterization.

The present report provides the first material evidence of Nerocila orbignyi (Guérin-Méneville, 1832) collected from two different landing centres of the Chilika lagoon, thus claiming the first report of this parasite from India. One of the specimens was recorded from the host fish species Plotosus canius Hamilton 1822, constituting the first host record for this isopod. A key for the identification of N. orbignyi among its congeners is also provided. Molecular characterization of Cytochrome C Oxidase I (COI) gene of N. orbignyi was based on one specimen submitted for the first time to the NCBI database. This parasite is differentiated from the other available sequences of its related congeners retrieved from the NCBI and BOLD database by 26-34% in the Kimura 2 Parameter (K2P) distance and belongs to a separate cluster in Maximum likelihood (ML) tree analysis.

Ariosoma indicum sp. nov., a new species of congrid eel (Anguilliformes: Congridae: Bathymyrinae) from the Indian waters.

Ariosoma indicum sp. nov. is described herein based on 12 specimens [(335-433 mm total length (TL)] collected off the Arabian Sea of southwest coast of India and 7 specimens from Digha Mohana, off the Bay of Bengal of northeast coast of India. The new species is distinguished from congeners in having the following combination of the characters: anus positioned anterior to middle of total length, pre-anal length 40.0%-43.1% of TL; short wedge-shaped pointed vomerine teeth patch, three or four rows in anterior portion, tapering posteriorly with four uniserial teeth; supraorbital canal with four or five pores; pre-dorsal vertebrae 9-10; pre-anal vertebrae 49-53; total vertebrae 141-146; body greenish-brown in colour; extremities of the lower jaw with minute dark pigmentation patches before the rictus, bicoloured pectoral fin. A. indicum shares few characters with the Indian water species, Ariosoma gnanadossi, but readily differs from the latter in having more pre-anal vertebrae (49-53 vs. 47 in A. gnanadossi); fewer lateral-line pores (130-137 vs. 145); shorter tail (54.9%-57.9% TL vs. 60.1% TL); smaller eye (15.1%-17.7% HL vs. 19.2% HL); smaller interorbital width (11.8%-15.7% HL vs. 18.2% HL); longer upper jaw (26.9%-30.2% HL vs. 19.2% HL). In addition, molecular analysis using partial mitochondrial COI gene suggests that A. indicum is genetically closer to Ariosoma maurostigma and Ariosoma melanospilos with a divergence of 15.0% and 15.8%, respectively, and forms a well-supported monophyletic clade.

A new Congrid eel, Rhynchoconger smithi sp. nov. (Anguilliformes: Congridae), from the Bay of Bengal, India.

A new Conger eel species is described based on four specimens collected from Petuaghat fishing harbour, West Bengal, India. The combination of morphological characters and molecular data are discordant with the seven congeners currently recognized. Rhynchoconger smithi sp. nov. can be distinguished by having head smaller than trunk; pre-anal length more than three times in total length; a small eye, diameter 2.0-2.2 in snout length; rictus ending at a vertical through posterior margin of pupil; ethmovomerine teeth patch small, with 58-74 blunt teeth arranged in seven to eight irregular rows; vomerine teeth patch small, with 18-28 granular teeth arranged in four to six irregular rows, distinctly separated by narrow spaces from the ethmovomerine and maxillary teeth; three supraorbital pores and one supra-temporal pore; and 159+ to 164 total vertebrae. Moreover, R. smithi differs significantly from four congeners, R. nitens, R. flavus, R. ectenurus and R. gracilior, with Kimura two-parameter (K2P) distances 14.6%-20.3%.

A new species of the congrid eel genus Ariosoma (Anguilliformes: Congridae) from the south-west coast of India.

A new congrid eel species, Ariosoma maurostigma sp. nov., is described on the basis of 24 specimens collected from the deep-sea trawl by-catch, Kalamukku Fishing Harbour, off Kerala, Arabian Sea. The new species differs from all other congeners in having the following combination of characters: dark mark or spot on the posterodorsal margin of the eyes; dorsal surface of head with two faint darkish bands across the anterior and posterior margin of the eye; origin of the dorsal fin before the pectoral-fin base; short vomerine teeth patch, ST pores 3, 1 median pore and 1 lateral pore on each side just behind the median pore; preanal vertebrae 47-51; precaudal vertebrae 54-57; total vertebrae 136-142; total pores 129-134. The phylogenetic analysis reveals that the new species is closely related to Ariosoma melanospilos and Ariosoma anale, with divergences of 13.8% and 14.9%, respectively.

Confirmation on the occurrence of Cymothoa indica, and first record of Norileca indica, with a note on new host records of Nerocila arres, and Nerocila depressa (Isopoda: Cymothoidae) from Odisha coast, India.

The parasitic isopod Cymothoa indica Schiöedte and Meinert, 1884 was recorded from the buccal cavity of the host Glossogobius giuris (Hamilton, 1822) collected from Chilka Lake, Odisha in 1924, but its identification was doubtful as mentioned by the author in his book on "Fauna of Chilika Lake: Tanaidacea and Isopoda". The present report of parasitic isopod C. indica from the buccal cavity of the host Sphyraena obtusata Cuvier, 1833 collected from the water of Bay of Bengal, Gopalpur-on-Sea confirms its occurrence along the Odisha coast. The record of the isopod parasite Norileca indica (H. Milne Edwards, 1840) from the branchial cavity of the host Atule mate (Cuvier, 1833) collected from the water of Bay of Bengal, Gopalpur-on-Sea is the first record of this parasite from the coastal water of Odisha, India. The record of Nerocila arres Bowman and Tareen, 1983 from the caudal peduncle of the host fish species Terapon puta Cuvier, 1829, and the isopod N. depressa Milne Edwards, 1840 from the host fish species Megalaspis cordyla (Linnaeus, 1758) are the new host records for these respective parasites.

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.

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.

A new species of the genus Cirrhimuraena (Anguilliformes: Ophichthidae) from the Bay of Bengal, India.

A new species of the genus Cirrhimuraena (Anguilliformes: Ophichthidae), Cirrhimuraena indica sp. nov., is described based on eight specimens collected from the Paradip (Odisha) and Petuaghat harbours (West Bengal) along the Bay of Bengal. The species is distinct in having the upper jaw fringed with 16-17 cirri before posterior nostril and 4-5 in between the anterior and posterior nostrils on the side; dorsal fin originates above the level of gill opening, predorsal length is 9.3-10.9 in total length; the head is relatively large, the length is 9.3-9.8 in total length; no infraorbital pores are observed between the nostrils; teeth are numerous, small, conical and in bands on each jaw; pores are present before the gill opening 10-11 and before anus 47-48; pectoral-fin length is 2.4-2.8 in head length; predorsal vertebrae are 8-10, pre-anal vertebrae 43-47 and total vertebrae 164-169. In the maximum likelihood tree analysis for COI gene, the new species belongs to the same clade as the other congener of Cirrhimuraena chinensis and is separated from the species morphologically and genetically.

A new white-spotted moray eel, Gymnothorax aurocephalus sp. nov. (Muraenidae: Muraeninae) from Andaman Sea, India.

Gymnothorax aurocephalus sp. nov. is described herein based on 4 specimens. Three were collected from off Swaraj Dweep Island of Andaman and Nicobar Islands (AN Islands) from a depth of 125-130 m and one specimen off Interview Island, AN Islands at a depth of 90 m. This new species is distinguishable from its congeners by the following combination of characters: chocolate brown color overlain with small irregular white spots, golden skin shadings close to rictus; anus slightly before midbody; pointed and serrated jaw teeth; uniserial teeth in jaws and vomer; vertebral formula 7/61/148-149. The species is compared to all its congeners with white spots.

A review of the genus Strophidon (Anguilliformes: Muraenidae), with description of a new species.

Strophidon McClelland is a muraenid genus with characteristic appearance of a very elongated body, a large mouth cleft and anteriorly placed eyes. The nomenclature and taxonomic history of species within Strophidon are contentious and its members are easily misidentified. In the present study, species of the genus Strophidon are revised based on morphological and molecular data, and five species are considered valid, including S. dawydoffi Prokofiev, S. dorsalis (Seale), S. sathete (Hamilton), S. ui Tanaka and a new species, S. tetraporus. Strophidon tetraporus sp. nov. is described based on 15 specimens from Indonesia, the Philippines, Taiwan and Vietnam with the unique characteristic of the constant presence of the fourth infraorbital pore among species of Strophidon. The intraspecific variation of vertebral formula within S. dorsalis is discussed based on molecular data. Muraena macrurus Bleeker and Thyrsoidea longissima Kaup are synonyms of S. sathete that can be distinguished from the most similar congener S. ui by a longer tail, smaller eyes and more inner maxillary and inner dentary teeth. A key to identify species of Strophidon is provided. The distribution and maximum size of each species are also re-evaluated.

Ophichthus kailashchandrai sp. nov. (Anguilliformes: Ophichthidae): a new species of snake eel from Indian waters, Bay of Bengal.

A new snake eel (Anguilliformes: Ophichthidae: Ophichthinae) species, Ophichthus kailashchandrai sp. nov., is described from three specimens, collected from the Shankarpur fishing harbour located on the northern part of the Bay of Bengal, West Bengal, India. Ophichthus kailashchandrai sp. nov. is distinguished from its congeners by having its dorsal-fin origin at the posterior third of the pectoral fin, preanal length 2.6-2.8 in TL, uniserial maxillary and mandibular teeth and vertebral count (predorsal vertebrae 14-15, preanal vertebrae 54-55, and total vertebrae 180-182).

A new species Ophichthus chennaiensis sp. nov. (Anguilliformes: Ophichthidae) from the southeast coast of India.

A new species of snake eel, Ophichthus chennaiensis sp. nov. (Anguilliformes: Ophichthidae: Ophichthinae), is described on the basis of a specimen collected from dumped fish disposed of by bottom trawlers at Kasimedu fishing harbour, Chennai. Ophichthus chennaiensis sp. nov is distinguished from its congeners by having its dorsal-fin origin one pectoral-fin length behind the pectoral-fin tip, preanal length 2.4 in TL, biserial maxillary, uniserial mandibular teeth, biserial to uniserial vomerine teeth, and its vertebrae (predorsal 19, preanal 53, and total vertebrae 154).