Indian Council of Agricultural Research
CENTRAL MARINE FISHERIES RESEARCH INSTITUTE

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Reproductive strategy of milk shark, Rhizoprionodon acutus (Ruppell 1837), along north-eastern Arabian Sea

The reproductive characteristic of Rhizoprionodon acutus were investigated using 684 specimens collected along Gujarat coast (India) of the north-eastern Arabian Sea. The sex ratio between male and female (1:1.13) was not found to be significantly different. Male and female sharks were found to mature at total lengths of 61.5 cm and 61.3 cm, respectively. Large and ripe follicles were observed throughout the year, which indicates that the breeding season extends all through the year. However, a significant increase in maximum follicle diameter was observed during February and March in the first quarter and during October and November in the last quarter of the year, which indicates that a portion of the population shows temporal preferences for breeding. This is also corroborated by the increase in the number of mature females with visible eggs in their ovary. Increase in the number of ready to spawn pregnant females was observed during March to May, followed by an increase in the number of postpartum females during May to June. The larger mean size of embryos was also recorded during May and, therefore, it can be presumed that a major parturition event happens during May. The uterine fecundity was found to be significantly influenced by maternal body size and varied from three to seven embryos per litter. Unlike male sharks, the female sharks showed significant variation in the monthly hepato-somatic index (HSI) which was significantly higher in January, after which it showed a gradual decreasing trend probably due to maternal nutrient investment during gestation.


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New records of Pontocaris affinis affinis and Pontocaris propensalata from Quilon bank of Southeastern Arabian Sea

This paper reports on two crangonid shrimps, Pontocaris affinis affinis and Pontocaris propensalata from Southeastern Arabian Sea. Continuous surveys in the Quilon bank yielded two new records of Pontocaris, which were found on the continental slope at 250–300 m depth. A 4.1% of genetic divergence between the 16S DNA sequences of the two species was noticed. Quilon bank is the most productive ground for deep-sea shrimps, at 250–350 m depth lying between 8°N and 9°N Lat of the southeastern Arabian Sea. In particular, this region is an important ground for deepwater exploitation and records for a number of non-penaeid shrimps’ distribution (Suseelan 1985; Rajan et al. 2001; Kurup et al. 2008). Currently, we noticed the crangonid shrimp Pontocaris affinis affinis (Alcock, 1901) and Pontocaris propensalata Spence Bate, 1888 are distributed in this region. Earlier, these species were recorded from Bombay, Bay of Bengal and Madagascar of Indian Ocean at a depth of 102–175 m (Chan 1996). The present work reports the taxonomic documentation of these species along with mitochondrial DNA sequences (COI & 16S), obtained from the trawls operated off the Southwest coast of India. Pontocaris affinis affinis and Pontocaris propensalata were collected from the deep sea fishing harbour, Sakthikulangara, Kerala, India. The specimens were caught from the commercial trawlers (mesh size 20–26 mm) operated in the Quilon region during 2014 to 2016. The species was identified following the description and keys by Alcock (1901) and Chan (1996). The collected specimens were preserved in 90% ethanol, and are deposited at Marine Biodiversity Museum, Central Marine Fisheries Research Institute, Cochin, India.

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Morphometric and molecular characterisation of Tenuiproboscis keralensis n. sp. infecting marine and brackish water fishes

A new species of acanthocephalan infecting marine and brackish water fishes from the south-west coast of India is described. The parasite belongs to the genus Tenuiproboscis, and the fish hosts include Lutjanus argentimaculatus, L. ehrenbergii, Siganus javus, Epinephelus malabaricus, E. coioides, Scatophagus argus, Parascolopsis aspinosa, Caranx ignobilis, Gerres filamentosus and Lates calcarifer. The parasite inhabits mid- and hindgut regions and is characterised by an elongated, cylindrical, bulbous and posteriorly tapering metasoma and a claviform proboscis having 14-15 rows of 14-15 hooks each. Females larger than males, measured 3898.16-10,318.00 ?m (6430.00 ± 1417.30) in length and 458.93-1435.68 ?m (929.81 ± 250.39) in width. Males measured 3234.89-8644.20 ?m (5729.50 ± 1176.60) in length and 388.30-1584.61 ?m (795.88 ± 184.12) in width. Parasites recovered from different host species showed morphological/morphometric variations. However, principal component analysis (PCA) revealed significant overlapping of characters indicating their similarities. Proboscis profiling based on variations in size and position of hooks also yielded similar results. Further, in molecular phylogenetic analysis, parasites from different fish hosts formed a monophyletic clade with strong bootstrap support, again indicating their conspecific nature. These morphological/morphometric variations can be ascribed to differences in host species. Morphology and morphometrics in combination with PCA, proboscis profiling and molecular analysis suggest the present acanthocephalan parasite is different from other described species of Tenuiproboscis. Hence, it is considered as a new species and named T. keralensis n. sp. Prevalence, intensity and abundance of the parasite in different hosts are also discussed.

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Effect of cadmium in the gills of green tiger prawn, Penaeus semisulcatus

The aim of this study was to determine the acute toxicity levels of cadmium for Penaeus semisulcatus and elucidate the impact of this heavy metal on gills at two sublethal (250 and 500 ?g L-1) levels for a period of 14 days. The median lethal concentration level (LC50) of cadmium in 24, 48, 72 and 96 h for P. semisulcatus were 8180, 5160, 4000 and 2680 ?g L-1. The gills of the shrimps were dissected out and processed for light and electron microscopic studies. The light microscopic studies revealed several alterations in the histoarchitecture of the gills and the prominent changes include deformity of the secondary gill lamellae, infiltration of hemocytes, malformation at the tip of gill filament, lifting of lamellar epithelium, hyperplasia and swelling of the gill lamellae. The ultrastructural examination exposed detachment of gill epithelium, formation of electron dense deposits in the cuticle, disrupted and damaged microvilli, shrunken nucleus, vacuole formation, swollen mitochondria with disoriented cristae, fragmented endoplasmic reticulum and numerous vacuoles with electron dense granules. These alterations impair vital physiological functions, such as respiration and osmoregulation of the gills, which in turn affect the survival of P. semisulcatus. Therefore, the present study suggests that efficient remedial measures should be adopted to prevent the occurrence of cadmium contamination in the aquatic environment.

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Influence of sediment chemistry on mangrove-phosphobacterial relationship

The study reveals importance of sediment chemistry in mangrove-phosphobacterial relationship. The various physicochemical parameters of sediment, bacterial distribution, and acidic- alkaline phosphatase activity were studied in Avicennia marina mangrove sediments. The sampling sites were four mangrove forests along West India. Rhizospheric, pneumatophoric and bulk/non-rhizospheric sediment were collected. The rhizospheric sediment showed higher bacterial activity. The pH was observed low in the rhizospheric sediment and good abundance of phosphate-solubilizing bacteria (PSB). This was also supported by other physico-chemical parameters. Acid phosphatase activity was found to be higher in rhizospheric sediment indicating acid production at rhizosphere by microbial action and root exudation. It is the first study indicating that alkaline phosphatase activity was observed to be higher in pneumatophoric sediment. This coincides with higher number of phosphatase-producing bacteria (PPB) and high inorganic P in the pneumatophoric sediment, revealing that this region of A. marina harbours favourably more PPB with utilization of organic P by bacterial load and conversion to inorganic forms stressing that strong bonding exists between mangrove-sediment-phosphobacterial relationships.

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Gonadal Assessment of Picnic Sea Bream Acanthopagrus berda, a Potential Aquaculture Candidate for Indian Waters

Gonadal assessment of Acanthopagrus berda (Forsskål 1775), a commercially and recreationally important fish from Indian waters, was studied by collecting 250 fishes from the Korapuzha estuary, Calicut, Kerala using cast net during December 2015 to January 2016. External morphology of the gonads reveals that A. berda is bisexual (with ovo-testis) in nature with the ovarian lobe in the mid-dorsal region of the abdominal cavity and the testicular lobe as a band along the ventro-lateral wall with a major portion running along the extreme posterior region of the gonad. Males were dominant in lower length classes (17–23 cm) while females dominated in upper length classes (24–43 cm), confirming protandrous hermaphroditism in the species. Gonado-somatic index (GSI) was significantly higher (P<0.05) for the females. Males and transitional groups were showing almost similar GSI. External morphological and histological evaluation of the gonads of A. berda during the 2-month study revealed the presence of different developmental stages such as matured testis with oozing milt, an intermediate gonad structure with an anterior thin ovary-like structure and a posterior thick testis-like morphology indicating a transitional ovo-testis, maturing ovary and matured ovary. The simultaneous availability of milt oozing males and matured females from the wild indicates the opportunity for development of captive breeding, seed production and hatchery technology for this important commercial food fish.

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