P. Laxmilatha’s research while affiliated with Central Marine Fisheries Research Institute and other places

Statolith growth increments were analysed in the bigfin reef squid, Sepioteuthis lessoniana lineage B, for estimating the age and growth in the Gulf of Mannar Biosphere Reserve (GOM), southeast coast of India. The identification of S. lessoniana lineage B was determined by mitochondrial cytochrome c oxidase I gene sequence. The statolith increment age analysis indicated that the wild-captured squid population of S. lessoniana in the study area undergoes rapid growth. The age of S. lessoniana in males ranged from 61 (95 mm dorsal mantle length (DML)) to 220 d (390 mm DML), while it was 64 (98 mm DML) to 199 d (340 mm DML) in females. The average daily growth rate in males and females was 1.63 and 1.55 mm DML d ⁻¹ , respectively. The instantaneous growth rate varied from 0.85 (210 d) to 4.1% (110 d) for males and 0.65 (190 d) to 3.7% (110 d) for females. The age at first maturity was 114 and 120 d for males and females, respectively. Back-calculated hatching dates and the attainment of maturity in females suggested that the reproduction of S. lessoniana is year-round, with two distinct spawning peaks during July–August and February months; accordingly, the hatching dates were spread throughout the year, with the presence of two cohorts. Based on the statolith data, it can be concluded that S. lessoniana lineage B in the GOM has a potential lifespan of up to 7 months. This finding contradicts the previous growth estimates based on length-frequency data, which underestimated the true growth potential of this species.

The occurrence of the Japanese hooked squid Onykia loennbergii in the Arabian Sea is reported here based on reexamination of a previously collected and misidentified specimen in the course of research on oceanic cephalopods from the Arabian Sea. The individual’s dorsal mantle length (DML) measured 325 mm and it weighed 493 g. The individual was a mature male with a relatively long penis (165 mm) with 73 spermatophores. The current report forms the first confirmed report of the genus Onykia in the tropical Arabian Sea.

The oceanic cephalopod fauna of the Arabian Sea has not been well studied. The Hawaiian flying squid Nototodarus hawaiiensis (Oegopsida: Ommastrephidae) is known to have a very broad, disjunct distribution in tropical to subtropical waters. In the present study, the squid Nototodarus hawaiiensis is reported for the first time from the Arabian Sea. Five females ranging in size from 62 to 128 mm dorsal mantle length (DML) were collected. Age estimates based on the statolith-increment analysis ranged from 79 to 132 days, with growth rates ranging from 0.78 to 0.99 (mean = 0.93) mm DML/day. Back-calculated hatch dates occurred from November to January. Stomach-content analysis revealed that the dominant prey was crustaceans.

The present study investigates Vibrio outbreak in the hatchery system designed for larval rearing of shovel-nosed lobster Thenus unimaculatus in India. High larval mortalities during the episode led to an almost complete loss of the larval stock during the first 10 days. Microscopic examination revealed heavy fouling of the phyllosoma appendages. Histopathological analysis showed the presence of bacteria in larval tissues. Investigation by scanning electron microscopy revealed the formation of bacterial plaques on appendages and adhesion of bacteria on fine setae in heavily infected larvae. Bacteria isolated from larvae and identified by 16S rRNA sequencing and phylogenetic analysis indicated that the strains were closely related to luminescent Vibrio campbellii and Vibrio harveyi. The virulence potential of Vibrio strains isolated from larvae was evaluated through an experimental infection. The study helps to understand microbial infection and its impact on phyllosoma survival and may allow a more effective health management regime to improve larval survival in the hatchery phase.

Among the various marine fishery resources, prawns occupy the most important position because of its high export value. India is the world’s largest exporter of prawn with the export value of $2.6B in USD raising India’s market share in global prawn export to 19.2% in 2018. The ever increasing demand of prawns in export market makes the fishery more and more lucrative and charming. The prawn fishery of India during 1958-2018 ranged from 62,768 t to 4,60,026 t with an average of 2,38,764 t. The highest catch was in 2011. In 2018 half of the catch was formed by penaeid prawns and the other half was formed by non-penaeid prawns. The catch formed around 10 to 15 % of the total marine catch with an average of 12%.

The shallow coral reef ecosystems along the Indian coast are being threatened by anthropogenic global ocean warming and increased frequency of coral bleaching in the recent past. Identification and conservation of deeper reef habitats are essential as they serve as a source of larvae and livestock to replenish the shallow reef habitats. Information on the location and spatial extent of the mesophotic coral ecosystems (MCEs) and their biodiversity is poorly known in the continental shelf of the east coast of India. In this study, we have documented the species diversity of MCEs at a depth of 30-40 m off Puducherry along the east coast of India. In total, 12 species of corals, including 5 black corals and 16 octocorals, 4 species of sponges and 31 species of coral-associated benthope-lagic fish species were recorded. Subergorgia sp. was the most dominant species of octocorals and found extensively as gorgonian forests. The MCEs reported in this study raise important questions about the origin and connectivity of the coral populations in this region to the other major coral reef ecosystems along the east coast. Understanding the physical processes and hy-drographic features around the MCEs, off Puducher-ry will reveal more information about the distribution and colonization of coral communities and their vulnerability to changes in future.

Introduction Jellyfish is a common word used for any gelatinous animal in marine waters. These include a wide variety of stinging and non-stinging jellyfishes. Jellyfishes are the oldest animal on planet earth from Pre-Cambrian period, and passed through 500 million years of natural selection. The term jellyfish generally refers to gelatinous zooplankton including medusae of the phylum Cnidaria(scyphomedusae, hydromedusae, cubomedusae and siphonophores) and planktonic members of the phylum Ctenophora, Salps and Pyrosomes etc. The true jellyfishes are coming under the three Cnidarian classes viz., Hydrozoa, Scyphozoa and Cubozoa and seasonally swarm in the coastal waters.

An experiment was conducted to evaluate the biochemical changes and digestive enzyme activities of juvenile Panulirus homarus lobsters kept under three different feeding regimes, namely starvation, feeding with live clam and feeding with formulated feeds. A marked reduction in the hepatosomatic index (HSI) and a decrease in levels of both protein and lipid in the hepatopancreas of starved animals were observed at the end of the trial. Results indicate that hepatopancreas forms the primary organ for mobilization of energy reserves and that both proteins and lipids are mobilized as energy sources during starvation. Starvation induced a significant increase in proteolytic digestive enzymes of the hepatopancreas. In the group fed on formulated diet, amylase activity was found to be high, probably in response to the high carbohydrate content of the feed used in the present study. These animals also had a significantly lower free amino acid content in the hepatopancreas Histological studies showed that feeding with formulated diet-induced vacuolation in the hepatopancreas caused by hypertrophy of B cells, and a distinct thickening of the lumen walls. These results suggest difficulty in metabolism and mobilization of nutrients absorbed from formulated feeds in tropical spiny lobsters.