This study provides the first documentation of three deep conspecific lineages within Panulirus polyphagus in the Indian Ocean, bridging the gap in genetic research. Comparative mitogenomics between lineages (L) at both species and family levels, evolutionary relationships and heterogeneity of sequence divergence within Decapoda, and divergence time estimation were performed. The characterized mitogenomes ranged from 15,685–15,705 bp in size and exhibited a typical pancrustacean pattern. Among the three lineages, L1 predominated the Bay of Bengal, L2 the Arabian Sea, and L2.a, a less common lineage genetically closer to L2, was restricted to the latter region. A minor lineage L1.a, was observed in the Coral Triangle area. All PCGs displayed evidence of purifying selection across species and family levels. The largest genetic distance (K2P) between lineages was 9 %, notably between L1.a and L2.a. The phylogenetic tree subdivided the Achelates into Palinuridae and Scyllaridae, and the topology demonstrated a distinct pattern of lineage diversification within P. polyphagus. AliGROOVE analysis revealed no discernible divergence in Decapoda. The diversification of P. polyphagus appears to have occurred during Miocene, with further diversification in Pliocene. Furthermore, genetic stocks and population connectivity recognized here will provide valuable insight for spatial management planning of this dwindling resource.

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Tamil Nadu and its southern coast are well-known for seaweed diversity and abundant resources in India. Brown seaweeds are primary habitat producers in reef environments. The objective of this study was to assess the spatiotemporal variation in diversity and abundance of brown seaweed species along the intertidal region at selected coastal locations on the southern coast of Tamil Nadu, India. The sampling was performed monthly at six coastal locations, namely Hare Island (HI), Tuticorin Harbour (TH), Chinna Muttom (CM), Arockiapuram (AP), Vedhalai (VD), and Mandapam (MP), along the intertidal region during low tides between January 2021 and December 2021. A total of 36 brown seaweed species were identified at six locations, namely Sargassum (9 species), followed by Padina (5 species), Turbinaria (3 species), Dictyota (3 species) and 16 species each of others. In the context of different locations, the highest species diversity was observed at HI (35) and the lowest at CM (21) during the study period. The highest abundance was recorded at CM (19.80?kg?wt m−2), while the lowest was reported at AP (9.51?kg?wt m−2). Sargassum and Turbinaria exhibited the highest prevalence across all the locations. Among different seasons, the maximum species diversity was recorded during PoMoN (26), whereas the minimum species diversity was recorded during PrMoN (11). Similarly, the highest abundance was seen during PoMoN, whereas the lowest abundance was reported during PrMoN. These findings offer crucial foundational data for the preservation and exploitation of brown seaweeds.

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Fanged sea bream, Sparidentex jamalensis Amir et al. (Pak J Zool 46(2):471–477, 2014) has been recently recorded for the first time in Indian waters from Korapuzha, Kadalundi and Moorad estuaries, Calicut, Kerala. Previously this species was reported only from Pakistan waters globally and till date there are no other reports available on the distribution of this species elsewhere. The morphometric measurements and meristic counts of the specimens collected in the present study were similar to those specimens reported from type locality with few variations. The variations observed in comparison with specimens from Pakistan are the counts of dorsal-fin spines (11–12 vz 11); dorsal-fin rays (11–12 vz 11); anal-fin rays (81/2 – 9 vz 8) pored lateral-line scales (45- 48 vz 45- 47) and in the number of gill rakers in the upper limb (6- 9 vz 6- 7). The difference observed in morphometric and meristic characters owes to the origin of species from two different geographical regions or genetic differences or environmental impact, or combination of all the above. The present report indicates an extension of the geographical distribution range of S. jamalensis from its localities. Identification of the species was further confirmed using DNA barcoding.

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Successful breeding program for hermaphrodites needs planned broodstock collection. The presented work aims to study the dynamics of broodstock availability of Acanthopagrus berda along selected stretches of Indian coast to facilitate scientific broodstock management. Broodstock availability was recorded for three consecutive years from two geographic locations, Karwar [offshore (beach area) using shore seine and inshore (estuarine area) using hook and lines, cast net and gillnet] and Calicut (inshore using hook and lines, cast net and gillnet). In both regions, most of the stocks were collected between the post-monsoon and pre-monsoon seasons (August to March). At Calicut, a considerable quantity of broodstock was available during all lunar phases except the new moon phase, while at Karwar, it was available except for the first and third quarter and full moon with assured availability during the waxing and waning phases. At Karwar, in the shore seine, the broodstock was available only from August to November, but in cast net, the broodstock was available from August to February. The brooders collected from the Calicut coast were significantly (Welch's statistics p < 0.05, Hedge's g = 0.79) larger (25.476 ± 0.32 cm) than those obtained from the Karwar (21.64 ± 0.17 cm). The highest mean length was observed in the case of fish collected by hook and line, cast net and gill net at Calicut (25.47 ± 0.31), followed by cast net (21.79 ± 0.52) and shore seine (21.60 ± 0.17) at Karwar. The estimated length of sex reversal (L50) was 25.50 cm total length (TL) with a considerable overlap in sex category in the size range of 20 − 30 cm. Welch ANOVA (One-Way) for difference in mean length affirmed no significant difference, and hence the probability of getting a higher number of a particular sex during a given lunar phase could not be assumed.

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The present study delves into the reproductive characteristics of Metapenaeopsis andamanensis, a commercially significant deep-water shrimp collected from Sakthikulangara, off Kollam, India (8°56′60.78″ N/76°32′34.27″ E) during September 2019 to May 2022. Despite its economic importance, the reproductive traits of this species remain elusive. This research comprehensively examines macroscopic and microscopic features associated with gonadal maturity stages, including determination of size at first maturity (CL50), gonadosomatic index, and fecundity of M. andamanensis. Male-to-female sex ratio was noted as 1:1.03 using chi-square analysis. The smallest mature individuals were observed at 12 mm and 16 mm carapace length for males and females, respectively. Macroscopic observation categorized females into five groups based on gonadal coloration, while microscopic examination identified seven stages using histological characteristics. Notably, the absence of cortical crypts in the periphery of oocyte cytoplasm, a characteristic feature of the genus Metapenaeopsis, was observed in this species. Males were classified into two categories based on macroscopic and microscopic observation. The gonadosomatic index ranged from 4.25 to 10.13 for mature female individuals, exhibiting a significant increase until stage IV. Continuous spawning was observed, with a peak in May and November. The size at first maturity for females and males was determined as carapace length (CL) 23.05 mm and 17.53 mm, respectively. The average absolute fecundity was calculated as 53,889 with an average relative fecundity of 9934 oocytes. This investigation contributes valuable insights into the reproductive traits of the deep-water penaeid shrimp M. andamanensis, facilitating the development of effective management strategies for sustainable fisheries.

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