Insights into the divergent evolution of the oceanic squid Sthenoteuthis oualaniensis (Cephalopoda: Ommastrephidae) from the Indian Ocean.

Sthenoteuthis oualaniensis is known for its complex population structure with three major transoceanic forms (viz. middle-sized, dwarf, and giant forms) whose taxonomic status has been disputed for decades. This integrated taxonomic study examines these prevenient morphotypes gathered on cruises in the Indian Ocean to ascertain their status in the evolutionary history of the species. Molecular analyses employing mitochondrial (COI, ND2) and nuclear (H3) markers revealed four genetically distinct and novel lineages of the species in the Indian Ocean, representing three morphotypes from the Arabian Sea and one from the Southern Indian Ocean. The mitochondrial-based phylograms revealed two distinct clades in the species: "dwarf forms + giant form" and "middle-sized forms," which further branch into geographically structured evolutionary units. Species delimitation analyses recovered five distinct clades, namely, the Arabian Sea giant and dwarf forms, Equatorial, Eastern Typical, and Other Middle-sized forms, representing the consensus molecular operational taxonomic units. H3 being heterozygous could not resolve the phylogeny. Haplotype network and AMOVA analysis of mtDNA genes indicated explicit phylogeographic structuring of haplotypes, whereas these outputs and PCA results were incongruent with the morphological grouping. Phenetic features distinguishing the morphotypes were sometimes plastic and mismatched with the genotypes. The giant form was genetically close to the dwarf forms, contradicting the earlier notion that it descended from the middle-sized form. It may be assumed that the dwarf form evolved following sympatric speciation and adaptation to warm equatorial waters, while the focal features of the Western Arabian Sea guide toward allopatric speciation of the giant form.

Inter-cohort growth patterns of pharaoh cuttlefish Sepia pharaonis (Sepioidea: Sepiidae) in Eastern Arabian Sea

Sepia pharaonis is an important commercial species endemic to the tropical Indo-Pacific region. Despite its commercial significance, only few information on natural populations is available. This study was aimed to describe the aspects of size-composition, length-weight relationship, catch rates, seasonal recruitment and inter-cohort growth patterns of S. pharaonis population (Clade C), distributed along the Eastern Arabian Sea (South-West coast of India). For this, the Dorsal Mantle Length (DML) and weight of cuttlefishes was obtained from commercial trawl catches, from April 2002 to October 2006. Data was analyzed by normal length-weight methods such as von Bertalanffy. A total of 12 454 cuttlefishes, ranging in length from four to 41cm were analyzed. Size-composition patterns discriminated two pulses in recruitment to the fishery, discernible by a decrease in the monthly mean size of the population. The DMLs of the two seasonal cohorts were subjected to modalprogression analysis using the Bhattacharya’s method for the estimation of growth. The estimated parameters L∞ and K in von Bertalanffy Growth Function (VBGF) were used to model growth curves in length for the cohorts. The first cohort, (post-monsoon cohort) which supports the major fishery, was composed of mediumsized, fast growing individuals, whereas the second cohort (pre-monsoon cohort), comprised of slow growing and large-sized individuals. There were differential growth characteristics between the sexes and the life span was estimated at less than 2.3years for males and 2.1years for females. Negative allometric growth in weight (W) with length (L) was observed for males (W=0.33069.L2.5389) and females (W=0.32542.L2.6057). The females were heavier compared to males at any given mantle length, and the males were found to attain larger ultimate lengths. The major fishing season for cuttlefish was from May to November, when higher monthly catch rates of 1.67-13.02kg/h were observed in comparison with 0.03-0.85kg/h in December-April. Seasonal catch rates indicated a migratory life cycle of S. pharaonis between offshore and inshore coastal zones.

Sepia pharaonis es una importante especie endémica comercial del trópico Indo-Pacífico. A pesar de su valor comercial, hay muy poca información de sus poblaciones naturales disponible. En este estudio se describen aspectos como composición de tallas, relación longitud-peso, tasas de captura, reclutamiento estacional y patrones de crecimiento entre cohortes de la población (Clado C), distribuidos a lo largo del Mar Arábigo del Este (costa Suroeste de India). Se obtuvo la Longitud del Manto Dorsal (LMD) y el peso de las capturas de los arrastres comerciales, de Abril 2002 a Octubre 2006. Los datos fueron analizados mediante FiSAT y von Bertalanffy. Se capturó un total de 12 454 sepias, con una longitud entre 4-41cm. Los patrones de composición de tallas discriminaron dos pulsos en el reclutamiento de la pesquería, perceptibles por una disminución en el tamaño promedio mensual de la población. Los LMD de las dos cohortes estacionales se sometieron a un análisis de progresión modal mediante el método de Bhattacharya para la estimación del crecimiento. La primera cohorte (después de los monzones) mantiene la principal pesquería, se compone de individuos medianos de rápido crecimiento, mientras que el segundo grupo (pre-monzón) está compuesto por individuos de crecimiento lento y de gran tamaño. Se encontraron diferencias en las características de crecimiento entre sexos y la duración de vida útil se estima en menos de 2.3 años para machos y 2.1 años para hembras. Se observó crecimiento alométrico negativo entre el peso (W) y la longitud (L) para machos (W=0.33069. L2.5389) y hembras (W=0.32542.L2.6057). Las hembras fueron más pesadas en comparación con los machos en cualquier longitud de manto. La temporada de pesca más importante fue de mayo a noviembre, cuando se tuvieron las tasas de captura mensual más altas, de 1.67-13.02kg/h en comparación con 0.03-0.85kg/h entre diciembre y abril. Las tasas de captura estacional indican un ciclo de vida migratorio de S. pharaonis entre las zonas marinas y costeras de las áreas someras.

Biomarkers of environmental contaminants in field population of green mussel (Perna viridis) from Karnataka-Kerala coast (South West coast of India).

The green mussel Perna viridis was sampled from relatively clean and contaminated sites along the Kartanata-Kerala coast (south west coast of India) to study the tissue concentration of trace metals and biological responses to stress (biomarkers) such as sister chromatid exchange (SCE), chromosomal aberration, micronucleus (MN) test, hemic neoplasia (HN), Chromotest (Ames test) and comet assay. In general, mean tissue concentrations of toxic trace metals collected from 25 sampling sites were found to be below the World Health Organisation (WHO) permissible concentration given for seafood. The digestive gland extract of mussels from all 25 sampling sites showed negative reaction for mutagenic activity (Ames test) in the absence of metabolic activation. Very low levels of chromosomal aberration, SCE, MN, HN and comet cells were observed in mussels collected from both the urban associated and relatively clean sites. This study seems to indicate that that the coastal waters of Karnataka and Kerala are minimally contaminated with genotoxic and carcinogenic chemicals.

Monitoring trace metal contaminants in green mussel, Perna viridis from the coastal waters of Karnataka, southwest coast of India.

The green mussel (Perna viridis) is widely distributed in the coastal waters of Asia and is used in mussel watch programmes for monitoring environmental contaminants throughout the region. Green mussels representing different size groups and habitats were sampled from their natural beds at 28 locations in the inshore waters of Karnataka (southwest coast of India) to analyze the tissue concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. Tissue concentrations of Cr, Cu, Fe, and Pb were significantly higher in smaller mussels than in the larger size group. Significantly higher concentrations of Cr, Cu, Fe, Mn, and Ni were observed in mussels sampled from intertidal beds when compared to mussels from the subtidal beds. The sampling sites were categorized into industrial sites (IS), urban sites (US), and nonurban sites (NS) based on principal component analysis of metal concentrations in mussel. Spatial variations in tissue concentrations of all metals were observed except for Zn. Generally, the levels of toxic trace metals like Pb, Cd, Ni, and Cr in the whole tissue of P. viridis were within safe limits throughout the coast of Karnataka. However, relatively high concentrations of Cd, Cr, and Pb were observed in the whole tissue of green mussels collected from the industrial sites (IS), which may be derived from a variety of anthropogenic activities.