M. Harikrishnan

A molecular approach towards the taxonomy of fresh water prawns Macrobrachium striatum and M. equidens (Decapoda, Palaemonidae) using mitochondrial markers.

Abstract Genus Macrobrachium includes freshwater prawns which inhabit most diverse habitats ranging from low saline areas to inland hill streams and impounded water bodies. Being morphologically conserved, this genus has been exposed to severe disputes related to their taxonomy, systematics and phylogeny. Macrobrachium striatum and M. equidens represent two morphologically related congeneric species within this genus. Earlier, M. striatum was considered as a striped form of M. equidens. Though these species are now well-described morphologically and differentiated into two species, no molecular level investigation has been carried out in support of their speciation. We report a study on M. striatum and M. equidens with emphasis to their molecular data through mitochondrial markers (16S ribosomal RNA and cytochrome oxidase subunit I). Results obtained from developed molecular markers of the two species revealed considerable genetic differentiation between them. Phylogram generated using Minimum evolution and Neighbour joining analyses differentiated M. striatum and M. equidens as two independent species. Genetic distance data showed high interspecific divergence (ranging from 3.9% to 17.0% for 16S rRNA sequences and 13.8% to 21.0% for COI sequences) between M. striatum and M. equidens confirming the findings of phylogram. Hence, it could be delineated that M. striatum and M. equidens represent two distinct species within genus Macrobrachium with emphasis to their morphology and genetics.

Reassessing the species status of Pseudodiaptomus malayalus Wellershaus, 1969 and P. binghami Sewell, 1912 (Calanoida: Pseudodiaptomidae) from India based on morphology and mitochondrial cytochrome oxidase I gene sequences

Abstract Pseudodiaptomus binghami Sewell, 1912 was first described from the Rangoon River (now Yangon River) estuary, Myanmar. Pseudodiaptomus malayalus Wellershaus, 1969 previously known as P. binghami malayalus, is a typical brackish-water calanoid copepod from Cochin Estuary, Kerala. Morphological examination of P. malayalus and P. binghami collected from Cochin Estuary and the Nambur canal in Andhra Pradesh revealed crucial differences between the two congeners. Female specimens of P. malayalus exhibited marked differences from those described by Wellershaus. They are (1) the number of terminal spines on P5, (2) ornamentation of GS, (3) ornamentation of Ur1–4, (4) length ratio of the Ur and CR segments and (5) length:width ratio of the CR setae. Furthermore, significant and discrete morphological differences were observed between the two Indian species in their P5 and urosome. But the male specimens of P. malayalus did not show any major differences from the original description. In addition, distance matrix data revealed 22% interspecific divergence values which in turn confirmed the status of P. malayalus and P. binghami as two distinct species.

Evolutionary history of genus Macrobrachium inferred from mitochondrial markers: a molecular clock approach

Abstract Caridea, an infraorder of shrimps coming under Pleocyemata was first reported from the oceans before 417 million years followed by their radiation recorded during the Permian period. Hitherto, about 3877 extant caridean species were accounted within which one quarter constitute freshwater species. Freshwater prawns of genus Macrobrachium (Infraorder Caridea; Family Palaemonidae), with more than 240 species are inhabitants of diverse aquatic habitats like coastal lagoons, lakes, tropical streams, ponds and rivers. Previous studies on Macrobrachium relied on the highly variable morphological characters which were insufficient for accurate diagnosis of natural species groups. Present study focuses on the utility of molecular markers (viz. COI and 16S rRNA) for resolving the evolutionary history of genus Macrobrachium using a combination of phylogeny and timescale components. It is for the first time a molecular clock approach had been carried out towards genus Macrobrachium in a broad aspect with the incorporation of congeners inhabiting diverse geographical realms including endemic species M. striatum from South West coast of India. Molecular results obtained revealed the phylogenetic relationships between congeners of genus Macrobrachium at intra/inter-continental level along with the corresponding evolutionary time estimates.

Fish meal replacement with squilla (Oratosquilla nepa, Latreille) silage in a practical diet for the juvenile giant freshwater prawn, Macrobrachium rosenbergii de man, 1879

Replacement of fish meal with squilla silage in practical diet for the juvenile giant freshwater prawn, Macrobrachium rosenbergii, was evaluated. Five iso-nitrogenous and iso-caloric diets were prepared in which protein requirements were met with 100% fish meal (control, diet 1) and squilla silage replacing fish meal at 25, 50, 75 and 100% (diets 2, 3, 4 and 5, respectively). Water stability and water absorption of five feeds revealed significant differences (P < 0.05). The weight gain varied between a maximum of 248.50 ± 34.07% in diet 4 to lowest 132.45 ± 14.34% in diet 1. The average daily gain in weight in grams varied from 0.091 ± 0.01 (diet 5) to 0.154 ± 0.04 (diet 3), whilst the specific growth rate and gross growth coefficient values were recorded highest in diet 4. Highest survival rates (86.66 ± 5.77%) were recorded in both experimental diets 4 and 5. Low feed conversion ratio of 1.19 ± 0.21 was recorded from diet 4, whilst the highest value of 2.16 ± 0.09% was estimated from the diet 5. Proximate carcass composition showed highest crude protein content in post-larvae fed with diet 5 (47.24%) in contrast to lowest diet 1 (36.12%). Lipid values fluctuated significantly between 2.45 and 7.18% (P < 0.05) between treatments. The ash content significantly increased from diet 1 (16.34%) to diet 5 (20.69%) (P < 0.05). Highest feed efficiency (gain/feed) value was recorded in diet 4 (1.52 ± 0.22), whilst the diet 5 showed lowest value (0.99 ± 0.06). The results suggested that squilla silage can be utilised up to 75% of the protein in prawn diets for fish meal replacement.

Morphological and molecular identification of marine copepod Dioithona rigida Giesbrecht, 1896 (Crustacea:Cyclopoida) based on mitochondrial COI gene sequences, from Lakshadweep sea, India

Abstract Morphological identification of the marine cyclopoid copepod Dioithona rigida in combination with sequencing a 645 bp fragment of mitochondrial cytochrome oxidase c subunit I (mtCOI) gene, collected from offshore waters of Kavarathi Island, Lakshadweep Sea, is presented in this study. Kiefer in 1935 classified Dioithona as a separate genus from Oithona. The main distinguishing characters observed in the collected samples, such as the presence of well-developed P5 with 2 setae, 5 segmented urosome, 12 segmented antennule, compact dagger-like setae on the inner margin of proximal segment of exopod ramus in P1–P4 and engorged portion of P1-bearing a spine, confirmed their morphology to D. rigida. A comparison of setal formulae of the exopod and endopod of D. rigida with those recorded previously by various authors are also presented here. Maximum likelihood Tree analysis exhibited the clustering of D. rigida sequences into a single clade (accession numbers KP972540.1-KR528588.1), which in contrast was 37–42% divergent from other Oithona species. Further intra-specific divergence values of 0–2% also confirmed the genetic identity of D. rigida species. Paracyclopina nana was selected as an out group displayed a diverged array. The present results distinctly differentiated D. rigida from other Oithona species.

Re-description of Lysirude channeri (Decapoda Crustacea: Raninidae) from Bay of Bengal, Indian Ocean

Frog crabs (Family Raninidae) are cryptic, burying marine brachyuran crabs adapted for inhabiting soft and sandy bottoms across a wide bathymetric range of tropical to low-latitude temperate regions. The present account encompasses re-description of Lysirude channeri from a depth range of 614–655 m in Bay of Bengal, India. Morphological examination of 76 specimens agreed with earlier type descriptions in having two antero-lateral spines, but this contradicts with the specimens from the South China Sea and off the Philippines. In addition, some specimens from the present study revealed the presence of two carpal spines instead of one described before. However, the genetic congruency of the collected specimens were inferred by developing molecular marker viz. mitochondrial cytochrome oxidase subunit I (mtCOI) gene sequences, representing the first molecular data for Lysirude channeri . Phylogram and genetic distance data (up to 0.60%) justified the genetic congruency of Lysirude channeri as well as the interspecific divergence (up to 15.2%) between Lysirude channeri and Lyreidus brevifrons . Hence, the present study provides complete morphological and molecular data for re-describing the frog crab Lysirude channeri and also delineates its speciation from other related brachyuran crabs.

Reproductive traits of deep-sea armoured shrimp, Glyphocrangon investigatoris from Bay of Bengal, Indian Ocean

Details on size at first maturity, embryo number and size, brood chamber volume and reproductive output of deep-sea armoured shrimp, Glyphocrangon investigatoris caught off the south-east coast of India by using EXPO trawl from 633 m depth in FORV ‘Sagar Sampada’ are reported here. Eighty-four female shrimps ranging from 17.29–36.31 mm carapace length and 2.28–16.54 g weight formed 7.73% of total catch, 30% of which was constituted by embryo-bearing females. Regression of weight on carapace length revealed negatively allometric growth (r 2 = 0.85, P

Morphological and molecular description for Glyphocrangon investigatoris Wood-Mason & Alcock, 1891 emphasizing its phylogenetic relationship

Abstract Genus Glyphocrangon, the only representative of Family Glyphocrangonidae, comprises about 89 species. According to previous records, this species is known to inhabit a depth range of 145–410 fathoms in Bay of Bengal. A thorough scrutiny of literature revealed a detailed morphological description of G. investigatoris and little molecular database. As part of an exploratory research survey conducted in Bay of Bengal, specimens of this species were collected from trawl catches off Paradeep, Orissa. In our present study, an attempt was made to develop its DNA barcode based on mitochondrial Cytochrome oxidase subunit I (mtCOI) and to establish its phylogenetic relationship with other species of genus Glyphocrangon. The developed mtCOI sequences of G. investigatoris exhibited its genetic identity favoring its morphological description.