Biology subjects

Bhakat, S.

Publications and source records attributed to Bhakat, S..

7 recordsLinked to original sources

bioRxiv2020

Revision of Indian Bipaliid species with description of a new species, Bipalium bengalensis from West Bengal, India (Platyhelminthes: Tricladida: Terricola)

A new species of Bipaliid land planarian, Bipalium bengalensis is described from Suri, West Bengal, India. The species is jet black in colour without any band or line but with a thin indistinct mid-dorsal groove. Semilunar head margin is pinkish in live condition with numerous eyes on its margin. Body length (BL) ranged from 19.00 to 45.00mm and width varied from 9.59 to 13.16% BL. Position of mouth and gonopore from anterior end ranged from 51.47 to 60.00% BL and 67.40 to 75.00 % BL respectively. Comparisons were made with its Indian as well as Bengal congeners. Salient features, distribution and biometric data of all the 29 species of Indian Bipaliid land planarians are revised thoroughly. Genus controversy in Bipaliid taxonomy is critically discussed and a proposal of only two genera Bipalium and Humbertium is suggested.

zoology↗

bioRxiv2020

Deviation of Dyar's rule in the post-embryonic development in millipedes - a comprehensive analysis.

Dyars value on the basis of length and width of nine polydesmid and 15 non-polydesmid millipede species were calculated. The value of polydesmid millipede ranged from 1.50 to 1.78 and that of non-polydesmid millipede ranged from 1.08 to 1.45. Weight progression factor was determined for nine species of millipede (two polydesmid and seven non-polydesmids). The result showed that the mean weight progression factor in polydesmid is 2.54 while that of non-polydesmid is 1.95. Both the results showed that Dyars value in polydesmida is significantly higher compared to that of non-polydesmida. In polydesmida, the number of stadium is only eight with higher Dyars value (mean 1.61) while in non-polydesmida, where number of stadium is more than eight have lower Dyars value (mean 1.23). As in other arthropods, Dyars value is inversely proportional to the number of stadium in millipede. The present study also affirmed Enders hypothesis in favour of adaptive importance of Dyars rule. Deviations from Dyars constant in these two group also support Crossbys growth rule. The variation of Dyars value in these two groups of millipede is related to the development time and habitat utilization. The variation of weight progression factor in these two groups is also linked to the development time as observed in other arthropods.

zoology↗

bioRxiv2020

Population ecology of Trigoniulus corallinus (Gervais) (Diplopoda: Spirobolida).

A population of Trigoniulus corallinus (Gervis) in an open land rich in organic matter is studied for a year. Population density and biomass ranged from 2.13 to 56.31per m2 and 1026.38 to 8494.38 per m2 respectively. Various indices showed that population of T. corallinus is aggregated in distribution in the peak period of their abundance and this is due to patchy distribution of food, soil moisture and sexual attraction. Monthly age structure showed adult and late stadia are abundant in June, October and November while August population covered all the stadia. In the developmental stages, length and width progression factor of T. corallinus ranged from 1.11 to 1.98 (mean 1.43) and 1.10 to 1.56 (mean 1.31) respectively. Weight progression factor in female is higher compared to that of male and this may due to more accumulation of egg forming tissue in female. Population density and biomass is significantly correlated with minimum temperature and rainfall.

zoology↗

bioRxiv2020

Mating pattern, duration and multiple mating in Chondromorpha severini Silvestri (Diplopoda: Polydesmida).

Mating behaviour of Chondromorpha severini, a polydesmid millipede was studied in the field and in the laboratory condition. Copulating pair follows the general rule of love play before actual act of coitus. Mating duration varied from one to 25 minute with an average of eight minute. Mating frequency was maximum in early and late hours of day. In the multiple mate preference experiment, 10 pairs of male and female were used to calculate preference index (Pi) of individual sex. Preference index varies from 0.65 to 0.91. The implication of multiple mating has been discussed in detail. The study confirmed that i) the species belongs to polygynandrous mating system where males are the pursuers and females are the accomplishers ii) short and long duration mating is related to mate acquisition and mate guarding respectively

zoology↗

bioRxiv2020

A new species of Travassosinema (Oxyuridomorpha: Travassosinematidae) from an Indian millipede, Trigoniulus corallinus (Gervais)

Travassosinema bengalensis n. sp. is described from the hind gut of the spirobolid millipede, Trigoniulus corallinus (Gervais) from West Bengal, India. Females of the new species differ from the only known Indian species, T. travassosi Rao, 1958 by several characters namely tail length, length of oesophagous, size of egg, extension of umbraculum etc. It is very similar to other three species of Travassosinema, T. travassosi, T. thyropygi Hunt, 1996 and T. claudiae Morffe & Hasegawa, 2017 as all of them lack lateral alae and body contraction posterior to vulva. Except T. claudiae, it differs from all other species from millipedes by longest tail length (60% SL) and differs from T. claudiae by shorter oesophagous length and location of vulva. A new method for presentation of morphometric data (in percentage to standard length) in nematode is suggested. On the basis of phylogenetic analysis, it is suggested that umbraculum bearing genera, Indiana, Pulchrocephala should be excluded from the family Travassosinematidae.

zoology↗

bioRxiv2020

A new species of leaf fish, Nandus banshlaii (Perciformes: Nandidae) from West Bengal, India

Nandus banshlaii, sp. nov. is described from the Banshlai River of West Bengal. This species is distinguished from all its congeners in having a golden brown body in live and a combination of characters like longest head and snout length (44.28% SL and 35.58% HL respectively) and from its two Indian congeners in containing largest eye diameter (22.22% HL), longest pre-dorsal length (47.16% SL), shortest pectoral fin length (14.60% SL) and smallest dorsal fin base length (45.53% SL).Like all three congeners of Ganga-Brahmaputra-Meghna river basin of Gangetic delta it possess a dark spot on caudal peduncle. To differentiate the present species from other two Indian congeners of Nandus, N. nandus and N. andrewi, PCA and heatmap is performed and a key of all three species is also provided.

zoology↗

bioRxiv2020

Flap dynamics in pepsin-like aspartic proteases: a computational perspective using Plasmepsin-II and BACE-1 as model systems

The flexibility of a {beta} hairpin structure known as the flap plays a key role in catalytic activity and substrate intake in pepsin-like aspartic proteases. Most of these enzymes share structural and sequential similarity. In the apo form of the proteases, a conserved tyrosine residue in the flap region is in dynamic equilibrium between the normal and flipped states through rotation of the{chi} 1 and{chi} 2 angles. In this study, we have used apo Plm-II and BACE-1 as model systems. Independent MD simulations of Plm-II and BACE-1 remained stuck either in the normal or flipped state. Metadynamics simulations using side-chain torsion angles ({chi}1 and{chi} 2 of tyrosine) as collective variables sampled the transition between the normal and flipped states. Qualitatively, the two states were predicted to be equally populated. The normal and flipped states were stabilised by H-bond interactions to a tryptophan residue and to the catalytic aspartate, respectively. Further, mutation of tyrosine to an amino-acid with smaller side-chain, such as alanine, reduced the flexibility of the flap and resulted in a flap collapse (flap loses flexibility and remains stuck in a particular state). This is in accordance with previous experimental studies, which showed that mutation to alanine resulted in loss of activity in pepsin-like aspartic proteases. Our results suggest that the rotation of the tyrosine side-chain is the key movement that governs flap dynamics and opening of the binding pocket in most pepsin-like aspartic proteases.

biophysics↗