Ontogenetic trajectory and allometry of Diplonychus rusticus (Fabricius), an Oriental aquatic bug (Hemiptera: Belostomatidae) from the Western Ghats of India.

Despite being one of the dominant groups in freshwater ecosystems, morphological and ontogenetic studies on aquatic Hemiptera have received little attention in the Oriental region. We present the ontogenetic trajectory and allometry of the widespread Oriental belostomatid species, Diplonychus rusticus (Fabricius) for the first time. We have measured nine different morphological variables throughout the growth of the bug using both field captured and laboratory reared specimens. Our results suggest that the developmental instars can be distinguished by the size variables, as seen in the Principal Component Analysis. On the basis of a CHAID (Chi-squared Automatic Interaction Detection) based regression tree, we also show that the characters - total length without head and maximum width - prove to be adequate for effective instar identification. The multivariate allometric growth pattern shows that different body parts exhibit different types of allometry. This is apparent in the allometry exhibited by forelegs and mid and hind legs, which show allometry of opposite polarities. This may be due to the different functions attributed to these body parts. Our results show that the growth pattern in D. rusticus is comparable with the New World genus Belostoma, suggesting a conserved growth pattern in the family Belostomatidae.

First molecular phylogeny of scorpions of the family Buthidae from India.

Scorpions of the family Buthidae are widespread species in India. While studies are available on diversity and distribution of Indian buthid scorpions, no information is available on the phylogenetic relationships among the members of the family, within India and Asia in general. In the current study, we provide the first molecular phylogeny of buthid scorpions from central western India based on the mitochondrial cytochrome oxidase subunit I (COI) gene. Our analysis confirms the current placement of the species, previously assigned to Mesobuthus in the genus Hottentotta. However, the analysis also suggests that the member of this genus from India form a monophyletic group distinct from the members of Hottentotta from Africa. Species of Lychas formed a monophyletic group. Although Orthochirus was nested within the larger clade of buthidae comprising genera such as Androctonus, Buthacus, Buthus and Odontobuthus, the exact phylogenetic placement will require more taxonomic sampling of the known genera of Buthidae. We also show that there is a substantial genetic variation among the populations of medically important scorpion species Hottentotta tamulus, and the genetic distance is linearly correlated with the geographical distance between the populations.