Karyotypic and Morphometric Analysis of A Predatory Rove Beetle, Paederus littoralis (Coleoptera: Staphylinidae) from Jammu Region of Outer Himalayas, India

Published by Oriental Scientific Publishing Company © 2018 This is an Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/ ), which permits unrestricted Non Commercial use, distribution and reproduction in any medium, provided the original work is properly cited. Karyotypic and Morphometric Analysis of A Predatory Rove Beetle, Paederus littoralis (Coleoptera: Staphylinidae) from Jammu Region of Outer Himalayas, India

Beetles of family Staphylinidae are commonly known as rove beetles.It is one of the richest families of Coleoptera with species that are mostly predacious.More than 45000 species of Staphylinid beetles are known worldwide and possibly over 75% of tropical species are still not described 1 .These beetles have efficient role in biological control of cereal aphids 2 .The earliest karyological investigations on the beetles of family Staphylinidae were carried out by Stevens 3,4 .As lot of cytogenetic research work has been done on other families, little attention was paid on the chromosomal studies of family Staphylinidae and approximately 57 species are cytogenetically known today 5,6,7,8,9,10 .During present investigation chromosomal analysis was done to study karyomorphometrical and meiotic details of this beetle.

Material and Methods
Adult specimens of Paederus littoralis were collected from the agricultural fields of Talab Tillo area of Jammu region during April-May 2016.They were found in the soil due to their predatory habit, feeding on insects and other soft bodied invertebrates.Adult male beetles were used for present chromosomal studies.Slides were prepared by staining method described by Rozek 11 with some modifications.
Beetles were anesthetized and dissected on a clean glass slide to obtain their testes which are found in the last segments of the abdomen.Testis tissue was treated with 0.7% KCl for 10-15 minutes.After hypotonic treatment, few drops of freshly prepared Cornoys fixative (3:1 absolute methanol and glacial acetic acid) were poured on the tissue.Then the tissue was stained with a drop of 1% aceto-orcein stain.After few seconds the tissue was covered with a clean coverslip and then squashed by vertical pressure applied gently by the thumb.The temporary mounts were sealed with wax and later made permanent.Stained slides were scanned under Olympus camera aided microscope and results were photographed under CH20i BIMF microscope attached with Sony SSC-DC378P camera under 1000X magnification.
The karyomorphometrical analysis (table 1) of the spermatogonial metaphase complement showed the absolute length of autosomes to vary from 1.19ìm to 0.50ìm while the X and Y chromosome measured 0.65ìm and 0.10ìm respectively.All the chromosomes showed a gradual decrease in size.Meiotic observations included the stages diplotene, diakinesis and metaphase-I (fig.2).There were present fifteen autosomal bivalents in the form of thick condensed rods in diplotene stage (fig.2b).Diakinesis is represented by fifteen ring shaped autosomal bivalents with almost terminalized chiasmata (fig.2c).Sex pair was also visible in the form of a parachute.Metaphase-I showed highly condensed autosomal bivalents and a sex bivalent showing parachute configuration formed by a large X and  a small dot like y chromosome (fig.2d).The sex chromosomes showed specific parachute type morphology, the characteristic feature of most Coleopteran species represented by Xy p (fig. 2d).
The diploid chromosome number of this species was also confirmed through the diakinesis and metaphase-I stage (fig.2c,d) in which 15 autosomal bivalents and a sex bivalent (Xy p ) were recorded.

discussion
Paederus littoralis presented a diploid chromosome number of 2n=30+Xy p in males.The diploid chromosome number in family Staphylinidae varies from 2n=18 to 2n=56 7 .From the subfamily Paderinae, diploid chromosome number 2n=36 (n=17+Xy p ) has been found in Paderius rubrathoracicus but the sex mechanism was same as shown in the present studied species 12 .They also reported the presence of heteromorphic male sex pair in the form of a parachute during diplotene stage of meiosis-I.In genus Paederus the following chromosome numbers were recorded: n B& =10+Xyp in one species, n B& =14+Xyp in one species, n B& =15+Xyp also in one species and n B& =16+Xyp I four species 6,13,14 .conclusion Paederus littoralis showed diploid chromosome number 2n=32 in males.There were present 22 metacentric, 3 submetacentric, 6 subtelocentric and 1 telocentric chromosomes.Sex mechanism was found to be Xy p in which X is submetacentric and y as a rounded telocentric body.Meiosis represented by diplotene, diakinesis and metaphase-I stages.

acKnowledgeMents
Thanks are due to Prof. Seema Langer, HOD Zoology, University of Jammu for providing necessary lab facilities.