Chromosomes of four species of dobsonflies, in the genus Protohermes (Megaloptera, Corydalidae, Corydalinae) from East Asia.

Abstract

We analyzed chromosomes of four species of East Asian dobsonflies (Megaloptera: Corydalidae): Protohermesgrandis (Thunberg, 1781), P.immaculatus Kuwayama, 1964, P.disjunctus Liu, Hayashi et Yang, 2007 and P.costalis (Walker, 1853). The chromosome number in all species was 2n = 24, consisting of 11 pairs of autosomes plus the XX chromosomes in females and the Xy_p in males. The karyotype of P.immaculatus which occurs in near the central part of the Ryukyu Islands, and is a vicarious species of P.grandis, was similar to the karyotype of P.grandis. On the other hand, the karyotype of P.disjunctus, which is from the Sakishima Islands, and is a vicarious species of P.costalis, resembled that of P.costalis. The X chromosomes are submetacentric, while the Y is the smallest, dot-like chromosome of the set. The sex chromosomes of the first meiotic metaphase (MI) spermatocytes in all species invariably appear as a bivalent-like structure known as parachut bivalents Xy_p, suggesting that the species in this genus share a common sex-bivalent mechanism.