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

We analyzed chromosomes of four species of East Asian dobsonflies (Megaloptera: Corydalidae): <i>Protohermesgrandis</i> (Thunberg, 1781), <i>P.immaculatus</i> Kuwayama, 1964, <i>P.disjunctus</i> Liu, Hayashi et Yang, 2007 and <i>P.costalis</i> (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 <i>P.immaculatus</i> which occurs in near the central part of the Ryukyu Islands, and is a vicarious species of <i>P.grandis</i>, was similar to the karyotype of <i>P.grandis</i>. On the other hand, the karyotype of <i>P.disjunctus</i>, which is from the Sakishima Islands, and is a vicarious species of <i>P.costalis</i>, resembled that of <i>P.costalis</i>. 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.