The Korean shuttles mudskipper Periophthalmus modestus has paired olfactory organs on its snout, consisting of anterior and posterior nostrils, a single olfactory canal with sensory and nonsensory epithelia, and a single accessory nasal sac. Its sensory epithelium consists of numerous islets forming a pseudostratified layer and contains various cells: olfactory receptor neurons, supporting cells, basal cells, lymphatic cells (LCs), and axon bundles. The sensory epithelium is a stratified squamous layer comprising stratified epithelial cells, mucous cells (MCs) with glycogen, flattened cells (FCs), LCs, and unidentified cells. Specific structures are as follows: (a) a tubular anterior nostril projecting outward, (b) a slit posterior nostril, (c) an elongated olfactory canal, (d) an ethmoidal accessory nasal sac, (e) axon bundles found only in the basal layer of the sensory epithelium, (f) FCs only at the top of the nonsensory epithelium, and (g) glycogen‐containing MCs. Such structures seem to be unique in that they have not been observed in most teleost fishes spending their whole life in water.

Hybrid sterility is an inevitable phenomenon in the speciation process to avoid indiscriminate increases in species, but it is not always unconditional. We used computer assisted sperm analysis (CASA) to analyze sperm motility of Cobitis hankugensis, Iksookimia longicorpa, and their unisexual natural hybrids. In parental species, the sperm concentrations of C. hankugensis and I. longicorpa were 11.6 ± 4.8 × 10 9 and 16.5 ± 6.8 × 10 9 , respectively. For sperm motility, the total motility was higher in the parental species (C. hankugensis, 91.3%; I. longicorpa, 87.5%) than other hybrids. After 1 min, the motility duration was reduced to 14% in C. hankugensis and 3.3% in I. longicorpa. This result could indicate that the duration of sperm motility of C. hankugensis is longer than that of

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Background. During the course of evolution, numerous taxa abandoned canonical sex and reproduced asexually. Examination of the Cobitis hankugensis - Iksookimia longicorpa asexual complex already revealed important evolutionary discoveries tackling phenomena like interspecific hybridization, non-Mendelian inheritance, polyploidy and asexuality. Yet, as in other similar cases, the investigation is hampered by the lack of easily accessible molecular tools for efficient differentiation among genomotypes. Material and methods. Here, we tested the cross-species amplification of 23 microsatellite markers derived from distantly related species and investigated the extent to which such markers can facilitate the genome identification in non-model hybrid complex. Results. We found that 21 out of 23 microsatellite markers amplified in all genomotypes. Five of them could be used for easy diagnosticity of parental species and their hybrids due to species-specific amplification profiles. We also noted that three markers, i.e. IC654 and IC783 derived from Cobitis choii and Iko_TTA01 from Iksookimia koreensis, had dosage-sensitive amplification efficiencies of species-specific alleles. This could be further used for reliable differentiation of genome composition in polyploids. Conclusions. The present study introduces a noninvasive method applicable for diagnosis of ploidy and genome composition of hybrids, which are not clearly distinguished morphologically. We showed that very detailed information may be obtained even from markers developed in distantly related taxa.

No abstract