Early life history of the eastern Korean tetraploid spined loach, iksookimia yongdokensis (Pisces: Cobitidae)

Abstract. We investigated whether tetraploidy in Iksookimia yongdokensis adds more species specific variation in its early life history characteristics. To this end, morphological and temporal characteristics were analysed using artificial fertilisation and laboratory culture, and the results were compared to seventeen other species of the family Cobitidae. Extensive comparison of these characteristics among the cobitid species showed that tetraploid I. yongdokensis was apparently longer in egg diameter (1.54 ± 0.08 mm), hatching size (5.8 ± 0.15 mm in total length), and time to hatching (65 hours after fertilisation) than the other diploid cobitid species. With respect to these characteristics, I. yongdokensis was most similar to the congeneric species of Iksookimia (except I. pacifica). Next closest in similarity, were the other two species of different genera, Kichulchoia brevifasciata and Cobitis takatsuensis. Notably, all of the species with similar characteristics to I. yongdokensis were coincident in that they prefer a similar habitat, that being a bottom of pebbles and cobbles in middle to upper streams. In conclusion, the present study indicates that characteristics of the early life history of cobitid species are associated with both taxonomic closeness and habitat type.