A part of the Japan Sea form of the threespine stickleback, Gasterosteus aculeatus, spawns in the seawater tidal pools of western Hokkaido Island, Japan

Abstract

SynopsisThe Japan sea form of the threespine stickleback, Gasterosteus aculeatus, was found to spawn in the seawater tidal pool of the Cape Benkei, western Hokkaido Island, Japan, in 2001 and 2003. Nest-guarding males, adult females and juveniles of this form were also observed in four tidal pools of the Capes Benkei, Kabuto and Kamui, in 2001-2003. Otolith Sr:Ca ratios in sticklebacks collected from these tidal pools were relative high from the core to the edge, suggesting they lived in seawater environments throughout its life cycle. These findings suggest that a part of the Japan Sea form's individuals in western Hokkaido Island have the potential to breed in the coastal sea and the life history style has evolved in dependence on the seawater environment.2

Migratory history of the giant mottled eel (Anguilla marmorata) in the Bonin Islands of Japan

“…2004b) and Salvelinus leucomaenis (Arai & Morita 2005); and sticklebacks, Gasterosteus aculeatus (Arai et al. 2003a; Kume et al. 2006) and Pungitius pungitius (Arai & Goto 2008).…”

Sea‐run migratory behaviour in the Japan Sea form of three‐spined stickleback Gasterosteus aculeatus in the tidal pool of eastern Hokkaido Island, Japan

“…In addition, salinity in this tidal pool was relatively high (average 30). The Japan Sea form inhabited and bred in relatively high salinity environments (Kume et al , 2005, 2006), such as the seawater tidal pools of western Hokkaido Island, during the breeding season (Kume et al , 2006) but not during the non‐breeding season (T. Kuwahara & M. Kume, unpubl. data), suggesting the sea‐run individuals had left the tidal pools.…”

The genomic landscape at a late stage of stickleback speciation: high genomic divergence interspersed by small localized regions of introgression

“…Reasons for this population growth remain unclear but it is surprising, particularly since G. nipponicus is unable to colonise freshwater environments [42,58], which might be expected to increase effective population size due to meta-population dynamics. A possible explanation is that a lack of dependence on freshwater for spawning [41,62,63] and greater foraging efficacy on marine prey [42] means G. nipponicus is better adapted for exploiting an abundant marine environment Unidirectional mitochondrial introgression might also be caused by female mate choice [64], Our previous behavioural studies indicate that Japan Sea females often mate with Pacific Ocean males, while Pacific Ocean females rarely mate with Japan Sea males [36,37], Hybrid females from Japan Sea female and Pacific Ocean male crosses are fertile [37] and will carry Japan Sea mitochondrial DNA. Backcrossing of these hybrids to Pacific Ocean males would result in unidirectional mitochondrial introgression from the Japan Sea to Pacific Ocean.…”

“…Reasons for this population growth remain unclear but it is surprising, particularly since G. nipponicus is unable to colonise freshwater environments [42,58], which might be expected to increase effective population size due to meta-population dynamics. A possible explanation is that a lack of dependence on freshwater for spawning [41,62,63] and greater foraging efficacy on marine prey [42] means G. nipponicus is better adapted for exploiting an abundant marine environment. Unidirectional mitochondrial introgression might also be caused by female mate choice [64].…”