Divergence of ovipositor length and egg shape in a brood parasitic bitterling fish through the use of different mussel hosts

Abstract

Bitterling fishes deposit their eggs on the gills of living mussels using a long ovipositor. We examined whether ovipositor length (OL) and egg shape correlated with differences in host mussel species in the family Unionidae among populations of the tabira bitterling (Acheilognathus tabira) in Japan. Bitterling populations that use mussels in the sub‐family Anodontinae possessed longer ovipositors and more elongated eggs than those using mussels of Unioninae, as expected from the difference in host size between the sub‐families (anodontine mussels are larger than unionine mussels). Based on a robust phylogeny of A. tabira populations, we demonstrated that the evolution of both OL and egg shape were correlated with host differences, but not with each other, suggesting that these traits have been selected for independently. Our study demonstrates how adaptive traits for brood parasitism may diverge with host shift due to different host availability and/or interspecific competition for hosts.

Phylogenetic relationships of Acheilognathidae (Cypriniformes: Cyprinoidea) as revealed from evidence of both nuclear and mitochondrial gene sequence variation: Evidence for necessary taxonomic revision in the family and the identification of cryptic species

“…Acheilognathus tabira (endemic to Japan) is represented by five subspecies based on differentiation in morphological characters, coloration, and their geographic distributions. Discrimination among these subspecies was also observed in genetic data (Arai et al, 2007;Kitamura et al, 2012). In our analysis of samples of four of the five subspecies (A. t. tohokuensis not sampled) gene trees corroborated their sharing of a well-supported common lineage.…”

“…Previous phylogenetic studies of bitterlings have been limited in character and/or taxon sampling (Bohlen et al, 2006;Chang et al, 2009;Kitamura et al, 2012;Yang, Q. et al, 2011;Zhu and Liu, 2006). Bohlen et al (2006) proposed that Rhodeus in Europe was sister to the Asian species Rhodeus sericeus.…”

“…Fertilization occurs in the mussel gill cavity and development is completed in the host mussel gill chamber (Smith et al, 2004). This breeding association makes species of bitterlings a focus of research aimed at understanding coevolutionary dynamics, life-history evolution, sexual selection, sperm competition, development and mate choice (Agbali et al, 2011;Casalini et al, 2009;Kitamura et al, 2012;Mills et al, 2005;Reichard et al, 2006Reichard et al, , 2007Reichard et al, , 2012; .…”

Population-specific responses to an invasive species

“…Most bitterling fishes use several mussel species as hosts, but often express a preference for particular species [13]. Host mussel preference may vary among bitterling populations [14,15]. Hosting bitterling embryos is costly to mussels and they have evolved adaptations to eject bitterling eggs and embryos, mirrored by counter-adaptations in bitterling embryos to avoid ejection [14,16 -18].…”

Pseudo but actually genuine:Rhodeus pseudosericeusprovides insight into the phylogeographic history of the Amur bitterling

“…Acheilognathinae (bitterlings) is a taxonomic subfamily of approximately 60 small freshwater fish species that are divided into three genera: Acheilognathus, Tanakia, and Rhodeus (Arai & Akai 1988;Nelson 2006;Kitamura et al 2012). Over the last several decades, this subfamily has attracted scientific interest among evolutionary biologists due to the unique breeding behavior of its members, which includes obligate spawning in the gill cavities of living freshwater unionid and margaritiferid mussels (Smith et al 2004;Spence & Smith 2013).…”