Tanakia signifer BERG, 1907

Korean Bitterling

SynonymsTop ↑

Acheilognathus signifer Berg, 1907

Etymology

Tanakia: named for Shigeho Tanaka (1878-1974), an “accomplished” ichthyologist from the Imperial University of Tokyo, in combination with the Latin suffix -ia, meaning ‘belonging to’.

signifer: from the Latin signum, meaning ‘mark, sign’, and -fer, from fero, meaning ‘to bear or have’, probably in reference to the broad whitish marginal band on the dorsal fin.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Endemic to the Korean peninsula where it occurs in southern North Korea and northern South Korea. It is considered endangered in the latter, where it occurs only in the Han river system, and many populations have already been extirpated.

Type locality is ‘Pungtung, Korea’, which appears to refer to a locality now located in Kangwon province, North Korea.

Habitat

Typically occurs in cool, clean, relatively shallow water flowing over substrates of coarse sand or gravel, and with vegetated margins.

Maximum Standard Length

65 – 75 mm.

Reproduction

Bitterlings (see ‘Notes’) exhibit an unusual spawning symbiosis in which the interlamellar spaces of the paired inner and outer gills of living unionid mussels are used as a spawning substrate.

During the reproductive period females develop a long ovipositor which is used to deposit eggs through the mussel’s exhalant siphon. Males then move in to males release milt into the mussels’ inhalant siphon in order to fertilize them while aggressively defending the area against other males. The embryos and emergent fry possess characteristic morphology, physiology, and behaviour, which enables them to remain in the host mussel until they swim free after 2-6 weeks, depending on species.

Adult females tend to spawn in more than a single mussel during each spawning season, and multiple clutches from several females of one or more bitterling species may be hosted in a single mussel.

Although most bitterlings spawn in spring a few Acheilognathus species do so in autumn, with the hatched embryos exhibiting arrested development during winter. Studies suggest this to represent a genetically determined diapause and that all species adopting this strategy evolved from a common ancestor.

In terms of host selection some bitterlings are species-specific whereas others are not. A. signifer is known to utilise at least two species, for example.

NotesTop ↑

This species is not traded for ornamental purposes but captive populations are maintained in South Korea, at least.

In the orginal description it is diagnosed by lacking a dark marking at the upper extremity of the operculum, lacking longitudinal dark bands on the body and caudal-fin, possessing a deep brown dorsal-fin with marginal white band, an anal-fin with several longitudinal cross bars, and blackish ventral fins.

The genus Acheilognathus contains at least 39 valid species and is thus the most diverse within the nominal subfamily Acheilognathinae (see below). Members of Acheilognathus are identified by the following combination of shared characters: body compressed, rhomboid, or moderately elongate; depth of body almost 2/3 in its standard length; head small, its length about 1/2 in body depth; lateral line complete or incomplete; barbels absent or present; branched dorsal-fin rays 8–18, branched anal-fin rays 7–14; number of branched dorsal-fin rays minus number of branched anal-fin rays –1-5; serration of pharyngeal teeth developed; two white transverse bands on dorsal-fin rays in both males and females; diploid chromosome number 42 or 44; wing-like yolk sac projection not developed.

Acheilognathins comprise a group of fishes most commonly referred to as bitterlings, the majority of which are found in eastern Asia with two in Europe. Although the taxonomical composition of this assemblage has been a subject of debate, most researchers now agree that there are three genera; Acheilognathus, Rhodeus, and Tanakia. The number of species is less certain with conflicting estimates ranging from 45-70.

Preliminary genetic research suggests the existence of two major clades, one comprising a monophyletic Acheilognathus and the other Rhodeus and Tanakia, both of which are probably paraphyletic.

All bitterlings reproduce using bivalve mussels as an intermediate host for eggs and fry, and this is a particular conservation concern given the ongoing deterioration of freshwater habitats throughout their range since these hosts typically require good water quality.

References

1. Berg, L. S., 1907 - Annals and Magazine of Natural History (Series 7) v. 19: 159-163
   Description of a new cyprinoid fish, Acheilognathus signifer, from Korea, with a synopsis of all the known Rhodeinae.
2. Cheng, P., D. Yu, S. Liu, Q. Tang, and H. Liu, 2014 - Zoological Science 31(5): 300-308
   Molecular Phylogeny and Conservation Priorities of the Subfamily Acheilognathinae (Teleostei: Cyprinidae).
3. Kawamura, K. and K. Uehara, 2005 - Journal of Fish Biology 67(3): 684-695
   Effects of temperature on free‐embryonic diapause in the autumn‐spawning bitterling Acheilognathus rhombeus (Teleostei: Cyprinidae).
4. Kawamura, K., T. Ueda, R. Awai, and C. Smith, 2014 - Zoological Science 31(5): 321-329
   Phylogenetic Relationships of Bitterling Fishes (Teleostei: Cypriniformes: Acheilognathinae), Inferred from Mitochondrial Cytochrome b Sequences.
5. Reichard, M., J. Bryja, M. Polačik, and C. Smith, 2011 - Molecular Ecology 20(17): 3631-3643
   No evidence for host specialization or host‐race formation in the European bitterling (Rhodeus amarus), a fish that parasitizes freshwater mussels.