One unusual species, Coilia sp. (Engraulidae, Pisces) from the Yellow Sea

Abstract

Four specimens of unknown Coilia sp. were collected for the first time from the Yellow Sea in 2008 and compared with Coilia mystus and Coilia nasus. Coilia sp. showed similar morphology to C. mystus and C. nasus, but differed in that its tail was considerably shorter. We conducted an analysis of the morphological and genetic characteristics in an effort to clarify the taxonomic position of Coilia sp. In counts and measurements, Coilia sp. were well distinguished from C. nasus by the number of scutes (42–44 in Coilia sp. vs. 40–45 in C. mystus vs. 45–55 in C. nasus), ratio of dorsal base length to head length (43.4–47.6 vs. 37.9–47.6 vs. 33.0–41.0), and eye length to head length (19.2–20.8 vs. 17.0–22.4 vs. 13.8–18.2). In caudal skeleton of Coilia sp., urostyle, hypural and epural bones were not observed; instead of them, caudal fin rays were supported by the last vertebra, neural and haemal spines' extension. The molecular phylogenetic relationship was analyzed using 414 base-pair 12S rRNA mitochondrial DNA sequences. The Kimura-2-parameter distance between Coilia sp. and C. mystus was 0.3%, but was 1.3% between Coilia sp. and C. nasus. Both the neighbor-joining tree and maximum-likelihood tree showed that Coilia sp. are closely clustered with C. mystus. Therefore, our results suggest that the Coilia sp. may be a deformed fish of C. mystus.