A new Pseudodiaptomus (Copepoda, Calanoida) from Korea supported by molecular data

Abstract

A new species, Pseudodiaptomus koreanus sp. nov. (Calanoida, Pseudodiaptomidae), which has so far been identified as P. inopinus Burckhardt, 1913, is described from Korean estuaries. This new species differs from P. inopinus in the broad and short posterior process of the female genital flap, rounded posteriocentral projection between the gonopores, presence of a posterodorsal spinule on the fifth pediger of the male, and a row of fine ventral spinules on the male second urosomite. The new species is also distinguishable from P. nansei Sakaguchi and Ueda, 2010 by the presence of a row of fine spinules along posterior margins of the second and third pedigers in both sexes, rounded posteromedial projectionbetween the gonopores, separation of ancestral segment XXI and compound segments XXII–XXIII of the male right antennules, and a row of fine ventral spinules on the male second urosomite.

Genetic analysis on <i>Pseudodiaptomus inopinus</i> (Copepoda, Calanoida) species complex in Japan: revival of the species name of <i>P. japonicus</i> Kikuchi, 1928

“…In the previous study, we called the two forms the Japan Sea group and the Pacific group, respectively. In the present study, however, we call the former the short-process form (henceforth, SP-form) and the latter the long-process form (henceforth, LP-form), because we subsequently found that the SP-form occurred not only along the Japan Sea coast but also along the Pa- , figure 2A-C, respectively; C, H and J, Soh et al (2012), figure 2C, 6B and 7C, respectively; I, K and L, Sakaguchi and Ueda (2010), figure 8C, 2C and 5E, respectively;D, Burckhardt (1913), figure 9 of plate 11F; E and F, Kikuchi (1928), figures 13 and 14 of plate 19, respectively. Arrowheads a, b and c indicate the posterior process of the genital operculum, the central part of the genital flap surrounding gonopores, and the tip of the distomedial process on the first exopodal segment, respectively.…”

“…However, some morphological differences can be found between the Korean and Japanese populations. Comparing the illustrations of P. koreanus by Soh et al (2012) with those of P. japonicus (as the Japan Sea group by Sakaguchi & Ueda 2011, and as P. inopinus by Sakaguchi & Ueda 2010), for example, the tip of the distomedial process on the first exopodal segment of the female fifth leg is round in P. japonicus (Fig. 1G) but more acute in P. koreanus (Fig.…”

“…The shape of the genital operculum is very similar in having short posterior processes and the genital flap triangularly surrounding the gonopores (Fig. 1A, C) (Sakaguchi & Ueda 2010, Soh et al 2012). However, some morphological differences can be found between the Korean and Japanese populations.…”

“…It has been suggested that P. inopinus is a species complex , Soh et al 2012. Sakaguchi & Ueda (2010) and Soh et al (2012) described P. nansei Sakaguchi & Ueda, 2010 from the Nansei Islands, southern Japan, and P. koreanus Soh et al, 2012 from Korea, respectively, both of which had so far been identified to P. inopinus. Soh et al (2012) suggested that the P. inopinus species complex includes further cryptic species.…”

“…Hence, we analyzed their genetic differences, using the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear ribosomal internal transcribed spacer 1 (ITS1) regions, the latter of which is more variable than the ITS2 region and was recommended for inter-population surveys of Pseudodiaptomus by Sabia et al (2017). Soh et al (2012) analyzed the same regions of P. koreanus, the species to be compared with the present specimens. The present paper describes the results of our genetic analyses and clarifies the taxonomic status of the P. inopinus species complex.…”