One specimen (38.3 mm SL) of Neoclinus lacunicola Fukao, 1980, belonging to the family Chaenopsidae, was first recorded from Ulleung Island, Korea (East Sea, otherwise known as the Sea of Japan) on 5 January 2021. This species was characterized by paired external pores of incomplete lateral line running from the upper margin of the opercle, seven pairs of supraorbital cirri arranged in two rows, occipital region with a pair of cirri, and 13 rays of pectoral fin. This species is morphologically similar to the Neoclinus toshimaensis Fukao, 1980, but differs in the number of cirri on the supraorbital (6–7 versus 9–11 cirri). This study documents the first report of N. lacunicola in Korean waters and proposes the new Korean name of ‘eol-lug-bi-neul-be-do-la-chi’ for the species. For the confirmation of the identity of the species, a partial gene sequence of the mt COI (570 bp) of N. lacunicola was obtained for the first time.

Neoclinus species, tube blenny, new record, rocky shore, East Sea, Sea of Japan

The family Chaenopsidae comprises 96 species belonging to 14 genera distributed worldwide, with one genus and eight species occurring in Japanese waters (Aizawa and Doiuchi 2013; Nelson et al. 2016), but only two species representing a single genus have recently been recorded in Korean waters (Kim and Kang 1991; Myoung et al. 2021). The tube blennies (Chaenopsidae) are reef-associated marine fishes, mainly distributed in warm North and South American waters (Nelson et al. 2016). Generally, small-sized, usually elongated and compressed, with a large mouth. The supraorbital and nasal cirri are present or absent (Murase et al. 2015). They exhibit a hiding behavior in crevices between rocky matrices, but occasionally inhabit empty gastropod shells (empty barnacles and empty worm shells) (Stephens and Springer 1971; Fukao 1980; Fukao and Okazaki 1987). Such behavior is advantageous to protect their bodies from potential predators and to care for their spawned eggs within the habitats (Murase and Sunobe 2011; Froese and Pauly 2020).

Neoclinus lacunicola Fukao, 1980 was firstly reported as a new species in 1980 (Fukao 1980) and later, several studies have reported on the taxonomic checklists, phylogeny, and encyclopedic information (Patzner et al. 2009; Aizawa and Doiuchi 2013; Lin and Hastings 2013; Soniyama et al. 2020). However, there is still a lack of information on its biology and ecology.

To date, one species of tube blennies, i.e., Neoclinus bryope (Jordan et Snyder, 1902) has firstly been reported in Korean waters (Kim and Kang 1991) and, more recently, Myoung et al. (2021) documented the first record of Neoclinus chihiroe Fukao, 1987 in Dokdo, Korea; consequently, a total of two species have been recorded in Korean waters. This study provides the first record of an additional chaenopsid species (N. lacunicola) collected from Ulleung Island, describes its morphological characteristics, and records its mitochondrial DNA cytochrome c oxidase subunit I (mt COI) sequences.

One specimen of N. lacunicola was collected from Tonggumi (37°27′33.50′′N, 130°51′28.84′′E) in the coastal waters of Ulleung Island, Gyeongsangbuk-do, Korea (East Sea, otherwise known as the Sea of Japan), by a SCUBA diver on 5 January 2021 (Fig. 1). Sampling was conducted at a depth of approximately 22 m, close to the shoreline during the day and the sample was transported to the laboratory immediately after capture in a living condition, using a small fishbowl with seawater. In the laboratory, an image of the specimen was taken, it was euthanized and then meristic counts and body morphometrics were recorded following the method of Hubbs and Lagler (1958). The specimen was measured to the nearest 0.1 mm using digital Vernier calipers and a microscope. The specimen was then preserved in 5% formalin for 24 h and later transferred to 70% ethanol for depositing at the Marine Biodiversity Institute of Korea (MABIK).

Figure 1. 

Map showing the sampling area of Neoclinus lacunicola from Tonggumi, Ulleung Island, Korea.

To compare molecular data, total genomic DNA was extracted from the muscle tissue using 10% Chelex resin (Bio-Rad, Hercules, CA). A portion of the mitochondrial COI gene was amplified using universal primers (Ward et al. 2005). PCR was performed in a 20 µL reaction tube containing 1 µL genomic DNA, 2 µL 10× PCR buffer, 2 µL 2.5 mM dNTP, 1 µL of each primer, 0.1 µL Ex-Taq DNA polymerase, and 12.9 µL sterile distilled H₂O, using a thermal cycler (MJmini PTC-1148, Bio-Rad USA). The PCR profile consisted of initial denaturation at 95°C for 5 min, followed by 34 cycles of denaturation at 95°C for 1 min, annealing at 50°C, extension at 72°C for 1 min, and a final extension at 72°C for 5 min. PCR products were purified using ExoSAP-IT (United States Biochemical Corporation USA) and sequenced, using an ABI PRISM BigDye Terminator v.3.1 Ready Reaction cycle sequencing kit (Applied Biosystems Inc. USA) on an ABI 3730xl DNA analyzer (Applied Biosystems Inc.). We compared our molecular data with those of the mtDNA COI sequences from other Neoclinus species obtained from GenBank (National Center for Biotechnology Information, www.ncbi.nlm.nih.gov). Sequences were aligned using ClustalW (Thompson et al. 1994) in BioEdit, version 7 (Hall 1999). The genetic divergences were calculated using the Kimura 2-parameter (K2P) (Kimura 1980) model with Mega 6 (Tamura et al. 2013). Phylogenetic trees were constructed using the neighbor-joining method (Saitou and Nei 1987) in Mega 6 (Tamura et al. 2013), with confidence assessed, based on 1000 bootstrap replications.

In this study, one specimen of chaenopsid fishes has been collected from Ulleung Island with body elongated and compressed, no scales, supraorbital and nasal cirri present (Williams 2003; Nelson et al. 2016). The body morphometrics of the specimen were well matched with the original description of N. lacunicola with paired external pores of the incomplete lateral line, seven pairs of supraorbital cirri, occipital region with a pair of cirri, and 13 rays of pectoral fin (Fukao 1980; Aizawa and Doiuchi 2013). There are some differences between the presently reported specimen and that described by Fukao (1980); the differences were mainly the anal origin to pelvic insertion and slightly shorter length of caudal peduncle and longest pectoral ray length. Nonetheless, it is consistent with original descriptions with the main features of no black spot between first and second dorsal spines, occipital region with a pair of cirri, and seven pairs of supraorbital cirri (Fukao 1980; Aizawa and Doiuchi 2013; Murase et al. 2015). The body morphology of N. lacunicola is almost similar to Neoclinus toshimaensis Fukao, 1980, but distinctly different in the number of supraorbital cirri (6~7 in N. lacunicola vs. 9~11 in N. toshimaensis) (Fukao 1980; Aizawa 2002; Aizawa and Doiuchi 2013). The findings of two chaenopsids of the genus Neoclinus, namely, N. bryope and N. chihiroe were recently reported from Korean waters (MABIK 2020; Myoung et al. 2021). Neoclinus lacunicola is easily distinguished from the other two by lacking the black spot between first and second dorsal spines (without a black spot in N. lacunicola vs. with black spot in N. bryope and N. chihiroe) (Fig. 2B) (Aizawa 2002; Aizawa and Doiuchi 2013). The specimen collected in this survey had a black spot in the membrane of the second and third dorsal spines. This morphological character i.e., the presence or absence of a black spot between first and second dorsal spines, is one of the things that distinguish between males and females of Neoclinus monogrammus Murase, Aizawa et Sunobe, 2010 (see Murase et al. 2010) and it cannot be classified as Neoclinus species according to the taxonomic key suggested by Aizawa and Doiuchi (2013). For the presently reported specimen, yellow pelvic fins are key to distinguishing it as a female, despite the presence of black spots in the second and third dorsal spines membrane (Murase et al. 2015). Therefore, the presence or absence of the black spot is thought to be more variable in the same species than previously considered. In addition, our specimen was well distinguished from Neoclinus nudus Stephens et Springer, 1971 and N. bryope was well separated from other congeners by genetic distances (d) of range 0.141 and 0.191 when a comparison of mitochondrial DNA COI sequences is made (Fig. 3). Therefore, this study documents the first record of N. lacunicola in Korean waters and suggests the new Korean name of ‘eol-lug-bi-neul-be-do-la-chi’ for the species.

Chaenopsid fishes, occurring in Korean waters, have previously been known only as two species (N. bryope and N. chihiroe), but an additional species has now been reported through this study. The ecological characteristics of chaenopsid fishes are known that they do not have large movements and inhabit small caves between rocks or in empty gastropod tubes (Stephens and Springer 1971; Fukao and Okazaki 1987; Fukao 1990). Due to this characteristic, their distribution ranges are expected to be considerably narrow (Hongjamrassilp et al. 2020). However, although the mobile abilities are limited within the habitat ranges, their larvae have potential dispersal possibilities through the oceanographic processes, including currents (Murase et al. 2015). According to Murase et al. (2015), the distribution range of N. lacunicola has been extended northwards along with the Tsushima Current and this study confirmed such northern distribution of the species. Although this species has firstly been reported to Korean waters, it is also expected that a number of individuals live in eastern Korean waters as well as Dokdo. In addition, because of the scarcity and the narrow habitat range of the species, there is a need for more ecological information, including their genetic group structure, geographic distribution range, and larval dispersals.

We are grateful to Mr. Min-Su Woo and Mr. Jin Young Shin, Korea Institute of Ocean Science and Technology for their assistance with sampling. This research was funded by the Korea Institute of Ocean Science and Technology (grant numbers PE99913, PN90190). This work was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2020R1F1A1051773).