Three specimens of a rare labrid, Suezichthys notatus (Kamohara, 1958) were recently collected from local markets, which were captured from deep-water off northern and southwestern Taiwan, and represent a new record for Taiwan. Suezichthys notatus can be distinguished from its congeners by a combination of characters: scale rows above lateral line 2½; low scaly sheath present at base of dorsal and anal fins; dorsal-fin element IX, 11; anal-fin elements III, 10; lateral line scales 25‒26, each with simple, unbranched laterosensory canal tube; cheek scale rows behind and below eye 2 and 2‒3 respectively; a group of prominent dark blotches extending from the interorbital region dorsoposteriorly; body depth at dorsal-fin origin 3.7‒3.9 in standard length; short pelvic fin without filamentous extension, 2.2‒2.5 in head length. Suezichthys resembles the labrid genus Pseudolabrus, comparison of Taiwanese species of Suezichthys with those of Pseudolabrus are given.

biodiversity, Indo-Pacific, morphology, taxonomy

The labrid fish genus Suezichthys was originally proposed by Smith (1957) as Suezia (a name preoccupied in Crustacea), and subsequently replaced by Suezichthys (see Smith 1958). Suezichthys is a group of small, sexually dimorphic fishes occurring on sandy bottoms and rocky reefs of the Indo-Pacific and the southwestern Atlantic region. Some of the species are found on deep bottoms or mesophotic reefs, e.g., Suezichthy notatus (Kamohara 1958), which have been collected at deeper than 119 m (Shimada 2013).

The genus currently comprises 12 valid species. Russell and Westneat (2013) recognized 11 species, including a new species, Suezichthys rosenblatti Russell et Westneat, 2013, from Juan Fernandez and Isla San Felix off the coast of Chile. Another species, Suezichthys devisi (Whitley, 1941), although not recognized by Russell and Westneat (2013), was regarded as valid by Kuiter (1993). Suezichthys was redefined by Russell (1985) and Russell and Westneat (2013). It superficially resembles the labrid genus Pseudolabrus, but is distinctive in some osteological characters. Suezichthys is also morphologically similar to Halichoeres, but differs by having cheeks scaly (vs. naked); gill membranes forming a free fold across the isthmus (vs. broadly attached); and anal-fin elements III, 10–12 (mostly III, 10 vs. III, 11–13) (Russell 1985; Russell and Westneat 2013).

In Taiwan, only one species, Suezichthys gracilis (Steindachner et Döderlein, 1887) has been documented (e.g., Shen et al. 1993). It is found in coastal marine habitats, often occurring on shallow reefs and adjacent sandy bottoms. Recently, the first author obtained specimens of a rare labrid from local fish markets, which occurred in the catches of deep-water line fisheries off northern and southwestern Taiwan. This species was subsequently recognized as Suezichthys notatus, the second species of Suezichthys recognized in Taiwan. In this work, a detailed description of specimens of S. notatus from Taiwan, comparisons with S. gracilis, and comments on species of Pseudolabrus from Taiwan are given.

Counts, measurements, and terminology generally follow Russell and Randall (1981) and Russell (1985), except where indicated. The format of the description generally follows Randall and Kotthaus (1977). Definition of the initial phase (IP) and terminal phase (TP) follow Warner and Robertson (1978). Measurements were taken by digital or analog calipers based on the length of the measured items, recorded to the nearest 0.1 mm. Standard length (SL) and head length (HL) were used throughout. Pectoral-fin counts are given as the total number. Caudal-fin length was measured from the posterior edge of the hypural plate to the uppermost tip of the fin. Osteological characters were determined by X-radiographs. For the determination of associations of the hemal (haemal) arch and caudal vertebrae, the X-radiographs were taken by putting the specimen at an angle of ca. 45 degrees between the lateral surface and the X-ray source. Counts were recorded from the left side of the specimens unless otherwise indicated. Specimens of S. notatus were deposited at the Pisces Collection of National Marine Museum of Biology and Aquarium, Taiwan (NMMB-P).

Specimen examined. NMMB-P34163, 119.5 mm SL, northern Taiwan, near the “Three Northern Islands” region (e.g., Pinnacle Islet, Crag Islet, and Agincourt Islet), ca. 100‒150 m depth, captured by hook-and-line, purchased from Keelung Fish Market, 16 Apr. 2020, coll. CNT. NMMB-P35255, 121.5 mm SL, same as NMMB-P34163, 28 Mar. 2021. NMMB-P35256, 110.4 mm SL, Kaoshiung, southwestern Taiwan, by hook-and-line, purchased from Chienchen Fishing Port, 1 Apr. 2021.

Comparative materials. Suezichthys gracilis: NMMB-P5157, 5 specimens, 85–113 mm SL, An-pin, Tainan, Taiwan, 01 Jan. 1965; NMMB-P26423 and NMMB-P26425, 60 and 67 mm SL respectively, Ke-tzu-liao, Kaohsiung, Taiwan, 18 Jun. 2017; Pseudolabrus eoethinus, NMMB-P2194, 118 mm SL, Hou-bi-hu, Pingtung, Taiwan, 01 Nov. 2011; NMMB-P4106, 3 specimens, 105–133 mm SL, Hou-bi-hu, Pingtung, Taiwan, 31 Aug. 2002; NMMB-P27484, 117 mm SL, Hengchun, Pingtung, Taiwan, 02 Nov. 2017; NMMB-P34434, 3 specimens, 112–140 mm SL, Ao-di, northeastern Taiwan, purchased in Keelung Fish Market, 01 Mar. 2020. Pseudolabrus sieboldi, 5 specimens, 140–151 mm SL, Pom-cha-yu, 20 Dec. 2006; NMMB-P20794, 136 mm SL, Da-shi, Yilan, Taiwan 12 Nov. 2012; NMMB-P20796, 133 mm SL, Da-shi, Yilan, Taiwan, 12 Nov. 2012; NMMB-P34433, 125 mm SL, Ao-di, northeastern Taiwan, purchased in Keelung Fish Market, 01 Mar. 2020; NMMB-P34720, 137 mm SL, Keelung Fish Market, northern Taiwan, 30 Oct. 2020.

Suezichthys notatus (Kamohara, 1958) was briefly described from a single specimen collected from Okinoshima, Kochi Prefecture, Japan. Russell (1985) noted the holotype of S. notatus had been re-examined by Takeshi Yamakawa, who reported a 16 total gill rakers, instead of 4 + 1 + 9 = 14 as given by Kamohara (1958). The specimen from Taiwan has more gill rakers, e.g., 17‒20, on the first gill arch.

Species of Suezichthys share similar meristic counts; they have a combination of the following characters: Dorsal-fin rays IX, 11 (rarely 12–13); anal-fin rays III, 10–12; caudal-fin rays (5–6 + 2 + 12–13 + 2 + 5‒6); total pectoral-fin rays 12–14 (mostly 13, the uppermost 2 rays unbranched, the dorsalmost rudimentary); lateral line scales 25–26 (usually 25); scales rows below lateral line 7½ (Russell 1985, Russell and Westneat 2013; this study). Suezichthys notatus can be classified into the species group with 2½ scales above the lateral line, and distinguished from these close congeners by the following combination of characters: dorsal-fin rays IX, 11 (only IX, 12–13 in Suezichthys ornatus (Carmichael, 1819)); lateral-line scales with unbranched laterosensory canal tube (unbranched in the whole genus except Suezichthys bifurcatus Russell, 1986); IP and TP with black blotch or blotches above dorsoposterior margin of eye (Fig. 2B, C).

Kamohara (1958) compared S. notatus with S. gracilis and noted the former has more lateral-line scales and fewer scale rows on the cheek. However, the counts of these characters in Russell (1985) and our study do not differ greatly between the two species.

In Taiwan, only two species of Suezichthys are recognized. The Taiwanese specimens of S. notatus and S. gracilis (Fig. 5) differ in various characters: a longer head in S. notatus (2.8‒3.0 vs. 3.1–3.4 in SL in S. gracilis); greater body depth at the origin of dorsal fin (3.7‒3.9 vs. 4.1–4.7 in SL); greater predorsal length (3.0‒3.2 vs. 3.3–3.5); pelvic fin short (2.2‒2.5 vs. 1.3–2.2 in HL); pelvic fin of terminal phase individual short, when appressed its tip not reaching the anus (vs. long, with a slightly filamentous extension, when appressed its tip reaching the anus or slightly beyond the origin of anal fin); scale rows above lateral line 2½ (vs. 1½); a low scaly sheath presents on the base of dorsal and anal fin (vs. without).

Figure 5. 

Fresh and live coloration of Suezichthys gracilis. (A) TP individual, KAUM-I.113342, 91 mm SL, collected from Ke-tzu-liao, Kaoshiung, southwestern Taiwan (photo by Keita Koeda, credit to the Kagoshima University Museum); (B) IP, at Long-dong, northeastern Taiwan, depth ca. 12 m (photo by Chen-Lu Lee).

In coloration, S. notatus and S. gracilis are both overall pinkish and have a black spot present on the fin membrane between the 1^st and 2^nd spine in TP specimens. However, both IP and TP of S. notatus do not possess a lateral stripe on the body (vs. present on both phases of S. gracilis, red in IP and olive-green in TP); presence of black spots on the interorbital region dorsoposteriorly in S. notatus in TP (Fig. 2), or a large black spot at posterior end of dorsal-fin base (vs. none of these present in both phases of S. gracilis).

The morphology of hemal spines of caudal vertebrae differs between S. notatus and S. gracilis from Taiwan (Fig. 4). The hemal arches form a large hemal canal associated with anterior caudal vertebrae of the 10^th to 12‒13^th vertebrae in S. notatus (Fig. 4A); in contrast S. gracilis has only a single hemal arch with a large hemal canal, associated with the 10^th vertebra (Fig. 4B). Russell (1985) stated that the hemal arches with large hemal canal are on the 10^th to 12^th vertebrae of S. notatus, but in one of our specimens (NMMB-P34163) the 13^th vertebra also has a large hemal canal.

As stated in previous literature, Suezichthys superficially resembles Pseudolabrus. In Taiwan, two species of Pseudolabrus are also recorded (Shen and Wu 2011): Pseudolabrus eoethinus (Richardson, 1846) and Pseudolabrus sieboldi Mabuchi et Nakabo, 1997 (Fig. 6). Meristic and morphometric data were obtained from Taiwanese specimens of Pseudolabrus species to compare with the two Taiwanese Suezichthys species (Tables 1, 2). Suezichthys species differ from Pseudolabrus species (based on Taiwanese specimens) as follows: fewer rows of scales above lateral line in Suezichthys, 1½–2½ (vs. 3–4 in Pseudolabrus); fewer cheek scale rows + below eye (3 vs. 4–6); shallower body depth at dorsal-fin origin (3.7–4.7 vs. 2.8–3.1 in SL); narrower bony interorbital width (6.4–7.4 vs. 4.9–5.4 in SL); shorter 1^st dorsal-fin spine (5.8–8.0 vs. 4.4–5.6 in SL). However, as mentioned in Russell (1985), these characters do not clearly separate the two genera. More significantly, Suezichthys is distinct from Pseudolabrus in having the following characters: anterior preneural zygopophyses fused, slightly expanded (vs. separate, small); urohyal with a posteroventral spike-like extension (vs. no spike); and laterosensory canal tube of lateral line simple tubular, bifurcate or branched (vs. only bifurcate or multi-branched).

Figure 6. 

Fresh coloration of Pseudolabrus eoethinus (A1‒A2) and P. sieboldi (B1–B2), captured off northeastern Taiwan. (A) P. eoethinus, NMMB-P34434 (both specimens), A1: TP individual, 140.5 mm SL; A2: IP, 111.8 mm SL; (B) P. sieboldi, NMMB-P34433, B1: TP, 124.5 mm SL; B2: NMMB-P34720, IP, 137.1 mm SL.

This study was supported by National Museum of Marine Biology and Aquarium, Pingtung (NMMBA), National Taiwan Ocean University, Keelung (NTOU), and the National Museum of Marine Science and Technology, Keelung (NMMST). We express our sincere thanks to Dr Barry Russell (Museum and Art Gallery of the Northern Territory, Australia) for providing comments on the manuscript, Dr Hiroyuki Motomura (the Kagoshima University Museum), and Dr Keita Koeda (the Kuroshio Biological Research Foundation, Kochi Prefecture, Japan) for kindly providing the color specimen image, Dr Chen-Lu Lee (NMMST) for providing underwater photography and ecological information, and Chia-Ho Chan (NMMBA) for the curatorial assistance.