Peristedion richardsi Kawai, 2016

Wada, Hidetoshi, Hata, Harutaka & Motomura, Hiroyuki, 2019, First Northern Hemisphere Record of a Poorly Known Armored Searobin Peristedion richardsi (Actinopterygii: Teleostei: Peristediidae) from Taiwan, Species Diversity 24, pp. 203-207 : 203-205

Peristedion richardsi Kawai, 2016

( Figs 1–3 ; Table 1)

Peristedion richardsi Kawai, 2016: 336 , figs 1, 2, 3D, 4A (original description, type locality: Java, Indonesia; additional locality, Flores Sea ).

Material examined. KAUM –I. 127304, female, 197.2 mm SL, off Dong-gang , Pingtung County, Taiwan (22°39′N, 120°24′E), trawl, 24 December 2018, coll . by K. Koeda and H . Hata , obtained at Dong-gang Fish Landing Port .

Description of Taiwanese specimen. Counts and measurements are given in Table 1. Body fusiform, covered with bony plates. Head large, depressed; snout broad. Trunk inflated. Perifacial rim prominent, originating on anterior margin of lower jaw and terminating on posterior edge of preopercular. Rostral projections narrowly separated ( Fig. 2 ), spatulate and broad (width 1.6 times interspace between projections) with straight margins on base of medial aspects; ventral sensory pores on each side; 1st sensory pore slightly behind tip of rostral projection, anterior edge of 4th sensory pore anterior to anterior edge of premaxilla. Rudimentary spine on base of each rostral projection. Mouth large, inferior. Both jaws, vomer and palatines without teeth. Posterior tip of upper jaw not reaching to below anterior margin of orbit; lower jaw with small posterior ridge, posterior tip extending beyond anterior margin of orbit. Three groups of clustered barbels on lower lip: 1st group with three barbels on each side, 2nd with five (left) and six (right) barbels, 3rd with single filamentous barbel on each side with 31 (left) and 28 (right) branches. Six groups of barbels on chin, comprising 22 (left) and 23 (right) barbels in total: 1st group with three barbels clustered on each side, 2nd with three, 3rd with four, 4th with four, 5th with four; and 6th with four (left) and five (right). Gill rakers on 1st arch comb-like. Gill membrane narrowly united to isthmus. Eye large. Interorbital concave. Single spine with ridge on opercle. No spines on nasal, lateral ethmoid and mesethmoid. Single ridge on 4th infraorbital below orbit. Frontal-1 spine strong. Frontal-2 spine minute. Parietal spine stout. Posttemporal spine weak. Bony plates on body primarily in four rows, each plate with single backwardly directed spine; dorsal row: 1st plate largest; backwardly directed spine on each plate decreasing in size posteriorly except for last two plates; upper lateral row: 26–37th plates with forwardly directed spine; 1st to 5th plates smaller, slanted obliquely downward; lower lateral row: terminating at caudal peduncle; 25–27th plates alternately sutured (as zigzag) with contralateral plates along ventral mid-line; ventral row: backwardly directed spine on each plate decreasing in size posteriorly, reducing to low ridge, except for last two plates; row of plates absent at caudal peduncle. Two large bony plates with low ridge anterior to anus. Dorsal fin originating level with anterior margin of 2nd plates of dorsal row, ending level with 28th plates. Anal fin originating level with 2nd plates of ventral row, ending just below end of dorsal-fin base. Tip of joined pectoral fin rays just reaching anus. Two detached pectoral-fin rays thick, upper ray much longer than lower ray. Tip of pelvic fin just reaching anus. Caudal fin weakly emarginated.

Coloration of preserved specimen ( Fig. 1 ). Head, body and all fins light brown with grey vermiculate pattern posterodorsally on head, and dorsal and upper lateral bony plates. Dorsal fin edged with black. Pectoral fin with a central black spot and a black bar posteriorly. Peritoneum black. Fresh coloration unknown.

Distribution. Southern coast of Java and Flores Sea, Indonesia, and southern Taiwan ( Kawai 2016; this study: Fig. 3 ).

Remarks. Examination of the Taiwanese specimen (KAUM–I. 127304, 197.2 mm SL; Fig. 1 ) showed it to be a mature female, many relatively large-sized eggs (ca. 0.9 mm diameter) issuing from the cloaca. The specimen was clearly assignable to Peristedion , lacking teeth on the upper jaw and having the posterior pairs of bony plates in the contralateral lower lateral rows sutured along the midline, both being diagnostic of the genus as defined by Kawai (2008). Moreover, it agreed well with the diagnosis of Peristedion richardsi given by Kawai (2016), having the following features: dorsal row bony plates 32; upper lateral row bony plates 37; chin barbels 22 (total); anterior edge of 4th sensory pore of rostral projection located anterior to anterior edge of premaxilla; perifacial rim prominent, originating near anterior margin of lower jaw; spatulate rostral projections separated by very narrow interspace (projection width 1.6 times in interspace) ( Fig. 2A, B ), with straight margins basally on medial aspects; and upper free pectoral ray longer than joined rays.

However, the Taiwanese specimen differed from the Indonesian type specimens of P.richardsi in having slightly high- er counts of dorsal- and anal-fin rays (VIII, 23 dorsal-fin rays and 23 anal-fin rays vs. VIII, 22 and 22 in the former; Kawai 2016) and a vermiculate pattern on the dorsal surface (vs. no distinct pattern; Kawai 2016). Ranges of dorsal and anal-fin ray numbers greater than two have been reported in other congeners ( P. orientale , P. liorhynchus , P. riversandersoni , and P. amblygenys ; Ho et al. 2013; Ono and Kawai 2014; Kawai 2016), and similar color variations are known in P. nierstraszi Weber, 1913 (junior synonym of P. riversandersoni ; Ho et al. 2013; Kawai 2016), suggesting that the above variations in P. richardsi are simply intraspecific. Although, the Taiwanese specimen also differed from the type specimens in 16 of 23 morphometric characters, such were likely due to ontogenetic proportional changes, the present specimen (197.2 mm SL) being much larger than the other known specimens (115–132 mm SL).

Peristedion richardsi is most similar to P. amblygenys , distributed in the East China and South China seas, including Taiwanese waters, and the Indian Ocean off Indonesia ( Ho et al. 2013; Ono and Kawai 2014), both having the anterior edge of the 4th rostral projection sensory pore anterior to the anterior edge of the premaxilla, a prominent perifacial rim originating near the anterior lower-jaw margin, and rostral projections with a straight basal margin on the medial aspects ( Kawai 2016). However, P. richardsi is distinguishable from P. amblygenys in having spatulate rostral projections (vs. triangular in P. amblygenys ) with a very narrow interspace, the projection width 1.33–1.73 times in interspace (vs. moderate interspace, projection width 0.86–1.08 in interspace; Kawai 2016).

Since P.richardsi has been recorded only from Indonesian waters ( Kawai 2016), the Taiwanese specimen represents the first Northern Hemisphere record of the species.

Figures

Fig. 1. Photographs of preserved specimen of Peristedion richardsi (KAUM–I. 127304, 197.2mm SL). Top to bottom: dorsal, lateral, and ventral views.

Fig. 2. (A) Dorsal and (B) ventral views of head of preserved specimen of Peristedion richardsi (same individual as Fig. 1).

Fig. 3. Distributional records of Peristedion richardsi. Open and closed symbols indicate previously published and new records, respectively.