Bull. Natn. Sci. Mus., Tokyo, Ser. A, 32(1), pp. 29–37, March 22, 2006 Myersina adonis, a New Species of Shrimp-associated Goby (Pisces, Perciformes, Gobiidae) from the Andaman Sea Koichi Shibukawa1 and Ukkrit Satapoomin2 1 Department of Zoology, National Science Museum, 3–23–1 Hyakunin-cho, Shinjuku-ku, Tokyo 169–0073, Japan e-mail: [email protected] 2 Phuket Marine Biological Center, P.O. Box 60, Phuket 83000, Thailand e-mail: [email protected] Abstract A new shrimp-associated goby, Myersina adonis, is described based on seven speci- mens (21.7–31.3 mm in standard length) collected from shallow seagrass beds on the Andaman coast of Thailand. Myersina adonis is distinguished from the congeners in having: VI-I, 10 dorsal- fin rays; I, 9 anal-fin rays; 53–61 longitudinal scales; 4–5ϩ14–17ϭ18–21 gill rakers; united gill membranes with a distinct free rear margin across the isthmus at least in males (but not pro- nounced in most females); five transverse rows of sensory papillae on cheek; dorsal half of the body mottled with charcoal gray, without distinct longitudinal stripes; three faint, dusky vertical bars on side of belly; and a wedge-shaped black spot on pectoral-fin base. When alive or fresh, there are minute bright blue spots scattered on the head and body; minute reddish spots on the jaws; three or four irregular rows of red spots on the second dorsal fin; and a series of alternating red and yellow spots on membrane between first and second spines of the first dorsal fin in males. Key words : Myersina adonis, new species, Gobiidae, shrimp-associated goby, Andaman Sea. Myersina Herre, 1934, is an Indo-Pacific fish Myersina larsonae Allen, 1999, should be placed genus of the gobiid subfamily Gobiinae (sensu in the other shrimp-goby genus Stonogobiops Pezold, 1993), and comprises small to moderate- (citing personal communications from both G.R. sized (up to ca. 100 mm SL) marine or brackish- Allen and D.F. Hoese to R. Winterbottom). Ac- water gobies, symbiotically associated with cording to Winterbottom (2002), the genus is alpheid shrimps (snapping shrimps or pistol characterized by having the following combina- shrimps). The genus was recently redefined by tion of features: cycloid scales only but no scales Winterbottom (2002), who provisionally recog- along midline of nape, or on head or pectoral-fin nized following seven species within it: M. filifer base; scales increasing in size from anterior to (Valenciennes in Cuvier & Valenciennes, 1837); posterior on body; elongate first dorsal fin at least M. macrostoma Herre, 1934; M. pretoriusi in males; two preopercular sensory canal pores; (Smith, 1958); M. yangii (Chen, 1960); M. crocata sensory papillae on cheek in a well-developed (Wongratana, 1975) [Note.–most previous au- transverse pattern; gill membranes fusing in ven- thors use the specific name M. crocatus, but it tral midline and attaching to isthmus at the point, should be spelled as crocata (as done by Senou or forming a free fold across it and attaching to & Nin, 2003) because the gender of Myersina is isthmus medially anterior to the point of fusion; feminine (Eschmeyer, 1998)]; M. lachneri Hoese no teeth on vomer. Characters unique to Myersi- & Lubbock, 1982; M. nigrivirgata Akihito & na amongst the gobiines have never been pro- Meguro, 1983. In addition, Winterbottom (2002) posed, and the monophyly of the genus has there- suggested that Cryptocentrus shigensis Kuroda, fore not been determined. 1956, was possibly assigned to Myersina, and During our research on fish fauna of seagrass 30 Koichi Shibukawa and Ukkrit Satapoomin bed and mangrove areas at the Libong Island, rows from just dorsoposterior to upper attach- Trang Province of Thailand, in 2003, the senior ment of opercular membrane (i.e., anteriormost author collected six specimens of an undescribed scale or scale row) backward to mid-base of cau- species of shrimp-associated goby. Subsequently, dal fin; three methods of transverse scale count three additional specimens of this species were given in the descriptive accounts; circumpedun- collected from the other parts of the Andaman cular scale count—number of scales along a coast of Thailand (Phrathong and Phuket Islands) zigzag vertical line through narrowest point of by the junior author. The species, herein de- caudal peduncle; gill rakers counted on outer scribed as new, agrees entirely with the definition side of first arch, including all rudiments; count of Myersina proposed by Winterbottom (2002), of pseudobranchial filaments includes all rudi- but readily distinguished from its congeners in ments. Pectoral fin rays counted and numbered coloration and several other details. from dorsal to ventral. Scales (except for circum- pecuncular) and paired-fin rays counted bilateral- ly. Osteological features were taken from radi- Materials and Methods ographs. The methods of Akihito et al. (1984) Institutional abbreviations for materials exam- are used in describing the pattern of the interdigi- ined follow Leviton et al. (1985), with an addi- tation of the dorsal-fin pterygiophores between tional code, PMBC, for Reference Collection of the neural spines (“P–V”). Cephalic sensory Phuket Marine Biological Center. canals and papillae were examined on specimens Measurements were made point-to-point with stained with Cyanine Blue, and notations on calipers under a dissecting microscope to the them follow Akihito et al. (1984) and Miller nearest 0.01 mm. The methods for measurements (1986), respectively. All fish lengths given are follow those of Hubbs & Lagler (1958), with ex- standard lengths (SL). ceptions given below (“snout tip” refers to the mid-anteriormost point of the upper lip): head Myersina adonis sp. nov. length—tip of snout to posterior end of head (Figs. 1–3, Table 1) including gill membrane; interorbital width— least width between innermost rims of right and Myersina species. Shibukawa, 2005: 62 [Libong Island; left eyeballs; jaw length—snout tip to the posteri- color photograph of male (NSMT-P 65985, now re-reg- ϭ ormost point of lips; head width and depth were istered as PMBC 21030 holotype), and brief descrip- tion]. measured at posterior vertical margin of preoper- cule; body depth was measured at the anal-fin Holotype. PMBC 21030, male, 30.5 mm SL, origin; nape width—distance between dorsalmost eastern coast of Libong Island, Trang Province, ends of gill openings; preanal and prepelvic Andaman Sea, Thailand, 1 m depth, 10 Mar. lengths—snout tip to the origin of each fin; pec- 2003 (collected by K. Shibukawa). toral-fin length—the base to tip of the longest Paratypes. AMS I.43770-001, 1 specimen ray; pelvic-fin length—distance between the an- (female), 28.5 mm SL, collected with holotype; terior margin of the base of pelvic-fin spine and NSMT-P 65987, 1 specimen (male), 30.6mm SL, the distal tip of the longest segmented ray; collected with holotype; NSMT-P 65979, 1 speci- heights of pelvic-fin frenum and interradial men (female, cleared and stained), 27.7 mm SL, membrane—least heights; lengths of fin spines collected with holotype; NSMT-P 65980, 1 and rays—between the anterior margin of the specimen (male), 21.7 mm SL, collected with base to distal tip of each ray. The methods for holotype; PMBC 20177, 1 specimen (female), counts follow Akihito et al. (1984), except for 25.8 mm SL, east coast of Phrathong Island, the following: longitudinal scale count—number Phangnga Province, Andaman Sea, Thailand of oblique (anterodorsal to posteroventral) scale (9°04.95ЈN, 98°20.25ЈE), 0 m depth, 2 July 2003 New Shrimp-associated Goby from Andaman Sea 31 (collected by U. Satapoomin); ROM 79683, 1 scales from second dorsal-fin origin downward specimen (female), 31.3 mm SL, collected with and backward to anal-fin base 20 (2), 21 (5), 23* holotype. (3), 24* (1) or 25 (1); predorsal scales 0* (7); cir- Non-type material. PMBC 21030, 2 speci- cumpeduncular scales 24 (1), 26 (1) or 28* (5); men (female, 30.0 mm SL; male, 29.2 mm SL), gill rakers 4ϩ14 (1), 4ϩ15* (4), 4ϩ17 (1) or east coast of Phuket Island, Andaman Sea, Thai- 5ϩ15 (1); pseudobranchial filaments 9 (1), 10* land, tidepools in intertidal seagrass bed, 0 m (2), 11 (4); vertebrae 10ϩ16ϭ26* (7); P-V 3/II depth, quinardine, 15 Nov. 2005 (collected by U. II I I 0/9* (7); epural 1* (7); anal-fin pterygio- Satapoomin). phores anterior to first haemal spine 2* (7); Diagnosis. Myersina adonis is distinguished pleural ribs on third to tenth precaudal vertebrae* from its other congeners in having the following (7). combination of characters: VI-I, 10 dorsal-fin Proportional measurements are given in Table rays; I, 9 anal-fin rays; 53–61 longitudinal scales; 1. Body moderately elongate and compressed. 4–5ϩ14–17ϭ18–21 gill rakers; united gill mem- Head slightly compressed, its width 84.6–93.8% branes with a distinct free rear margin across of depth. Snout short, its length shorter than eye isthmus at least in male (but not pronounced in diameter; snout not protruding beyond upper lip. most females); five transverse rows of sensory Eye dorsolateral, large, its diameter 26.0–28.8% papillae on cheek, including two rows in front of of head length; interorbital space narrow, its longitudinal row b; dorsal half of body mottled width narrower than pupil diameter and 4.6– with charcoal gray, without distinct longitudinal 6.1% of head length. Shallow transverse trough stripes; three faint, dusky vertical bars on side of just behind eye. No cutaneous ridge along dorsal belly; a wedge-shaped black spot on pectoral-fin midline of nape. Gape oblique, forming an angle base; and, when alive or fresh, minute bright blue of about 30 degrees with body axis. Lower jaw spots scattered on head and body; minute reddish projecting anteriorly beyond upper jaw; posterior spots on jaws; three or four irregular rows of red end of jaws to about a vertical line through poste- spots on second dorsal fin; a series of alternating rior end of eye; jaw length 47.9–52.5% of head red and yellow spots on membrane between first length.