Friday, June 8, 2018

[Ichthyology • 2018] Cryptocentrus nanus • A New Species of Dwarf Shrimpgoby (Teleostei: Gobiidae) from Fiji


Cryptocentrus nanus  Greenfield & Allen, 2018


Black Dwarf Shrimpgoby  ||  OceanScienceFoundation.org 
photo: Hiroshi Nagano

Abstract

A new species of alpheid-shrimp-associated goby is described from Fiji based on 9 specimens, 17.2-23.4 mm SL. Diagnostic features include an exceptionally small size at maturity, a uniform black color, possession of vomerine teeth, a rounded caudal fin, 65-81 scales in the longitudinal series, 0-15 predorsal scales, body depth at pelvic-fin origin 4.4-5.2 in SL, snout length 4.4-8.4 in HL, and caudal-peduncle depth 3.3-3.8 in HL.

Key words: taxonomy, systematics, ichthyology, coral-reef fishes, gobies, alpheid shrimp, symbiosis, Pacific Ocean, biogeography


Figure 5. Underwater photograph of small black shrimpgoby, possibly Cryptocentrus nanus, from Palau, Micronesia (photo: Hiroshi Nagano)
Figure 1. Cryptocentrus nanus, live holotype, CAS 244342, 23.4 mm SL female, Yadua Island, Fiji, aquarium photograph (photo: D.W. Greenfield). 

Cryptocentrus nanus, n. sp.
Black Dwarf Shrimpgoby

Diagnosis. Dorsal-fin elements IV-I,10; anal-fin elements I,8–I,9; pectoral-fin rays 16; scales in longitudinal series 65–81; predorsal scales 0–15; anterior scales cycloid, posterior scales ctenoid; anterior part of breast, prepelvic region, and pectoral-fin base naked; head naked except on side of nape and predorsal region, where scales extend anteriorly to about level of middle of operculum; body depth at pelvic-fin origin 4.4–5.2, mean 4.8; vomerine teeth present; gill opening extending forward to a vertical at posterior edge of preoperculum or slightly anterior; dorsal-fin spines progressively longer to fourth, longest 1.6–2.7 in HL; caudal fin rounded, 2.7–3.1 in HL; pectoral fins reaching level of anus or just beyond (3.7–4.7 in SL); pelvic fins reaching posteriorly to anus (3.6–4.3 in SL); live individuals black, fins black with clear distal margins; adults mature at 23.4 mm SL or less.  

Underwater photograph of small black shrimpgoby, possibly Cryptocentrus nanus, from Palau, Micronesia.
photo: Hiroshi Nagano

Etymology: The specific epithet is from both the Latin and Greek noun nanus (dwarf), referring to the new species’ particularly small size compared to other species in the genus. It is treated as a noun in apposition.

Distribution and habitat. The new species is currently known only from Fiji, but possibly occurs also at Palau based on a photograph by Hiroshi Nagano of a similarly colored goby (Fig. 5), illustrated as Cryptocentrus D in Myers (1999: 240, Plate 152J). The habitat consists of sand bottoms in 8.2–10.7 m depth. The alpheid-shrimp partner remains unidentified, but a specimen is deposited in the fish collection of CAS as CAS 244


David W. Greenfield and Gerald R. Allen. 2018.  Cryptocentrus nanus, A New Species of Dwarf Shrimpgoby from Fiji (Teleostei: Gobiidae).  Journal of the Ocean Science Foundation. 30; 28-38. OceanScienceFoundation.org/josf30c.html

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