Elacatinus jarocho, Michael S. Taylor & Lad Akins, 2007

Michael S. Taylor & Lad Akins, 2007, Two new species of Elacatinus (Teleostei: Gobiidae) from the Mexican coast of the Gulf of Mexico., Zootaxa 1425, pp. 45-51 : 46-48

Elacatinus jarocho , sp. nov.

Jarocho Goby

Figures 1,2

Elacatinus jarochus (nomen nudum), Reef Environmental Education Foundation newsletter, Spring 2005.

Type series: Holotype: UF 162592, Ahogado de Guilligan, Gulf of Mexico, Veracruz, Mexico; 19°13.06'N, 96°03.22'W; 18 m depth; March 2004.

Paratypes: UF 162593 (2 specimens), same as holotype. UF 162594 (2 specimens), La Banquilla Reef, Gulf of Mexico, Veracruz, Mexico; 19°13.39'N, 96°05.71'W; 16 July 2005.

Diagnosis: Elacatinus jarocho is readily distinguished from other species of Elacatinus (s.s.) by the disjunct yellow lateral stripe that appears as a dash over the eye and on the caudal fin, a yellow medial stripe on the snout, and a black ovoid to rectangular spot at the base of the caudal fin, immediately ventral to the yellow dash.

Description: Morphometrics of all type specimens (15.3-27.2 mm SL) as a percent of standard length (mean): head length, 26.8-28.5 (27.6); body depth at dorsal origin, 15.5-18.3 (17.8); caudal peduncle depth, 10.5-12.9 (11.5); eye diameter, 8.2-10.5 (9.1); snout length, 4.0-5.9 (4.8); upper jaw length, 9.1-11.7 (10.2); pectoral fin length, 11.5-22.2 (18.1); pelvic fin length, 14.0-17.0 (15.1); caudal fin length, 15.4-20.3 (18.0). Fin ray counts (mode): D. VII, 11-12 (11); A. 9-11 (11); pectoral rays, 15-17 (16). None of the dorsal spines are elongated.

The body is unscaled and somewhat laterally compressed. The subterminal mouth is U-shaped, lacks a rostral frenum, and the tongue is truncate. The conical teeth are set in 1-2 rows. Males have a slender, conical genital papilla; females have a blunt papilla.

Coloration: In life, the body is a translucent, dark bluish-grey. A disjunct, bright yellow lateral stripe occurs just above the midline. The anterior segment of the yellow stripe originates anterior to the eye and extends posteriorly to the dorsal edge of the preoperculum. The posterior segment of the yellow stripe begins at the caudal peduncle and extends into the caudal fin rays (Fig. 2). The snout is marked with a yellow medial stripe, which begins near the upper lip and widens slightly to end between the eyes. A dark, broad lateral stripe begins at the anterior tip of the head, extends along the full length of the body just below the midline, and terminates at the caudal peduncle. A black ovoid to rectangular spot on the caudal fin originates at the terminus of the dark lateral stripe and terminates in the caudal rays. The black caudal spot is adjoined to the yellow caudal dash. The ventral surface below the dark lateral stripe is pale to translucent white. All fins are translucent or transparent. No sex- or age-related coloration differences are apparent.

In preservative, the medial yellow stripe on the snout is marked by melanophores, and is surrounded by a narrow zone devoid of melanophores. The rest of the snout anterior to the eyes, and the upper lip, are dusky. A thin strip of melanophores extends from behind the eye to trail off on the operculum. This strip demarcates the ventral edge of the anterior yellow segment. The anterior and posterior yellow segments, and an interconnecting zone above the body midline are devoid of melanophores; the trunk is otherwise evenly covered with scattered melanophores. The dark caudal spot is clearly visible. Medial fin elements are outlined with melanophores.

Comparisons: The combination of the lateral stripe and completely unscaled body places E. jarocho in the subgenus Elacatinus ( Boehlke and Robins 1968) . Elacatinus jarocho is the only species of Elacatinus (s.s.) thus far known to have a disjunct lateral stripe. Two other species, E. chancei (Beebe and Hollister) and E. tenox ( Boehlke and Robins) , have yellow lateral stripes restricted to the head, but these species do not have a yellow dash on the caudal fin, and neither species has been reported from the Gulf of Mexico. A complete lateral stripe (no disruption) is found on all other species of Elacatinus (s.s.). Elacatinus oceanops , which is commonly observed on the same reefs as E. jarocho , has a solid blue lateral stripe (no yellow), no medial stripe on the snout, an inferior mouth, and rests on living coral and rocky substrate (Colin 1975) instead of schooling in the water column.

Distribution: Elacatinus jarocho is known only from the Veracruz reef system near Veracruz, Mexico. Specimens were observed as far north as Isla De Lobos (21°29.36'N, 97°13.53'W) and as far south as Anton Lizardo (approximately 19°04.41'N, 95°50.21'W) .

Etymology: The specific name, jarocho, is applied as a noun in apposition. Jarocho is the common local name for Veracruzanos, the native people of Veracruz, Mexico. We are pleased to honor the Jarocho, who have embraced the protection and conservation of the Veracruz reef system. The proper pronunciation is hahROH-cho.

Remarks: Elacatinus jarocho was found between 3-25 m depth on high profile coral reefs typically dominated by Montastrea cavernosa (Linneaus) , M. annularis (Ellis and Solander) , Colpophyllia natans (Houttuyn) and skeletal reef framework. Elacatinus jarocho joins E. atronasus ( Boehlke & Robins) as the only two species in the genus to school in the water column. Small to large aggregations (12-60 individuals) of E. jarocho were normally found close to the reef near high profile corals or overhangs. Such reef structure presumably provides shelter from direct sunlight because aggregations were usually observed in darker, shaded areas rather than in direct sunlight. Individuals of E. jarocho , unlike E. atronasus , were never observed stationary on any substrate, but rather hovered continuously about 5-25 cm above the reef (Fig. 2), frequently in association with Coryphopterus hyalinus Boehlke & Robins or C. personatus (Jordan & Thompson) . This species was not observed to clean other species or interact in other symbiotic relationships. Small and large individuals coexisted in the same aggregations and did not display territorial or hierarchical behaviors. Individual fish would often, though not always, move slowly toward cover when approached to less than 1 m by scuba divers.