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versión On-line ISSN 2007-8706versión impresa ISSN 1870-3453
Rev. Mex. Biodiv. vol.82 no.1 México mar. 2011
The ringtail tonguefish, Symphurus ocellaris, a new addition to the marine fish fauna of Mexico (Cynoglossidae, Pleuronectiformes).
La lengua cola ocelada, Symphurus ocellaris, una nueva adición a la ictiofauna de México (Cynoglossidae, Pleuronectiformes).
Albert M. van der Heiden*, Marcela RuizGuerrero and Héctor G. PlascenciaGonzález
Centro de Investigación en Alimentación y Desarrollo, A. C. Unidad Mazatlán en Acuicultura y Manejo Ambiental, Av. SábaloCerritos s/n "Estero del Yugo" Apartado postal 711, 82010 Mazatlán, Sinaloa, México.
Recibido: 26 agosto 2009
Aceptado: 28 mayo 2010
Eleven specimens of the ringtail tonguefish, Symphurus ocellaris Munroe and Robertson, 2005, were obtained from off the coasts of Chiapas and Colima, Mexico. Previously, this species was known only from the 2 type specimens collected off the Pacific coast of Panama. Our finding constitutes the first record of the species in Mexico and the second known occurrence of the species. The northern distribution limit of S. ocellaris is now extended by 11.5 degrees latitude or about 3 400 km of the eastern Pacific coastline, from Panama to Colima, Mexico.
Key words: range extension, geographical distribution, eastern Pacific, Panama, Mexico.
Se recolectaron 11 individuos de la especie lengua cola ocelada, Symphurus ocellaris Munroe y Robertson, 2005, frente a las costas de Chiapas y Colima, México. Hasta el momento, la especie sólo era conocida a partir de 2 ejemplares tipo recolectados frente a la costa pacífica de Panamá. El presente descubrimiento constituye el primer registro para México y un segundo reporte conocido de la especie. Se extiende el ámbito de distribución norteña de la especie en 11.5 grados de latitud (aproximadamente 3 400 km de línea de costa del Pacífico oriental), desde Panamá hasta Colima, México.
Palabras clave: ampliación, ámbito geográfico, Pacífico oriental, Panamá, México.
The symphurine tonguefishes of the eastern Pacific were poorly known and difficult to identify until around 1990, when T. H. Munroe and collaborators published a series of descriptions of new species belonging to the genus Symphurus, mostly based on the dissertation of Mahadeva (1956): Munroe and Mahadeva (1989), Mahadeva and Munroe (1990), Munroe (1990), Munroe and Nizinski (1990), and Munroe et al. (1991). Recently, a new species of tonguefish, Symphurus ocellaris Munroe and Robertson, 2005, was described from the Pacific coast of Panama, based on 2 specimens, increasing the number of eastern Pacific species of Symphurus to 18 (Munroe et al., 1995; Munroe and Robertson, 2005).
Several specimens of S. ocellaris were obtained during an extensive collecting effort for demersal fishes on the continental shelf of the Gulf of Tehuantepec in 19911992 and 2 additional specimens were caught in the coastal waters off the state of Colima in 1996. Only recently, however, could the specimens be classified as S. ocellaris (Fig. 1AD), after having examined all the Symphurus specimens in our institutional fish collection (CIAD) obtained from many cruises carried out along the eastern Pacific coast of Mexico, including the Gulf of California.
Methods for counts and measurements and general terminology are according to Munroe (1998). Institutional abbreviations are as listed in Leviton et al. (1985); Centro de Investigación en Alimentación y Desarrollo, A. C. is abbreviated as CIAD. The common English and Spanish name used here, ringtail tonguefish and lengua cola ocelada, are taken from Robertson and Allen (2006).
The external morphology of our symphurine tonguefishes collected from off the coasts of Colima and Chiapas corresponds to that of the type material of S. ocellaris from Panama provided by Munroe and Robertson (2005); only the pupillary operculum is somewhat less conspicuous in our specimens. Our specimens and the types of S. ocellaris also coincide in measurements and counts, except, however, for the interdigitation (ID) pattern of proximal dorsalfin pterygiophores and neural spines (Tables 1 and 2). The predominant ID arrangement in our specimens is 14322 (present in 9 out of 11; Fig. 2) whereas both type specimens of S. ocellaris have a 13422 ID pattern.
In view of the fact that Munroe (1992) and Munroe and Robertson (2005) stated that the ID pattern serves as an important diagnostic character for the identification of symphurine tonguefishes it is essential to address the discrepancy mentioned above. The 14322 ID arrangement, typically present in our specimens, only occurs in but 2 eastern Pacific Symphurus species, S. fasciolaris and S. leei (predominant 14322 ID pattern 69% and 62% and variant ID pattern 13422, 6% and 7%, respectively; number of specimens 39 and 198, respectively; Munroe, 1992). However, compared to our specimens, Symphurus leei differs in general body shape, in lacking the ocellated caudal spot, and in presenting a higher number of dorsal and analfin rays (93104 and 7888 vs. 9397 and 7681) whereas S. fasciolaris, although possessing a prominent, ocellated caudal spot, differs noticeably in general body shape and size (at least 162 mm SL vs. 135 mm maximum SL), in number of caudalfin rays (10 vs. 12, an extremely conservative character within the species of the genus) and in overall body coloration (see coloration below). Thus none of our specimens pertain to S. leei or S. fasciolaris.
Notwithstanding the difference in predominant ID pattern, we considered our specimens to be conspecific with S. ocellaris because of their similarity in measurements, meristics, external morphology, and presence of a prominent ocellated caudal spot (see below). Identifying our specimens as S. ocellaris was also supported by the results obtained by Castillo Velázquez (2001) who perceived an opposite situation in ID pattern between specimens of S. chabanaudi captured along a short geographic range (n = 22; 26°49' and 16°11' northern latitude; from Baja California Sur to Guerrero, Mexico) and Munroe's 1992 specimens captured over a very wide range (n = 132; from the northern Gulf of California to Colombia): predominant 14322 ID pattern (59.1%) and 15322 variant ID pattern (40.9%) vs. the predominant 15322 (53%) and variant pattern 14322 (14%), respectively. Apart from weakening the importance of ID patterns as a diagnostic character in species identification, S. chabanaudi, at least within part of its geographic range, represents a third eastern Pacific Symphurus species that shares the predominant 14322 pattern with our specimens, and thus a comparison is necessary. Symphurus chabanaudi may be larger in size than our specimens (maximum SL at least 233 mm, common to 210 mm SL vs. 135 mm maximum SL) and it lacks the ocellated caudal spot, and possesses a higher number of dorsal and analfin rays (98109 and 8292 vs. 9397 and 7681 in our specimens).
Additional arguments in considering our specimens to be conspecific with S. ocellaris are the following. The description of S. ocellaris was only based on 2 specimens, which, according to Munroe and Robertson (2005), makes it difficult to determine whether the 134 pattern is the predominant one for this species. Also, the 13422 ID pattern found in both type specimens of S. ocellaris is a highly unusual one among the 77 species currently recognized in the genus Symphurus. Only one other species, S. callopterus, features this predominant ID pattern, although only in 64% of the 191 specimens examined and the variant pattern being 14322 in 14% of them, which is the same variant pattern as in our specimens. Symphurus callopterus, however, lacks the ocellated caudal spot, and possesses a higher number of dorsal and analfin rays, 105114 and 9188 vs. 9397 and 7681 in our specimens (Munroe, 1992; Munroe and Robertson, 2005; Eschmeyer and Fricke, 2009). In addition, fidelity for a predominant ID pattern may be low; according to Munroe (1992), although average fidelity for the predominant ID pattern in 69 species was approximately 78% per species, values ranged from 37 to 100% per species.
The coloration in alcohol of our specimens conforms in many aspects with the detailed description given by Munroe and Robertson (2005). Some differences in coloration on the ocular side, however, were observed: 1 specimen is dark brown instead of light to medium brown (Fig. 1C); all specimens are devoid of the numerous, small, irregular white markings present in the type material; all except 3 of our specimens show 1 to 5 irregular, faint to prominent crossbands (Fig. 1A, B); head and body scales are more uniformly brown, instead of having their distal halves darker than their proximal halves, but present the posterior margins distinctly outlined with dark pigment. In all specimens, the isthmus is devoid of pigment and the blind side does not present the interrupted, medial series of dark spots located deep within the dermis of the posterior third of the body of the paratype. The number of anterior dorsalfin rays without pigmentation ranges from 0 to 5 (1 specimen with all rays pigmented, 1 specimen with 1, 3 with 2, 3 with 3, 2 with 4, and 1 with 5 rays unpigmented) instead of 2 to 4 for the type specimens (holotype 2, paratype 4). Among all 18 eastern Pacific species of the genus Symphurus, besides S. ocellaris, only S. fasciolaris presents an ocellated spot on the caudal fin (Fig. 1E; Munroe and Robertson, 2005).
The 2 type specimens of S. ocellaris were caught near Coiba Island, off the Pacific coast of Panama. Given that no additional specimens of this species are reported upon in the literature, our findings extend the distributional range of the species northwards by about 11.5 degrees latitude or 3 400 km of coastline and constitute the first record of S. ocellaris in Mexico. Since the type material was collected at 720 m depth, Munroe and Robertson (2005) believed the species to be a shallowwater occupant. Considering, however, that all our specimens were obtained from deeper waters, between 23 and 64 m, S. ocellaris is to be classified as a shallow to mediumdeep water form. As well as the holotype, our specimens were obtained over soft bottom by otter trawl.
Material examined (measurements are in SL): Symphurus ocellaris: Mexico, Colima: CIAD 199617, 2(115.5116.9 mm), DEMIII, depth 2040 m, off Playa El Coco. Golfo de Tehuantepec, Chiapas: CIAD 199123, 2(121.2125.9 mm), CEEMEXP4, station 19A, depth 34 m, off Barra de Tonalá (15°53.8' N 93°54.4' W); CIAD 1991115, 2(114.8134.5 mm), CEEMEXP5, station 19, depth 35 m, off Barra de Tonalá (15°54.0' N 93°55.1' W); CIAD 199232, 1(118.4 mm), CEEMEXP7, station 29, depth 42 m, off mouth of Río Nicolás (14°58.5' N 92°59.9' W); CIAD 199135, 1(114.0 mm), CEEMEXP4, station 37, depth 23 m, off Barra de San Simón (14°42.4' N 92°32.3' W); CIAD 199136, 1(107.3 mm), CEEMEXP4, station 38, depth 45, off Barra de San Simón (14°29.9' N 92°31.0' W); CIAD 199137, 1(119.7 mm), CEEMEXP4, station 39, depth 64 m, off Barra de San Simón (14°21.7' N 92°32.9' W); SIO 9176 (ex CIAD 199129), 1(114.0 mm), CEEMEXP4, station 28, depth 28 m, off Río Nicolás (15°08.3' N 92°58.7' W). Symphurus fasciolaris: Mexico, Golfo de California, CIAD 198516, 5(117134 mm), CORTES 2, station 37, depth 36 m, Norte de Rocas Consag (31°15.2' N 114°22.1' W).
Specimens from the Gulf of Tehuantepec were collected during the CEEMEX cruises with the R/V El Puma (Commission of the European Communities Contracts TS2.0213.E and CI1.0431.E). Specimens from Colima were obtained during the DEMERSAL cruises with the R/V BIP V and provided by Luz Estela Rodríguez Ibarra. Valerie Williams Holland kindly revised the manuscript for correct use of the English language. Valentín Zambrana Torres generously put his medical equipment at our disposal and provided the high quality radiographs. Levid Torres Guzmán's interest and support of our research is also greatly appreciated.
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