Mugil margaritae, Menezes, Naércio A., Nirchio, Mauro, Oliveira, Cláudio De & Siccharamirez, Raquel, 2015

Menezes, Naércio A., Nirchio, Mauro, Oliveira, Cláudio De & Siccharamirez, Raquel, 2015, Taxonomic review of the species of Mugil (Teleostei: Perciformes: Mugilidae) from the Atlantic South Caribbean and South America, with integration of morphological, cytogenetic and molecular data, Zootaxa 3918 (1), pp. 1-38 : 26-29

Mugil margaritae new species

( Fig. 10 )

All specimens from Venezuela.

Holotype: MBUCV-V-35725, SL 151 mm, Boca de Río/Nova Esparta, Isla Margarita, 10°58’14”N, 64°10’13”W, 2007, M. Nirchio.

Paratypes: MBUCV-V-35726 (11, SL 90–166 mm), MZUSP 115346 (4, SL 126–165 mm) collected with holotype; LBP 6129 (1, SL 265 mm), San Bernardo/Zulia, 11°00’06”N, 71°36’28”W, 2006, H. Briceño, M. Dávila & N. Flores.

Diagnosis. Mugil margaritae is distinguished from M. liza , M. curvidens and M. trichodon in having 3 spines and 9 branched anal fin rays in adults or 2 spines, 1 unbranched and 9 branched anal fin rays in juveniles (vs. 3 spines and 8 branched anal fin rays in adults or 2 spines, 1 unbranched and 8 branched anal fin rays in juveniles). Mugil margaritae differs from M. incilis in having the dorsal-fin origin midway between the snout tip and the caudal-fin base and 17–18 longitudinal scale rows around the caudal peduncle (vs. the dorsal-fin origin much closer to the snout tip than to the caudal-fin base and 20–23 longitudinal scale rows around the caudal peduncle) and from M. brevirostris , M. curema and M. rubrioculus in having 40–44 oblique scale rows from the dorsal limit of the pectoral-fin base to the caudal-fin base and 13–15 (usually 14) longitudinal scale rows from the dorsal-fin origin to the pelvic-fin origin (vs. 35–39 oblique scale rows from the origin of the pectoral-fin limit to the caudal-fin base and 12–13, usually 13 oblique scale rows from the limit of the pectoral-fin base to the caudal-fin base)

Description. Morphometric data presented in table 11. Maximum examined body length 265 mm SL. Body elongate, compressed, moderately deep compared to congeners. Greatest body depth at vertical through spinous dorsal-fin origin. Dorsal profile of head and body convex from tip of snout to spinous dorsal-fin origin; straight from this point to soft dorsal-fin origin, slightly convex from this point to caudal peduncle, concave along caudal peduncle. Ventral profile of head and body convex from tip of lower jaw to anal-fin origin, slightly concave from this point to vertical through caudal-fin base. Orbital diameter equal to snout length. Eye covered with adipose tissue, except for oval-shaped central area in adults. Adipose tissue almost absent in specimens smaller than 30–35 mm SL.

Anterior spinous dorsal fin with 4 slender spines connected by membrane, n = 23. Spinous dorsal fin-origin about midway between snout tip and caudal-fin base. Posterior soft dorsal-fin rays i, 8 in adults, n = 23. Unbranched pectoral-fin rays ii, first ray much smaller than second; branched rays 13–15, 14.6 (15), n = 23. Tip of pectoral fin not reaching vertical through spinous dorsal-fin origin, extending to vertical through about middle of pelvic fin-length. Pelvic fin with I,5. Tip of pelvic-fin reaching vertical through base of fourth dorsal-fin spine. Anal-fin rays with II, i, 9 in specimens smaller than 30–35 mm SL, III, 9 in adults, n = 23.

Mouth subterminal. Tip of maxilla extending slightly beyond anterior border of orbit. Teeth on upper and lower lips minute, unicuspid, spatulate, with slightly curved tips ( Fig. 10 A). External upper lip teeth larger than inner teeth. Single row of teeth smaller than upper lip teeth on lower lip.

Scales spinoid, spines rudimentary on surface of scales, not projecting on scale margin ( Fig. 10 B). Transverse scale rows from dorsal limit of pectoral-fin rays to caudal-fin base 40–44, 40.8 (40), n = 23. Horizontal scale rows from spinous dorsal-fin origin to pelvic-fin origin 13–15,14 (14), n =23. Horizontal scale rows around caudal peduncle 17–18,17.9 (18), n = 23. Soft dorsal and anal fins densely scaled except for narrow scaleless distal area. Basal portion of pectoral fin fully covered by small scales extending between interradial membranes but not reaching distal margin of fin. Modified axilla scale dorsal to pectoral-fin 2.5 times as long as pectoral-fin length in holotype. Modified axilla scale dorsal to pelvic twice as long as pelvic fin in holotype. Gill rakers close set, 48–85 (71) on ceratobranchial portion of first arch, increasing in number ontogenetically ( Fig. 2 ).

Color in alcohol. Body dark dorsally; dark color fading ventrally towards midlateral portion of body, whitish on abdominal region. Central portion of scales of longitudinal scale rows from midbody to dorsal midline of body slightly darker than remainder of scales, forming inconspicuous horizontal stripes in live or recently preserved specimens. All fins pale, with few scattered dark chromatophores. Distal margin of caudal fin darker than remaining parts of fin. Anterodorsal basal portion of pectoral fin with relatively large dark spot extending over basal portions of ten dorsalmost branched rays, with vertically elongate whitish spot under it extending along bases of fourth through eleventh branched rays.

Cytological and molecular data. The karyotype of Mugil margaritae possesses a complement of 2N+24 composed of 22M + 2SM chromosomes with a conserved arm number FN=48. NORs are located on the telomeric region of the long arm of the metacentric chromosome pair N o 1 and C-bands are distributed on the pericentromeric and telomeric regions of all chromosomes with some chromosomes displaying intercalary heterochromatic blocks, some being more conspicuous ( Nirchio et al., 2005).

The molecular analyzes showed that the number of nucleotid differences between M. margaritae and the remaining analyzed species ranges from 8.7 to 64.0 (16S) and 29.4 to 107.2 (COI) (tables 2 to 5). The genetic distance between this species and the remaining analyzed ones ranged from 0.015 to 0.129 (16S) and 0.047 to 0.191 (COI) (tables 6 and 7). The dendrogram in Fig. 3 shows that this species is genetically most similar to M. curema .

Etymology. The species is named after Isla Margarita, Venezuela, a locality where the type species was collected.

Distribution. Mugil margaritae is known from two localities along the Venezuelan coast ( Fig. 4 ) and was captured together with M. trichodon , M. rubrioculus and M.incilis at one of these two localities.

Figures

FIGURE 2. Regression of number of gill rakers versus standard length for the examined species of Mugil. Data from M. trichodon unavailable.

FIGURE 3. Dendrograms obtained by the neighbour-joining method using the Kimura- 2 - parameters model of nucleotide substitution for the data of genes COI (a) and 16 S (b). The numbers represent the groups frequencies observed using 1,000 bootstrap pseudoreplicas. Values below 50 % are not represented.

FIGURE 4. Map of central and northern South America showing collecting sites and type localities (white star and light blue star) of species of Mugil. Pink dot: Mugil trichodon, M. rubrioculus and M. incilis (Venezuela); white star: holotype of M. margaritae; white dot: M. margaritae; yellow dots: M. incilis (Brazil); green dots: M. rubrioculus (Brazil); light blue dot: M. brevirostris; blue star: neotype of M. brevirostris; red dots: M. curvidens. Some symbols may represent more than one locality.

FIGURE 10. Mugil margaritae. Holotype, MBUCV-V- 35725. A—Detail of mouth showing dentition. B—Detail of scales located on dorsal region of body below dorsal-fin base.