Mugil incilis Hancock 1830

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 : 24-26

Mugil incilis Hancock 1830

( Fig. 9 )

Mugil incilis Hancock, 1830: 127 (type locality: Guyana); neotype: BMNH 1933.8.2.69, designated by Thomson, 1997: 491; Steindachner, 1879: 26 (only specimens originating from Demerara); Jordan & Swain, 1884: 266 (only specimens originating from northern coast of South America); Jordan & Evermann, 1896: 812 (only specimens originating from Pará, Brazil); Fowler, 1903: 744 ( Surinam); Schultz, 1949: 111 ( Venezuela); Menezes, 1983: 3 (only specimens originating from northern to northeastern Brazilian coast); Menezes & Figueiredo, 1985: 23 (only specimens originating from northern to northeastern Brazilian coast; Thomson, 1997: 491 (only specimens originating from Guyana, Suriname and Brazil); González-Bencomo et al. 1997: 159 (Lago de Maracaibo, Venezuela); Aguilera, 1998: 51, Venezuela); Keith et al., 2000: 26 ( Guyana); Menezes et al., 2003: 65 (only specimens originating from southern Caribbean to northeastern Brazilian coast); Harrison, 2003: 1083 (only specimens originating from southern Caribbean region to northeastern Brazilian coast; size, habitat, biology and fisheries; distribution).

Mugil guentheri Steindachner, 1864: 37 (type locality: Guyana)

Mugil xinguensis Steindachner, 1907: 489 (type locality: Providência, Rio Xingu, Brazil).

Myxus calancalae de Beaufort, 1940: 112 (type locality: lower Río Calancala, near San Antonio, Goajira, Colombia; Nijssen et al., 1982: 91 (type catalog); Thomson, 1997: 487 (synonym of Mugil curema ); Harrison et al., 2007: 91 (examination of 3 syntypes and indication of synonymy with Mugil incilis ).

Material examined. LBP18386, 3, SL 139–175 mm, Brazil, Pará: Bragança, foz do Rio Caeté, 0°56’48”S, 46°37’02.4”W; LBP 9059, 2, SL 320–340, Vigia, 0°51’43.2”S, 48°08’21”W; MZUSP 77656, 1. SL 38–57, Praia do Mosqueiro, 1°17’10.4”S, 48°33’30.4”W; MZUSP 77667, 1, SL 98 mm Salvaterra, Praia do Jubim, 1°03’32”S, 48°33’30”W; MZUSP 67529, 1, SL 225 mm, Vigia, 0° 08’06.6”S, 48°13’33”W; MZUSP 3743, 1, SL 170 mm, Belém, 1°45’S, 48°46’06”W; MZUSP 67413-14, 3, 145– 147 mm, Maranhão: Ilha de São Luís, Rio Curuçá, approximately 2°31’S, 44°16’W; MZUSP 43588, 1, SL 170 mm, Lagoa dos Viana, sistema Pindaré-Mirim, 3°21’06.6”S, 48°13’33”W; ECAM uncatalogued, 10, SL 112–234 mm, Venezuela: Isla de Margarita, Laguna La Acequia, Boca de Río, 10°57’40”N, 64°11’11”W.

Diagnosis. Mugil incilis is the only species from the study area having the dorsal-fin origin much closer to the snout tip than to the caudal-fin base and is further distinguished from M. liza , M. curvidens and M. trichodon in having 3 spines and 9 branched rays in adults or 2 spines, 1 unbranched ray and 9 branched rays in juveniles (vs. 3 spines and 8 branched rays in adults or 2 spines, 1 unbranched ray and 8 branched rays in juveniles), from M. curema , M. rubrioculus and M. brevirostris in having 41–44 oblique scale rows from the dorsal limit of the pectoral-fin base to the caudal-fin base (vs. 35–39 oblique scale rows from the dorsal limit of the pectoral-fin base to the caudal-fin base) and from M. margaritae in having 20–23 longitudinal scale rows around the caudal peduncle (vs. 17–18 longitudinal scale rows around the caudal peduncle).

Description. Morphometric data presented in Table 10 . Maximum examined body length 340 mm SL. Body elongate, compressed and moderately deep compared to congeners. Greatest body depth at vertical through spinous dorsal-fin origin. Dorsal profile of head and body slightly convex along tip of snout, straight from vertical through anterior border of orbit to vertical through spinous dorsal-fin origin, slightly convex from that point to caudal peduncle, straight to slightly concave along caudal peduncle. Ventral profile of head and body convex from tip of lower jaw to pelvic-fin origin, straight from this point to anal-fin origin, slightly concave along caudal peduncle. 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 = 24. Spinous dorsal fin-origin closer to snout tip than to caudal base. Posterior soft dorsal-fin rays i, 8 in adults, n = 24. Unbranched pectoral-fin rays ii, first ray much smaller than second; branched rays 14–15, 14, 8, n = 24. Tip of pectoral-fin falling short of vertical through spinous dorsal-fin origin, extending to vertical through about one-third of pelvic fin-length. Pelvicfin rays with I, 5. Tip of pelvic-fin reaching vertical through base of fourth dorsal-fin spine. Anal fin with II, i, 8 in specimens smaller than 30–35 mm SL, III, 8 in adults, n = 24.

Mouth subterminal. Tip of maxilla extending slightly beyond vertical through anterior border of orbit. Single row of minute, unicuspid, spatulate teeth with slightly curved tips on both lips ( Fig. 9 A). Teeth on upper lip slightly larger and more widely spaced than slender teeth on lower lip.

Scales spinoid, spines well-developed on surface of scales and projecting posteriorly along scale margin ( Fig. 9 B). Transverse scale rows from dorsal limit of pectoral-fin base to caudal-fin base 42–47, 44.6, n = 23. Horizontal scale rows from spinous dorsal-fin origin to pelvic-fin origin 13–14, 13.7, n =23. Horizontal scale rows around caudal peduncle 20–23, 21, 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 base about 2.5 times as long as pectoral fin in 175 mm SL specimen (LBP 9061). Modified axilla scale dorsal to pelvic fin twice as long as pelvic fin in same specimen. Gill rakers close set; 23–68 rakers on ceratobranchial portion of first arch, increasing in number ontogenetically ( Fig. 2 ).

Color in alcohol. Body dark dorsally; dark color fading ventrally towards midlateral region, whitish on abdominal region. Central portion of scales of longitudinal scale rows from midlateral region to dorsal midline of body slightly darker, forming inconspicuous horizontal stripes in live or recently preserved specimens. Pelvic and anal fins pale with few scattered dark chromatophores. Spinous dorsal, soft dorsal, pectorals and caudal fins with scattered dark chromatophores. Distal margin of caudal fin slightly darker than remaining parts of fin. Anterodorsal tip of soft dorsal fin dark. Anterodorsal basal portion of pectoral fin with small dark spot extending over basal portions of unbranched rays and ten dorsalmost branched rays, with vertically elongate whitish spot under it extending through bases of remaining ventralmost branched rays.

Cytogenetic and molecular data. The chromosome complement of Mugil incilis is composed of 48 acrocentric chromosomes (FN=48). The largest chromosome pairs, classified as number 1, show a subcentromeric secondary constriction. C-banding showed heterochromatic blocks at the centromeric/pericentromeric regions of all chromosomes, which were more conspicuous on chromosomes 1, given the C-positive signals include the secondary constrictions. AgNO3 and fluorescent in situ hybridization (FISH) with 45S rDNA demonstrated that the nucleolus organizer regions are indeed located on the secondary constrictions of chromosome pair number 1 with 5S rDNA located on this same chromosome pair, near the NOR’s, though signals are closer to the centromeres and of smaller size, compared to those of the major ribosomal gene clusters ( Hett et al., 2011).

The molecular analyzes showed that the number of nucleotide differences between M. incilis and the remaining analyzed species ranges from 34.0 to 63.6 (16S) and 97.7 to 106.9 (COI) (Tables 2 to 5). The genetic distance between this species and the remaining analyzed species ranged from, 0.061 to 0.148 (16S) and 0.166 to 0.198 (COI) (tables 6 and 7). The dendrogram in Figure 1 shows that this species is genetically most similar to M. margaritae and M. curema .

Distribution. Mugil incilis is known from the Venezuelan coast to northern Brazil (Maranhão), always associated with low salinity water or even freshwater and has been captured together with M. trichodon and M. rubrioculus ( Fig. 4 )

Remarks. Examination of one specimen from Sapucaia, Rio Paraíba, Brazil (MNRJ 2150) identified by Ribeiro (1915) as Mugil incilis revealed it to be Mugil curema Valenciennes. The material from Ilha do Bom Jesus, Baía de Guanabara, Rio de Janeiro (MNRJ 3657, 5 specimens and MNRJ 3658, 12 specimens) also identified as M. incilis , actually represented M. curema and M. liza respectively.

One specimen from San Bernardo/Zulia, Venezuela (LBP 6128) has the origin of the spinous dorsal fin closer to the tip of the snout than to the caudal-fin base, which is the main character that distinguishes Mugil incilis from all the other Mugil species. This specimen, however, has fewer transverse lateral series scales (39 vs. 42–47) and might represent a new species as indicated by Siccha-Ramirez et al. (2014: 91) based on molecular data. This specimen is included in the present analysis as Mugil sp. (tables 2 to 7).

Figures

FIGURE 1. Mugil brevirostris, MZUSP 31446. A—Detail of mouth showing part of dentition. B—Detail of scales located on dorsal region of body below dorsal-fin base.

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

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 9. Mugil incilis, LBP 9061. A—Detail of mouth showing dentition. B—Detail of scales located on dorsal region of body above pectoral-fin base.

Tables

TABLE 10. Morphometrics of Mugil incilis. Standard length in mm; measurements through head length are percentages of standard length; last eight entries are percentages of head length.

Characters	n	range	mean	SD
Standard length	24	38.0–340.0	170.7
Body depth	24	21.7–027.4	0 24.5	1.5
Snout to dorsal-fin origin	24	71.0–075.8	0 73.6	1.3
Snout to pectoral-fin origin	24	23.5–027.4	0 26.0	1.1
Snout to pelvic-fin origin	24	34.3–038.6	0 36.4	1.0
Snout to anal-fin origin	24	64.0–071.4	0 68.4	2.0
Caudal peduncle depth	24	010.2–011.7	0 10.8	0.4
Caudal peduncle length	24	017.2–021.1	0 19.0	0.9
Pectoral-fin length	22	017.2–022.3	0 20.0	1.2
Pelvic-fin length	22	015.0–018.7	0 16.8	1.0
Head length	24	023.2–029.4	0 25.3	1.5
Head width	14	057.1–065.8	0 63.6	2.5
Head depth	22	062.5–068.5	0 65.2	1.8
Lip thickness	24	003.4–005.8	0 0 4.8	0.5
Mouth width	24	024.2–029.7	0 27.0	1.5
Mouth depth	14	022.0–025.3	0 23.8	1.0
Horizontal orbital diameter	24	023.3–026.6	0 24.8	1.0
Snout length	24	021.4–025.8	0 23.3	1.2
Upper jaw length	24	025.0–028.5	0 26.8	1.0