Scleromystax salmacis, Britto & Reis, 2005

Britto, Marcelo R. & Reis, Roberto E., 2005, A new Scleromystax species (Siluriformes: Callichthyidae) from coastal rivers of Southern Brazil, Neotropical Ichthyology 3 (4), pp. 481-488 : 482-486

Scleromystax salmacis , new species

Figs. 1-2

Holotype. MCP 38388 (female, 36.7 mm SL) Brazil, Santa Catarina, Praia Grande, arroio Molha Coco in Vila Rosa nearly 5.5 km northwest from Praia Grande , 29º10’14"S 49º58’53"W; V. A. Bertaco & J. F. Pezzi da Silva , 25 Mar 2002.

Paratypes (all from Brazil, Santa Catarina). MCP 29299 (4, 1 cs, 33.2-37.2 mm SL) same data as holotype. MCP 23624 (1, 30.7 mm SL) Praia Grande, arroio Molha Coco in Vila Rosa nearly 5 km northwest from Praia Grande , 29º10’13"S 49º58’49"W; E. H. L. Pereira, R. E. Reis & J. F. Pezzi da Silva , 21 Jul 1999 . MCP 17801 (2, 41.3-48.2 mm SL) Nova Veneza, rio CedroAlto , approx. 28º38’S 49º30’W; S. Althoff, 12 Mar 1993 . UFRJ 140 (2, 32.9- 33.7 mm SL) Nova Veneza, creek (“canal”) tributary of rio São Bento ; F.A. Bockmann, 5 Mar 1990 .

Non-type material ( Brazil, Santa Catarina). MCP 28729 (24, 3 cs, 21.1-53.1 mm SL) Florianópolis, creek tributary of rio Ratones, 27º30’40"S 48º29’11"W; 25 Oct 2001. MCP 28744 (3, 33.8-41.9 mm SL) Florianópolis , creek tributary of rio Ratones, at Bairro Ratones, 27º30’31"S 48º29’33"W; 25 Oct 2001 .

Diagnosis. Scleromystax salmacis differs from its congeners by the following features: presence of only one perforated dorsolateral body plate (vs. none or 2-5 perforated dorsolateral body plates); ventral keel of scapulocoracoid orientated towards anterior margin of bone, its anterior portion surpassing horizontal through middle of mesial border of scapulocoracoid (vs. keel parallel to posterior margin of the scapulocoracoid, not surpassing horizontal through middle of mesial border of bone); preopercular-opercular region similar in males and females, with only minute, scattered odontodes (vs. males with developed odontodes inserted in fleshy papillae); and dorsal and pectoral fins equal in length on both sexes (vs. dorsal and pectoral fins of males 2-3 times as long as those fins in females).

Among Scleromystax species, the new taxon is most similar to S. macropterus , differing from this species mainly by the absence of a black spot on the base of the median caudalfin rays (vs. presence), a higher number of pectoral-fin rays (I,8,i vs. I,7,i), males with somewhat more slender bodies (25.7- 30.5% in SL [range 26.3-28.8% in type series] vs. 30.4-34.6% in SL), and transverse blotches along body more irregular than those in S. macropterus . In addition to differences in coloration, external features, and osteological characters noted above, the new species differs from S. barbatus (a sympatric species) by having a deeper caudal peduncle (12.3-15.3% in SL [range 12.6-15.3% in type series] vs. 8.0-12.0% in SL), a larger interorbital distance (29.4-33.7% in HL [range 30.3- 33.7% in type series] vs. 20.0-26.0% in HL), and a smaller snout length (39.9-45.5% in HL [range 39.9-43.6% in type series] vs. 45.0-52.0% in HL).

Description. Morphometric data presented in Table 1 . Head compressed with slightly convex dorsal profile in cross section and roughly triangular in dorsal view ( Fig. 1 ). Snout rounded and slightly elongate. Head profile convex from upper lip to tip of posterior process of parieto-supraoccipital, with very slight convexity just anterior to nares. Profile of body slightly convex along dorsal-fin base. Postdorsal-fin body profile concave to adipose-fin spine; markedly concave from this point to caudal-fin base. Ventral profile of body nearly straight from isthmus to anal-fin origin, with pronounced convexity just anterior to pelvic fin. Profile markedly concave from first anal-fin ray to caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye round, located dorsolaterally on head; orbit delimited dorsally by frontal and sphenotic, ventrally by infraorbitals. Anterior and posterior nares close to each other, only separated by flap of skin. Anterior naris tubular. Posterior naris close to anterodorsal margin of orbit, separated from orbit by distance equal to twice diameter of naris. Mouth small, subterminal, width nearly equal to bony orbit diameter. Maxillary barbel elongate, reaching anteroventral limit of gill opening in some individuals. Maxillary barbel slightly longer than outer mental barbel. Inner mental barbel fleshy. Small rounded papillae cover entire surface of all barbels, upper and lower lips, and isthmus. Minute odontodes scattered between pectoral and pelvic girdles. Gill membranes united to isthmus. Four branchiostegal rays covered by thick layer of skin; distal two rays united at their tips by branchiostegal cartilage. Teeth on upper pharyngeal tooth plate 42(1) [38(1) or 39(2) in non-type specimens], and on fifth ceratobranchial 31(1) [29(1) or 30(2) in non-type specimens].

Nasal, frontal, sphenotic, compound pterotic, and parietosupraoccipital visible externally, all covered by thin layer of skin and bearing minute scattered odontodes. Frontal fontanel elongate, covered by thin layer of skin, and reaching middle of parieto-supraoccipital. Nasal slender, slightly curved laterally, mesial border contacting frontal and mesethmoid. Frontal roughly rectangular; anterior expansion in contact with nasal bone and mesethmoid, posterior portion contacting sphenotic and parieto-supraoccipital. Sphenotic trapezoid in shape, contacting parieto-supraoccipital dorsally, compound pterotic posteriorly, second infraorbital ventrally. Compound pterotic roughly pipe-shaped, with slender posterior expansion contacting first dorsal body plate dorsally, and first lateral-line ossicle posteriorly. Ventral margin of compound pterotic contacting opercle and cleithrum. Parieto-supraoccipital quadrangular with posterior expansion triangular and elongate, but not reaching nuchal plate. Minute odontode-bearing platelets between parieto-supraoccipital posterior process and nuchal plate.

Two narrow infraorbital bones, externally visible, covered by thin layer of skin; both bearing few minute odontodes. First infraorbital expanded anteriorly. Opercle exposed, ovoid in shape and roughly elongate, with angular free border. Preopercle externally visible, slender and covered by thin layer of skin. Interopercle triangular, partially covered by thin layer of skin, partially covered by thick skin. Opercle, preopercle, and interopercle with minute odontodes scattered over their surfaces.

Trunk lateral line composed of one perforated dorsolateral body plate and two laterosensory canals, reduced to small ossicles; one specimen (MCP 29299, 37.2 mm SL) without perforated dorsolateral body plates. Lateral-line canal entering neurocranium through compound pterotic, splitting into two branches before entering sphenotic: pterotic and preoperculomandibular each with single pore. Sensory canal continuing through compound pterotic, entering sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, other branch entering frontal through supraorbital canal. Supraorbital canal with two branches: epiphyseal branch that opens in frontal bone, and anterior branch that runs through nasal bone. Nasal canal with single opening at each end. Infraorbital canal runs through entire second infraorbital, extending to infraorbital 1 and opening into two pores. Preoperculomandibular branch not connected to preoperculomandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively.

Body plates with minute odontodes restricted to posterior margins. Nuchal plate exposed. Cleithrum exposed laterally. Dorsolateral body plates not touching counterparts at middorsal line. Narrow middorsal groove extends from last dorsal-fin ray to first preadipose platelet. Dorsolateral body plates 25(1) or 26*(4) [25(1), 26(8), 27(4), or 28(1) in non-type specimens]; ventrolateral body plates 23*(5) [23(4), 24(8), or 25(2) in non-type specimens]; dorsolateral body plates along dorsal-fin base 6(2) or 7*(3) [6(5), 7(8), or 8(1) in non-type specimens]; dorsolateral body plates from adipose fin to caudal-fin base 7(2) or 8*(3) [7(1), 8(7), or 9(6) in non-type specimens]; preadipose platelets 5(4) or 6*(1) [5(1), 6(3), 7(5), 8(3), 9(1), or 10(1) in non-type specimens]. Precaudal vertebrae 9(1) [8(2) or 10(1) in non-type specimens]; caudal vertebrae 15(1) [15(2) or 17(1) in non-type specimens]; 6(1) pairs of ribs, first pair conspicuously larger than others.

Dorsal fin roughly triangular; its origin just posterior to third dorsolateral body plate. Dorsal spine shorter than first three branched rays. Distal tip of dorsal spine slightly curved posteriorly. Anterior and posterior borders of dorsal spine smooth. Dorsal-fin rays I,7(1), I,8*(3), or I,9(1) [I,8(13) or I,9(1) in non-type specimens]. Adipose fin roughly triangular; its origin separated from base of last dorsal-fin ray by 8(2), 9*(2), or 10(1) dorsolateral body plates. Anal fin roughly triangular; its origin located just posterior to 13th ventrolateral body plate, at vertical through posterior margin of last preadipose platelet. Anal-fin rays ii,6*(3) or ii,7(2) [ii,5,i(6) or ii,6(8) in non-type specimens]. Pectoral fin roughly triangular; its origin located just posterior to gill opening. Ossified portion of pectoral spine shorter than first two branched rays. Distal tip of spine with minute segmented unossified portion. Pectoral spine with welldeveloped serrations along entire posterior border. Pectoral-fin rays I,8,i*(5) [I,8,i(12) or I,9,i (1) in non-type specimens, one specimen (UFRJ 140, 33.7 mm SL) I,6,i]. Ventral keel of scapulocoracoid orientated to anterior margin of bone, its anterior portion surpassing horizontal through middle of mesial border of scapulocoracoid ( Fig. 3 ). Pelvic fin ellipsoidal; its origin just below second ventrolateral body plate, at vertical through base of third branched dorsal-fin ray. Pelvic-fin rays i,5*(5). Caudal fin bilobed; both lobes equal in size. Principal caudal-fin rays i,6/6,i, one specimen (MCP 29299, 34.9 mm SL) i,6/4,i; five upper and four lower procurrent caudal-fin rays.All fins with minute odontodes scattered over all rays.

Color in alcohol. Ground coloration of head light brown. Small, irregular, dark brown blotches scattered over dorsal and lateral surface of head and snout. Several concentrated chromatophores forming irregular dark brown stripe along side of snout from anteroventral margin of orbit to corner of mouth. Anterior naris with series of minute brown chromatophores more concentrated at margin. Thin faint brown ring surrounding orbit. Maxillary and outer mental barbels light brown, with minute, scattered, small dark brown blotches on proximal half. Inner mental barbel unpigmented. Preopercle brown. Chromatophores scattered over preopercle, opercle and region corresponding to adductor mandibulae muscle, forming several irregular small blotches, more concentrated on free bor- der of opercle and region of articulation between opercle and interopercle. Ventral region of head yellowish white, with few scattered chromatophores on branchiostegal membranes close to cleithrum.

Ground color of trunk light brown. Large dark brown blotch on cleithrum, faint in its middle region. First dorsolateral body plate with dark brown blotch encompassing its anteroventral region and posteroventral region of parieto-supraoccipital. Three large, irregular, roughly elongate, dark brown blotches along body plates; largest blotch, just below dorsal spine, with dorsal extension reaching dorsal-spine base, and ventral extension reaching to pelvic-fin base; second blotch between dorsal and adipose fins, with ventral expansion reaching ventral tip of ventrolateral body plate; and third blotch just below adipose-fin spine (confluent with second blotch in some specimens), extending from preadipose platelets to anal-fin base. Several chromatophores forming small, irregular, faint blotches between first and second trunk blotches. Irregular, faint-brown, thin stripe on dorsal portion of dorsolateral body plate between first dorsal-fin ray base and third trunk blotch. Small, irregular, dark brown blotch just below last dorsal-fin ray. Several scattered chromatophores on dorsolateral body plate. Irregular, roughly curved, dark brown blotch on caudal peduncle; confluent with caudal fin pigmentation in some individuals. Ventral surfaces of body yellowish white.

Ground color of all dorsal-fin elements yellowish white; interradial membranes hyaline. Roughly triangular, diffuse blotch from dorsal spine to fourth/fifth branched dorsal-fin ray. Several chromatophores forming diffuse irregular stripe on mid-distal portion from second or third to sixth dorsal-fin branched rays; some individuals with several chromatophores on distal tip of fin from third to sixth branched ray. Scattered chromatophores on last two dorsal-fin rays. Ground color of anal-fin rays yellowish white. Interradial anal-fin membranes hyaline. Diffuse brown stripe on middle region of anal fin, not including anal-fin unbranched ray. Adipose-fin spine light brown with dark brown blotch on distal tip. Adipose-fin membrane with several scattered chromatophores, more concentrated on posterior border. Three to four series of small, diffuse, dark brown blotches restricted to pectoral-fin rays, not extending onto membranes. Ground color of all pectoral-fin rays and spine light brown; interradial membranes hyaline. Pectoral spine with scattered dark brown chromatophores. Pelvic fin hyaline, with diffuse brown blotch on mid-proximal portion from second to fourth unbranched ray. Ground color of caudal-fin rays yellowish white; caudal-fin membranes hyaline. Caudal fin with three to four series of small, dark brown blotches restricted to rays and forming poorly defined arched thick bands.

Sexual dimorphism. According to Nijssen & Isbrücker (1980:135) and Britto (2003), corydoradine males can be recognized by the lanceolate shape of the genital papilla. However, this condition is unreliable as a means for distinguishing the sexes in smaller individuals (juveniles) (Nijssen & Isbrücker, 1980; Lima & Britto, 2001). Among previously described Scleromystax species males with well-distinguishable genital papillae also have other dimorphic features that help to distinguish them (see Diagnosis), although those features show a variable degree of development within the genus (see Discussion). Scleromystax salmacis sampled in the present study has no dimorphic conditions besides the shape of the genital papillae at any stage of development (compare Figs. 1 and 2 ), raising some questions as to the most useful features to distinguish Scleromystax (see Discussion).

Habitat and ecological notes. The type locality is a small pond near the arroio Molha Coco. The pond is surrounded by grass and is partially shaded by low trees and bamboo shrubs. The water is clear and slow flowing, and the bottom is formed by rocks covered by a thin layer of mud. The pond is fed by a very small creek and is periodically flooded by the main stream. Other species collected along with Scleromystax salmacis at the type-locality are Steindachnerina biornata , Mimagoniates rheocharis , Astyanax scabripinnis , Hollandichthys sp., Rineloricaria aequalicuspis , Pareiorhaphis nudula , and Phalloceros caudimaculatus . The rio Ratones, on the other hand, has a sandy bottom and specimens were collected on an open, sand bank.

Holotype Paratypes Non-type specimens

Females Males Females Males

Mean (n=5) Range Mean (n=3) Range Mean (n=4) Range Mean (n=5) Range Standard length (mm) 36.7 37.8 30.7 - 48.2 34.4 32.9 - 37.2 45.6 37.9 - 53.1 32.5 31.0 - 33.8 Percents of Standard length

Depth of body 29.8 28.5 25.8 - 30.9 27.8 26.3 - 28.8 28.5 27.1 - 29.1 28.2 25.7 - 30.5 Predorsal distance 45.9 46.7 44.1 - 48.8 48.1 47.1 - 49.9 44.4 43.4 - 45.8 45.7 44.7 - 47.9 Prepelvic distance 47.2 48.1 46.2 - 50.8 49.1 47.8 - 49.8 45.7 44.2 - 46.5 47.3 46.4 - 48.3 Preanal distance 77.3 78.5 77.2 - 79.7 79.1 78.6 - 79.5 77.3 76.6 - 78.9 76.3 73.6 - 77.6 Preadipose distance 84.1 84.1 83.2 - 85.4 84.1 83.0 - 85.6 83.1 82.2 - 84.4 83.6 81.1 - 85.5 Length of dorsal spine 15.4 14.9 10.4 - 17.5 16.6 16.1 - 17.0 13.7 12.7 - 15.4 14.1 12.5 - 15.4 Length of pectoral spine 22.0 20.9 19.1 - 24.5 22.8 21.6 - 23.9 19.8 18.1 - 21.6 20.6 18.0 - 22.4 Length of adipose-fin spine 9.1 9.1 7.9 - 11.1 9.9 9.2 - 10.6 8.6 7.8 - 9.9 9.7 8.9 - 10.2 Depth of caudal peduncle 13.8 13.4 12.6 - 14.0 14.4 13.7 - 15.3 12.7 12.3 - 13.6 13.9 13.1 - 14.5 Dorsal to adipose distance 22.8 24.3 21.9 - 27.2 23.5 22.6 - 24.4 25.4 23.1 - 26.4 23.4 21.8 - 24.6 Length of dorsal-fin base 18.5 18.2 16.7 - 21.2 18.6 17.8 - 19.2 17.1 16.5 - 17.8 17.3 16.1 - 18.8 Maximum cleithral width 13.0 12.5 11.9 - 13.6 12.1 11.6 - 12.4 14.3 11.7 - 15.9 13.5 12.1 - 14.8 Head length 39.1 38.0 36.0 - 39.9 38.7 37.8 - 39.6 36.1 34.9 - 37.1 36.5 35.1 - 37.4 Length of maxillary barbel 11.9 11.5 5.3 - 14.6 13.8 9.9 - 16.1 13.4 9.6 - 18.5 12.3 8.8 - 16.6 Percents of Head length

Head depth 76.7 74.1 73.2 - 74.8 73.3 72.3 - 74.1 73.5 72.1 - 76.1 73.8 70.7 - 76.6 Least interorbital distance 30.3 31.9 30.3 - 33.7 31.5 30.3 - 32.5 30.0 29.4 - 30.4 32.3 29.8 - 33.5 Horizontal orbit diameter 18.5 18.6 16.3 - 21.5 18.0 17.9 - 18.2 17.0 15.6 - 18.4 20.4 19.1 - 21.6 Snout length 39.9 41.8 40.6 - 42.9 42.1 40.5 - 43.6 43.6 42.7 - 44.5 42.8 40.7 - 45.5 Least internareal distance 17.9 18.5 17.0 - 22.0 19.8 17.6 - 23.0 20.1 19.2 - 21.6 20.0 18.8 - 21.1

Distribution. Rio Mampituba and rio Araranguá basins in southern Santa Catarina State of Brazil ( Fig. 4 ). Non-type specimens were collected in the rio Ratones, a small coastal river drainage in Florianópolis. This species has the southernmost distribution in the genus.

Etymology. Scleromystax salmacis , is named after the character of Ovid’s tale, “The fountain of Salmacis”. From the Greek Salmacis, a nymph who had fallen in love with Hermaphroditus, the son of Hermes and Aphrodite. To avoid letting him go, Salmacis leapt upon him, and they both tumbled into the waters of her fountain, legs and arms twisted around each other. Filled with despair, the nymph shouted to the heavens, imploring the Fates or the gods never to allow the two of them to be separated. From her strength of will and his divine heritage, between the thrashing of the pure water and the twisting of limbs, the two merged into one form. It had one pair of arms, one set of legs, one head and one face but was both male and female at the same time. So Hermaphroditus, who was both male and female in name, cursed the pool for making him the same in body. To this day men hesitate to drink or bathe in waters taken from the fountain of Salmacis in fear that a similar fate shall befall them as well.

In allusion to its very subtle sexual dimorphism when compared to other Scleromystax species. A noun in apposition.

Figures

Fig.1. Scleromystaxsalmacis, holotype,MCP 38388, female,36.7 mm SL, arroio Molha Coco, PraiaGrande, Santa Catarina, Brazil.

Fig. 2. Scleromystaxsalmacis,paratype, MCP 29299, male,37.2 mmSL, arroioMolha Coco,Praia Grande, Santa Catarina,Brazil.

Fig. 3. Ventral view of right pectoral girdle of Scleromystax salmacis, paratype, MCP 29299, 33.2 mm SL. Double-headed arrow showing orientation of the proximal portion of the ventral keel of the scapulocoracoid.

Fig. 4. Geographic distribution of Scleromystax salmacis. T = type-locality.

Tables

Table 1. Morphometric data of Scleromystax salmacis.