Cambeva alphabelardense Costa & Feltrin & Katz 2022, sp. nov.

Cambeva alphabelardense sp. nov.

urn:lsid:zoobank.org:act: 13FDAD9A-CEDC-4027-A79D-FCC3E09CF166

Figs 1, 2A–C, 3–4

Diagnosis

A small species, maximum recorded adult size 46.4 mm SL, diagnosed by the presence of four pelvicfin rays and the combination of the following features: posterior nostril about equidistant from anterior nostril and from orbit; a compact broad autopalatine, its width about equal to its length excluding anterior cartilage and postero-lateral process; presence of an anterior broad and rounded projection on the interopercle; five pectoral-fin rays; six or seven opercular odontodes; 20–23 premaxillary teeth; 24–25 dentary teeth; jaw teeth always pointed; largest rays of the dorsal and anal fins longer than the respective fin bases; dorsal and anal fins rounded; head width 83.5–91.3% of the head length; interorbital length 27.0–31.2%; mesethmoid robust, its width at the base of cornua about four fifths of autopalatine width (Fig. 2A); metapterygoid deeper than long (Fig. 2B).

Differential diagnosis

Cambeva alphabelardense sp. nov. is distinguished from all other congeners by having four pelvicfin rays (vs. five rays whenever the pelvic fin is present). Cambeva alphabelardense sp. nov. differs from all other congeners, except C. betabelardense sp. nov., by the relatively more anterior position of the orbit, making the posterior nostril nearly equidistant from anterior nostril and orbit, a compact broad autopalatine, its width about equal to its length excluding anterior cartilage (Fig. 2A; vs. width conspicuously smaller than that length), and the presence of an anterior broad and rounded projection on the interopercle (Fig. 2B; vs. never a similar projection). Cambeva alphabelardense sp. nov. is distinguished from C. betabelardense sp. nov. by having fewer pectoral-fin rays (five vs. six), fewer opercular odontodes (6–7 vs. 12), fewer teeth on the premaxilla (20–23 vs. 30–34) and dentary (24–25 vs. 30–34), jaw teeth always pointed (vs. anterior-most teeth incisiform), largest rays of the dorsal and anal fins longer than the respective fin bases (vs. shorter), a wider head (head width 83.5–91.3% of the head length, vs. 73.7–78.5%), a wider interorbital distance (27.0–31.2% of the head length, vs. 21.6– 26.2%), a very robust mesethmoid, its width at the base of the cornua about one third of the distance between tips of cornua (Fig. 2A; vs. about one fifth, Fig. 2D), and a deeper metapterygoid that is subrectangular and deeper than long (Fig. 2B; vs. subtriangular and longer than deep, Fig. 2E).

Etymology

The species epithet ʻ alphabelardense ʼ (ʻalphaʼ, the first letter of the Greek alphabet, and ʻabelardenseʼ, Portuguese word referring to people born in Abelardo Luz municipality) is an allusion to the first new species described for this area.

Material examined

Holotype BRAZIL • 1 ex., 43.4 mm SL; Santa Catarina State, Abelardo Luz Municipality, stream tributary to middle Rio Chapecó, Rio Uruguai basin; 26°32′19″ S, 52°25′17″ W; 805 m a.s.l.; 20 Mar. 2021; C.R.M. Feltrin leg.; UFRJ 6990.

Paratypes (n = 21) BRAZIL • 11 ex., 23.6–46.3 mm SL; same collection data as for holotype; UFRJ 6991 • 1 ex. (C&S), 41.8 mm SL; same collection data as for holotype; UFRJ 6992 • 3 ex., 34.1–39.7 mm SL; same collection data as for holotype; CICCAA 12706 • 4 ex., 29.8–46.4 mm SL; same locality as for holotype; 15 Jul. 2020; A. Bianco, F.H. Llanos and C.R.M. Feltrin leg.; UFRJ 6993 • 2 ex. (C&S), 34.3–39.5 mm SL; same collection data as for preceding; UFRJ 6994.

Description

GENERAL MORPHOLOGY. Morphometric data appear in Table 1. Body relatively slender, subcylindrical and slightly depressed anteriorly, compressed posteriorly. Greatest body depth in area just anterior to pelvic-fin base. Dorsal and ventral profile of head and trunk slightly convex, approximately straight on caudal peduncle. Skin papillae minute. Anus and urogenital papilla in vertical through anterior portion of dorsal-fin base. Head sub-rectangular in dorsal view, almost rectangular. Anterior profile of snout slightly convex in dorsal view. Eye small, dorsally positioned in head, in its anterior half. Posterior nostril located approximately mid-way between anterior nostril and orbital rim. Tip of maxillary and rictal barbels posteriorly reaching interopercular patch of odontodes; tip of nasal barbel usually posteriorly reaching area just anterior to opercular patch of odontodes, sometimes shorter, reaching midway between orbit and opercular patch of odontodes. Mouth subterminal. Jaw teeth 20–23 on premaxilla, 24 or 25 on dentary, pointed and slightly curved, arranged in two irregular rows. Branchial membrane attached to isthmus only at its anterior-most point, in ventral midline. Dorsal and anal fins rounded, long, their length larger than respective fin base; total dorsal-fin rays 10–11 (i–ii + II + 7), total anal-fin rays 9 (ii + II + 5); anal-fin origin at vertical through posterior half of dorsal-fin base. Dorsal-fin origin at vertical through centrum of 20 th or 21 st vertebra; anal-fin origin at vertical through centrum of 23 rd or 24 th vertebra. Pectoral fin subtriangular in dorsal view, narrow, posterior margin slightly convex, first pectoral-fin ray terminating in short filament, about 10–20% of pectoral-fin length; total pectoralfin rays 5 (I + 4). Pelvic fin subtruncate, its posterior extremity in vertical just anterior or just posterior to dorsal-fin origin; pelvic-fin bases medially separated by small interspace, about half pelvic-fin base width; total pelvic-fin rays 4 (I + 3). Caudal fin subtruncate, often asymmetrical with dorsal portion slightly longer than ventral one; total principal caudal-fin rays 13 (I + 11 + I), total dorsal procurrent rays 21 (xx + I), total ventral procurrent rays 15 (xiv + I).

LATEROSENSORY SYSTEM. Supraorbital sensory canal continuous, connected to posterior section of infraorbital canal posteriorly. Supraorbital sensory canal with 3 pores: s1, adjacent to medial margin of anterior nostril; s3, adjacent and just posterior to medial margin of posterior nostril; and s6, in transverse line through posterior half of orbit; pore s6 nearer orbit than its paired homologous pore. Single infraorbital sensory canal segment, with two pores, corresponding to pore i10, adjacent to ventral margin of orbit, and pore i11, posterior to orbit; anterior segment of infraorbital canal absent. Postorbital canal with 2 pores: po1, in vertical line above posterior portion of interopercular patch of odontodes, and po2, in vertical line above posterior portion of opercular patch of odontodes. Lateral line of body short, with 2 pores, posterior-most pore in vertical just posterior to pectoral-fin base.

OSTEOLOGY (Fig. 2A–C). Mesethmoid robust, its width at cornua bases about four fifths of autopalatine width; anterior margin slightly concave, often with slight middle projection; mesethmoid cornu narrow, with rounded extremity. Lateral ethmoid articulated with autopalatine by broad articular facet. Antorbital thin, narrow, and short; sesamoid supraorbital slender, without processes, short, its length about twice antorbital length. Premaxilla sub-trapezoidal in dorsal view, laterally narrowing, moderate in length, longer than maxilla. Maxilla boomerang-shaped, slightly curved. Autopalatine sub-rectangular in dorsal view, broad, its width about equal to its length excluding anterior cartilage; medial margin almost straight and with small projection, lateral margin slightly concave; autopalatine posterolateral process minute, almost indistinct. Metapterygoid large and thin, sub-rectangular, deeper than longer. Quadrate slender, dorsal process with constricted base, dorsoposterior margin separated from hyomandibula outgrowth by small interspace. Hyomandibula long, with well-developed anterior outgrowth; middle portion of dorsal margin of hyomandibula slightly concave. Opercle long, longer than interopercle, opercular odontode patch slender, its depth slightly shorter than half length of dorsal hyomandibula articular facet; opercular odontodes 6 or 7; odontodes pointed, nearly straight, transversely arranged; dorsal process of opercle short, extremity rounded; opercular articular facet for hyomandibula with prominent sub-rectangular flap, articular facet for preopercle well developed, rounded. Interopercle moderate, about two thirds hyomandibula length, with pronounced anterior rounded projection; interopercular odontodes 20–22; odontodes pointed, arranged in irregular longitudinal rows. Preopercle compact, with short ventral projection. Parurohyal robust, lateral process narrow, sub-triangular, latero-posteriorly directed, tip pointed; parurohyal head well-developed, with prominent anterolateral paired process; middle foramen oval; posterior process moderate in length, about half distance between anterior margin of parurohyal and anterior insertion of posterior process. Branchiostegal rays 7. Vertebrae 37. Ribs 12 or 13. Two dorsal hypural plates, partially or completely fused, corresponding to hypurals 3 + 4 + 5; single ventral hypural plate corresponding to hypurals 1 + 2 and parhypural.

COLOURATION IN ALCOHOL (Fig. 1). Flank, dorsum and head side with dense concentration of small dark brown spots over pale yellow background; spots irregularly shaped, arranged in irregular longitudinal rows, slightly larger and often coalesced on dorsal portion, slightly darker along flank midline. Nasal and maxillary barbels dark brown, rictal barbel pale yellowish brown. Venter and ventral surface of head white. Unpaired fins hyaline with minute dark grey dots. Paired fins hyaline.

COLOURATION IN LIFE. Similar to colouration in alcohol, but light yellowish brown pigmentation slightly more intense on trunk.

Distribution and habitat

Cambeva alphabelardense sp. nov. is known only from the type locality area in the middle Rio Chapecó drainage, Rio Uruguai basin, southern Brazil (Fig. 3). The type locality is situated in the headwaters of a narrow stream, altitude about 800 m a.s.l., with clearwater, clay bottom and dense marginal vegetation mainly composed of ferns (Fig. 4). This short area, about 600 m long, corresponds to a small residual fragment of the original vegetation consisting of a mixed rainforest. This area is now surrounded by a vast area occupied by soya plantations. However, there is no evidence of siltation in the stream. Cambeva alphabelardense sp. nov. was only found in the well-preserved residual fragment, where the stream was about three or four meters wide and about one meter deep. All specimens, collected with small dip nets (40 × 30 cm) during daylight, were found buried in vegetal debris (mostly tree ferns, and other plant remnants) on the bottom of stream banks. The well-developed marginal vegetation partially shades. Considering the small area occupied by the species, the high level of environmental decline around that area, and the unsuccessful attempts to find other similar biotopes in the region, C. alphabelardense sp. nov. should be regarded as highly threatened with extinction.