Microcambeva mucuriensis, Costa & Katz & Mattos & Rangel-Pereira, 2019

Costa, Wilson J. E. M., Katz, Axel M., Mattos, José L. O. & Rangel-Pereira, Filipe S., 2019, Two new species of miniature psammophilic sarcoglanidine catfishes of the genus Microcambeva from the Atlantic Forest of eastern Brazil (Siluriformes: Trichomycteridae), Journal of Natural History 53 (29), pp. 1837-1851 : 1837-1851

Microcambeva mucuriensis sp. nov.

( Figures 1–2 )

Holotype

UFRJ 12123, 25.2 mm SL; Brazil: Estado da Bahia: Município de Mucuri: Rio Mucuri close to the bridge on road BR-101, 18.098°S, 39.893°W, altitude about 25 m above sea level (asl); A. Katz, F. Pereira and J.L. Mattos, 18 July 2016.

Paratypes

UFRJ 11091, 22 ex., 14.5–19.3 mm SL ; UFRJ 11028 , 4 ex., 14.2–17.2 mm SL ; UFRJ 11841 , 5 ex., 15.3–19.05 mm SL (C&S) ; CICCA 03525 , 2 ex., 16.2–17.1 mm SL ; all collected with holotype.

Diagnosis

Microcambeva mucuriensis is distinguished from all other congeners except M. draco and M. jucuensis by the presence of a distal widening on the posterior process of the autopalatine (vs absence) and a rudimentary anterior autopalatine ossification, consisting of a minute thin ossification, with its length about one-fourth the width of the anterior cartilage of the autopalatine (vs ossification well developed in M. barbata , its length nearly equal to the width of the anterior cartilage head of autopalatine; autopalatine ossification absent in M. ribeirae ). Microcambeva mucuriensis is distinguished from M. jucuensis in having a thin interopercle, with a well-developed anterior process (vs interopercle robust, with a rudimentary anterior process) and fewer opercular odontodes (9–12 vs 13–15). Microcambeva mucuriensis differs from M. draco in having fewer premaxillary teeth (19 or 20 vs 24 or 25), a longer nasal barbel, nearly reaching the anterior margin of the orbit (vs reaching the anterior margin of the posterior nostril), a shorter pectoral-fin filament, its length about 5–10% of the pectoral-fin length excluding the filament (vs about 30%), and the sesamoid supraorbital equal in length to or shorter than the antorbital (vs longer).

Description

Morphometric data appear in Table 1 . Body slender, subcylindrical and slightly depressed anteriorly, compressed posteriorly. Greatest body depth at vertical line just in front of pelvic-fin base. Dorsal and ventral profiles of head and trunk slightly convex, approximately straight on caudal peduncle. Anus and urogenital papilla in vertical line through posterior third of dorsal-fin base. Head narrow, sub-triangular in dorsal view. Anterior profile of snout convex in dorsal view. Eye elliptical, dorsally positioned in head. Posterior naris slightly nearer to anterior naris than to anterior margin of orbit. Tip of maxillary barbel reaching base of opercular patch of odontodes; tip of rictal barbel reaching middle part of interopercular patch of odontodes; tip of nasal barbel reaching anterior margin of orbit. Mouth subterminal. Chin region with paired finger-like projections. Jaw teeth conical, arranged in two series: 17–19 teeth on premaxilla, 13–16 on dentary. Branchial membrane attached to isthmus only at its anterior point. Opercular odontodes 9–12, interopercular odontodes 7–9. Dorsal surface of neurocranium with broad lozengeshaped fontanelle between frontals and anterior portion of sesamoid supraorbital. Branchiostegal rays 6.

Dorsal and anal fins subtriangular; dorsal-fin rays ii + 5 + ii, anal-fin rays ii + 4 + I; rudimentary unsegmented ray immediately posterior to both dorsal- and anal-fin origin; anal-fin origin in vertical line posterior to dorsal-fin base. Caudal fin slightly forked, ventral portion slightly longer than dorsal portion; principal caudal-fin rays 13 (i–ii + 10–11 + i), dorsal procurrent rays v–vii, ventral procurrent rays v–vi. Pelvic fin slightly pointed, its tip reaching vertical line through middle of dorsal-fin base, pelvic-fin bases medially separated by interspace nearly equal to pelvic-fin base width; pelvic-fin rays i + 4. Pectoral fin subtriangular in dorsal view, first pectoral-fin ray terminating in short filament reaching about 5–10% of pectoral-fin length without filament; pectoral-fin rays i + 6. Dorsal-fin origin on vertical line through vertebra 16, anal-fin origin on vertical line through vertebra 20 or 21, pelvic-fin insertion on vertical line through vertebra 12 or 13. Vertebrae 34 or 35. Ribs 3 or 4.

Mesethmoidal region and adjacent structures ( Figure 2 (a)). Anterior margin of mesethmoid nearly straight, mesethmoid cornua narrow, rod-like. Antorbital and sesamoid supraorbital rod-like, both approximately equal in length. Premaxilla slender, subtriangular, bearing prominent sharp lateral process. Maxilla slender, laterally terminating in long and sharp process. Autopalatine elongate, lateral margin nearly straight, medial margin concave; width of middle portion about three-quarters of autopalatine cartilage width; latero-posterior process of autopalatine slender and long, about two-thirds autopalatine length without latero-posterior process, with subterminal widening creating arrow shape in dorsal view; cartilaginous head of autopalatine prominent, its length about onethird of autopalatine length without latero-posterior process; anterior autopalatine ossification rudimentary, scale-like.

Suspensorium and opercular apparatus ( Figure 2 (b)). Metapterygoid minute, subtriangular, its greatest length about half length of antero-dorsal portion of quadrate. Quadrate slender, its length about 60% length of hyomandibula without anterior process, its depth about one-quarter total length of quadrate; dorsoposterior process rudimentary or absent. Hyomandibula with narrow, pointed anteriorly directed process, its length about 70% hyomandibula longitudinal length excluding process, its tip anteriorly reaching vertical line through anterior fifth of quadrate length. Opercle moderately slender, odontode patch width about three-fifths width of dorsal portion of hyomandibula. Interopercle thin and relatively narrow, width of distal portion of odontode patch about half width of dorsal portion of hyomandibula; anterior process well developed.

Colouration in life ( Figure 1 (a)). Trunk and head almost translucent. Small superficial melanophores arranged in longitudinal zones, along mid-lateral, dorso-lateral and middorsal portions of trunk, and scattered on post-orbital area and central portion of dorsal surface of head. Internal dermal layer of trunk with row of alternating elongate dark grey and pale orangish-yellow spots along mid-lateral line of body; another similarly coloured row between pectoral-fin base and anus. Dark grey stripe between nasal barbel and orbit. Iris pale yellow, with small superficial melanophores. Fins hyaline, with dark chromatophores concentrated on their basal side forming small black spots.

Colouration in alcohol. After fixation, specimens became opaque light yellowish grey. Superficial chromatophores still visible.

Distribution and habitat notes

Microcambeva mucuriensis is known from a single locality (18°05 ʹ 53 ʺ S, 39°53 ʹ 36 ʺ W), in the middle section of the Rio Mucuri, which comprises an isolated river basin of eastern Brazil, with a course of about 320 km ( Figure 3 ). In the type locality area, about 30 km from the sea, the river width was about 85 m and the river margin was occupied by a dense forest ( Figure 4 ). Collection was made during the dry season, when the water was clear and sand banks were exposed. Microcambeva mucuriensis was collected during sunlight on the sandy bottom, close to the border of an emerged central sand bank.

Etymology

The name mucuriensis refers to the occurrence of the new species in the Rio Mucuri.

Figures

Figure 1. Microcambeva mucuriensis sp. nov., UFRJ 12123, holotype, 25.2 mm standard length: (a) left lateral view (in life); (b) left lateral view (preserved); (c) head, dorsal view; (d) head, ventral view.

Figure 2. Osteological structures of Microcambeva mucuriensis sp. nov., UFRJ 11841, paratype, 17.6 mm standard length: (a) mesethmoidal region and adjacent structures, left and middle portions, dorsal view; (b) left suspensorium and opercular series, lateral view. Larger stippling represents cartilaginous areas. aao, autopalatine anterior ossification; apw, autopalatine posterior process widening; iap, interopercular anterior process. Scale bar: 0.5 mm.

Figure 3. Map of geographical distribution of Microcambeva: white square, M. draco; black square, M. mucuriensis; star, M. jucuensis; circle, M. barbata; triangle, M. ribeirae.

Figure 4. Rio Mucuri at the type locality of Microcambeva mucuriensis, Mucuri, Bahia, Brazil.