Microlepidogaster roseae, Martins, 2022

Martins, Fernanda O., 2022, A new species of Microlepidogaster (Loricariidae: Hypoptopomatinae) from rio Pardo, a coastal drainage in eastern Brazil, Zootaxa 5150 (2), pp. 269-281 : 270-278

Microlepidogaster roseae , new species

( Fig. 1 ; Tab. 1–2 )

Microlepidogaster sp. n. “Pardo”. — Martins, 2016: 183, 187 (phylogenetic relationships)

Type material. Holotype. MZUSP 126736 , female, 37.1 mm SL, Brazil, Minas Gerais State, Santo Antônio do Retiro, rio Sussuarana, tributary to rio Preto , rio Pardo drainage, 15°23’41.03”S 42°36’31.8”W, 8 Aug 2012, J.L.O. Birindelli, F.C.P. Dagosta, M.V. Loeb, W. Meireles.

Paratypes. All collected with holotype. MZUSP 112424 , 40 , 21.4–37.5 mm SL. MZUEL 21730 , 4 (1 c&s), 21.1–38.6 mm SL. DZSJRP 23196 , 3 (1 c&s), 31.7–38.9 mm SL .

Diagnosis. Microlepidogaster roseae differs from all congeners by having the anterior portion of snout with a large odontode-free band, extending laterally from the anterior tip of snout to the anterior portion of postrostral plate 2 ( Fig. 2 ) (vs. anterior odontode-free band completely absent or restricted to the anterior portion of snout, only where the plates are also absent); transverse process of second dorsal-fin pterygiophore exposed and bearing odontodes ( Fig. 3 ) (vs. transverse process covered by dorsal series of lateral plates); and exposed area of pectoral girdle extending up to mesial symphysis, with odontodes restricted to coracoid ventral expansion and few odontodes, generally a single row, in the cleithrum ( Fig. 4 ) (vs. exposed area restricted to lateral portion of girdle in M. discontenta , M. discus , and M. negomata , or exposed area extending up to the middle portion of pectoral girdle, with odontodes occupying equally the cleithrum and coracoid expansions in M. arachas , M. dimorpha , M. longicolla , and M. perforata ).

The following features are also useful to diagnose M. roseae within the genus: anterior portion of compound supraneural plus first dorsal-fin proximal radial contacting the neural spine of the 7th vertebra (vs. 8th or 9th vertebra in M. negomata and M. perforata ; 9th vertebra in M. arachas ; 10th vertebra in M. discontenta ; and 10th or 11th vertebra in M. longicolla ); pectoral axillary slit present, in both juveniles and adults (vs. pectoral axillary slit present only in juveniles in M. arachas , M. discontenta , M. discus , M. longicolla , and M. negomata ); odontodes at anterior portion of snout small and slightly pointed (vs. leaf-shaped odontodes in M. dimorpha and M. perforata ); mid-dorsal lateral series of plates surpassing the vertical through the end of dorsal fin ( Fig. 5 ) (vs. mid-dorsal lateral series reduced, never surpassing that point in M. longicolla and M. perforata ); median series of lateral plates complete, reaching the end of the caudal peduncle ( Fig. 5 ) (vs. median series of lateral plates terminating two plates before the end of the caudal peduncle in M. perforata ); iris operculum present (vs. iris operculum absent in M. perforata ); odontodes on caudal peduncle randomly distributed (vs. odontodes on caudal peduncle conspicuously arranged in longitudinal lines in M. discontenta ); and absence of unperforated platelets on skin covering swimbladder opening (vs. two to five unperforated platelets in that area in M. negomata ).

Description. Morphometric and meristic data in Tables 1 and 2 . Dorsal body profile slightly convex from snout tip to posterior tip of parieto-supraoccipital; almost straight to dorsal-fin origin; descending at dorsal-fin base; almost straight towards to caudal-fin origin. Ventral body profile almost straight from snout tip to pelvic-fin origin; ascending from that point to end of anal-fin base; and straight towards to caudal-fin origin. Greatest body depth variable, at parieto-supraoccipital posterior tip or at dorsal-fin origin. Greatest body width at opercle region, gradually tapering towards to caudal fin. Caudal peduncle ellipsoid in transverse section, slightly flattened dorsally and ventrally.

Anterior margin of snout rounded in dorsal view; tip of snout naked, without rostral plates. Eye small, dorsolaterally placed on head. Iris operculum present. Compound pterotic quadrangular in shape, its posterior extension poorly developed, not reaching rib of sixth vertebra; compound pterotic fenestrae irregular in shape and variable in size, smaller in dorsal and larger in ventral portion of bone. Infraorbital canal entering infraorbital series via sphenotic. Parieto-supraoccipital not forming dorsal wall of swimbladder capsule.

Odontodes on head and body small and slightly pointed, not arranged in conspicuous rows. Bony crests and hypertrophied odontodes on parieto-supraoccipital and compound pterotic absent. Lips oval, papillose; lower lip not reaching pectoral girdle; papillae gradually smaller toward lip edges. Maxillary barbel reduced, free from oral disk. Teeth slender and bifid; median cusp larger and rounded, lateral cusp smaller and pointed. Premaxillary teeth 16–25 (19). Dentary teeth 14–22 (19). Accessory teeth absent in adults and juveniles, at least in specimens larger than 21.1 mm SL.

Dorsal-fin rays II,6–7 (7); originating posteriorly to vertical through end of pelvic-fin base; tip of adpressed rays almost or reaching vertical through end of anal-fin base; spinelet small, somewhat triangular in shape, locking mechanism non-functional. Anterior portion of compound supraneural plus first dorsal-fin proximal radial contacting neural spine of seventh vertebra. Pectoral-fin rays I,6; originating immediately behind opercular opening; tip of adpressed first ray surpassing vertical through end of pelvic-fin base. Pectoral girdle exposed almost in its entire extension; odontodes restricted to coracoid ventral expansion (except for a single row in cleithrum). Arrector fossa partially enclosed by ventral laminar expansions of coracoid and cleithrum; opening extending laterally, slightly passing halfway towards pectoral-fin base. Pectoral axillary slit present in both adults and juveniles. Pelvic-fin rays i,5; unbranched ray shorter than branched rays. Anal-fin rays i,5. Caudal-fin rays i,14,i; concave, lobes equal in size or subequal, lower lobe slightly longer than upper; 4 dorsal and 3–4 ventral procurrent rays. Adipose fin absent.

Body entirely covered by dermal plates, except for ventral part of head, region overlying opening of swimbladder capsule, around pelvic-fin origin, and region anterior to urogenital opening. Abdomen entirely covered with small-sized plates irregularly distributed; smaller specimens without plates or with sparse plates between pelvic fins; lateral abdominal plate series absent. Mid-dorsal series of lateral plates surpassing vertical through end of dorsal fin, almost complete except for about five plates. Median lateral plate series complete and uninterrupted with 27 plates. Vertebrae 30.

Color in alcohol. Ground color of dorsal surface of head dark brown. Pair of longitudinal inconspicuous light stripes dorsally in head, beginning medially at tip of snout and running to nares, extending laterally to orbital edge, and proceeding to compound pterotic posterior tip. Ground color of body light brown on dorsal, lateral and ventral portions. Inconspicuous dark brown lateral stripe, approximately two plates wide, extending from compound pterotic posterior edge to end of caudal peduncle. Four dark brown dorsal saddles, extending lateroventrally and fused to lateral stripe: first at dorsal-fin origin; second at end of dorsal-fin base; third after vertical line passing through end of anal-fin base, and fourth at end of caudal peduncle. All fins, except for caudal, with hyaline membranes and medium to dark brown, small, and elongate blotches along rays, more evident in unbranched rays and first and/or second branched ray. Caudal fin almost entirely dark brown, except for distal tip of dorsal and ventral lobes and hyaline mesial blotch in each lobe. All dark stripes, saddles, and blotches inconspicuous in life ( Fig. 6 ).

Sexual dimorphism. Males with conspicuous urogenital papilla immediately posterior to anus (vs. absent in females); adult males with dermal flap on the dorsal surface of unbranched thick ray of pelvic fin (vs. absent in females); and males with longer pelvic fin extending almost to or even surpassing anal-fin origin (vs. pelvic fin not reaching anal-fin origin in females).

Distribution. Microlepidogaster roseae is only known from the rio Sussuarana, tributary to rio Preto, rio Pardo drainage, Minas Gerais State, Brazil ( Fig. 7–8 ). The type locality is part of a Priority Conservation Area for fishes, categorized as insufficiently know by Ministério do Meio Ambiente (MMA, 2000), which recommended a scientific investigation in the region, due to probable biological importance.

Etymology. The species epithet roseae is in honor to Roselene Silva Costa Ferreira, biologist since 1990, of Universidade Estadual Paulista (UNESP), campus São José do Rio Preto, for her dedication to the maintenance of DZSJRP fish collection, and especially for her support and mom-care to all the students who have ever been in the Ichthyology section.

Figures

FIGURE 1. Microlepidogaster roseae, MZUSP 126736, holotype, female, 37.1 mm SL, Brazil, Minas Gerais State, tributary of rio Preto, rio Pardo drainage.

FIGURE 2. Snout of Microlepidogaster roseae, showing the odontode-free band in lateral (A) Anterior view, (B) Paratype, MZUSP 112424, 39.0 mm SL, female. C) Head of c&s preserved specimen in lateral view, paratype, MZUEL 21730, 33.4 mm SL, female. D) In detail, the limited area in which odontodes are absent, from anterior tip of snout to anterior portion of the postrostral plate 2 (fused to postrostral plate 3, in this specimen). Scale bar = 1 mm.

FIGURE 3. Transverse process of second dorsal-fin pterygiophore of Microlepidogaster roseae, paratype, DZSJRP 23196, 31.7 mm SL, male, the arrow showing the exposed portion bearing odontodes. Scale bar = 0.5 mm.

FIGURE 4. A) Pectoral girdle of Microlepidogaster roseae in ventral view, paratype, MZUEL 21730, 33.4 mm SL, female, with exposed area, bearing odontodes, extending to the mesial symphysis. B) In detail: odontodes of exposed area almost completely restricted to the coracoid expansion, except for a single row in the cleithrum (white line indicates the limit between cleithrum and coracoid and the opening of arrector fossa). Scale bar = 1 mm.

FIGURE 5. Lateral plates of Microlepidogaster roseae, paratype, MZUEL 21730, 33.4 mm SL, female. Scale bar = 1 mm.

FIGURE 6. Live specimen of Microlepidogaster roseae. Photo by José Birindelli.

FIGURE 7. Southeastern and eastern Brazil showing type locality of Microlepidogaster roseae (☆) and geographic distribution of M. arachas (□), M. dimorpha (⌓), M. discontenta (Ó), M. discus (△), M. longicolla (✞), M. negomata (○), and M. perforata (◇), based on type series (except for M. perforata). Orange shaded areas indicate Priority Conservation Areas.

FIGURE 8. Type locality of Microlepidogaster roseae, rio Sussuarana, tributary to rio Preto, rio Pardo drainage. Photo by José Birindelli.