Ancistrus miracollis, Bifi & Oliveira & Py-Daniel, 2019

Bifi, Alessandro Gasparetto, Oliveira, Renildo Ribeiro de & Py-Daniel, Lúcia Rapp, 2019, A new species of Ancistrus Kner, 1854 (Siluriformes: Loricariidae) from rio Madeira basin, Amazonas State, Brazil, Neotropical Ichthyology 17 (2) : -

Ancistrus miracollis , new species

urn:lsid:zoobank.org:act:4D62A4E1-4BAF-4A2E-9112-3941327D3618

Fig. 1-2 , Tab. 1

Holotype. INPA 57624 , male, 66.7 mm SL; Brazil: Amazonas State : Apuí , comunidade Terra Preta , igarapé do Mureru , tributary of rio Sucunduri, rio Madeira basin, 7°45’45”S 58°49’00”W, 29 Jun 2006, L. H. Rapp Py- Daniel, C. E. Marinelli & C. S. da Silva.

Paratypes. All from Brazil: Amazonas State : Apuí: rio Madeira basin : INPA 26144 , 1 , 59.0 mm SL, igarapé located just off the trilha do Inferno , tributary of rio Sucunduri, 8°34’41”S 59°9’13”W, 23 Jun 2006, O. S. Pereira . INPA 26433 , 27 (25 alc., 21.7-64.4 mm SL and 2 c&s 48.9-54.0 mm SL) ; MCP 54133, 2 , 45.0- 48.7 mm SL ; MPEG 38161 , 2 , 51.1-56.2 mm SL ; MZUSP 124264 , 2 , 47.5-59.5 mm SL, same data of holotype .

Diagnosis. Ancistrus miracollis is diagnosed from its congeners by having thin light vertical bands on the trunk, sometimes incomplete (vs. plain, with black or white spots, or unpigmented body). Furthermore, the new species can be distinguished from other Ancistrus species described from the rio Madeira basin by pectoral-fin length surpassing the pelvic-fin origin (vs. not reaching or just reaching the pelvic-fin origin in A. marcapatae , A. megalostomus and A. montanus ); larger cleithral width 33.5-36.9% in SL (vs. 27.7-33.0% in A. montanus ); smaller dentary width 45.3-54.4% in interorbital distance (vs. 64.6-86.6% in A. marcapatae and 64.9-91.4% in A. melagostomus ); and by possession of an adipose-fin (vs. adipose-fin absent in A. verecundus ).

Description. Morphometric data and counts in Tab. 1 . Head and trunk moderately depressed. Dorsal profile of body convexly raising from tip of snout to dorsal-fin origin, then straight or slightly convex to adipose fin, and concave from that point to caudal fin. Ventral profile of body straight, slightly convex on caudal peduncle. Caudal peduncle compressed; slightly flattened ventrally.

Snout large and rounded in dorsal view, with large naked margin bordered by dermal platelets on lateral portion; extension of naked area on snout large, representing ¾ of snout length. Adult males with small- to middle size tentacles (sometimes branched) along lateral border of snout and longitudinally aligned along mesethmoid, bifurcating caudally to nares; tentacles small and less numerous in females, limited to one series on lateral border of snout. Evertible cheek plates supporting (17-33) hypertrophied odontodes (cheek spines). Head covered by dermal bones; dorsum covered by dermal plates, except at dorsal-fin base.

Eye mid-sized, 15.8-19.8% of HL, dorsal orbit not raised; dorsolaterally positioned. Interorbital region slightly concave. Exposed portion of opercle roughly triangular; supra-opercular region with few platelets near compound pterotic.

Oral disk circular covered with small papillae; lower lip wide with papillae reducing in size toward its margin; maxillary barbel short, attached to lip by membrane and with reduced free tip. Premaxillary and dentary tooth rows short; teeth short, thin, numerous, bifid and curved inward. Cusps spatulated and asymmetrical, with mesial cusp larger and wider than lateral cusp. Only one small buccal papilla positioned between premaxillae.

Five series of lateral plates, three lateral series on the narrowest portion of caudal peduncle. Mid-dorsal and midventral series not surpassing adipose fin. Median series supporting lateral line. Short odontodes on fin rays and body plates. Ventral surface devoid of plates from snout tip to anal-fin insertion. Base of first anal-fin pterygiophore exposed, forming preanal platelet-like element, sometimes covered by skin but supporting small odontodes.

Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin origin; dorsal fin usually reaching or surpassing preadipose plate when adpressed; dorsalfin spine flexible, shorter than head length. Adipose-fin spine short, slightly curved downward. Pectoral-fin spine inflexible and slightly curved inward, with hypertrophied odontodes and tentacles on its distal portion; pectoral-fin surpassing adpressed pelvic-fin origin. Pelvic fin flexible and curved inward, depressed pelvic-fin spine surpassing origin of anal fin. Anal fin short. Caudal-fin margin obliquely truncate with ventral unbranched ray longer than dorsal one. Fin-ray formula: dorsal II,7; pectoral I,6; pelvic i,5; anal i,3-4; caudal i,14,i. Total vertebrae: 27 (two specimens).

Color in alcohol. Body background color dark gray or brown. Dorsal part of head with rounded light spots, on predorsal and dorsum region in some specimens; light vertical bars on trunk, variably incomplete, usually more conspicuous on caudal peduncle region. Barred pattern showing some variation ( Fig. 2 ). Ventral surface of head and abdomen yellowish to light brown, brown on ventral surface of caudal peduncle. All fins with alternating dark and light spots on rays, organized in transverse bands in some specimens.

Sexual dimorphism. Ten males and 11 females measured; largest male and female with 66.7 mm and 67.4 mm SL, respectively. Mature males have small- to middle-sized tentacles in the dorsal region and border of snout. Females can have fewer and shorter tentacles than males limited to one series on lateral border of snout, usually two to four on each side of snout.

Geographical distribution. Ancistrus miracollis is only known from the Mosaico of Conservation Units of Apuí on southern Amazon State, near the border with Mato Grosso State, Brazil. The new species was found in small streams flowing to the rio Sucunduri, affluent of lower rio Madeira ( Fig. 3 ).

Etymology. From the latim mirus = wonderful, surprising and collis = hill, mountain, in allusion to the beauty of the species with unique pattern color of Ancistrus and its sampling site in the highlands of the Parque Estadual do Sucunduri, more specifically in the Sucunduri Dome, an allusion to its elevation that can reach up to 350 m, very peculiar for this area. An adjective.

Conservation status. The type locality of A. miracollis (igarapé do Mureru) is not an easily accessible place and the sampling was made possible through governmental funds from the state of Amazonas (Secretaria de Desenvolvimento Sustentável do Amazonas - SDS). The Mosaic of Apuí comprises nine conservation units, seven considered of sustainable usage, and two State Parks under full protection. Thus, we suggest that A. miracollis be categorized as LC (Least Concern) under the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2017) of extinction risk.

Comments on taxonomic status of Ancistrus marcapate: Three species have been described from ríos Beni and Madre de Dios basins: A. bolivianus , A. heterorhynchus and A. marcapatae ( Fig. 4 ). The examination of the type material revealed no differences between these three species, but that they share some uncommon features such as: teeth with elongated principal cusp sharpened and at least three times larger than lateral cusp; pectoral-fin not surpassing the pelvic-fin origin; and anterior adiposefin keel formed by four to six plates. Furthermore, these species have a slightly concave profile between adipose and caudal fins; dentary length (24.9-29.5% in HL), and fins with dark spots forming transverse bands. These characters combinations distinguish them from the majority of Ancistrus species. Thus, based on these observations we recognize A. bolivianus and A. heterorhynchus as junior synonyms of A. marcapatae ( Fig. 5 ).

Figures

Fig. 1. Ancistrus miracollis, INPA 57624, holotype, 66.7 mm SL, male; Brazil, Apuí, rio Sucunduri drainage, lower rio Madeira basin.

Fig. 2. Color pattern variation in Ancistrus miracollis. Standard length from top to bottom, left to right: 27.7 mm SL, 30.3 mm SL, 35.5 mm SL, 41.2 mm SL, 48.4 mm SL, 51.6 mm SL, 58.4 mm SL (all from INPA 26433), 60.1 mm SL (INPA 24144).

Fig. 3. Partial map of the Brazilian Amazon, showing the distribution of Ancistrus miracollis. Red star indicates type locality.

Fig. 4. Dorsal, lateral and ventral views (left to right) of Ancistrus bolivianus: NMW 43475, 65.6 mm SL, syntype; A. heterorhynchus: BMNH 1911.12.20.35-36, 63.2 mm SL, syntype; A. marcapatae: BMNH 1902.5.29.211, 79.1 mm SL, holotype.

Fig. 5. Ancistrus marcapatae, MUSM 57853, 54,6 mm SL, male; Peru, Manu, rio Madre de Dios drainage, rio Adanrayo.