Paracanthopoma malevola, Pinna & Dagosta, 2022

Pinna, Mário de & Dagosta, Fernando Cesar Paiva, 2022, A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus, Papéis Avulsos de Zoologia 62, pp. 1-90 : 42-47

Paracanthopoma malevola , new species ( Fig. 24 )

Holotype: INPA 59836 , 20.0 mm SL, Brazil, Amazonas , Apuí , Igarapé das Araras (trib. to rio Guariba; rio Aripuanã drainage) (08°46′10″S, 60°26′40″W), col., W. Pedroza et al., 05 Nov 2008.

Paratypes: All from Brazil: INPA 31566 , 6 ex (1 SEM), 15.7-19.0 mm SL (collected with holotype) ; LIRP 11893 , 2 ex, 17.5-19.7 mm SL, Rondônia, Machadinho D′Oeste, Igarapé Preto (trib. to rio Ji-Paraná ), upstream from rapids sector, at Tabajara village (08°52′49.94″S, 62°05′17.20″W), col., F. Bastos et al., 14 Sep 2013 ; LIRP 14342 , 2 ex, 19.8-25.6 mm SL, Mato Grosso, Sapezal, rio Juruena (12°54′15″S, 58°54′33″W), col., R. Ilário, 01 Apr 2008 ; MCP 36217 , 32 ex, 14.3-20.7 mm SL, Rondônia, Igarapé Bananeiras (rio Madeira drainage), at road BR-425, North of Guajará-Mirim , ca. 110 km S of road BR-364 (10°38′28″S, 65°17′34″W), col., P. Buckup et al., 25 Jul 2004 ; MCP 36224 , 14 ex, 14.4-22.5 mm SL, Amazonas, unnamed Igarapé, ca. 43 km E of rio Madeira, by Transamazônica road (07°37′11″S, 62°40′57″W), col., R. Reis et al., 27 Jul 2004 ; MZUSP 121845 , 1 ex, 19.9 mm SL, Amazonas, Manicoré, rio Macaco (trib. to rio Branco ) in Parque Nacional Campos Amazônicos (08°27′20.88″S, 61°42′01.08″W), col., O. Oyakawa et al., 02 Oct 2016 ; MZUSP 122042 , 3 ex, 18.6-23.4 mm SL, Amazonas, Manicoré, igarapé tributary to rio Manicoré (07°52′53.40″S, 61°18′23.17″W), col., O. Oyakawa et al., 04 Oct 2016 ; MZUSP 122109 , 1 ex, 21.9mm SL, Amazonas, Manicoré, rio Manicorezinho , ( rio Branco drainage) at side road 15 km south of Transamazônica road (BR-230) at District of Santo Antônio do Matupi (07°59′57.33″S, 61°22′53.52″W), col., O. Oyakawa et al., 04 Oct 2016 ; MZUSP 122492 , 19 ex, 17.1-20.1 mm SL, Amazonas, Apuí, Igarapé II at side Road Dom Pedro (06°50′22.34″S, 59°42′26.89″W), col., O. Oyakawa et al., 09 Oct 2016 ; MZUSP 122699 , 1 ex, 18.3 mm SL, Amazonas, Apuí, igarapé tributary to rio Apuí , ca. 30 km from Apuí towards Vila de Sucunduri (07°08′45.38″S, 59°37′12.00″W), col., O. Oyakawa et al., 10 Oct 2016 ; MZUSP 122705 , 9 ex, 16.1-18.3 mm SL, Amazonas, Apuí, Camaiú , rio Camaiú near bridge at Transamazônica road (BR-230) (06°55′59.81″S, 59°19′48.36″W), col., O. Oyakawa et al., 11 Oct 2016 ; MZUSP 122770 , 7 ex, 14.5-20.7 mm SL, Amazonas, Apuí, igarapé at side road of Transamazônica road (BR-230), 40 km south of Apuí from Rua Bahia (07°27′50.94″S, 59°51′22.18″W), col., O. Oyakawa et al., 13 Oct 2016 ; MZUSP 122793 , 2 ex, 18.2-20.3 mm SL, Amazonas, Apuí, igarape at side road starting at Transamazônica road (BR-230), 9 km before ferry-boat across rio Sucunduri (06°50′05.28″S, 59°07′42.60″W), col., O. Oyakawa et al., 11 Oct 2016 ; MZUSP 126816 , 4 ex (2 c&s), 16.4-19.2 mm SL, collected with holotype .

Non-type specimens: MZUSP 122243, 7 ex, 15.3-16.4 mm SL, Brazil, Amazonas, Apuí, rio Roosevelt drainage (trib. to rio Aripuanã, rio Madeira system), small igarapé at side road joining Transamazônica road (BR-230) to Amazon Roosevelt Lodge (07°33′05.40″S, 60°41′39.62″W), col., Oyakawa et al., 06 Oct 2016.

Diagnosis: Paracanthopoma malevola is distinguished from all congeners by the presence of 18or19median premaxillary teeth (the most numerous in Paracanthopoma , which otherwise have 3 to 13 median premaxillary teeth). The rectangular, broader than long, shape of the median premaxillary tooth patch (vs. roughly squarish, triangular or roundish) also distinguishes the species from all congeners except Pc. satanica . Distinguished from the latter species also by the more numerous opercular (11 or 12; vs.5 or 6) and interopercular (7 or 8; vs.4 or 5) odontodes; by the fewer vertebrae (40; vs. 42 or 43);by the fewer caudal-fin procurrent rays (19-21 dorsally and 18-20 ventrally; vs. 32 dorsally and 30-32 ventrally); by one additional ventral principal caudal-fin ray (6 + 7; vs. 6 + 6); and by the presence of dark pigment on dorsum forming a series of irregular spots along each side of dorsal midline (vs. no dark pigment on dorsum or only few sparse dark dots not forming any pattern).

Description: Morphometric data for the holotype and paratypes are provided in Table 8 . Body elongate (HL 15.5-18.4% SL). Cross-section of body as broad as deep, or broader than deep (the latter when axillary gland tumescent) at pectoral-fin insertion and increasingly compressed posterior to that point,tapering to caudal fin. Dorsal profile of body nearly straight from head to origin of dorsal fin ( Fig. 24 ). Dorsal and ventral profiles of caudal peduncle straight or gently convex posterior to ends of dorsal and anal fins, spatulate, expanded by procurrent caudal-fin rays. Ventral profile of body nearly straight until pelvic-fin origin, but greatly distented in some specimens due to gut contents.Myotomes and longitudinal skeletogenous septum clearly visible through thin integument along whole body. Axillary gland very large, elongate in shape, extending along limit between hypaxial musculature and abdominal cavity and protruding markedly on surface of body when full with secretion. Anterior end of gland surrounding dorsoposterior, ventral and posterior margins of muscular pectoral-fin base, as thick corselet, extending posteriorly to beyond margin of adpressed pectoral fin (maximally to ca. 50% of fin length beyond its margin). Gland tapering to fine posterior tip, its large round or oval pore (sometimes collapsed as slit) located at its anterior portion, approximately at vertical through middle of pectoral-fin length. Posterior portion of gland extending posteriorly from region ventral to pore, and its size apparently related to amount of secretion stored, nearly invisible in some specimens.

Dorsal profile of head continuous with that of dorsum ( Fig. 24 ). Head longer than broad (head width 72.3-83.0% HL), snout very broad, semicircular with a continuous round anterior margin. Head muscles not entering skull roof. Head depressed (head depth 34.1-42.0% HL) with dorsal profile straight and horizontal until eye, then bending ventrally, straight or gently convex, to tip of snout. Ventral profile of head straight, flattened. Eye medium-sized (12.5-14.3% HL), without free orbital rim, located dorsolaterally on head and directed dorsolaterally. Integument over eye thin and transparent. Eye located at middle of HL, interorbital width larger than longitudinal diameter of eye. Eyelens largely constricted by iris, with oval pupil in specimens examined. Anterior nostril small, surrounded by short tubule of integument produced posteriorly into small pointed process,with double elastin cores. Anterior internarial width approximately equal to interorbital. Posterior naris slightly larger than anterior one, roundish or roughly triangular in shape, located close to anteromesial margin of eye and provided with anterior flap of integument ( Fig. 25 ). Center of posterior nares approximately at transverse line through anterior margin of eyes. Posterior internarial width narrower than interorbital and 2-2.5 times as wide as diameter of one nostril.

Opercular odontodophore small and oval, dorsolaterally located on head, on dorsal half of head depth in lateral view, anterodorsally to pectoral-fin base ( Fig. 25 ). Opercular odontodes 11 or 12 in number, disposed in two irregular rows. Odontode bases compressed, and their main axis oriented dorsoposteriorly in lateral view, with distal portions curved medially, especially those of inner row. Two or three caps of replacement odontodes interspersed with mature ones. Opercular periodontodal fold well-differentiated. Interopercular odontodophore more elongate in shape than opercular one, located ventrolaterally on head,slightly ventral to horizontal through origin of pectoral fin. Interopercular odontodes 7 or 8, directed posteroventrally, with tips curved dorsoposteriorly. Odontode bases strongly compressed, mostly positioned in single rows, with short second row posteriorly. Interopercular odontodophore closer to opercular one than to eye. Interopercular periodontodal fold of integument narrow but well-differentiated. Epiodontodeal velum thick, covering most of odontodes.

Mouth inferior (ventral), strongly flattened ventrally ( Figs. 24 , 25 ). Each premaxilla with one scalpelloid teeth attached to its distal tip, and one additional tooth socket with partly-formed tooth in parallel ( Fig. 4G ). Scalpelloid teeth deeply hidden in labial tissue and difficult to expose in preserved specimens without damaging soft tissue. Conical teeth absent on premaxilla ( Figs. 4G , 26 ). Upper lip very broad but poorly-differentiated, continuous with ventral surface of snout. Median premaxilla broad, with 18 or 19 teeth quite irregularly disposed in two poorly-defined rows ( Figs. 4G , 26 ). General shape of median premaxillary tooth patch (but not of underlying bone) rectangular in ventral view in alcoholic specimens. All teeth posteriorly oblique to ventral surface of median premaxilla at base and curved further posteriorly at distal pungent portion, those on lateral edge of median premaxilla also with some lateral curvature. Basal portion of all median premaxillary teeth somewhat compressed laterally. Some replacement tooth caps interspersed with mature dentition. Median premaxillary velum poorly-differentiated. Hypodontal pad of median premaxilla broad and rectangular, its posterior margin mostly straight,perpendicular to longitudinal head axis and occupying most of surface of upper jaw. Lower jaw narrow, composed mostly of roundish and mostly confluent dentary lobes, continuous with mental region posteriorly.Jaw cleft short directed posterolaterally, curved laterally at posterior end. Dentary diastema reduced to small median concavity between dentary lobes. Dentary teeth 4, loosely disposed at mesial end of dentary, arranged in two ventral and two dorsal ones, not aligned so that in ventral view three or four teeth simultaneously visible ( Figs. 4G , 26 ). Dentary teeth long, their axis anteriorly-directed at base, but curved dorsally or dorsolaterally at distal half. Median tooth of ventral row longer than others.

Branchiostegal velum forming large, continuous, round and posteriorly concave, free fold across whole of mental region ( Fig. 25 ). Dorsal portion of branchial membrane reaching and slightly overlapping anterior margin of pectoral-fin base. Branchial opening small, located anteriorly to pectoral-fin base, approximately equal to space between opercular and interopercular odontodophores. Maxillary barbel very short, extending maximally for half distance between its base and base of interopercular odontodophore; slightly longer in smaller specimens. Posterior point of its base anterior to vertical through anterior margin of eye in lateral view. Rictal barbel tiny, vestigial, undifferentiated externally in some specimens, located mesially to base of maxillary one. Nasal barbel vestigially represented by posterior elongated portion of fold around anterior naris described above, with double internal elastin core.

Lateral line short and straight, extending alongside dorsal margin of anterior portion of axillary gland. Terminal lateral-line pore immediately dorsal to axillary gland opening. Very short secondary branch splitting off ventrally from proximal portion of main canal, with corresponding pore opening anteriorly to midlength of main canal. Single lateral-line tubule poorly calcified, extending over part of main canal posterior to bifurcation.

Pectoral fin short (68.8-75.8% HL), roughly triangular in shape when expanded and gently convex anterior and posterior margins, its base on ventral half of body in lateral view. Pectoral-fin rays i + 5, with first ray not longer than other rays. Pelvic fins well separated from each other at base, with i + 4 rays. Pelvic splint present. Origin of pelvics close to origin of anal fin, well anterior to vertical through origin of dorsal-fin, entirely covering anus and urogenital papilla and extending posteriorly to origin of anal fin. Posterior margin of pelvic fin gently convex. Dorsal fin elongate, roughly triangular with roundish edge and gently convex distal margin. Dorsalfin rays ii + 6, plus 5 or 6 procurrent ones. Anal fin similar in shape to dorsal fin, with ii + 5 rays, plus 6 or seven procurrent ones. Origin of anal fin at or slightly posterior to vertical through origin of dorsal-fin. Caudal fin roughly rectangular, truncate with round edges and gently convex margin, as deep or deeper than maximum depth of caudal peduncle. Principal caudal-fin rays 6 + 7 in all specimens. Procurrent caudal-fin rays 19-21 dorsally and 18-20 ventrally.

Vertebrae 40 (n= 2). First dorsal-fin pterygiophore subsequent to neural spine of vertebra 21 (n = 1) or 22 (n = 1). First anal-fin pterygiophore subsequent to haemal spine of vertebra 22 (n = 2). Dorsal-fin pterygiophores 7 (n = 2). Anal-fin pterygiophores 6 (n = 2). Branchiostegal rays 4.

Pigmentation in preservative: Body mostly white. Two irregular rows of dark chromatophores on dorsum, extending along both sides of dorsal midline to base of dorsal fin. Isolated dark chromatophores spread over dorsal sides of abdominal wall, exposed in specimens with distended abdomens, otherwise retracted as inconspicuous dark line along dorsal limit of abdominal cavity. Short row of dark chromatophores along dorsal margin of lateral line.Some specimens with isolated small spots along longitudinal skeletogenous septum. Posterior part of neurocranium with dark brain pigment seen by transparency, forming irregular spots or uniform dark covering with anterior white recess. Integumentary chromatophores around margin of neurocranium, extending anteriorly between eyes. Dense dark fields anteriorly to eyes, adjacent and sometimes continuous with dark ring outlining nasal capsule. Margin of snout white. Dark spots around dorsal and anterior margins of opercular odontodophore. Dark line along dorsal, anterior or medial margins of interopercular odontodophore in some specimens. Most specimens with narrow dark markings along anterior margin of median premaxilla in ventral view. Regular series of spots, one per vertebra, along caudal peduncle, formed by internal chromatophores and gradually fading anteriorly. Few scattered spots on base of caudal-fin rays.

Etymology: From the Latin malevolus, meaning ill-disposed, inimical. An adjective.

Geographical distribution: Paracanthopoma malevola has been recorded from tributaries of the rio Madeira basin draining the Brazilian shield such as the rio Aripuanã, Machado, and Sucunduri. It is also found in the upper rio Madeira, in a tributary of the rio Mamoré, and in the upper rio Juruena (rio Tapajós basin) ( Fig. 27 ).

Remarks: Specimens in MZUSP 122243 differ from other samples of the species in having a much broader head, which expands abruptly at approximately the transverse line through the middle of the eyes. In typical Paracanthopoma malevola , the head is not only narrower but also widens gently and evenly along its length. While such differences result in striking visual distinctiveness in head shape, we found no additional corroborative evidence indicative of separate specific status and thus consider the rio Roosevelt sample as a populational variation of Pc. malevola .

Figures

Figure 4. Comparative chart of jaws and anterior portion of head of Paracanthopoma species, cleared and stained specimens, ventral views: (A) Pc. ahriman FMNH 105525;(B)Pc.alleynei MZUSP 103052;(C) Pc.cangussu MZUSP 86250;(D)Pc.capeta MZUSP 29154;(E) Pc.daemon MZUSP 95597;(F)Pc.irritans INPA 20529; (G) Pc.malevola MCP 36217;(H) Pc.parva MZUSP 30400;(I) Pc.saci MZUSP 125626; (J) Pc.satanica MZUSP 100149;(K) Pc.truculenta MZUSP 30404;(L) Pc.vampyra MZUSP 100138. Scale bars = 500 μm. Pc.carrapata not shown.

Figure 24. Paracanthopoma malevola, holotype, INPA 59836, 20.0 mm SL, Amazonas, Apuí, Igarapé das Araras. (A) Lateral view of body; (B) Dorsal view of head; (C) ventral view of head.

Figure 25. Paracanthopoma malevola, paratype,INPA 31566,SEM images of head.(A) Dorsal;(B)Ventral.Scale bar = 500 μm.

Figure 26. Paracanthopoma malevola, holotype,INPA 59836, CTscan images of head skeleton,(A) Lateral;(B) Dorsal;(C) Ventral.

Figure 27. Map of northern South America showing geographical distribution of Paracanthopoma irritans (dot) and Pc. malevola (triangle). Open symbols represent type localities. Some symbols may represent more than a single locality or lot of specimens.