Paracanthopoma satanica, 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 : 59-64

Paracanthopoma satanica , new species ( Fig. 36 )

Holotype: ANSP 178231 , 25.4 mm SL, Peru, Loreto, Prov. Maynas, caño Sabalito (a terra firme stream, part of río Amazonas drainage), ca. 42 km south of Iquitos (04°14.743′S, 73°24.953′W), col., M. Sabaj et al., 11 Aug 2001.

Paratypes: All collected with holotype. ANSP 189015 , 10 ex, 14.4-23.1 mm SL ; MZUSP 100149 , 5 ex, 20.9-24.9 mm SL (2 c&s, 1 SEM) ; MUSM 32799 , 3 ex, 15.7-22.8 mm SL .

Diagnosis: The presence of 13 teeth on the median pre-maxilla distinguishes this species from all congeners, which have either 11 or fewer, or 18 or 19 such teeth.The associated presence of seven teeth on the anterior row of the median premaxilla is equally diagnostic, and more accessible to observation than the complete count. The rectangular, broader than long, shape of the median pre-maxillary tooth patch (vs. roughly squarish, triangular or roundish) distinguishes the species from all congeners except Pc.malevola . Distinguished from the latter species by the fewer opercular and interopercular odontodes (5-6 and 4-5; vs. 11-12 and 7-8, respectively); by the more numerous vertebrae (42-43; vs. 40); by the more numerous caudal-fin procurrent rays (32 dorsally and 30-32 ventrally; vs. 19-21 dorsally and 18-20 ventrally); by the fewer median premaxillary teeth (13; vs. 18-19); by the fewer ventral principal caudal-fin rays (6 + 6; vs. 6 + 7); and by the lack of dark pigment on dorsum (or only few isolated dark spots not forming any pattern) (vs. two series of irregular dark spots alongside dorsal midline).

Description: Morphometric data for the holotype and paratypes are provided in Table 11 . Body elongate (HL 14.8-17.0% SL). Cross-section of body broader than deep at pectoral-fin insertion and increasingly compressed posterior to that point, tapering to caudal fin. Dorsal profile of body gently convex from head to origin of dorsal fin ( Fig. 36 ). Dorsal and ventral profiles of caudal peduncle convex along its posterior two-thirds, spatulate, expanded by procurrent caudal-fin rays. Ventral profile of body straight at pectoral-fin base and then gently convex until pelvic-fin origin, with some specimens with greatly distented abdomens 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. Gland tapering to fine posterior tip, its large round or oval pore 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 evidently related to amount of secretion stored.

Dorsal profile of head continuous with that of dorsum, its origin sometimes indicated by slight constriction of anterior end of epaxial musculature. Head longer than broad (head width 69.9-80.7% HL), snout very broad, semicircular with a continuous round anterior margin ( Fig. 36 ). Head muscles not entering skull roof. Head very depressed (head depth 33.3-41.1% 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 (14.3-18.1% HL), without free orbital rim, located dorsolaterally on head and directed dorsolaterally, with pronounced lateral component. Integument over eye thin and transparent. Eye located mostly within anterior half of HL, interorbital width approximately equal to longitudinal diameter of eye. Eyelens largely constricted by iris, with losenge-shaped pupil in specimens examined. Anterior nostril small, surrounded by short tubule of integument produced posteriorly into small pointed process ( Fig. 37 ), with double elastin cores. Anterior internarial width approximately equal to interorbital. Posterior naris slightly larger than anterior ones, roundish or roughly triangular in shape, located close to anteromesial margin of eye and provided with anterior flap of integument ( Fig. 37 ). Center of posterior naris approximately at transverse line through anterior margin of eyes. Posterior internarial width narrower than interorbital and three times as wide as diameter of one nostril.

Opercular odontodophore small and elongate, dorsolaterally located on head, on dorsal half of head depth in lateral view, anterodorsally to pectoral-fin base. Opercular odontodes mostly covered with integument, 5 or 6 in number, irregular and closely positioned as two or three large posterior ones and two or three smaller anterior ones. Odontode bases strongly compressed, and their main axis oriented horizontally in lateral view, with distal portions of larger posterior ones curved dorsoposteriorly. Two or three caps of replacement odontodes posteriorly to mature ones. Opercular periodontodal fold small and poorly-differentiated, extending shortly beyond tips of odontodes and mostly continuous ventrally with head integument. Interopercular odontodophore smaller than opercular one, located ventrally or ventrolaterally on head,aproximately at horizontal through origin of pectoral fin. Interopercular odontodes 4 or 5, directed posteroventrally, with tips curved dorsoposteriorly. Odontode bases strongly compressed, closely positioned in one irregular or two imbricated rows, with posterior ones largest. Interopercular odontodophore closer to opercular one than to eye. Interopercular periodontodal fold of integument poorly-differentiated, mostly continuous with head integument posteriorly. Epiodontodeal small and thick, mostly covering odontodes.

Mouth inferior (ventral), strongly flattened ventrally. Each premaxilla with one scalpelloid teeth attached to its distal tip, and one additional tooth socket, with partly formed tooth in parallel ( Figs. 4J , 38 ). Scalpelloid teeth deeply hidden in labial tissue and difficult to expose in preserved specimens without damaging soft tissue. Conical teeth absent on premaxilla. Upper lip very broad but poorly-differentiated, continuous with ventral surface of snout. Median premaxilla broad, with 13 teeth disposed in two rows, anterior one with 7 teeth (three on each side and median one) and posterior row with 6 (three on each side, separated by gap) ( Figs. 4J , 38 ). General shape of median premaxillary tooth patch (but not of underlying bone) roughly 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 component. Basal portion of all median premaxillary teeth strongly compressed laterally. Five or six replacement tooth caps posterodorsally to mature dentition. Median premaxillary velum poorly-differentiated. Hypodontal pad of median premaxilla broad and rectangular, its posterior margin straight or gently convex, 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 strongly directed laterally, perpendicular to longitudinal axis. 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 teeth usually visible ( Figs. 4J , 38 ). 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. 37 ). 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 for half distance to base of interopercular odontodophore or less; longer in specimens 16 mm SL or under, where it can nearly reach base of interopercular odontodophore. Posterior point of its base anterior to vertical through anterior margin of eye in lateral view. Base of maxillary barbel dorsally expanded. 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 straight, poorly calcified, extending for most of main canal posterior to bifurcation.

Pectoral fin medium-sized (64.4-78.6% HL), aproximately 75% of HL, with gently convex distal margin. First ray longer than others in few specimens. Pectoral-fin rays i + 5, its base on ventral side of body. Pelvic fin small, separated from each other at base, with i + 4 rays. Pelvic splint present. Origin of pelvics close to origin of anal fin, 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. Dorsal-fin rays ii + 6, plus 5 or 6 procurrent ones. Anal fin similar in shape to dorsal fin, with ii + 5 rays, plus 6 procurrent ones. Origin of anal fin at or slightly posterior to vertical through origin of dorsal-fin. Anal fin with same size, slightly smaller or slightly larger than dorsal one. Caudal fin squarish, truncate with round edges, slightly convex in some specimens, less deep than maximum depth of caudal peduncle. Principal caudal-fin rays 5 + 6 (holotype) or 6 + 6. Procurrent caudal-fin rays 32 dorsally and 30 or 32 ventrally.

Vertebrae 42 (n = 6) or 43 (n = 1). 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 21 (n = 1) or 22 (n = 1). Dorsal-fin pterygiophores 7 (n = 1) or 8 (n = 2), when later, last element vestigial. Anal-fin pterygiophores 6 (n = 2). Branchiostegal rays 3 or 4, when later, first element vestigial.

Pigmentation in preservative: Body almost entirely white. Sparse isolated dark chromatophores irregularly scattered along dorsum, extending along base of dorsal fin and anterior portion of dorsal edge of caudal peduncle. Isolated dark chromatophores spread over dorsal sides of abdominal wall, exposed only in specimens with distended abdomens, otherwise hidden along limit between abdominal cavity and trunk musculature. Neurocranium with dark brain pigment forming irregular spots seen by transparency. Smaller and less dense integumentary chromatophores along margins of neurocranium, extending anteriorly between eyes and nostrils and onto dorsolateral portion of snout. Margins of snout white. Olfactory capsule outlined as dark ring. Posterior nostril always with small dark spot in its interior. Few chromatophores sometimes along dorsal margin of opercular odontodophore. Some specimens with few dark markings on anterior portion of median premaxilla in ventral view. Regular series of spots, one per vertebra, along caudal peduncle, formed mostly by internal chromatophores on individual vertebrae, visible by transparency and gradually fading anteriorly. Scattered spots across base of caudal-fin rays, sometimes forming short irregular vertical line.

Etymology: Satanicus is an adjective (treated as Latin) derived from the Hebrew verb satan, meaning literally "to oppose″, but commonly used to refer to an enemy or the devil.

Geographical distribution: Paracanthopoma satanica is known from a single locality in a tributary to the upper Amazon drainage in Peru ( Fig. 45 ).

Biology: There are three specimens in the type series with distended abdomens obviously full of coagulated blood, the smallest of which is 15.6 mm SL. Some paratypes are gravid females with the abdomen distended both by the ovaries and by blood in the gut. The eggs are yellowish in color and firm to the touch,clearly distinguishable from the white and soft adipose bodies loated nearby.In the fullest female,the egg distribution extends superficially along the lateral surface of the posterior two-thirds of the abdominal cavity, in an arrangement progressively narrower posteriorly. There are at least 50 tightly packed eggs on each side, the largest of which are approximately 0.5 mm in diameter.

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 36. Paracanthopoma satanica, holotype,ANSP 178231,25.4 mm SL.Peru, Dept.Loreto,Maynas,Caño Sabalito.(A) Lateral view of body;(B) Dorsal view of head;(C) ventral view of head.

Figure 37. Paracanthopoma satanica, paratype,ANSP 178231,SEM images of head.(A) Dorsal;(B)Ventral.Scale bar = 500 μm.

Figure 38.Paracanthopoma satanica, holotype,ANSP 178231, CTscan images of head skeleton,(A) Lateral;(B) Dorsal;(C)Ventral.Specimen poorly calcified,some structures not properly shown.

Figure 45. Map of northern South America showing geographical distribution of Paracanthopoma saci (square); Pc. satanica (5-tip star); Pc.truculenta (dot); and Pc. vampyra (10-tip star). Open symbols represent type localities. Some symbols may represent more than a single locality or lot of specimens.