Paracanthopoma carrapata, 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 : 29-33

Paracanthopoma carrapata , new species ( Fig. 16 )

Holotype: MZUSP 100145 , 23.3 mm SL, Brazil, Rondônia, rio Madeira at Calama (08°01′42″S, 62°52′34″W), col M. Goulding, Feb-Apr 1980.

Paratypes: All collected with holotype. MZUSP 100142 , 2 ex, 17.3-22.8 mm SL ; MZUSP 100143 , 3 ex (1 c&s), 22.2-22.7 mm SL .

Diagnosis: Distinguished from all congeners by extremely large median premaxillary dentition, with the distal (post-bend) portion larger than the basal portion (vs. two portions approximately the same length or the basal longer than the distal). Distinguished from all congeners except Pc. daemon , Pc. parva , and Pc. truculenta by the presence of nine teeth on the median premaxilla (vs. 3 to 5 or 11 and more; sometimes 10 in Pc.daemon ); by the presence of a single median s6 pore, visible on the middle of skull posterior to eyes (vs. paired s6 pores, distant from midline of skull), and by the supraoccipital anteriorly produced into large pointed spike (vs. either anteriorly concave or straight across skull roof). Distinguished from all other Paracanthopoma except Pc. parva and Pc. truculenta by the posterior margin of the anal fin well posterior to vertical through that of the dorsal fin (vs. margins of two fins approximately at same vertical or that of anal fin only slightly posterior to that of dorsal fin); and by the deeply emarginate caudal fin (vs. truncate with round corners or slightly concave). Distinguished from Pc. daemon and Pc. truculenta by the robust structure of the palatine, especially of the lateral strut, wider than the central fenestra (vs. lateral strut less wide than the central fenestra). Distinguished from Pc. daemon and Pc. parva by the extensive invasion of the skull roof by head musculature, with widest exposed part of neurocranium approximately equivalent to, or less than, interorbital (vs. exposed part of neurocranium larger than interorbital). Distinguished from Pc. truculenta by the proportionally larger eye (13.9-14.4% HL; vs. 9.9-13.3); the longer head (20.9-22.2% HL; vs. 16.5-20.0); the more numerous opercular odontodes (four; vs. one or two) exposed on the surface of skin (vs. mostly hidden in integument); the continuous anterodorsal margin of the hyomandibula (vs. with a well-defined semicircular recess at its anterior half). Further distinguished from Pc. parva by the smaller interopercular odontododes, where the largest odontode is smaller than the long axis of the interopercle (vs. largest interopercular odontode longer than long axis of the bone) and by the interopercular odontodes being clustered at the distal end of the bone, with their insertions at approximately the same plane (vs. odontodes inserted partly towards the ventral margin of the interopercle, with their insertions tile-like at that area).

Description: Morphometric data for the holotype and paratypes are provided in Table 5 . Body moderately elongate (HL 20.9-22.2% SL).Cross-section of body as deep as wide at pectoral-fin insertion, increasingly compressed posterior to that point, tapering to caudal fin. Dorsal profile of body gently convex, nearly straight, from head to origin of dorsal fin ( Fig. 16 ). Dorsal and ventral profiles of caudal peduncle straight anteriorly, then gently convex at region of procurrent caudal-fin rays. Caudal peduncle low, slightly expanded by procurrent rays along posterior third or half. Ventral profile of body mostly straight, slightly convex near pelvic-fin origin ( Fig. 16 ), distended in specimen with full gut. Myotomes clearly visible along whole body. Longitudinal skeletogenous septum also evident along whole of body. Axillary gland small, not protruding markedly on surface of body and not reaching posterior margin of pectoral fin, covering only posterior half of pectoral-fin base. Its pore opening at vertical through midlength of pectoral fin.

Dorsal profile of head separated from that of dorsum by muscle limit. Head longer than broad (head width 59.8-69.3% HL). Snout broad, parabolic with a roundish-pointed tip, separated from rest of head by small constriction in dorsal view ( Fig. 16 ). Muscles covering most of dorsal part of head, with head width approximately 4.5 times the maximum width of exposed skull roof in dorsal view. Exposed area proportionally larger in small specimen (MZUSP 100142, 17.3 mm SL). Head deep for Paracanthopoma (head depth 39.3-51.5% HL), with convex dorsal profile, strongly curved ventrally anteriorly to eyes. Eye medium-sized (13.9-14.4% HL), without free orbital rim, located dorsolaterally on head and directed dorsolaterally ( Fig. 16 ). Integument over eye thin, entire eyeball visible through skin. Middle of eye slightly anterior to middle of HL, interorbital width approximately equal to longitudinal diameter of eye. Eyelens very large, taking most of lateral surface of eye and either entirely unconstricted by iris or constricted only marginally, with large round pupil in specimens examined. Anterior nostril small, surrounded by short tubule of integument produced posteriorly into small pointed process( Fig.16 ),with double elastin cores. Anterior internarial width slightly larger than interorbital. Posterior naris slightly larger than anterior ones, roundish or triangular,but sometimes with semilunar aspect because of partial occlusion by anterior flap of integument. Posterior naris positioned anteromesially to eye, their middle slightly posterior to transverse line through anterior margin of eyes ( Fig. 16 ). Posterior internarial width narrower than interorbital.

Opercular odontodophore very small, laterally located on head, approximately at, or slightly dorsal to, middepth of head. Odontodophore externally inconspicuous on general view of head, identifiable mostly by its proportionally small, elongate periodontodeal fold. Opercular odontodes 4, with 2 large posterior ones (one of which often in process of replacement), closely positioned and with tips strongly curved dorsally. Two anterior odontodes much smaller than posterior ones, only slightly curved dorsally. Interopercular odontodophore very small, located ventrolaterally on head, at or immediately ventral to horizontal through origin of pectoral fin, with 3 odontodes closely positioned in single row, much closer to opercular odontodophore than to eye. Interopercular periodontodal fold of integument small, oval in shape. Epiodontodeal velum thick, very small but proportional to size of odontodophore, entirely covering odontodes when extended.

Mouth inferior (ventral) and very large, occupying most of anterior part of head ventrally ( Fig. 16 ). Each premaxilla with single scalpelloid teeth attached to its distal tip (visible only in skeletal preparations), but actually two tooth sockets adjacently-positioned, one of which normally vacant, corresponding to half-formed replacement tooth adjacent to mature one. Two additional initial-stage replacement caps positioned nearby. Mature scalpelloid tooth with distal portion disproportionately reduced and very strongly curved over rest of teeth, with pungent tip nearly adpressed to margin of basal plate. Scalpelloid teeth deeply hidden in labial tissue, only exposed when premaxilla forcibly abducted. Conical teeth absent in premaxilla ( Fig. 17 ). Upper lip thick, sucker-like. Median premaxilla very large, with 9 teeth disposed in one anterior row of four (convex anteriorly), one posterior row of four (convex posteriorly), plus single middle tooth ( Fig. 17 ). Teeth on anterior row more or less evenly spaced, those on posterior row more widely spaced medially than laterally. All nine teeth perpendicular to median premaxilla at base, but strongly curved posteriorly at distal pungent portion, those of anterior row taller than those of posterior row. All median premaxillary teeth strongly laterally compressed basally. Numerous replacement tooth caps posterodorsally to mature dentition, creating crowded aspect at posterior limit of median premaxillary dentition. Median premaxillary teeth occupying almost all of upper jaw and most of interior of mouth ( Figs. 16 , 17 ). Median premaxillary velum absent. Hypodontal pad of median premaxilla thin or absent, not cushioning teeth. Lower jaw wide, with long dentary lobes mostly fused to each other at midline, continuous with mental region posteriorly. Lower jaw cleft deep and strongly directed posterolaterally, not reaching parallel to longitudinal axis and with broad space separating it laterally from inner margin of upper jaw ( Fig. 16 ). Dentary diastema poorly differentiated, represented by small concave, sometimes angulate area at midline ( Fig. 16 ). Rami of mandible very close together at midline.Dentary teeth 4, closely packed at mesial end of dentary, disposed in two pairs, one dorsal and one ventral ( Fig. 17 ). Axis of dentary teeth anteroventrally-directed at base, with distal portions curved dorsally or anterodorsally. Branchiostegal velum forming large, continuous, round and posteriorly concave,free fold across whole of mental region ( Fig. 16 ). Dorsal portion of branchial membrane partly covering anterior margin of pectoral-fin base. Branchial openings small, located anteroventrally to pectoral-fin base, spanning approximately for area between ventral margin of opercular odontodophore and ventral margin of interopercular odontodophore. Maxillary barbel very short and broad at base ( Fig. 16 ). Posterior point of is base at or slightly anterior to vertical through anterior margin of eye in lateral view, its tip extending posteriorly approximately to vertical through middle of eyes in lateral view. Mesial (or ventral) part of maxillary-barbel base adjacent to membranous outgrowth extending posteriorly from corner of mouth. Rictal barbel vestigial, located mesially to base of maxillary one and represented by triangular flap of integument, its base immersed in membranous expansion at corner of mouth ( Fig. 16 ). Rictal barbel sometimes difficult to identify among irregularities of surrounding integument flap, but homology with trichomycterid rictal barbel evident by well-developed internal core. Nasal barbel vestigially represented by posterior elongated portion of fold around anterior naris described above, with double internal elastin core.

Lateral line short, straight along most of its length and gently bent or curved dorsally at posterior portion. Its terminal pore approximately at vertical through midlength of pectoral-fin, at horizontal through center of eye in lateral view, at or slightly posterior to vertical through anterior margin of axillary pore. Short secondary branch splitting off ventrally from anterior portion of canal and running nearly in parallel to ventral margin of main canal, with corresponding pore opening approximately at midlength of main canal or slighly anterior to that point. Poorly-ossified lateral-line tubule extending for section of main canal between bifurcation and dorsal bending.

Pectoral fin very short (49.5-61.4% HL), with i + 5 rays, first one (unbranched) not longer than remaining rays. Distal margin of pectoral fin gently convex, its base near ventral margin of body in lateral view, when abdomen not distended by gut contents.Pelvic fins small, well-separated from each other at base, with i + 4 rays. Pelvic splint present. Origin of pelvics located approximately at vertical through origin of dorsal-fin, covering anus and extending posteriorly to origin of anal fin. Posterior margin of pelvic fin round. Dorsal fin small, broadly triangular with roundish apex, with gently convex distal margin and ii + 6 fin rays (ii + 5 in one specimen), plus 5 procurrent ones. Anal fin small, slightly more elongate than dorsal one, with gently convex distal margin and ii + 5 fin rays, plus 4 procurrent ones. Origin of anal fin posterior to vertical through middle of dorsal-fin base. Caudal fin strongly concave, with concavity more pronounced with growth. Principal caudal-fin rays 6 + 7. Procurrent caudal-fin rays 15 dorsally and ventrally.

Vertebrae 39 (n = 1). First dorsal-fin pterygiophore subsequent to neural spine of vertebra 20 (n = 1). First anal-fin pterygiophore subsequent to haemal spine of vertebra 23 (n = 1). Dorsal-fin pterygiophores 7 (n = 1). Anal-fin pterygiophores 6 (n = 1, but malformed in single c&s specimen). Branchiostegal rays 3 (n = 1).

Pigmentation in preservative: Body almost entirely white or uniform dark tan, with little or no dark chromatophores on surface of body. Narrow fields or spots of brain pigment seen by transparency along edges of posterior part of braincase.Some specimens with internal dark chromatophores visible along vertebrae of caudal peduncle.

Etymology: The specific epithet comes from carrapato (feminin declension, carrapata), which in Portuguese is a collective name for blood sucking ticks in general.

Geographical distribution: Paracanthopoma carrapata is known from a single locality in the middle rio Madeira in the Brazilian Amazon ( Fig. 20 ).

Biology: One specimen in MZUSP 100142 has the abdomen distended with coagulated blood.

Remarks: Few specimens of this species are known and it more material and data are needed. All specimens so far were collected sympatrically with Pc. truculenta , but in much lower frequencies. In the material examined, all individuals of Pc. carrapata were initially found in lots composed mostly of Pc. truculenta . The two species are obviously different and can be distinguished at a glance when mixed in a sample. Also occurring sympatrically and abundantly is Pc. parva , a species more difficult to distinguish from Pc. carrapata . The question arises as to whether Pc. carrapata may be based on a rare hybrid between Pc. parva and Pc. truculenta . Indeed, part of the character combination diagnostic of Pc. aparavalhada is intermediate between those two species. The shorter body, exposed opercular odontodophore and relatively larger eye approach conditions in Pc. parva , while the extensive invasion of the skull roof by head musculature resembles the situation in Pc. truculenta . The number of opercular odontodes in Pc.carrapata is also intermediate between the counts in the other two species. Against such interpretation is the fact that Pc. carrapata has at least one exclusively derived condition which is not phenotypically intermediate or paralleled in either Pc. parva or Pc. truculenta : the uniquely large size of the median premaxillary teeth, which have their distal portion (postbend) larger than the basal portion. The presence of an autapomorphic condition is taken as evidence that the taxon is an independent lineage.

Figures

Figure 16. Paracanthopomacarrapata, holotype,MZUSP 100145,23.3 mm SL,Brazil,Rondônia,Rio Madeira at Calama.(A) Lateral view of body;(B) Dorsal view of head;(C) ventral view of head.

Figure 17. Paracanthopoma carrapata, holotype MZUSP 100145, CTscan images of head skeleton,(A) Lateral;(B) Dorsal;(C) Ventral.

Figure 20. Map of northern South America showing geographical distribution of Paracanthopoma ahriman, (losenge); Pc. alleynei (pentagon), Pc. cangussu (cross), Pc. capeta (6-tip star); Pc. carrapata (inverted triangle), Pc. daemon (square). Open symbols represent type localities. Some symbols may represent more than a single locality or lot of specimens.

Tables

Table 5. Morphometric data of Paracanthopoma carrapata. Ranges, mean and SD include holotype. Abbreviations: min = minimum value; max = maximum value;n = number of specimens;SD = standard deviation.

	n	min	max	Mean	SD
Standard length (mm)	5	17.2	23.3	21.3
Percentages of SL
Total length	5	1.1	1.1	1.1	0.0
Body depth	5	8.6	12.7	11.1	1.7
Caudal peduncle length	5	14.7	16.7	15.5	1.0
Caudal peduncle depth	5	5.9	6.8	6.3	0.4
Predorsal length	5	73.4	75.6	74.0	0.9
Preanal length	5	78.1	80.2	79.0	0.8
Prepelvic length	5	69.5	74.4	71.3	2.0
Dorsal-fin base length	5	6.5	8.0	7.0	0.6
Anal-fin base length	5	4.3	6.7	5.4	0.9
Pectoral-fin length	5	9.7	12.1	10.8	0.9
Head length	5	20.9	22.2	21.5	0.5
Percentages of HL
Head width	5	59.8	69.3	63.9	4.1
Head depth	5	39.3	51.5	46.5	4.4
Pectoral-fin length	5	49.5	61.4	55.6	5.0
Interorbital	5	10.7	12.4	11.7	0.7
Eye diameter	5	13.9	14.4	14.1	0.2
Snout length	5	39.2	41.8	40.5	1.1
Mouth width	5	28.7	34.0	31.5	2.5
Anterior internarial width	5	17.5	20.4	19.2	1.1
Posterior internarial width	5	5.7	7.2	6.7	0.6