Gymnotus carapo caatingaensis, Albert, 2017

Albert, James S., 2017, Revision of the polytypic electric fish Gymnotus carapo (Gymnotiformes, Teleostei), with descriptions of seven subspecies, Zootaxa 4318 (3), pp. 401-438 : 427

Gymnotus carapo caatingaensis New Subspecies

Figure 3 B, Tables 3 and 4

Holotype: AUM 20624, 225 mm. Brazil, Piauí, Río Gurgueia aff. Río Parnaíba (08°32’24”S, 044°25’48”W).

Paratype: AUM 20624, 210 mm. Brazil, Piauí, Río Gurgueia aff. Río Parnaíba (08°32’24”S, 044°25’48”W).

Non-Types: AUM 20689 (2), 95–138 mm, Brazil, Piauí, Río Gurgueia , 25 km SW Urucui . AUM 2079 (4), 156–192 mm, Piauí, Parnaíba , between Santa Filomena and Jurumenha . AUM 20793 (4), 111–195 mm, Brazil, Piauí, Parnaíba , between Santa Filomenha and Jurumenha .

Description: Specimens of G. carapo from the Caatinga ecoregion in the Brazilian state of Piauí overlap substantially in morphometric and meristic PC-space with specimens from other localities ( Figures 4 , 5 , and 12). Gymnotus carapo caatingaensis is characterized by the following combination of statistically significant (p <0.01) traits when compared to the rest of the species as a whole (see Principal Components Analyses and t-tests): short head (HL 10.2%–12.2% TL, mean 11.2% vs. 10.4%–15.5%, mean 12.7% in all other subspecies), long postorbital distance (PO 63.2%–66.9% HL, mean 65.2% vs. 36.8%–66.5%, mean 61.2% in all other subspecies), long pectoral fins (P1 46.9%–58.0% HL, mean 52.3% vs. 36.3%–60.9%, mean 45.9% in all other subspecies) and short anal fin (AF 70.9%–80.1% TL, mean 75.8% vs. 69.4%–88.0%, mean 79.9% in all other subspecies).

Distribution: Known from Río Parnaíba basin in the Brazilian Piauí state of Piauí ( Figure 2 B).

Etymology: Subspecific epithet derived from the Caatinga ecoregion of northeastern Brazil, home to a characteristic arid scrubland and thorny scrub forest.

Figures

FIGURE 2. Geographic distribution of Gymnotus carapo. A. Closed circles show 111 localities of specimens used in morphometric analyses, and open circles show 191 other verified G. carapo localities. B. Collection localities color coded by subspecies. Note G. carapo is absent from the interior of the Brazilian shield and the Atlantic coast of Brazil from Ceará to Rio Grande do Sul.

FIGURE 3. Specimens illustrating variation in body shape and color pattern among seven subspecies of Gymnotus carapo A. G. c. australis, MLP 11222, 289 mm, Argentina, Misiones province, Río Iguazú basin, Arroyo Verde (25 ° 40 ’ 15 ” S, 053 ° 56 ’ 00.8 ” W); B. G. c. caatingaensis, AUM 20624, 225 mm. Brazil, Piauí, Río Gurgueia aff. Río Parnaíba (08 ° 32 ’ 24 ” S, 044 ° 25 ’ 48 ” W); C. G. c. carapo, UMMZ 190414, 146 mm. Suriname, Brokopondo, Marshal Kreek, aff. Suriname River (05 ° 14 ’ 24.9 ” N, 055 ° 05 ’ 58.6 ” W); D. G. c. madeirensis, UMSS 0 6964, 178 mm. Brazil, Amazonas, Río Beni (10 ° 51 ’ 44.302 ” S, 066 ° 04 ’ 50.300 ” W); E. G. c. occidentalis, UF 122820, 279 mm. Peru, Loreto, Iquitos (03 ° 43 ’ 51.73 ” S, 073 ° 15 ’ 3.83 ” W); F. G. c. orientalis, MCZ 45189, 165 mm. Brazil, Para, Parauapebas, Río Arari, Ilha de Marajó (01 ° 01 ’ S, 048 ° 58 ’ W); G. G. c. septentrionalis, ROM 83885, 233 mm. Guyana, Essequibo, Río Mazaruni (04 ° 55 ’ 33.208 ” N, 060 ° 36 ’ 53.784 ” W). Scale bars = 10 mm.

FIGURE 4. Landmarks used for geometric morphometric analyses. Fifteen landmarks were recorded for 88 morphologically mature specimens from seven subspecies of G. carapo Landmarks: 1) tip of snout; 2) tip of maxilla; 3) margin of maxilla; 4) external naris; 5) second pore of the supraorbital laterosensory canal; 6) point directly above midline of eye; 7) supraoccipital crest; 8) base of first anal fin ray; 9) anus; 10) seventh pore of the posterior marginal laterosensory canal; 11) anterior margin of eye; 12) posterior margin of eye; 13) top of preopercle; 14) top of opercle; 15) base of most ventral pectoral fin ray.

FIGURE 5. Principal components analysis of linear measurements for 175 specimens from seven subspecies of G. carapo: G. c. australis (AU, n = 25), G. c. caatingaensis (CT, n = 8), G. c. carapo (CA, n = 31), G. c. madeirensis (MD, n = 13), G. c. occidentalis (OC, n = 65), G. c. orientalis (OR, n = 16) and G. c. septentrionalis (SE, n = 15). Head length, head depth, body width and body depth load heavily on PC 1, while pre- and postorbital (PR and PO, respectively) and preanal (PA) lengths load heavily on PC 2. Note the substantial overlap in PC space between subspecies.