Gymnotus carapo australis, 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 australis New Subspecies

Figure 3 A, Tables 3 and 4

Holotype: MLP 11221 (1), 341 mm, Argentina, Misiones province, Río Iguazú basin, Arroyo Verde (25°40’15”S, 053°56’00.8”W).

Paratype: MLP 11222 (6), 262–321 mm, same locality as MLP 11221 .

Non-Types: MLP 11223 (4), 216–272 mm, Arroyo Deseado Chico (25°47’19,7”S, 054°01’45.0”W), cuenca Río Iguazú , Misiones. Col.: J. Casciotta, et al. II/2002 . MLP 11223 (7), 110–330 mm, Arroyo Deseado Chico (25°47’19.7”S, 054°01’45.0”W), cuenca Río Iguazú , Misiones. Col.: J. Casciotta, et al. II/2002 . MLP 11225 (3), 221–318 mm, Arroyo Lobo (25°42’32”S, 054°05’36”W), cuenca Río Iguazú , Misiones. Col.: J. Casciotta, et al. II/ 2002 . MLP 11226 (3), 268–274 mm, Arroyo Tateto (25°47’12.8”S, 053°58’12.9”W), cuenca Río Iguazú , Misiones. Col.: J. Casciotta, et al. II/2002 . MCP 19552 (3), 145–336 mm. MCP 6059 (3), 173–355 mm.

Description: Specimens of G. carapo from the southern fauna overlap substantially in morphometric and meristic PC-space with specimens from other localities ( Figures 4 , 5 , and 12). Gymnotus carapo australis 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): deep body (BD 67.0%–98.8% HL, mean 88.1% vs. 42.7%–106.6%, mean 83.6% in all other subspecies), wide head (HW 50.8%–66.8% HL, mean 61.6% vs. 49.1%–67.7%, mean 59.1% in all other subspecies), short pectoral fin length (P1 38%.8–48.0% HL, mean 43.5% vs. 29.0%–60.9%, mean 46.5% vs. in all other subspecies) and large anal-fin pterygiophore scales (APS 6– 7, mode 7 vs. 7–11, mode 9 in all other subspecies).

Distribution: Occurs in the southern humid Neotropics, including the greater La Plata (Paraná-Paraguay), Uruguay, and Jacuí basins ( Figure 2 B).

Etymology: Subspecific epithet derived from the Latin “australis” meaning “of the South”.

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.