Sternarchella patriciae

description

Description. A medium-sized apteronotid species, reaching 208 mm LEA. Pectoral fin size small, less than 80 % HL. PA % large, 54 - 72 % HL. Head width narrow, distance between lateral margins 36 - 48 % HL. Preorbital (snout) length moderate, 24 - 32 % HL. Postorbital distance large, 60 - 68 % HL. Eye diameter large, 6 - 11 % HL. Interorbital distance small, 15 - 20 % HL. Mouth wide, distance between ricti 18 - 25 % HL. Body depth less than HL. Scales absent on posterolateral portion of body. Scales large in size with 5 - 8 present above lateral line at mid-body. Scales dorsal to lateral line rhomboid at mid-body. Rictus extends to a vertical with mental symphysis, gape very small, less than twice eye diameter. Oral aperture superior, lower jaw extends anteriorly to upper jaw. Body cavity long; 14 - 15 pre-caudal vertebrae present. Proximal surface of first displaced hemal spine narrower then descending blade. One to two displaced hemal spines. Swim bladder not extending posterior to body cavity. Anal-fin pterygiophore length equal to or shorter than hemal spines. Anal-fin proximal small, shorter than hemal spine. Two rows of bones in caudal peduncle visible externally. Caudal pedun

Taxonomic revision of the deep channel electric fish genus Sternarchella (Teleostei: Gymnotiformes: Apteronotidae), with descriptions of two new species

description

Fig. 7, Tab. 2 urn: lsid: zoobank. org: act: 69 ECF 190 - DC 1 E- 445 A- 839 A- 08 ADD 219 D 1 B 4

Taxonomic revision of the deep channel electric fish genus Sternarchella (Teleostei: Gymnotiformes: Apteronotidae), with descriptions of two new species

diagnosis

Diagnosis. Sternarchella patriciae can be distinguished from all congeners by the presence of two rows of bones visible externally in caudal peduncle (vs. one row in S. duccis, S. orinoco, S. orthos, S. raptor, S. sima, and S. schotti) (shared with S. calhamazon and S. rex), the presence of a continuous membrane of tissue connecting the anal-fin base and caudal peduncle (vs. no membrane in S. duccis, S. orinoco, S. orthos, S. raptor, S. sima, and S. schotti) (shared with S. calhamazon and S. rex), the presence of a long body-cavity (14 - 15 pre-caudal vertebrae vs. 12 - 14 in S. calhamazon and 16 in S. duccis, S. orinoco, S. rex, S. sima, and S. schotti) (shared with S. orthos and S. raptor), the possession of a ridge or crown of thorny projections at border of parietal and supraoccipital and epioccipital ridges (Fig. 2 a; vs. absent S. calhamazon, S. duccis, S. orinoco, S. raptor, S. rex, S. schotti, and S. sima) and the presence of a ridge on the posterior dorsal surface of the basihyal (vs. ridge absent in S. calhamazon) (shared with S. duccis, S. orinoco, S. orthos, S. sima, S. schotti, S. rex, and S. raptor).

Taxonomic revision of the deep channel electric fish genus Sternarchella (Teleostei: Gymnotiformes: Apteronotidae), with descriptions of two new species

discussion

Remarks. Sternarchella patriciae is a member of the S. calhamazon clade with which it shares six synapomorphies. Sternarchella patriciae also shares the highly predatory lifestyle of other Sternarchella species, and exhibits a peramorphic version of the S. calhamazon body plan. These relatively peramorphic characters are: more robust ossification of the skull among specimens of comparable size, more and larger muscle attachment sites on the skull (e. g. crown of thorns at border of parietal and supraoccipital and along ridge of epioccipital; Fig. 2 a), a longer caudal peduncle (Fig. 10), more pre-caudal vertebrae (12 - 14 vs. 14 - 15), more teeth present on pharyngobranchial (14 or more vs. 12 or less), and an overall larger total body size (80 % larger). These phenotypes all allow feeding on larger prey items like small fishes and large aquatic invertebrates. Sternarchella patriciae is allopatrically separated from S. calhamazon, and has to date only been found in the Madre de Dios basin in the upper Madeira basin in Peru. Genetic data are not yet available for S. patriciae. Genetic analyses of other fish taxa distributed in the upper Madeira and Lowland Amazon basins report varyi

Taxonomic revision of the deep channel electric fish genus Sternarchella (Teleostei: Gymnotiformes: Apteronotidae), with descriptions of two new species