Sternarchella schotti

description

Description. Pectoral fin size small, less than 80 % HL. PA % moderate, 46 - 49 % HL. Head width narrow, distance between lateral margins 36 - 44 % HL. Preorbital (snout) length moderate, 30 - 33 % HL. Postorbital distance small, 59 - 67 % HL small. Eye diameter large, 7 - 10 % HL or more. Interorbital distance small, 12 - 17 % HL. Mouth narrow, distance between ricti 16 - 18 % HL. Body depth less than HL. Body translucent in living specimens, yellow or pink hue in living specimens. 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. Rictus extends to a vertical with mental symphysis. Oral aperture terminal, upper and lower jaws equal in length. Body cavity long; 15 - 16 pre-caudal vertebrae present. Proximal surface of first displaced hemal spine narrower then descending blade. Four to five curved displaced hemal spines. Swim bladder elongate past posterior limit of body cavity. Anal-fin pterygiophore length longer than hemal spines. Anal-fin proximal long, equal o

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

diagnosis

Diagnosis. Sternarchella schotti is readily distinguished from congeners by the presence of a large eye, ED, 7 - 10 % HL (vs. 6 - 9 % HL in S. calhamazon, S. duccis, S. orinoco, S. orthos, S. rex, S. raptor, and S. sima) (shared with S. patriciae), the presence of an ossified third basibranchial, the presence of four to five curved displaced hemal spines, and the presence of an elongate swim bladder that extends beyond the posterior limit of the body cavity.

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

discussion

Remarks. Sternarchella schotti is readily differentiated from sympatric congeners by the presence of a swim-bladder that extends beyond the posterior margin of the body cavity, visible when held up to a strong light source. Taxonomic status of Sternarchella terminalis. Sternarchella terminalis (Eigenmann & Allen, 1942) was originally described as Porotergus terminalis and reassigned to the genus Sternarchella by Mago-Leccia (1994). However, closer examination of the holotype of S. terminalis (IU or CAS 15994), collected near Iquitos, Peru, shows that it possesses the larger eye diameter and distinct configuration of displaced hemal spines that are diagnostic of S. schotti (Steindachner, 1868 b; fig. 5). We therefore conclude that S. terminalis (Eigenmann & Allen) is a junior synonym of S. schotti (Steindachner, 1868 b). A species with a similar external phenotype, also present in the Amazon and Orinoco basins, has been incorrectly referred to as S. terminalis in the Amazon previously (Ivanyisky, Albert, 2014; Lundberg et al., 2013), and was described as S. orthos Mago-Leccia (1994) from the Orinoco basin. Despite measurable morphometric variation among populations of this species i

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

distribution

Distribution and habitat. Distributed throughout the deep channels of the Amazon and Orinoco basins. Ivanyisky, Albert (2014) described S. schotti as being restricted to the Amazon basin (Fig. 17). However, a single juvenile specimen of S. schotti was found inhabiting the río Meta in Colombia, suggesting that S. schotti may have a wider range than originally hypothesized.

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