Astyanax clavitaeniatus

Astyanax clavitaeniatus was described in 2003, alongside Astyanax siapae, as a part of a redescription of congener Astyanax rupununi, which was formerly considered a synonym of Astyanax bimaculatus.[1] All four species are a part of the A. bimaculatus species complex, which also housed roughly a dozen other species when A. clavitaeniatus was described; this number changes regularly, given the complex phyletic relationships therein.[2] As of 2011, the A. bimaculatus species complex contained at least 20 species.[3] (Species in the A. bimaculatus group often share elements of pattern and coloration, including A. clavitaeniatus, but can further be linked by genetic evidence, such as chromosomal makeup.[3][4])

Astyanax clativaeniatus has no known synonyms.[5] It also lacks a common name;[6] "club-striped tetra" and "club-striped astyanax" have been suggested based upon its scientific name and physical descriptors.

Astyanax clavitaeniatus reaches roughly 7.2 cm (2.8 in) standard length (SL, without the tail fin included).[8] The body is deep, at least 37.4% the length of the body (but usually deeper), and slightly elongated. The caudal peduncle is thick. The snout, slightly pointed, is equal to or less than the diameter of the eye in length. The dorsal fin is situated at the midpoint of the body, and sports 12 rays (3 branched and 9 unbranched). There are 19 caudal-fin rays, 26–32 anal-fin rays, 8 or 9 pelvic-fin rays, and 12 or 13 pectoral-fin rays.[2] Early studies presented clear morphometric differences between A. clavitaeniatus, A. siapae, and A. rupununi, but more modern understandings recognize a great deal of overlap between the three.[9]

The coloration is generally similar to what most species in the A. bimaculatus complex present. Generally, the body ranges from sliver to silver-blue or silver-green, with a darker back and paler belly. There is a distinct humeral spot that is rounded or horizontal. Two vertical bars in a dark-brown color are present, with one intersecting the humeral spot and the other 2 or 3 scales behind. In others of the complex, there is often a dark spot on the caudal peduncle that continues onto the fin-rays; A. clavitaeniatus lacks the caudal spot and fin-ray pigmentation, instead presenting with a continued lateral stripe of greatly reduced width (roughly 1/5th of a scale).[10] There are also two silvery spots above the humeral spot, one just in front and one just behind. In alcohol, the coloration remains largely the same, though with plain silver instead of with touches of green or blue. The fins are largely clear.[2]

Astyanax clavitaeniatus was originally described from the Surumu river in Roraima, Brazil; paratypes were also collected from the Uraricoera river, in Fazenda Canadá creek and Pau Rocho creek.[2] Other specimens have been collected from the Río Takutu, as well as the Ríos Branco and Negro.[13] All of its habitats are found within the Amazon Basin.[8] Little else has been researched of its ecology, such as diet or behavior.

While it is not known to widely share its habitat with other species of Astyanax, it does live in sympatry with A. rupununi and A. bimaculatus in the Río Takutu. Other sympatric species include members of the genera Hemigrammus, Hyphessobrycon, Jupiaba, and Moenkhausia, as well as the tetra Iguanodectes spilurus.[14]

Astyanax clavitaeniatus has not been evaluated by the IUCN.[8] However, the Chico Mendes Institute for Biodiversity Conservation considers it a species of least concern ("pouco preocupante").[15] Various similar species of Astyanax, including multiple in the A. bimaculatus complex, are remarkably hardy and adaptable species, which likely remains the case for A. clavitaeniatus.[16]