Astronotus Swainson

Synonymy

Crenilabrus (Astronotus) Swainson, 1839. Nat. Hist. Fish. 2, pp. 173, 229 (type by monotypy Lobotes ocellatus Agassiz). Masculine.
Acara Heckel, 1840. Annln wien. Mus. Natges. 2, p. 338 (type by subsequent designation by Eigenmann & Bray (1894, p. 616), A. crassipinnis Heckel). Masculine.
Hygrogonus Günther, 1862. Catal. Fish. Br. Mus. 4, p. 303 (type by monotypy Lobotes ocellatus Agassiz). Masculine.

Astronotus ocellatus, from Spix & Agassiz (1829-1831)

Diagnosis

Astronotus, Chaetobranchus and Chaetobranchopsis uniquely possess large microbranchiospines bearing numerous spines on the exposed surface, very different from those of other cichlids in which the microbranchiospines are very small and with spines very few and restricted to lateral margins. Only Cichla has a few spines on the exposed surface. Astronotus can be distinguished from the other chaetobranchines by having African type lips instead of American type lips, i.e., the upper and lower lip folds meet in the angle of the mouth without the lower overlapping the upper. The lower pharyngeal tooth plate is fairly stout. The cephalic lateralis system includes 7 preopercular and 5 dentary openings. The lachrymal bone has only 3 lateralis openings. There are 6 infraorbital bones, the 3rd with a middle foramen.

Astronotus species are readily identified by their general appearance, especially the long soft dorsal and anal fins and the heavy scaly sheath covering the soft unpaired fins. The colour pattern is cryptic, with a seemingly irregular pattern of light and dark blotches and stripes, and a prominent spot on the caudal fin base, encircled with a red, yellow or silvery ring. Juveniles are black with contrasting white stripes.

The largest specimen measured so far is a 240 mm SL specimen of Astronotus crassipinnis.

Included species

Astronotus crassipinnis (Heckel, 1840)

Astronotus ocellatus (Agassiz, 1831)

Identification guide to species

Only two valid species are recognised; which see for distinguishing characters.

Etymology

Astronotus refers to the ocellated spots on the dorsal fin of A. ocellatus, and is composed of the Greek words astron, star, and notos, back.
Acará is the Tupi-Guarani name for cichlids, incorporated in Brazilian Portuguese. Treated as masculine in Portuguese and by the author, it retains its gender, masculine.
Hygrogonus, from the Greek words hygros, wet, soft, flexible, and gonia, angle, corner; apparently referring to the largely cycloid body scales, hinted at by Günther. The second word also might be gonos, borth, offspring, descendant, etc., but that interpretation seems far-fetched.

Geographical distribution

Astronotus is restricted to tropical lowlands, mainly floodplains and swamps, in Brazil, Peru, Bolivia, Paraguay, French Guiana, Venezuela, Colombia and Ecuador, including the Amazon basin, the Orinoco basin, the northern Paraguay basin, and the coast of Amapá and adjacent French Guiana.

References

EIGENMANN, C.H. & W.L. BRAY. 1894. A revision of the American Cichlidae. Ann. N.Y. Acad. Sci. 7: 607-624.
GÜNTHER, A. 1862. Catalogue of the fishes in the British Museum. Volume fourth London, 534 pp.
HECKEL, J. 1840. Johann Natterer's neue Flussfische Brasilien's nach den Beobachtungen und Mittheilungen des Entdeckers beschrieben. (Erste Abtheilung, die Labroiden.) Annln wien. Mus. Natges. 2: 327-470.
KULLANDER, S.O. 1986. Cichlid fishes of the Amazon River drainage of Peru. Swedish Museum of Natural History, Stockholm, 431 pp.
SPIX, J.B. & L. AGASSIZ. 1829 [& 1831]. Selecta genera et species piscium quos in itinere per Brasiliam annis MDCCCXVII-MDCCCXX jussu et auspiciis Maximiliani Josephi I. Bavariae regis augustissimi peracto collegit et pingendos curavit Dr. J.B. de Spix Monachii, 138 pp. [1829, pp 1-82; 1831, pp. 83-138.]
SWAINSON, W. 1839. The natural history of fishes, amphibians & reptiles, or monocardian animals, vol. II Lardner's Cabinet Cyclopaedia, Longman, Orme, Brown, Green & Longmans, London, 452 pp. Relevant pages 173(146kb), 229 (153kb), 230 (168kb)