Aequidens pallidus (Heckel)

Synonymy

Acara pallidus Heckel, 1840. Annln wien. Mus. Natges. 2, p. 347 (Rio-negro).
Centrarchus? vittatus Jardine, 1843. Nat. Libr. Ichthyol. 5, p. 161, pl. 14 (-).
Aequidens duopunctata Haseman, 1911. Ann. Carneg. Mus. 7, p. 338, pl. LVI (Manaos).

Acara pallidus. Holotype, NMW 33678, 63.3 mm SL. 'Brasil, Rio-negro.'. Photo: S.O. Kullander

Diagnosis

A moderately large (to about 140 mm long) Aequidens species with triserial predorsal scale pattern, relatively long pectoral fin (36.6-44.6% of SL) and 25-26 scales in the E1 row. It is most similar to A. tubicen, with which it shares an enhanced, wide light spot anterior to the caudal spot, lateral band high on the side, posteriorly positioned midlateral spot, and high vertebral count (14+13=27). It differs from A. tubicen in the colour pattern, having a supraorbital spot, lacking in A. tubicen, and a normal cheek spot (A. tubicen has a preopercular spot). The posterior part of the lateral band is uninterrupted at all sizes, whereas in A. tubicen it is divided into blotches. A. pallidus is similar also to A. diadema from which it can be distinguished by having more scales ( E1 scale row count 25-26 instead of 24), much narrower dark margins on dorsal flank scales, and more posteriorly situated midlateral spot (through E3 scales 12-15 instead of about 10-13). (Modified after Kullander & Ferreira, 1991.)

Acara pallidus. Freshly collected adult, NRM 18063 from Igarapé Tarumãzinho near Manaus. Photo: S.O. Kullander

Primary types

Acara pallidus — Holotype, NMW 33678, 63.3 mm SL. 'Brasil, Rio-negro.' Collected by J. Natterer. Date of collecting known.
Centrarchus vittatus — No types preserved.
Aequidens duopunctata — Holotype, FMNH 54033, 71.9 mm SL. Manaus. Collected 29 November 1909 by J.D. Haseman. Previously CM 2573.

Etymology

pallidus — Latin adjective meaning pale, referring to the coloration of the faded holotype.
duopunctata — Latin adjective meaning with two blotches, derived from the adjectives duo, two, and punctatus, spotted, referring to the prominent midlateral and caudal spots.

Geographical distribution

Middle and lower Rio Negro, Rio Preto da Eva, Rio Puraquequara and Rio Uatumã drainages.
Lifemapper map

Natural history

Collected in both lentic and lotic habitats, but restricted to black- and clearwaters. Goulding et al. (1988) found chiefly fish and detritus in stomachs of Rio Negro specimens.

Local names

Not recorded.

References

GOULDING, M., M.L. CARVALHO & E.G. FERREIRA. 1988. Rio Negro. Rich life in poor water. The Hague.
HASEMAN, J.D. 1911. An annotated catalog of the cichlid fishes collected by the Expedition of the Carnegie Museum to Central South America, 1907-10. Ann. Carneg. Mus. 7: 329-373.
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. & E.J.G. FERREIRA. 1991. A new Aequidens species from the Rio Trombetas, Brasil, and redescription of Aequidens pallidus. Zool. Scr. 19: 425-433.