Acarichthys Eigenmann

Synonymy

Acarichthys Eigenmann, 1912. Mem. Carneg. Mus. 5, p. 500 (type by original designation Acara heckelii Müller & Troschel). — Masculine.

Acarichthys heckelii. Live adult specimen collected from the Rio Arapiuns, Brazil, 1992. Photo: R. Stawikowski.

Diagnosis

The general appearance is similar to Geophagus, but the epibranchial lobe is completely wanting. Kullander & Nijssen (1986) associated Acarichthys with Guianacara with which it shares an anteroventral entopterygoid process, wide flattened lateral commissure, wide dorsal lamina on the parasphenoid and basisphenoid, a narrow fenestra between coracoid and cleithrum, and the inner branch of the first ray of pelvic fin longer than the outer branch in adults.

Acarichthys is uniquely distinguished by a dorsal shelf on the urohyal, hyperdeveloped nasad process of the lateral ethmoid, and mediad curved anterior margin of the distal postcleithrum.

A number of characters distinguish from Guianacara, but are not unique: Microbranchispines are present on the external face of the three posterior gill arches (absent in Guianacara). Vertebrae 14+15 instead of 13+13 or 13+14; abdominal hemal arches present. Pectoral radials are sutured as in some geophagines. Dorsal spines few (12-14, instead of 15). Calyx less developed and hyomandibular-metapterygoid suture absent. Guianacara is similar to cichlasomines in having a very small, globular interarcual cartilage, whereas Acarichthys has a longer interarcual cartilage, in contact with epibranchial 1 and resembling the condition in Geophagus. Acarichthys has a single supraneural., whereas Guianacara species have one or two.

Kullander (1986) reviewed A. heckelii on the basis of Peruvian specimens.

Included species

Acarichthys heckelii (Müller & Troschel, 1849)

Acara Heckelii Müller & Troschel, 1849, in Schomburgk, Reisen Brit. Guiana 3, p. 624 (Sümpfen der Savanne).
Geophagus Thayeri Steindachner, 1875. Sber. k. Akad. Wiss. Wien Math.-natw. Cl. 71, p. 108, Pl. III, Fig. 2 (Amazonenstrom bei Teffé, Villa bella, Obidos, Cudajas, Tonantins, Jatuarana, Ueranduba, Serpa, Rio Tapajos, R. Trombetas, R. negro, R. Xingu, See Hyanuary, José Assù, Saraca, Alexo und Lago maximo etc.)
Acara subocularis Cope, 1878. Proc. Amer. philos. Soc. 17, p. 696 ([Amazonian Peru]).

Primary types

Acara heckelii — Lost.
Geophagus thayeri — Syntypes: NMW 74135. 1. Itacoatiara; NMW 9249-9254. 5. Amazonen-Strom; NMW 17046-17048. 3. Amazonenstrom; NMW 17050-17051. 2. Amazonen-Strom; NMW 17052-17054. 3. Amazonen-Strom; NMW 17055-17057. 3. Amazonenstrom; NMW 17058-17060. 2. Lago Janauari; NMW 17061-17064. 3. Rio Tapajós; NMW 17066. 1. Amazonenstrom; NMW 17067-17070. 4. Amazonen-Strom; NMW 17101-17102. 1. Itacoatiara; NMW 17103-17110. Several. Tajapuru; NMW 17119-25. Several.; NMW 23819-23821. 3. Lago Janauari; NMW 24012. 1. Lago Janauari; NMW 24094-24095. 2. Lago José Fernandes; NMW 24096. 7. Lago Janauari; NMW 24105-24106. 2.'D. Justa Brasil'; NMW 24107-24108. 2. Rio Tapajós; NMW 24109-24110. 2. Rio Negro; NMW 24111-24114. 3. Itacoatiara; NMW 24115-24116. 2. Parintins; NMW 24133-24138. 6. Lago Janauari; ZSM 27335.1. Itacoatiara. It is likely that there are more syntypes, not yet located.
Acara subocularis — Lost.

Etymology

Acarichthys — Acara, another cichlid genus, in its turn from the Tupi-Guarani name for cichlid, acará, and ikthys, Greek noun meaning fish.
heckelii — for Jacob Heckel (1790-1857), Austrian ichthyologist, the first reviser of the family Cichlidae (Heckel, 1840); derived from the latinised form of the patronym, Heckelius.
thayeri — for Nathaniel Thayer, sponsor of the so-called Thayer Expedition.
subocularis — sub, Latin preposition meaning below, beneath, next to; in compound words after, behind, less; and ocularis, Latin adjective based on the noun oculus, eye, and referring to eye properties. Meaning not explained by Cope, but apparently the name refers to the relatively small and posteriorly situated eye.

Geographical distribution

Peru (Amazonas, Putumayo drainage), Venezuela (upper Orinoco), Brazil (Solimões, Amazonas, Negro, Branco drainages), Guyana (Essequibo drainage). Acarichthy heckelii occurs only in lowlands along the mainstream Amazon river, and along the Rio Branco and Essequibo. Only one specimen is recorded from Venezuela (unpublished), and needs verification.

Local names

Not recorded.

References

COPE, E.D. 1878. Synopsis of the fishes of the Peruvian Amazon, obtained by Professor Orton during his Expeditions of 1873 and 1877. Proc. Amer. philos. Soc. Philad. 17: 673-701.
EIGENMANN, C.H. 1912. The freshwater fishes of British Guiana, including a study of the ecological grouping of species and the relation of the fauna of the plateau to that of the lowlands. Mem. Carneg. Mus. 5: xxii+ 578 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. Stockholm, 431 pp.
KULLANDER, S.O. & H. NIJSSEN.1989. The cichlids of Surinam. E.J. Brill, Leiden and other cities, XXXIII+256 pp.
EIGENMANN, C.H. 1912. The freshwater fishes of British Guiana, including a study of the ecological grouping of species and the relation of the fauna of the plateau to that of the lowlands. Mem. Carneg. Mus. 5: xxii+ 578 pp.
SCHOMBURGK, R. [1849.] Reisen in Britisch-Guiana in den Jahren 1840-1844. Im Auftrag Sr. Mäjestat des Königs von Preussen ausgefuhrt von Richard Schomburgk. Dritter Theil. Versuch einer Fauna und Flora von Britisch-Guiana Nach Vorlagen von Johannes Müller, Ehrenberg, Erichson, Klotzsch, Troschel, Cabanis und Andern. Leipzig, I-VIII, 533-1260