Symphysodon Heckel

Symphysodon Heckel, 1840. Annln wien. Mus. Natges. 2, p. 332 (type by monotypy S. discus Heckel). — Masculine.

Symphysodon discus. Holotype of S. d. willischwartzi, MZUSP 15375, 110.7 mm SL. Photograph © S.O. Kullander.

Diagnosis

Very deep, strongly compressed body and extensively scaly dorsal and anal fins. Dorsal and anal fins are long, D. VIII-X.28-33, A. VI-IX.27-31. Caudal swimbladder diverticula reach to the 13th hemal spine and are not associated with ribs. Unique traits include the three extrascapulars (other cichlids have two, rarely one) and edentulous second pharyngobranchial (otherwise only in the African genus Cyclopharynx Poll). Both oral and pharyngeal jaws and dentition are greatly reduced. (Adapted from Kullander, 1986.)

There are several recent reviews of this genus, focussing, however, on species and subspecies characters: Schultz (1960), Burgess (1981), Kullander (1986), Kullander (1996).

Included species

Symphysodon aequifasciatus Pellegrin, 1904

Symphysodon discus var. aequifasciata Pellegrin, 1904. Mém. Soc. zool. Fr. 16, p. 250 (Teffé (Brésil); Santarem (Brésil)).
Symphysodon discus tarzoo Lyons, 1959. Tropicals Mag., p. 6, fig. p. 7 (Leticia, Columbia).
Symphysodon aequifasciata axelrodi Schultz, 1960. Trop. Fish Hobby. 8 (10), p. 14, fig. p. 9 (Belem, Brazil, Amazon River).
Symphysodon aequifasciata haraldi Schultz, 1960. Trop. Fish Hobby. 8 (10), p. 11, fig. p. 8 (Benjamin Constant, Brazil in the Amazon).

Symphysodon discus Heckel, 1840

Symphysodon discus Heckel, 1840. Annln wien. Mus. Natges. 2, p. 333 (bei Barra do Rio-negro im Flusse selbst).
Symphysodon discus willischwartzi Burgess, 1981. Trop. Fish Hobby. 29 (7), p. 37, fig. p. 37 (Rio Abacaxis (a tributary of the Rio Madeira), Brazil).

Primary types

Symphysodon aequifasciata axelrodi. — Holotype, USNM 179831, 101.1 mm SL. Brazil, Est Pará, Belém. No date. H.R. Axelrod.
Symphysodon aequifasciata haraldi. — Holotype, USNM 179829, 112.9 mm SL. Brazil, Est Amazonas, Benjamin Constant. No date. H.R. Axelrod & H. Schultz.
Symphysodon discus. — Holotype, NMW 35612, 98.6 mm SL. Brazil, Est Amazonas, 'Rio Negro'. 2 Nov 1833. J. Natterer.
Symphysodon discus tarzoo. — Not located, possibly no specimens preserved (Kullander, 1996).
Symphysodon discus willischwartzi. — Holotype, MZUSP 15375, 110.7 mm SL. Brazil, Est Amazonas, Rio Abacaxis. No date. H.R. Axelrod et al.
Symphysodon discus var. aequifasciata. — Syntypes, MNHN 02-130, 1. Brazil, Est Pará, Santarém. No date. Jobert; MNHN 02-134-135, 2, 90.6-122.5 mm SL. Brazil, Est. Amazonas, Tefé. No date. Jobert.

Identification guide to species

The two nominal species currently recognized can be distinguished by colour pattern. Symphysodon discus has a distinct pattern of dark undulating lines covering the sides and a dark vertical bar across the middle of the side much more intense than the other vertical bars. Symphysodon aequifasciatus has all vertical bars similar in width and intensity; horizontal stripes do not show in preserved specimens except occasionally on nape and on anal fin base.

A form from the Maués is not yet known from museum material, but has been reported in aquarium literature and may be distinct. It is similar to S. aequifasciatus but has the middle bar on the side intensified though not wider than the other bars.

Symphysodon aequifasciatus from Tefé can be recognized by yellow anterior sides and red spots over much of the sides. Life colours vary considerably in S. aequifasciatus but it remains to be investigated how the variation correlates with distribution, environmental conditions, sex and ontogeny.

Symphysodon aquifasciatus freshly collected from the Rio Juruá in Brazil. Photograph © S.O. Kullander.

Analysing meristic data Kullander (1996) found that S. discus averages lower meristics than S. aequifasciatus, but Western Amazonian S. aequifasciatus have lower counts than central and eastern Amazonian S. aequifasciatus, similar to S. discus.

Etymology

Symphysodon — symphysis, Greek noun meaning grown together, from sym (syn), together, and physis, meaning growth, body form, appearance; odous, and Ionic odon, Greek noun meaning tooth. The name refers to the few teeth which located over the area where the two jaw halves meet (the symphysis).
aequifasciatus — aequus, -a, -um, Latin adjective meaning same or equal; fasciatus, -a, -um, Latin adjective of fascia, band, girdle, bandage. The name refers to the equally wide dark stripes across the sides, different from the pattern with a dominant middle bar in S. discus.
axelrodi — for Herbert R Axelrod, US publisher of aquarium and other pet literature. Collector of type series.
discus — discos, Greek noun meaning discus, i.e., a circular disk for throwing in athletic competition. The name refers to the shape of the body
haraldi — for Harald Schultz, German-Brazilian ethnographer, also aquarist, collected and sold collections to USNM and ZSM. Collector of type series.
tarzoo — contraction of "Tarpon Zoo", an ornamental fish export firm in Leticia, from which the specimens serving the original description were exported.
willischwartzi — for Willi Schwartz, German-Brazilian ornamental fish exporter in Manaus, Brazil. Deceased 1981. Obituary: Anonymous, 1981. Willi Schwartz is dead. Tropical Fish Hobbyist, 29(6): 82.

Geographical distribution

Symphysodon aequifasciatus is collected along the mainstream Rio Solimões and Rio Amazonas in Brazil, and also in the Río Putumayo-Içá in Peru and Brazil (and probably Colombia). A record from the Rio Muiuçu (Rio Tapajós above Jacareacanga) is doubtful. There are many more localities reported in aquarium literature, but within the same general area of distribution. Symphysodon discus on the other hand is restricted to the lowermost parts of the Rio Negro, Abacaxis and Trombetas.

Geographical distribution of Symphysodon species. After Kullander (1996), slightly modified.

References

BURGESS, W.E. 1981. Studies on the family Cichlidae: 10. New information on the species of the genus Symphysodon with the description of a new subspecies of S. discus Heckel. Trop. Fish Hobby. 29 (7): 32-42.
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.
LYONS, E. 1959. Symphysodon discus Tarzoo. New blue discus electrify aquarium world. Tropicals Mag. 4 (3): Cover, 6-8, 10.
KULLANDER, S.O. 1996. Eine weitere Übersicht der Diskusfische, Gattung Symphysodon Heckel. DATZ Sonderheft Diskus: 10-16.
PELLEGRIN, J. 1904. Contribution à l'étude anatomique, biologique et taxinomique des Poissons de la famille des Cichlidés. Mém. Soc. zool. France 16: 41-399.
SCHULTZ, L.P. 1960. A review of the pompadour or discus fishes, genus Symphysodon of South America. Trop. Fish Hobby. 8 (10): 5-17.