Geophagus sp. "Orange Head"
(Click for Further Information)
Geophagus sp. "Araguaia Orange Head"
Geophagus sp. "Tapajos Orange Head"
Comments: These are some thoughts and observations on distinguishing between Araguaia and Tapajos Orange Heads:

Black Horizontal Band: The current suggested method to distinguish Geophagus sp. "Araguaia Orange Head" from Geophagus sp. "Tapajos Orange Head" is the presence of a black horizontal band (Weidner 2000, p166) positioned between the lateral spot and the head which becomes visible under certain circumstances. This appears not to be the case, as the Tapajos variant can and does show this band, however the Araguaia variant seems to be able to show an almost jet black band and show it more often. Tapas seem to flash it on for a few minutes then it disappears, whereas Araguaia can show it for hours at a time.

Lateral Spot Shape and Position: Weidner also discusses differences in lateral spot shape and position. He suggests Tapas have a more roundish spot which lies below the upper lateral line and ends at the fish's horizontal axis, while in the Araguaia variant the lateral spot is somewhat longer, it also lies below the upper lateral line but ends a scale width above the lower lateral line.

The lateral spot in Araguaia (observing ten adult specimens) does seem to be not quite round, but more a rough/untidy/jagged edged spot. Some specimens can and do show a nice round spot but generally this is not the case. The positioning of the spot does seem to follow Weidners description, however some specimens do have the spot reaching the lower lateral line.

The Tapajos variant has been a bit harder to observe due to the lack or uncertainty of true specimens. In the small number of Tapas I have observed the spot is more rounded but can be oval in shape. The outline of the spot seems to be more smooth and probably gives it a more rounded appearance. Generally the spot does reach the lower lateral line but again in some fish this is not the case.

Head and Body Shape: There appears to be no differences in head shape between the two variants. There is a Tapajos line here that seems to have a bluntly shaped head, but pictures of wild Tapajos in Blehers Discus book shows that this isn't a trait. In regards to body shape, Weidner suggests that the Tapajos variant has a deeper body profile and refers to the Araguaia variant as slimmer. I have seen many tall bodied Araguaia, generally mature fish. Tapas do appear to be shorter in body length (in relation to height) giving them the impression of a taller body.

Head and Gill Operculum Colouration: Head colouration in young adult specimens of the Tapajos variant seems to be more an orange colour and can appear almost fluorescent orange (Bleher's discus 2006, p 269 shows a fluorescent orange colour). I have been told that this orange colour can intensify to red. In the Araguaia variant the colouration is more towards a red and is evident even when there is only a hint of colour present.

One characteristic which seems to distinguish the two variants is the colouration present on the gill operculum of mature male G. sp. "Tapajos Orange Head". I have never observed any colouration on the gill operculum in mature male G. sp. "Araguaia Orange Head" (it seems to be only present on the head area).

Upper Caudal Peduncle Colour: A recent observation is that Tapas can show an orange stripe on the upper caudal peduncle area (between the rear dorsal fin and the start of the caudal fin). This seems to be linked to head colouration intensity and is more prevalent in males. Female Tapas do show some colouration but it is not nearly as intense as in males. Bleher's discus has a picture (dorsal view) which shows this colouration. Some Araguaia, usually dominant males, do show colouration here however it is red and does not really resemble a solid stripe. It looks more like patches of colour on each scale in this area. More fish need to be examined before anything conclusive can be said.

Body Base Colouration: The Tapajos variant appears to have a clean white/cream body base colour (Weidner suggests yellow) and very rarely shows a grey sheen. On the other hand the Araguaia variant seems to show this grey sheen almost all of the time when in adulthood and in certain pictures shows an olive base colour.

Conclusions: In saying all this, these are only observations and what is written here may change. It should still be remembered that it is very difficult to identify with 100% certainly between the variants.