Caught! In the past, a few feather tetras of the species Hemiodus immaculatus came to us as bycatch together with the very rarely imported species Argonectes longiceps (https://www.aquariumglaser.de/en/09-characoids-tetra-relationship/argonectes-longiceps-2/). Both fish look very similar and apparently form a symbiotic relationship in nature. How exactly this symbiosis works, however, is still completely unexplored. Now we have once again received a shipment of “Argonectes longiceps”. The typical horizontal swimming style (Hemiodus species usually swim at an angle, like Thayeria spp.) and the coloration were a good match for Argonectes, so we booked the animals as such.
As Argonectes is a real rarity, they were placed in the photo tank after acclimatization. A close-up of the teeth showed: these are not Argonectes, but Hemiodus!!! The imitation of the two species is truly phenomenal. If you know about them, you can of course see other differences: Hemiodus immaculatus has comparatively larger scales and a dark V-pattern in the caudal fin with a transparent fin margin, whereas in Argonectes longiceps the caudal fin (which is relatively smaller, by the way) has a dark margin and the dark pattern elements are mainly confined to the caudal fin lobes.
Hemiodus immaculatus is widely distributed in the two large rivers Amazon and Orinoco and their tributaries in Bolivia, Brazil, Colombia and Venezuela. However, there are indications that some of these species are cryptic (= externally unrecognizable but genetically distinct). Our specimens come from Colombia.
Hemiodus immaculatus reaches a length of about 25 cm. The species is not quite as skittish as its prettier conspecific H. gracilis. The peaceful animals therefore fit well in larger community aquariums.
For our customers: the fish have code 258254 on our stock list. Please note that we only supply the wholesale trade.
Text & photos: Frank Schäfer
