| Biology: |
Collected specimens were deeply buried into massive leaf-litter deposits in isolated pools in the riparian forest (with some sites had no standing water, while other were up to 70-cm deep). All these pools join the main river channel during the high-water season and which possibly allows specimens to move and colonize suitable habitats. The new species so far has only been found in temporary pools, during the low-water period and its whereabouts during the flood season are yet unknown (in large measure due to difficulties in collecting during such time). The only other fish consistently associated with Tarumania walkeri is an undescribed species of the catfish (Phreatobius, although some other species, mostly represented as juveniles, have been sporadically caught in the same pools, (Microsternarchus bilineatus, Brachyhypopomus beebei, Apistogramma sp., Aequidens pallidus, Scoloplax dolicholophia, Microphilypnus amazonicus, Curimatopsis sp., Brycon sp., C. punctatus, Nannostomus eques, Copella cf. nattereri); all of which are probably just stray specimens that accidentally got trapped in the pools because of water-level changes in the hydric cycle. It is likely that this species follows the water-substrate interface along the hydric cycle, thus staying in more superficial layers when there is plenty of standing water and sinking into deep substrate as the water level recedes. This fish feeds on invertebrates, some captured specimens regurgitated whole small freshwater shrimps (Euryrhynchus). Accessory aerial respiration was observed, in the form of air taken via the mouth and held temporarily in the branchial cavity, which, along with the gular region, then becomes noticeably inflated. In the aquarium, the aerial respiration is induced by low-water conditions, observed fish gulped air at surface and kept it in the oral cavity for nearly 35 s before expelling an air bubble to take another gulp almost immediately and the same fish repeated such behaviour up to ten times in sequence. A large live nematode (Goezia spinulosa) was found in the branchial cavity of a specimen and also on the gills and in the intestines. Live specimens can move equally easily forwards and backwards, its pelvic fins can move independently of each other and deflect 180 degrees anteriorly. This fish displays remarkable stability and manoeuvrability in the water column and can remain stationary in contorted positions in narrow spaces amidst irregular substrate (not contacting any surface) (Ref. 116356). |