Taxonomy & naming
Delturus angulicauda was originally described by Franz Steindachner in 1877. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Delturus angulicauda (Steindachner, 1877), the parentheses indicating that the species was first placed in a different genus and later transferred to Delturus.
The species belongs to the subfamily Delturinae — a small, relict lineage of loricariids restricted to the Atlantic coastal drainages of eastern Brazil, and one of the family's more isolated branches. The genus name Delturus derives from the Greek deltos, a small board or writing tablet, combined with oura, meaning tail, in reference to the shape of the caudal region. Burgess's 1989 'An atlas of freshwater and marine catfishes' serves as a principal reference for the species.
Morphology
Delturus angulicauda reaches a maximum recorded size of about 7.5 in standard length (SL), making it a medium-sized loricariid. The body bears the heavy bony-plate armour characteristic of the family, and the genus name alludes to the distinctive form of the caudal region (deltos, 'writing tablet', + oura, 'tail').
Detailed colour and meristic descriptions beyond the size figure are confined to the primary taxonomic literature and are not reproduced in summary databases. The species' robust, flattened form is consistent with its life in strong current, where a low profile and powerful sucker help it hold position on rock.
Habitat
Delturus angulicauda is endemic to the Mucuri River basin of eastern Brazil, an Atlantic coastal drainage. FishBase records it as a freshwater, demersal, tropical species. It is a fast-water (rheophilic) specialist: individuals are usually found in the main river channel over rocky bottom where the water current is very strong.
This preference for high-energy, well-oxygenated riffle and channel habitat sets the species apart from the many loricariids associated with slow margins, leaf litter, or submerged wood. Specific water-chemistry measurements (temperature, pH, hardness) have not been published in the accessible sources.
Feeding
No species-specific dietary study has been published for Delturus angulicauda. As a rock-dwelling loricariid of fast water, it is expected to graze the aufwuchs — algae, biofilm, and associated microfauna — that coats stones in well-lit, oxygen-rich current, in the general manner of other rheophilic suckermouth catfishes. Stomach-content data confirming this for the species is not available.
Mating
No data has been published on the courtship or mating behaviour of Delturus angulicauda.
Breeding
No data has been published on the reproductive biology of Delturus angulicauda. There are no documented spawning records, clutch sizes, or parental-care observations for the species, in the wild or in captivity.
In the aquarium
Delturus angulicauda is essentially undocumented in aquarium keeping. It is a strong-current, high-oxygen rheophile rather than a typical aquarium pleco, and the demands of replicating its main-channel rapids habitat — vigorous flow, cool well-oxygenated water, and a bare rocky bottom — place it well outside ordinary community-tank conditions. No reliable husbandry, feeding, or breeding-in-captivity records exist for the species.
Conservation
The IUCN Red List assessed Delturus angulicauda as Least Concern (LC) on 7 November 2018. The species' restriction to a single Atlantic coastal basin means that localised threats — damming, sedimentation, and alteration of flow regimes in the Mucuri system — could nonetheless affect it, since rheophilic fishes are particularly sensitive to the loss of fast-water habitat. At present, however, it is not considered threatened.