Taxonomy & naming
Microlepidogaster arachas was described in 2013 by Fábio F. Roxo (in the original publication the authorship is given as Martins, Calegari & Langeani), in Zootaxa 3608(5): 379–388. The species is recognised as valid and is linked in the Catalog of Fishes (species id 72622).
The genus Microlepidogaster belongs to the subfamily Hypoptopomatinae — the dwarf suckermouth catfishes, a group of small loricariids of the Atlantic and Paraná drainages of South America. The genus name refers to the small scales (plates) of the belly region.
The species is diagnosed from its congeners (except Microlepidogaster perforatus) by an anterior compound supraneural plus first dorsal proximal radial contacting the neural spine of the ninth vertebra; it further has 18–29 dentary teeth, a complete median lateral plate series reaching the end of the caudal peduncle, a continuous lateral line, and 20–24 mid-dorsal plates. It carries no L-number.
Morphology
Microlepidogaster arachas is a very small loricariid, reaching about 1.5 in in standard length. The body is elongated and armoured with the bony plates characteristic of the family.
Fin counts comprise 8 dorsal soft rays and 6–7 anal soft rays, with 31 vertebrae. The lateral plate series is complete and continuous, the median lateral row reaching the end of the caudal peduncle, with 20–24 mid-dorsal plates. The dentaries bear 18–29 teeth.
Like other members of the genus, M. arachas is a facultative air-breather, able to take atmospheric air when dissolved oxygen is low. No data on sexual dimorphism has been published for the species.
Habitat
The species occurs in tributaries to the rio Araguari, rio Perdizes, and rio Dourados, all within the rio Paranaíba drainage of the upper rio Paraná basin, in Minas Gerais, southeastern Brazil. It is a freshwater, demersal fish of tropical streams.
No specific in-situ measurements of temperature, pH, or conductivity have been published. The facultative air-breathing ability noted for the genus suggests tolerance of warm, oxygen-poor conditions that can develop in small lowland streams, but microhabitat detail for this species is not documented.
Feeding
No direct dietary study of Microlepidogaster arachas has been published. As a dwarf hypoptopomatine with a ventral suckermouth and numerous fine dentary teeth, it is presumed to graze periphyton — algae, diatoms, and biofilm — from submerged surfaces, the typical feeding mode of the subfamily. Specific gut-content data is not available.
Mating
No data on courtship or mating behaviour has been published for Microlepidogaster arachas. No species-specific observations are available.
Breeding
No breeding records exist for Microlepidogaster arachas, in the wild or in captivity. Spawning site, clutch size, and parental care are all undocumented. The species is not established in the aquarium hobby, and no captive-spawning reports are available.
In the aquarium
Microlepidogaster arachas is not part of the ornamental trade and has no documented husbandry record. No species-specific captive parameters or care guidance can be given without fabrication.
Dwarf hypoptopomatines as a group are small, peaceful algae-grazers, but the facultative air-breathing and stream origin of this genus are the only ecologically grounded notes available — and these are inferences about the genus, not tested requirements for this species.
Conservation
The IUCN Red List assessed Microlepidogaster arachas as Least Concern (LC), with the assessment dated 7 November 2018. The listing indicates no major range-wide threats identified at the time of assessment.
The species occupies several tributary systems within the rio Paranaíba drainage, a region subject to intensive agriculture and water-resource development in the Brazilian Cerrado. While currently of least concern, the small headwater streams it inhabits are locally vulnerable to changes in land use, sedimentation, and flow.