Researchers have described a new species of the fish genus Sturisoma from Madeira River basin in Bolivia and Brazil.
Live specimen of Sturisoma reisi from Guaporé River basin. Image credit: Willian Ohara.
Sturisoma is a genus of Neotropical freshwater armored catfishes belonging to the subfamily Loricariinae.
First described in 1838 with Loricaria rostrata as the type species, the genus currently includes 10 recognized species.
“Sturisoma species, in general, show a conservative external morphology, and as it was pointed out by other authors, osteological characters within the genus also show little variation between congeners,” said Universidade Federal do Rio de Janeiro researchers Alejandro Londoño-Burbano and Marcelo Britto.
“Nonetheless, some body measurements were found, which even though show some overlap, could be considered as helpful in distinguishing the newfound species from some congeners.”
Scientifically named Sturisoma reisi, the new species shows subtle sexual dimorphism.
Sexual mature males of the new species show development of short dermal teeth on the sides of the head.
“Sturisoma reisi can be distinguished from all congeners by the presence of a middorsal longitudinal, thin dark stripe on the caudal peduncle, extending from the second or third plate posterior to the dorsal-fin base to the origin of the caudal fin, or slightly anterior; anteriormost abdominal plates, just posterior to the lower lip, square, not enlarged, smaller than anterior abdominal plates; and a middorsal longitudinal dark brown stripe from the first predorsal plate to near the dorsal-fin origin,” the scientists said.
Sturisoma reisi is known from Cautário, Itenéz, Guaporé, Mamoré, Machado and Soteiro rivers, in the Madeira River basin, of Bolivia and Brazil.
The species is known from 18 localities: 17 in Brazilian territory and one in Bolivian territory.
The extent of occurrence of Sturisoma reisi is almost 200,000 sq. km. Following the recommendations by the IUCN, the fish should be categorized as Least Concern.
“Sturisoma species are distributed entirely in cis-Andean rivers, and its richness is higher along the Amazonas River basin,” the authors said.
“With the description of Sturisoma reisi, the number of species at the upper Amazon basin increases to six valid species, along with Sturisoma brevirostre, Sturisoma graffini, Sturisoma guentheri, Sturisoma lyra and Sturisoma nigrirostrum, and it assembles the higher richness of the genus recorded on any region to date.”
“The identification of a new species for this region shows how underestimated, and poorly studied, the richness within Sturisoma is.”
“A taxonomic and phylogenetic analysis of the genus is being carried out by the authors to address the delimitation of species and evaluation of the diversity of the genus.”
The discovery of Sturisoma reisi is reported in a paper in the Journal of Fish Biology.
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A. Londoño-Burbano & M.R. Britto. 2023. A new species of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae), from the Madeira River basin, with a discussion of historical biogeography of western Amazonas and Paraguay River basins. Journal of Fish Biology 102 (1): 188-203; doi: 10.1111/jfb.15251
