Hemipsilichthys nimius, PEREIRA, REIS, SOUZA & LAZZAROTTO

Reis, Roberto E., Pereira, Edson H. L. & Armbruster, Jonathan W., 2006, Delturinae, a new loricariid catfish subfamily (Teleostei, Siluriformes), with revisions of Delturus and Hemipsilichthys, Zoological Journal of the Linnean Society 147 (2), pp. 277-299 : 286

HEMIPSILICHTHYS NIMIUS PEREIRA, REIS, SOUZA & LAZZAROTTO ( FIG. 8 )

Hemipsilichthys nimius Pereira, Reis, Souza & Lazzarotto, 2003: 5 : fig. 1 [type locality: Brazil: Rio de Janeiro: Parati: Rio Carrasquinho below the Cachoeira do Tobogã , upper Perequê-Açu basin, Penha , c. 7.5 km west of highway BR101, on the road from Parati to Cunha (23°12′51′ S 44°47′28 ′W)].

Specimens examined: Brazil: Rio de Janeiro: Holotype: MCP 33049 (105.1 mm SL), male, Rio Carrasquinho below the Cachoeira do Tobogã, upper Perequê-Açu basin, Penha , c. 7.5 km west of highway BR101, on the road from Parati to Cunha, Parati (23°12′51′S 44°47′28′W), 1 February 2003.

Paratypes: MCP 31990 (11, 45.7–98.1 mm SL), collected with the holotype . MCP 30671 (9 + 1 c&s, 35.9–102.2 mm SL), same locality of holotype, 18 October 2002 . MCP 31573 (1, 48.7 mm SL) Rio Taquari at Taquari Village, c. 2.2 km west of highway BR101, Parati (23°02′29′ S 44°41′34 ′W), 18 October 2002 .

Diagnosis: Hemipsilichthys nimius can be distinguished from H. gobio and H. papillatus by having eight (rarely seven or nine) branched rays in the dorsal fin (vs. always seven), by possessing the dorsalfin membrane expanded posteriorly, connecting the proximal half of the last dorsal-fin ray to the dorsum (vs. dorsal-fin membrane not expanded posteriorly), and by the V-shaped dorsal-fin spinelet ( Fig. 3 ) with functional dorsal-fin locking mechanism (vs. oval in H. gobio and absent in H. papillatus ). It can be further distinguished from congeners by its larger orbital diameter (15.3–16.9% HL vs. 8.6–11.8% in H. papillatus and 12.0–14.7% in H. gobio ).

Description: This species was recently described and illustrated by Pereira et al. (2003) and the description will not be repeated here. Morphometric data, however, are presented in Table 1 for comparative purposes.

Distribution: Hemipsilichthys nimius is only known from its type locality in the upper Rio Perequê-Açu and from the nearby Rio Taquari, in the southern coast of Rio de Janeiro state ( Fig. 5 ).

Ecology: The type specimens were collected in small coastal streams flowing through well-preserved Atlantic forest. Hemipsilichthys nimius was collected in localities between 100 and 370 m a.s.l., always in rocky substrate with fast flowing, clear water, under direct sunlight, and depths between 10 and 50 cm. Underwater observations indicate that H. nimius is most active during the night, grazing on the bottom ( Pereira et al., 2003).

Figures

Figure 3. Dorsal-fin spinelet of the Delturinae. A, Hemipsilichthys gobio, MCP 19780. B, H. nimius, MCP 31990. C, Del- turus brevis, MZUSP 69858. Scale bar 2 mm. DS1, first dorsal-fin spine or spinelet; DS2, second dorsal-fin spine.

Figure 5. Geographical distribution of the species of Delturus and Hemipsilichthys in south-eastern Brazil.

Figure 8. Hemipsilichthys nimius, holotype, MCP 33049, 105.1 mm standard length, male, Rio Carrasquinho below Cachoeira do Tobogã, upper Rio Perequê-Açu, Rio de Janeiro.