Ctenorillo jequitinhonha Cardoso & Ferreira 2024, n. sp.

Ctenorillo jequitinhonha Cardoso & Ferreira, n. sp.

(Figs 24-26; 27J; 28J, K)

urn:lsid:zoobank.org:act: 5CF8D003-88B7-465B-84EF-040FEC4FB7F2

TYPE MATERIAL. — Holotype. Brazil • 1♂ (7 mm, parts in slide), Minas Gerais state, Jequitinhonha municipality, Toca Juparanã cave; 16°25’3”S, 40°55’23”W; R. L. Ferreira leg., 7.IV.2017; ISLA96804. Paratypes. Brazil • 1 ♂ in slide; same data as holotype; ISLA96806 • 3 ♂, 8 ♀; same data as holotype; ISLA96805.

ETYMOLOGY. — The new species name is a noun in apposition that refers to the city and the Jequitinhonha River, one of the most important rivers in the north of Minas Gerais state; the type locality is within the drainage basin of the Jequitinhonha river. The word Jequitinhonha is of indigenous origin and means “wide river full of fish”.

DIAGNOSIS.— Dorsum covered with round tubercles with three rows on cephalon (4, 4, 4); three rows on pereonite 1 (2, 4, 7); two rows on pereonites 2-7 (6 + 4); and two paramedian tubercles on pleonites 3-5 and on telson. Pleopod 1 exopod with protruding distal portion, triangular, outer margin sinuous; endopod distal portion straight, twice longer than exopod.

DISTRIBUTION. — Jequitinhonha municipality, Minas Gerais state.

DESCRIPTION

Maximum size: ♂, 7 mm, ♀, 9 mm. Color grey with lateral margins depigmented (Fig. 26C, D). Dorsum covered with round tubercles (Fig. 24A, B): cephalon with three rows (4, 4, and 4 from front to back of vertex); pereonite 1 with 13 in three rows (2, 4 and 7); pereonites 2-7 with 10 (6+ 4); pleonites 3-5 and telson with two paramedian tubercles. Dorsal cuticle (Fig. 28J, K) with short triangular scale setae, pereonites 1-7 bearing one line of noduli lateralis per side on outer surface of posterior tubercle of second tubercle. Cephalon with frontal shield protruding above vertex; eye consisting of 16 ommatidia (Figs 24C; 28J). Pereonite 1 with posterior margin sinuous at sides; inner lobe of schisma rounded, extending beyond posterior margin of outer lobe; pereonite 2 with triangular ventral tooth reaching epimeron posterior margin (Fig. 24D). Pereonites 2-7 (Fig. 24A) with wide quadrangular epimera slightly bent outwards. Telson (Fig. 24E) hourglass-shaped, proximal portion broader than distal portion. Antennula (Fig. 24F) of three articles, second article shorter than first and third, third article with seven apical aesthetascs. Antenna (Fig. 24G) short and stout, flagellum shorter than fifth article of peduncle; second article of flagellum about three times as long as first. Buccal pieces as C. pelado Cardoso & Ferreira, n. sp. (Fig. 24 H-L). All pleopod exopods with monospiracular covered lungs. Uropod (Fig. 25A) protopod flattened, enlarged on basal portion; exopod outward, short, inserted dorsally close to medial margin of protopod.

Male

Pereopods without particular modifications (Fig. 25B, C). Pleopod 1 exopod (Fig. 25D) as wide as long, protruding distal portion, triangular, outer margin sinuous; endopod twice longer than exopod, distal portion straight. Pleopod 2 endopod as long as exopod (Fig. 25E). Pleopods 3-5 exopods as in Figure 25 F-H.

HABITAT

Specimens of C. jequitinhonha Cardoso & Ferreira, n. sp. were found in Toca Juparanã, a granite cave located in Jequitinhonha municipality, in northeastern Minas Gerais state, Brazil. The average annual temperature is around 25°C, with the minimum temperature of approximately 15°C and the maximum of 38°C. The rainy season lasts from October to April, with December being the wettest month (140 mm of precipitation). The dry season lasts from May to September, with July being the driest month (average of 3 mm of precipitation) (Álvares et al. 2013).

The Toca Juparanã cave is a granitic talus cave that was formed by water removal of smaller sediments between large collapsed granitic blocks. The cave has two entrances of irregular shape, delineated by the contact of boulders (Fig. 26A). The main chamber of the cave has an irregular floor made up of collapsed boulders (Fig. 26B) and is euphotic/disphotic due to the presence of two entrances located on either side of the chamber. There is a descending aphotic conduit from this chamber, which is crossed by a small hypogenic drainage. Specimens of C. jequitinhonha Cardoso & Ferreira, n. sp. were found under fallen rocks in this conduit trespassed by the small drainage, although the specimens were not observed close to the mainstream passage. The only visible organic resource in this area was plant debris brought by water, indicating that the isopods were likely feeding on this resource (Fig. 26 C, D).

The vegetation surrounding the cave represents a well-preserved secondary forest, although many areas in the region are deforested for pastures and monocultures, especially near the Jequitinhonha River floodplain (Fig. 26E). The cave receives no visitors and is unknown to most of the local population. As for other Ctenorillo herein described, no samplings were conducted outside caves in the area, thus C. jequitinhonha Cardoso & Ferreira, n. sp. is likely to occur in external habitats. Therefore, it is advisable that further studies including external samplings be conducted to better understand the species distribution.

REMARK

Ctenorillo jequitinhonha Cardoso & Ferreira, n. sp. differs from the Brazilian species by the round shape of tubercles, resembling C. iuiuensis Cardoso & Ferreira, n. sp. by the presence of two paramedian tubercles on pleonites 3-5 and on telson.