Rhombognathus picinguabensis, Pepato, Almir R. & Silveira, Paulo Sergio Amorim Da, 2015

Pepato, Almir R. & Silveira, Paulo Sergio Amorim Da, 2015, Two new species of Rhombognathus (Halacaridae, Trombidiformes) from a Mangrove in the northern littoral zone of São Paulo State (Brazil), Zootaxa 3905 (4), pp. 500-510 : 507-509

Rhombognathus picinguabensis sp. nov

( Fig. 3 )

Holotype. Female (UFMG-AC1200645) on algae associated to Rizophora mangle and Avicenia schaueriana at Fazenda River (23°21’38,5”S 44°50’38,5”W), 12 March 2005, water salinity: 2‰, coll. Silva, M. L., Tiago, C. G. & Pepato, A. R.

Paratypes. Female (UFMG-AC1200674) and male (UFMG-AC1200675) collecting data same as holotype.

Description. Female: Idiosoma 341–346 µm long, 231–243 µm wide. AD and OC almost smooth, PD slightly paneled, except for costulae which are pierced by canaliculi ( Fig. 3 A). AD 97 µm long, 110 µm wide with ds-1 at 0.51 of plate length, such setae 11–21 µm long, similar to posterior dorsal setae. Pair of glp-1 at 0.48 of AD length. AD length/width ratio 0.88. Posterior line of muscle scars at 0.76 of AD overall length. OC 121–123 µm long, 82–84 µm wide. Pairs of ds-2, ds-3, glp-2, glp-3 and a pore canaliculus on OC. Holotype bears two corneas, female paratype asymmetrically none and one cornea. Length/height ratio of OC 1.44–1.50. PD 220–221 µm long, 125–128 µm wide with only pair of ds-4 at 0.47–0.51 of its length, and pair of glp-4 at its posterior margin. AD 0.44 as long as PD. Adanal setae dorsal on anal papilla.

Gnathosoma ( Figs 3 B–C). 66–70 µm long, 74 µm wide, length: width ratio equal to 1.0 6 (paratype female). Rostrum 24–32 µm long, 21 µm wide (paratype female), equaling to 0.36–0.45 of gnathosoma length. Gnathosoma:Idiosoma ratio equal to 0.19–0.21.

All ventral plates fused ( Fig. 3 D). AE with two pairs of adjunct setae, PE without adjunct setae. Genital area surrounded by 5–6 pairs of pgs. Genital sclerites with two pairs of sgs. GO 70–74 µm long, 33–36 µm wide. The paratype female presents ovipositor everted. There are two pairs of anterior and three pairs of posterior stout and pectinate eugenital setae ( Fig. 3 F).

Leg chaetotaxy, bipectinate setae referred with roman numerals: leg I ( Fig. 3 G), 1,2,6,5,5(II),3; leg II ( Fig. 3 H), 1,2,6,5,5(I),3; leg III ( Fig. 3 L), 1,2,3,3,5(I),4; leg IV, 0,2,3,3,5(II),3. Telofemora I–IV with 4/2, 4/ 2, 3/0, and 3/1 dorsal/ventral setae; length: height ratio of telofemora I–IV in holotype female: 1.57; 1.81; 2.00; 2.0 6. Tarsus I with papiliform famulus, setiform solenidion (6–7 µm long) and pair of doublet eupathidia ( Fig. 3 K). Tarsus II with a setiform solenidion (7–8 µm long) and a pair of doublet eupathidia ( Fig. 3 I). Tarsus III with a single eupathid and a faintly pectinated spine ( Fig. 3 J). Tarsus IV with a single eupathid and a spine similar to that on tarsus III ( Fig.3 M). Lateral claws well-developed, medial one lacking. Dorsal accessory process vestigial.

Male. Idiosoma 354 µm long, 222 µm wide, similar to female in most features. AD 98 µm long, 110 µm wide. OC 126 µm long, 89 µm wide. PD 223 µm long, 136 µm wide. Genital area with 21 branched pgs ( Fig. 3 E). Genital sclerites with two pairs of sgs. Spermatophorotype absent in the individual observed. Tarsus IV ( Fig. 3 N) with a plumose seta and a pectinate spine as parambulacral setae.

Etymology. The specific epithet refers to “Vila de Picinguaba”, a fishermen village near to the type locality.

Remarks. Among Rhombognathus species, a leg chaetotaxy formulae combining Telofemura I–IV with 6,6,3,3 setae, Genua with I–IV 5,5,3,3 setae, and setae and claws with vestigial accessory process are also found in Rhombognathus parvulus Viets, 1939 ( Viets 1939) . This species can be easily separated from R. picinguabensis sp. nov. due the fusion of all dorsal plates in a single dorsal shield.

Figures

FIGURE 3. Rhombognathus picinguabensis sp. nov.: Female: A—Idiosoma, dorsal; B—Gnathosoma, ventral; C—Gnathosoma, medial; D—Idiosoma, ventral; F—Ovipositor; G—Leg I; H—Leg II; I—Tarsus II; J—Tarsus III; K—Tarsus I; L—Leg III; M—Tarsus IV; Male: E—Genital opening; N—Leg IV;. Scale bars: A, D: 100 µm; B, C, E-G, H, L, N: 25 µm; I, J, K, M: 10 µm.