Rhombognathus abirus Pepato & Silveira, 2015, sp. nov
Creators: name: Pepato, Almir R.
name: Silveira, Paulo Sergio Amorim Da
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Halacaridae
Rhombognathus
Rhombognathus abirus

description: Rhombognathus abirus sp. nov
(Figs 1–2)
Holotype. Female (UFMG-AC1200653), on algae associated to Rhizophora mangle pneumatophores at Fazenda River (23°21’55,5”S 44°50’18,6”W), 12 March 2005, water salinity: 6 ‰, coll. Silva, M. L., Tiago, C. G. & Pepato, A. R.
Paratypes. Female (UFMG-AC1200642), collecting data same as holotype; eleven males (UFMG- AC1200643, UFMG-AC1200647, UFMG-AC1200654–9, UFMG-AC1200661–3) 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.; male (UFMG-AC1200660), collecting data same as holotype; Protonymph (UFMG-AC1200664–5) 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.;
Description. Measurements as summarized in Table 1.
Female. Dorsal plates separate, almost smooth, areas of medial AD, anterior OC and regions of PD, corresponding to costulae in other species, pierced by canaliculi. Anterior dorsal plates with ds-1 at 0.53–0.54 of AD length, these setae 41–45 µm long. First pair of gland pores at 0.25–0.28 of AD length. Posterior line of muscle scars at 0.78–0.82 of AD overall length. Pairs of ds-2, glp-2 and glp-3 on OC, which also bears a couple of corneas and a pore canaliculus. Pair of ds-3, usually present on OC, is absent. Length/height ratio of OC 1.65–1.76. Posterior dorsal plate with only pair of ds-4 at 0.24–0.27 of its length, and pair of glp-4 at its posterior margin. Anterior dorsal plate 0.81–0.89 as broad as PD. Short and stout adanal setae dorsal on anal papilla.
Gnathosoma short, length: width ratio equal to 1.30. Rostrum 26–32 µm long, 36 µm wide, equaling 0.22–0.27 times the length of gnathosoma. Podocephalic channel running parallel and superficially on dorsal gnathosoma (Fig. 1 E). Two pairs of rostral setae placed on rostrum. Palpi four-segmented. Second palpal segment with one dorsal seta, third segment without setae, and fourth segment with three setae. Gnathosoma:Idiosoma ratio equal to 0.22–0.25.
Ventral plates AE, PE, and GP fused in a ventral shield, medially fused to the anal plate with lateral wedges of striated cuticle (Fig. 1 D). AE and PE with a single pair and zero adjunct setae, respectively. Genital area with five pairs of pgs. Genital sclerites with two pairs of sgs. GO 90–103 µm long, 46–57 µm wide. Only two pairs of genital acetabula discernible.
Leg chaetotaxy, bipectinate setae referred with roman numerals: leg I, 1,2,5–6,5(I),5(II),3; leg II, 1,2,5,5,5(II),3; leg III (Fig. 1 N), 1,1,2,3,5(I–II),4; leg IV (Fig. 1 M), 0,1,2,3,5(II),3. Telofemora I–IV with 4/1, 4/1, 2/0, and 2/0 dorsal/ventral setae; length: height ratio of telofemora I–IV: 2.46–2.76; 2.35– 2.68; 2.43–2.57; 2.18–2.43. Tarsus I with an arrowhead shaped famulus, setiform solenidion (5–6 µm long) and a pair of doublet eupathidia (Fig. 1 G). Tarsus II with setiform solenidion (6–7 µm long) and a pair of doublet eupathidia (Fig. 1 I). Tarsus III with a single eupathid and a pectinated spine (Fig 1 J). Tarsus IV with slender parambulacral setae and spine similar to that on tarsus III (Fig 1 O). Lateral claws well-developed, medial one lacking. Dorsal accessory process absent or vestigial. Claw shaft smooth.
Male. Similar to female in most features (Dorsal plates in Fig. 1 A, Legs I and II in Figs 1 K and H). AE, PE, and GP fused in a ventral shield, medially fused to the anal plate with lateral wedges of striated cuticle. Genital area with 20–26 branched pgs, ranging from 10–13 on each side of GO, including 1–2 pairs of basilar setae (Fig. 1 C). Genital sclerites with two pairs of stout pgs. Spermatophorotype 98–113 µm long, 111–131 µm wide, surpassing anterior edge of GO by 25–43 µm. Tarsus IV with a plumose setae and a spine as parambulacral setae (Fig. 1 L).
Tritonymph. Dorsal plates smaller than in adults (Fig. 2 G). Ventral plates AE, PE, and GP separated from each other by bands of striated cuticle (Fig. 2 J). AE with three pairs of setae, PE with four setae, both regions lack adjunct setae. On genital plate, three pairs of setae, medial one small and close to primordial genital opening. Leg chaetotaxy, bipectinate setae as Roman numerals: leg I (Fig. 2 H), 1,2,4,5(I),5(II),3; leg II (Fig. 2 K), 1,2,4,4–5,5(I- II),3; leg III (Fig. 2 L), 1,1,2,3,5(I),4; leg IV (Fig. 2 I), 0,0,2,3,5(II),3. Telofemora I–IV with 3/1, 3/1, 2/0, and 2/0 dorsal/ventral setae.
nοtewοrthy that R. validipes Bartsch, 2000, R. mayseri Bartsch, 2009 and R. caribaeus Bartsch, 2007 have their pοsteriοr cοrneae subdivided; Character 22 was split in 22a and 22b tο
accοunt fοr females and males, respectively; *, refers tο measurements taken frοm hοlοtype female, and **, refers tο thοse frοm hοlοtype male. When repοrting variatiοn, the mοst
cοmmοn value is in bοld; In the accοunt fοr R. levigatus Bartsch, 2000 values frοm Abe & Fernandes, 2011 are repοrted in parentheses.
......continued on the next page TABLE 2. (Cοntinued) areolatus Abe & 5,5,5,5 0,0,0,0 2,1,1,2 285‾300? 175‾195 68‾73 60‾65 0.23‾0.24 Abe & Fernandes, 2011
Fernandes, 2011
aribus sp.nov. 5,5,5,5 1,0,0,0 2,2,(1, 2),2 484‾526 461‾498 355‾416 105‾118 131‾151 0.22‾0.25 Τhis study Protonymph. Dorsal plates reduced (Fig. 2 A), ventral plates AE, PE, and GP separated from each other by bands of striated cuticle (Fig. 2 D). Three pairs of setae on AE, two setae on each PE. No setae on genital plate. Leg chaetotaxy, bipectinate setae as Roman numerals: leg I (Fig. 2 B), 1,2,3,4,5(II),3; leg II (Fig. 2 C), 1,2,3,4,5(I),3; leg III (Fig. 2 E), 1,0,2,3,5(I),4; leg IV(Fig. 2 F), 0,2,3,5,2–3. Telofemora I–III with 2/1, 2/1, 2/0, and femur IV with 2/0 dorsal/ventral setae.
Etymology. The word abiru means in Tupi-Guarani large, fat or stuffed by food.
Remarks. Abé (1998) provided a tabular key scoring 26 characters for distinguishing the 84 species known that far. In Table 2 we present an updated version of that key, including the 26 species described after its publication and the two species described herewith. In appendix we provide the character statements from Abé’s (1998) revision. The characters scored, even if they do not discriminate all known species; at least allow assigning them to small species groups. Rhombognathus abirus sp. nov. shares the chaetotaxy of telofemur, genu and tibia, and the lateral claws morphology with R. major Bartsch, 2005 (Bartsch, 2005a). The species may be distinguished due the lacking of adjunct setae on PE, third pair of dorsal setae on OC and ventral setae on basifemura III–IV. Rhombognathu s abirus sp. nov. also differs due the presence of two bipectinate setae on all tibiae II and most of tibiae III.
description: Published as part of 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), pp. 500-510 in Zootaxa 3905 (4) on pages 501-507, DOI: 10.11646/zootaxa.3905.4.4, http://zenodo.org/record/234614