Halacaroides antoniazziae, Pepato, Almir R., Tiago, Cláudio G. & Rocha, Carlos E. F., 2011

Pepato, Almir R., Tiago, Cláudio G. & Rocha, Carlos E. F., 2011, Psammophilous halacarid mites (Trombidiformes, Halacaridae) from the North Coast of São Paulo State, Brazil, Zootaxa 2823, pp. 47-60 : 55-57

Halacaroides antoniazziae sp. nov.

( Figs. 6 , 7 )

Material examined. Male holotype (MZSP-AC81), Pitangueiras Beach, 1 August 2004, coll. A. R. Pepato. Paratypes: 1female (MZSP-AC78), 1 male (MZSP-AC79), and 2 males and 1 female (Pepato’s collection), same site, date and collector.

Description. Female. Idiosoma spindle-shaped, length 255–275, width 108–133. Dorsal plates without conspicuous ornamentation, except piercing of inner layers by pore canaliculi. AD 61–68 long, 48–52 wide, with ds-1 at 0.32–0.34 of its length.

Second to fifth pairs of dorsal setae on striated cuticle. OC 19–25 long, 9–12 wide, with anterior muscle scar. Two small sclerites: anterior, midway between ds-2 and ds-3: posterior, before insertion of leg IV. PD 38–48 long, 25–30 wide. One pair of adanal setae dorsally on anal papilla. AE 41–48 long, 78–86 wide, undivided, with 3 pairs of setae. Two pairs of small sclerites on ventral side of idiosoma. GA weakly sclerotized, 60–65 long, 51–55 wide, with 3 pairs of perigenital setae. GO 28–33 long, 30–35 wide. Genital sclerites without subgenital setae. Ovipositor ending 35–44 from anterior margin of GA. Three pairs of genital acetabula underneath genital sclerites.

Gnathosoma slender, 163–173 long, 38–43 wide. Rostrum 0.52–0.55 of gnathosoma length. Palps 4-segmented. P2 with 1 seta placed distally. P3 with small spur. P4 with 3 basal setae and 2 distal spurs.

Chaetotaxy of legs as follows, spiniform setae indicated by roman numerals: leg I, 1,2,2,5,10,6; leg II, 1,3,3,4,6(II),4; leg III, 1,2,2,4(I),6(II),3; leg IV, 1,0,3,4(I),6(II),3. Tarsus I with 3/3 dorsal/ventral setae and pair of doublet eupathidia. Tarsus II with 3/1 dorsal/ventral setae; pair of doublet eupathidia unequal in length. Tarsus I with wide fossa membrane, other tarsi without well-developed fossa membranes. Claws of tarsi I-IV with dorsal accessory process each; claws of tarsi III-IV also with ventral pecten each.

Male. Idiosoma 255–265 long. Similar to female in most features, except for genital area. GA 65–70 long, 53– 60 wide, with 41–44 perigenital setae. GO 24–26 long, 9–11 wide, apart from anterior margin of GA by 36–38. Three pairs of subgenital setae on genital sclerites grouped 1:2. Two pairs of genital acetabula exterior, anterior pair internal to genital sclerites. Spermatophorotype extending 24-26 beyond anterior margin of GA.

Etymology. The name is dedicated to Dr. Marta Antoniazzi, for her kind help throughout the A.R.Pepato’s doctoral thesis.

Remarks. The genus Halacaroides was proposed by Bartsch (1981) on basis of two species, H. angustus Bartsch, 1981 and H. brevocularis Bartsch, 1981 , collected in the Magellan Strait, Chile. To these species, H. australiensis Bartsch, 2008 was recently added by Bartsch (2008). Halacaroides species share a spindle-shaped body, delicate idiosomal plates, inconspicuous gland pores, longitudinally spliced PE, long gnathosoma, slender and parallel-sided rostrum, both trito- and basi-rostral setae on rostrum. Palpal chaetotaxy as follows: P2 with distal seta, P3 with spur, P4 with three basal setae. Leg I is longer than leg II, and genua are shorter than tibiae and telofemora; tarsus I with three ventral setae, solenidion and famulus adjacent to lateral claw membrane; tarsus II with a single ventral seta and dorsomedial solenidion; tarsi III and IV without ventral setae.

Halacaroides antoniazziae sp. nov. differs from H. angustus and H. brevocularis by the presence of three sgs in males and none in females instead of five and two in the latter two species, respectively. Also, regarding the genital area, males have all genital acetabula beneath the genital sclerites in H. angustus and H. breviocularis , whereas the posterior two pairs of genital acetabula are external in H. antoniazziae sp. nov. Halacaroides australiensis differs from the new species described here by the presence of seven dorsal setae on the idiosoma, AE longitudinally divided, presence of a single pair of sgs on female genital sclerites and a single external acetabula in males. Besides, the new species differs from other congeners by having almost double number of pgs in male.

It is interesting to point out that H. antoniazziae sp. nov. was obtained only in a narrow section of Pitangueira Beach influenced by a small freshwater stream. Similar environmental setting was also observed for the type locality of H. australiensis . Since the function of genital acetabula is related to osmorregulation, this is remarkable that both species share external genital acetabula in males, a condition probably related to the hypertrophy of these structures. Other examples of such sexual dimorphism may be found among Acarothrix species ( Bartsch 2004c) and genera Rheolimnesia and Siboneyacarus , members of the cohort Hydrachnidia ( Panesar 2004).

Figures

FIGURE 6. Halacaroides antoniazziae sp. nov.: A, idiosoma of female in dorsal view; B, genitoanal area of male; C, idiosoma of female in ventral view; D, gnathosoma of female in ventral view; E, posterior epimeral plate of male. Scale bars: A, C = 50; B, D-E = 25 μm.

FIGURE 7. Halacaroides antoniazziae sp. nov., female: A, leg IV, lateral view; B, leg II, lateral view; C, leg III, lateral view; D, leg I, lateral view; E, tarsus I, lateral view. Scale bars: A – D = 50 μm; E = 25 μm.