Agauopsis dissimilis, Bartsch, 2015

Bartsch, I., 2015, The Agauopsis brevipalpus group (Acari: Halacaridae), descriptions of tropical Indo-West Pacific species, a key to all species, their geographical distribution and reflections on dispersal routes, Acarologia 55 (2), pp. 147-169 : 151-155

Agauopsis dissimilis n.sp. Figures 2 A-J, 3A-I

Material examined — Holotype female (ZRC.ARA.1381), Singapore, Pulau Ubin , Chek Jawa , 1°24’N, 103°59’E, green algae (Cladophorales) on trunk of Rhizophora sp. , 16 Oct. 2012. One male (ZRC.ARA.1382), one female (IB), Singapore, East Coast Park, 1°18’N, 103°55’E, green algae on stone packing, 06 Oct. 2004.

Diagnosis — Length of female 414 and 445 µm, of male 420 µm. AD with H-like costae; PD with two pairs of costae. Costae reticulated. Female PD almost as long as wide, male PD slightly longer than wide. Female and male PD about 1.3 times longer than AD. Anterior margin of female and male GA truncate. Male GA with 63 pgs; spermatopositor extending to anterior margin of GA. Length of gnathosoma about twice its width and 0.4 times the length of idiosoma. Length of rostrum almost same as that of gnathosomal base. Tectum with scaliform lamella. P-2 3.2-3.3 times longer than high. P-4 short, with single seta. Telofemur to tarsus I with 4, 2, 3, 1 blunt, denticulate spines. Tibia II with flattened, bipectinate ventromedial and spiniform, dentate ventral setae; tibiae III and IV with pair of slender, tapering setae. Claws II to IV with numerous delicate tines along medial flank.

Etymology — In its general shape this species is similar to other species of the brevipalpus group but differs in the character combination, hence the name derived from the Latin dissimilis , unlike, different.

Description — Females. Length 414 and 445 µm; holotype 414 µm long, 300 µm wide. Dorsal plates with costae, H-shaped on AD, oblique on OC and longitudinal on PD ( Figure 2B ). Costae with deep canaliculi, 6-10 arranged in polygons. Remainder of plates panelled, each polygon with about four to six delicate canaliculi ( Figure 2A ). AD slightly wider than long, length 148 µm, width 151 µm; transverse bar of H-shaped costa closer to anterior than to posterior margin of AD. Pair of gland pores level with anterior end of costae. OC 95 µm long, 78 µm wide, length 0.6 times that of AD. OC with two corneae, glp and pc; glp at 0.4; distance between posterior cornea, glp and pc almost the same ( Figure 2E ). PD 198 µm long, 196 µm wide, with widely arched anterior margin. PD with two pairs of costae; medial costae about three polygons wide, lateral costae two to three polygons. Pair of ds-1 on AD medial to gland pores (left seta vestigial in holotype), ds-2 to ds-4 on minute sclerites within striated integument, ds-5 on PD, within lateral margin of medial porose costae and at 0.4 relative to length of PD. Pair of ds- 6 in posterior margin of PD.

Ventral plates reticulated, with 9-11 peripherically arranged canaliculi within each polygon. AE 162 µm long, 285 µm wide, with three pairs of setae and pair of epimeral pores. Bases of trochanters I and II flanked by lamelliform epimeral processes. PE 162 µm long, not markedly extending beyond aperture of leg IV, with one dorsal seta and three ventral setae. GA 140 µm long, 147 µm wide, shorter than AE; anterior margin almost truncate. GO 85 µm long, 55 µm wide. Three pairs of pgs as illustrated ( Figure 2C ).

Length of gnathosoma 166 µm, width 82 µm, i.e. 2.0 times longer than wide. Rostrum and gnathosomal base almost equal in length ( Figure 2D ). Major parts of dorsal, lateral and ventral flank of gnathosomal base with porose areolae, i.e. integument pierced by canaliculi. Canaliculi minute or absent within pharyngeal field and pair of circular areolae on either side of pharyngeal field. One pair of maxillary setae on gnathosomal base, one pair in posterior fourth of rostrum. Tip of rostrum with two pairs of short, slender rostral setae. Tectum scaliform ( Figure 2F ). P-2 3.2 times longer than high ( Figure 2G ). P-3 slightly longer than high, its delicately dentate spine longer than this segment. P-4 1.5 times longer than P-3; with a single long seta.

Lateral flank of telofemur I reticulate. Integument of this and other segments and legs almost evenly pierced by numerous canaliculi; canaliculi also present on lateral flanks of trochanters III and IV. Medial flanks with few, less conspicuous canaliculi. Telofemora III and IV 2.4-2.6 times longer than high. Leg chaetotaxy (solenidia, famulus and parambulacral setae excluded; on leg I setae in Arabic, spines in Roman numerals; leg IV on one side deformed, this leg not included in chaetotaxy formula): leg I, 1, 2, 4+IV, 3+II, 6+III, 5+I; leg II, 1, 2, 6, 5, 6, 3; leg III, 1, 2, 3, 3, 5, 3; leg IV, 0, 2, 3, 3- 4, 5, 3. Ventral seta on telofemur III and IV near apical third of segment ( Figure 3B and C ). On genu I ventral spine shorter than ventromedial one ( Figure 3A ). Tibia II with two ventral spiniform setae, ventromedial one flattened, bipectinate, ventral seta dentate (cf. Figure 3E ). Tibiae III and IV each with a pair of smooth, tapering setae; setae longer than height of tibia. Tarsus I with pair of doubled pas, a solenidion, 2 µm long, and a famulus, the latter represented by an afferent canal within membrane of lateral fossa membrane ( Figure 3F ). Tarsus II medially with spiniform pas, laterally with one long and adjacent one short setiform pas (cf. Figures 3G and H ); small medial fossa membrane with 3-µm long solenidion on inner flank (cf. Figure 3I ). Medial fossary seta slightly more slender than lateral seta. Tarsi III and IV each with spiniform lateral pas; medial pas lacking. No fossa membranes on these tarsi. Claws I shorter than following claws, median claw bidentate. Claws II to IV with accessory process and pectines. Tines of pectines almost 2 µm long. Median claw of tarsi II to IV without dent-like process.

Male. Length 420 µm. Dorsal aspect similar to that of female but PD more slender, its anterior margin somewhat ovate ( Figure 2H ) and ds-1 slightly anterior to the level of gland pores. GA 1.1 times longer than AE; its anterior margin widely arched ( Figure 2I ). Distance between anterior margin of GO and that of GA almost equalling length of GO. Perigenital setae slender, 61 arranged in two rings around GO, a pair of setae outlying. Each genital sclerite with four to five short, spur-like sgs ( Figure 2J ). Spermatopositor 112 µm long, with three pairs of almost similar-sized lateral projections. Spermatopositor extending to anterior margin of GA.

Anomaly — Leg IV of the holotype is abnormal ( Figure 3D ), three tarsi arise from the tibia and the number and shape of setae differ from that generally found on this leg.

Remarks — The character slender, tapering ventral setae on tibiae III and IV is shared with A. arborea , a short P-4 with a single seta with A. obtusa Bartsch, 2005 . In contrast to A. arborea and A. obtusa , the rostrum of A. dissimilis is about as long as the gnathosomal base, that of A. arborea and A. obtusa is shorter, 0.8 times and 0.9 times, respectively. Agauopsis arborea bears two setae on P-4 and A. obtusa has spiniform and dentate setae on tibiae III and IV.

Distribution and Biology — Singapore. The three individuals have been extracted from green algae growing in the upper and middle tidal area on a trunk and on stone packing.

Figures

FIGURE 2: Agauopsis dissimilis n.sp.: A – median part of PD level with ds-5, female; B – idiosoma, dorsal, female; C – idiosoma, ventral, female; D – gnathosoma, ventral, female; E – lateral margin of OC, female; F – gnathosomal base, dorsal, female; G – palp, lateral, female; H – AD, OC and PD, dorsal, male; I – idiosoma, ventral, male; J – genitoanal plate, male. (ds-5, fifth dorsal seta; glp, gland pore; L-Ba, length of gnathosomal base; L-Ro, length of rostrum; pa, porose areola; pc, pore canaliculus) Scale line = 50 µm

FIGURE 3: Agauopsis dissimilis n.sp.: A – leg I, medial, female; B – leg III, medial, female; C – leg IV, medial, female; D – malformed leg IV, medial, female; E – basifemur to tarsus II, medial, male; F – tip of tarsus I, lateral, female (medial setae and claw omitted); G – apical tibia and tarsus II, medial, male; H – tip of tarsus II, lateral, male (medial fossary seta and claw omitted); I – tip of tarsus II, medial, male (lateral fossary seta and claw omitted). (fa, membrane with famulus; so, solenidion) Scale line = 50 µm