Acarothrix ampliumeris, Bartsch, 2006

Bartsch, Ilse, 2006, Copidognathines (Acari: Halacaridae) In Mangroves Of Singapore. I. Description Of Three Species, Raffles Bulletin of Zoology 54 (1), pp. 83-92 : 84-87

Acarothrix ampliumeris , new species

( Figs. 1-16 )

Material examined. – Holotype: Female, ZRC.ARA.480, Singapore, northern coast, end of Lim Chu Kang Road, mangrove, Cladophora mat (Chlorophyta) on muddy and sandy sediment, coll. I. Bartsch, 7 Oct.2004.

Paratypes: One male, ZRC.ARA.481, collecting data as above; one larva, ZRC.ARA.482, collecting data as above; one male, SMF, collecting data as above; one female, ZMH, collecting data as above; one male, ZMH, collecting data as above .

Diagnosis. – Length of idiosoma 294-325 µm. OC elongate; corneae lacking. PE more than half length of idiosoma. Pair of ds- 2 in striated integument. Gland pores between ds-4 and ds-5 small, almost inconspicuous. AE very wide. Male with 20-22 pgs. All tibiae with one bipectinate ventromedial and one long, smooth ventral seta; bipectinate seta on tibia II much longer than height of that segment; bipectinate seta of tibia III and IV wide. Claws with delicate accessory process but no pecten.

Etymology. – The anterior portion is unusual wide, hence the specific name ampliumeris , broad shouldered, derived from amplus (Latin), wide, broad and umerus (Latin), shoulder.

Colour. – Idiosoma pale or light brown. Eye spots small, black.

Description. – Female: Idiosoma short and wide, slightly flattened; with large interval between insertions of legs II and III. Length of idiosoma 294-309 µm, length of holotype 294 µm, width 175 µm. Median portions of AD and PD delicately reticulate. Length of AD 87 µm, width 78 µm; anterior margin arched, posterior margin triangular; pair of gland pores on minute cones at the level of insertion of leg I. OC elongate, but hardly reaching the level of insertion of leg III ( Fig. 1 ), length 104 µm, width 48 µm. With dark eye pigment beneath anterior portion of plate but no distinctly delimited corneae; gland pore and adjacent pore canaliculus in anterolateral margin of OC. Length of PD 172 µm, width 102 µm; anterior margin rounded; pair of delicate pores somewhat anterior to greatest width of PD, pair of gland pores on protuberances in posterior margin of PD. Pair of ds-1 on AD; ds-2 within striated integument between AD and OC (in holotype left ds-2 not seen); ds- 3 in middle of OC (at 0.5 relative to length of OC); ds-4 and ds-5 on PD near lateral margin. Adanal setae in ventral position, adjacent to anal sclerites.

Integument of ventral plates almost smooth. AE wide and long, extending far beyond insertion of leg II, its length 100 µm, width 175 µm; posterior margin very wide, truncate; three pairs of ventral setae only about as long as dorsal idiosomatic setae; pair of epimeral pores lateral to apodemes between epimera I and II ( Fig. 2 ); diameter of pores 6 µm, pores covered with numerous villi ( Fig. 3 ). Length of PE 182 µm, extending anteriad far beyond insertion of leg III, posteriad only slightly beyond insertion of leg IV; each plate with one dorsal seta and three ventral setae. Length of GA 122 µm, width 87 µm; with three pairs of pgs. GO large, length 72 µm, width 35 µm, its distance to anterior margin of GA equalling 0.34 of length of GO. Genital sclerites with one pair of sgs. Ovipositor extending slightly beyond GO.

Length of gnathosoma 92 µm, width 65 µm; pharyngeal field panelled, remainder of gnathosoma with almost smooth integument. Rostrum in ventral aspect triangular, almost as long as gnathosomal base ( Fig. 4 ); extending almost to about the level of seta on P-2. Tectum truncate. One pair of maxillary setae on gnathosomal base, the other pair in distal half of rostrum; two pairs of rostral setae at tip of rostrum. P-4 with three basal setae removed from basis by about length of P-3.

Legs I and II ( Figs. 5 and 6 ) almost equal-sized and shorter than legs III and IV ( Figs. 7 and 8 ). Telofemora with delicate villi, though in general integument of legs almost smooth. Tarsi without fossa membranes. Leg chaetotaxy (solenidia included, pas excluded): leg I, 1, 2, 5, 4, 6, 6; leg II, 1, 3, 5, 4, 6, 4; leg III, 1, 2, 3, 3, 5, 4; leg IV, 1, 2, 2-3, 3, 5, 3. Telofemur IV with the combinations 2/1 and 2/0 dorsal/ ventral setae. Ventral seta of genu I very long, slightly longer than that seta on genu II as well as ventral seta of tibia I. Ventral setae of genua III and IV slender and short. Tibia I with long ventral and bipectinate ventromedial seta. On tibia II that bipectinate ventromedial seta conspicuously long, length about twice height of segment, ventral seta long, smooth. Bipectinate seta of tibia III and IV very wide and almost as long as height of segment. Dorsolateral and dorsomedial fossary setae of tarsus I almost equal-sized ( Fig. 9 ); solenidion, length 10 µm, immediately adjacent to dorsolateral fossary seta ( Fig. 10 ); famulus represented by minute cap, length 1 µm. Tarsus I with one long ventral seta in basal third and one small eupathid seta near its tip. Basidorsal fossary seta of tarsus II wider than that of tarsus I, dorsomedial fossary seta very slender ( Fig. 11 ), dorsolateral fossary seta close to tip of tarsus, adjacent to solenidion. Tarsus III with four dorsal setae; pair of apical fossary setae slender. Basidorsal fossary seta of tarsus IV wider than corresponding seta of tarsus III; shape of apical fossary setae similar to setae on tarsi III. Tarsi I and II each with pair of doubled pas, tarsus III with eupathid medial and widened but tapering lateral pas, tarsus IV with pair of bristle-like pas.

Claws with very delicate accessory process; pecten lacking. All tarsi with small median claw, that of tarsus I bidentate, on the other tarsi upper tooth almost reduced.

Male: Length of idiosoma 314-325 µm. Dorsal aspect same as that of female. GA with rounded anterior corners; plate somewhat longer than but far from as wide as AE. GO in middle of GA, distance both to anterior margin of GA and end of genital sclerites slightly less than length of GO. Spermatopositor extending beyond GA, its length 95 µm, width 72 µm. GA with 10-11 pairs of pgs ( Fig. 13 ). Genital sclerites with four pairs of sgs; three pairs of sgs setiform, one pair spur-like. A pair of foveae (external genital acetabula) immediately posterior to sgs ( Figs. 12 and 13 ), foveae ca 4 µm in diameter and obscured by villi.

Protonymph: Not seen.

Larva: Length of idiosoma 177 µm. OC and PD distinctly shorter than in adults. Pair of ds-3 on OC, ds-4 and ds- 5 in margin of PD ( Fig. 14 ). AE wide; apodemes between epimera I and II extending backward beyond pair of epimeral pores ( Fig. 15 ); plate with two pairs of ventral setae. PE short, with single pair of setae. Shape of gnathosoma similar to that of adults. With three pairs of five-segmented legs, basi- and telofemora fused. Leg chaetotaxy: leg I, 1, 1+3 (basi- plus telofemur), 4, 5, 6; leg II, 1, 1+3, 4, 5, 4; leg III, 1, 1+2, 3, 5, 4. Bipectinate seta of tibia II rather slender, much longer than that seta on tibia I. Both ventral setae on tibia III rather slender, none distinctly bipectinate ( Fig. 16 ). Distance between two basal setae of tarsus III equalling height of tarsus.

Remarks. – Four species are at present known, all recorded

from tropical and warm-temperate shallow water habitats, from muddy areas periodically influenced by fresh water. Acarothrix ampliata Bartsch, 2004 , was collected amongst the vegetation of a small river emptying into Tampa Bay, Florida, USA, A. longiunguis Bartsch, 1997 , in soft mud in a northern Australian mangrove area, A. palustris Bartsch, 1990 , amongst surface sediment and its cover by green and red algae ( Cladophora , Caloglossa ) in Hong Kong, China, and A. umgenica in Avicennia mangroves in KwaZulu-Natal, South Africa ( Bartsch, 1990, 1997a, 2004; Proches, 2002).

Distinguishing characters between A. ampliumeris and the others are: the position of ds-2 (in A. ampliumeris within the striated integument anterior to the OC - in the other species in the margin or on the OC), the shape of the OC (in A. ampliumeris elongate, its posterior portion wide - in the other species either shorter or more slender), the gland pores on the PD (in A. ampliumeris one distinct pair on cones near posterior margin - in the other species two distinct pairs of pores, one pair between the ds-4 and ds-5, the other pair near the posterior margin), and the shape of the pectinate seta of tibia II (in A. ampliumeris long - in the other species short and wide).

Distribution. – Singapore, from algal mats in mangrove areas.

Figures

Figs. 1-8. Acarothrix ampliumeris, new species, female: 1. idiosoma, dorsal; 2, idiosoma, ventral; 3, left part of AE; 4, gnathosoma, ventral; 5, leg I, medial; 6, basifemur to tarsus II, medial; 7, leg III, medial; 8, leg IV, medial. Scale line = 50 µm.

Figs. 9-16. Acarothrix ampliumeris, new species: 9, tarsus I, lateral, female (medial fossary seta and claw in broken line, medial parambulacral setae omitted); 10, tip of tarsus I, lateral, female; 11, tarsus II, lateral, female; 12, genital opening, male; 13, genitoanal plate, male; 14, idiosoma, dorsal, larva; 15, idiosoma, ventral, larva; 16, tibia and tarsus III, medial, larva (lateral setae and claw in broken line). Scale line = 50 µm.