Ropohalacarus pallidus, Bartsch, 2013

Bartsch, I., 2013, Freshwater Halacarid Mites (Acari: Halacaridae) From Madagascar. New Records And The Description Of A New Species, Acarologia 53 (1), pp. 77-87 : 81-84

Ropohalacarus pallidus n. sp.

( Figures 1 and 2 )

Material examined — Holotype female and paratype deutonymph (slide), ZMH ; northern Madagascar, Antisiranana, Andapa, right affluent River Ambendrana downstream, large cascade, 600 m; 11 Nov. 2001; coll. R . Gerecke and T . Goldschmidt. Two paratype females (slide), ZMH ; collection data as above. One paratype female (in ethanol), ZMH ; collection data as above. Paratype deutonymph and protonymph (slide), author’s collection; collection data as above. One female (slide), female and protonymph (in ethanol), ZMH ; south central Madagascar, Fianarantsoa, Ionilahy , small stream crossing the railroad east from village, 200 m; 15 Aug. 2001; coll. R . Gerecke and T . Goldschmidt. One female (slide), author’s collection; collection data as above .

Etymology — Derived from the Latin adjective pallidus , pale, because the specimens lack pigment spots.

Diagnosis (female) — Length of idiosoma 217 – 238 µm. Anterior and posterior dorsal plate fused to a dorsal shield. All ventral plates fused and extending dorsad, anteriorly forming a frontal process. Second pair of dorsal setae and canaliculi in dorsal part of ventral shield. Genital sclerites with three pairs of acetabula. Gnathosoma about as long as wide. Second palpal segment with single seta. Tibiae I to IV with 3, 3, 2, 2 spiniform ventral setae. All tarsi lack ventral setae. Paired claws with delicate apical tines.

Description (female) — Length of idiosoma 217 – 238 µm, length of holotype 238 µm, width 132 µm. Idiosoma about 1.8 times longer than wide; its colour pale, without spots of eye pigment. Interval between insertions of legs II and III equalling almost half the length of idiosoma. Anterior and posterior dorsal plate fused to a shield, 215 µm long, 80 µm wide ( Figure 1a ). Ocular plates reduced, marginal parts incorporated into dorsomarginal parts of ventral shield. All ventral plates fused to a shield, its length 212 µm (from camerostome to end of anal cone). Ventral shield extending dorsad, forming frontal margin of idiosoma with its short, obtuse frontal process. Surface of dorsal shield with delicate porosity and faint foveate ornamentation ( Figure 1a ). Dorsal setae extremely small. First pair of dorsal setae within area equalling anterior dorsal plate, slightly posterior to level of insertion of leg I. Second pair of dorsal setae and canaliculi posterior to insertions of leg II, in dorsomarginal part of ventral shield. Dorsal shield with two pairs of setae, both pairs anterior to level of insertion of leg III. Adanal setae not seen. Area of anterior epimeral plate with three pairs of setae, lateral setae in marginal position. Each area of posterior epimeral plate with a ventral, a lateral but no dorsal seta. Area of genital plate with two pairs of perigenital setae. Genital opening in posterior part of ventral shield ( Figure 1b ). Length of genital opening 60 µm, width 36 µm. Each genital sclerite with three external acetabula arranged within a line. Acetabula 3 – 4 µm in diameter. Anal sclerites small.

Gnathosoma short, wider than long, its length 37 µm, width 40 µm. Rostrum wider than long, triangular in ventral aspect ( Figure 1d ). Tectum truncate. Palps extending beyond rostrum. Second palpal segment with single seta in apical half. Third palpal segment with spur in medial position ( Figure 1c ). Ventral seta of fourth palpal segment wider than dorsal seta.

All legs distinctly shorter than idiosoma. Legs III and IV slightly longer and more slender than legs I and II. Telofemora I and II about 1.5 times longer than high, telofemora III and IV 1.6 times. Leg chaetotaxy from trochanter to tarsus (parambulacral setae excluded): legs I and II, 0, 2, 3, 3, 7, 4; leg III, 1, 1, 2, 2, 5, 3; leg IV, 0, 0, 2, 3, 5, 2 ( Figure 2 a-d). Ventral spine on genu I slightly longer than length of that segment. Tibiae I to IV with 3, 3, 2, 2 ventral spines and 2, 2, 1, 1 short dorsal spurs. Tarsi I and II each with three fossary setae, a dorsolateral clavate solenidion but no ventral setae. Tarsus I with delicate porus that may be remnant of a famulus ( Figure 1e ). On tarsi I and II paired fossary setae unequal in length, dorsolateral seta somewhat thicker and longer than dorsomedial seta ( Figure 1f ). Tarsus III with three dorsal setae, one of setae in dorsolateral position and equalling a solenidion ( Figure 1g ). Tarsus IV with two dorsal setae, both equal in size. On tarsi III and IV dorsal fossary seta lacking. Paired claws with a slightly widened apical process, each process with four delicate tines. No tines on shaft of claw. Median claw slender, hook-like.

Deutonymph — Length of idiosoma 212 – 226 µm. Ornamentation of dorsal and ventral plates more intense than in female ( Figure 2e ). Anterior and posterior dorsal plate separated by few striae of soft integument. Ocular plates and dorsal part of posterior epimeral plates fused. First pair of dorsal setae on anterior dorsal plate, second pair of setae on dorsal part of anterior epimeral plate and medial to insertion of leg II, two pairs of setae on posterior dorsal plate. With striated (soft) integument between anterior epimeral plate and genital plate ( Figure 2f ). Anterior epimeral plate with three pairs of ventral setae, posterior epimeral plates with pair of lateral setae. Genital plate with single pair of perigenital setae and two pairs of acetabula. Acetabula 4 µm in diameter. Leg chaetotaxy from trochanter to tarsus (parambulacral setae excluded): legs I and II, 0, 2, 3, 3, 6, 4; leg III, 1, 1, 2, 2, 5, 3; leg IV, 0, 0, 2, 3, 5, 2. Tibiae I to IV with 2, 2, 2, 2 ventral spines and 2, 2, 1, 1 dorsal spurs. Tarsi I to IV with 4, 4, 3, 2 dorsal setae and 0, 0, 0, 0 ventral setae.

Protonymph — Length of idiosoma 155 µm. Dorsal aspect similar to that of deutonymph. Number and arrangement of dorsal idiosomatic setae and setae on anterior and posterior epimeral plates same as in deutonymph. Genital plate and posterior epimeral plates partly fused. Genital plate with single pair of acetabula ( Figure 2g ); perigenital setae lacking. Leg chaetotaxy from trochanter to tarsus (parambulacral setae excluded): legs I and II, 0, 2, 3, 3, 5, 4; leg III, 1, 1, 2, 2, 5, 3; leg IV, 0, 0+2 (basi- + telofemur), 3, 5, 2. Tibiae I to IV with 2, 2, 2, 2 ventral spines and 1, 1, 1, 1 dorsal spurs. Dorsal fossary seta absent on tarsus III and IV.

Variants — Tarsus II of one of the paratype females without dorsal fossary seta ( Figure 1h ) .

Remarks — Ropohalacarus pallidus is the second species of this genus. Characters which separate R. pallidus from R. uniscutatus are: (1) dorsal plates delicately foveate versus reticulate, (2) anterior margin equivalent to dorsal portion of anterior epimeral plate versus to anterior part of dorsal shield, (3) second pair of dorsal setae within dorsal portion of anterior epimeral plate versus in striated integument, (4) second palpal segment with single seta versus two setae, (5) genu I with three versus four setae, (6) tarsi I and II without versus with a ventral seta.

Figures

FIGURE 1: Ropohalacarus pallidus n. sp., female: a – idiosoma, dorsal; b – idiosoma, ventral; c – gnathosoma, lateral; d – gnathosoma, ventral (with outline of dorsal tectum); e – tarsus I, lateral (medial claw, fossary and parambulacral seta in broken line); f – tarsus II, dorsal; g – tarsus III, lateral (medial claw, fossary and parambulacral seta in broken line); h – tarsus II, lateral (medial fossary seta in broken line, medial claw and parambulacral seta omitted). (Scale bar = 50 µm) (ca, canaliculus; dfs, dorsal fossary seta; dlfs, dorsolateral fossary seta; dmfs, dorsomedial fossary seta; ds-2, second dorsal idiosomatic seta; so, solenidion; T, tectum)

FIGURE 2: Ropohalacarus pallidus n. sp.: a – leg I, ventromedial, female; b – leg II, ventromedial, female; c – leg III, ventromedial, female; d – leg IV, ventromedial, female; e – idiosoma, dorsal, deutonymph; f – idiosoma, ventral, deutonymph; g – posterior part of idiosoma, ventral, protonymph. (Scale bar = 50 µm) (pgs, perigenital seta)