Hydrachna skorikowi Piersig, 1900

Hajizadeh, Jalil & Hosseini, Reza, 2019, First record of larva of the water mite Hydrachna skorikowi Piersig (Acari, Hydrachnidia, Hydrachnidae) from Iran, Persian Journal of Acarology 8 (4), pp. 333-342 : 334-339

Hydrachna skorikowi Piersig, 1900

Hydrachna schneideri skorikowi Piersig, 1900: 483 .

Hydrachna skorikowi integra Viets, 1930: 224 .

Hydrachna skorikowi Davids et al., 2005: 50 .

LARVA

Diagnosis

Hypostomal sucker discoid; palpal tibiotarsus with five different sized spines; first coxal plate wider then long; third coxal plate with short fusiform setae; palpal tibiotarsus with two subequal setae.

Redescription

Dorsum ( Figs. 2B , 3 ) (n = 5) – The total body length 372 (360–380), the width 154 (143–170). Dorsal shield is very large, covered whole idiosoma, with the integument pointed. The dorsal shield length 228 (220–238), the width 154 (143–170). The anterior margin is straight with rounded corners. There are two pairs of eyes in the frontal part of the dorsal shield. Dorsal shield with 7 pairs of setae. The first two predorsal pairs of bristles are situated obliquely behind each other on the foremost part of the dorsal plate, those of the third pair lateral of the second pair of eyes and those of the fourth pair are in line with the three pairs of postdorsal setae along the lateral margins of the dorsal plate.

Venter ( Figs. 2A , 4 ) – There are three pairs of coxal plates, length of them from median line is: E1, 35 (25–40); E2, 32 (28–37); E3, 72 (65–77); the maximum widths are 48 (45–50), 58 (53–62) and 56 (52–60) respectively. Coxal plate 1 with two setae, length Eb1 50 (40–62) and Eb2 48 (40– 50; coxal plate 2 without setae and coxal plate 3 with one specific cone shape seta that inserted before the middle of plate, length 18 (15–20), this peculiar shape seta unknown in other species of this genus. The third pair of coxal plate is surrounded, for the greater part, by a distinct suture. Between the diverging third coxal plates is a diamond-shaped sclerite, containing the anal pore. The skin between the gnathosoma and the first coxal plates contains a number of transverse striae.

Gnathosoma ( Fig. 5 ) – The gnathosoma with 143 (135–155) long in middle line and 100 (95– 103) wide in posterior margin, gnathosoma with approximately 1/3 of the total body length. Hypostomal sucker discoid, skin space between gnathosoma and first coxal plates with striation.

Chelicerae ( Fig. 6A ) – Chelicera consisting of the basal segment and a blade-like fix digit with 3 small teeth near the tips. Length of chelicerae 48 (45–52).

Pedipalps ( Fig. 6B ) – Palp with 79 (73–80); lateral length and 73 (68–77); medial length. Length of pedipalpal segments: femur 35 (33–38); genu 17 (13–20); tibiotarsus 28 (25–30). Tibiotarsus with five unequal claws, one longer 22 (18–25) and four shorter and bent 15.

Legs ( Fig. 7 ) – The legs bear bristles and swimming hairs and terminate in a sickle-shaped claw. Legs with five segments (excluding coxal plates). Length of the legs: I, 170 (168–175); II, 167 (159– 180); III, 169 (160–180). The length of leg segments, trochanter, femur, genu, tibia and tarsus for legs I-III respectively: I, 24, 32, 26, 31, 57; II, 25, 29, 25, 33, 56; III, 25, 28, 23, 35, 59.

Material examined

Twelve larvae of Hydrachna skorikowi were separated from legs of two water boatmen species Corixa punctata (Illiger, 1807) and Sigara sp. (Corixidae) ( Fig. 8 ) that collected from light traps installed in campus of University of Guilan (37° 11' 37.02" N, 49° 38' 27.49" E, altitude 29 m a.s.l.) in Rasht, Guilan Province, Iran; July 25, 2004; May 14, 2019; May 17, 2019; coll. Jalil Hajizadeh and Reza Hosseini.

current study.

Remarks

Description of the Hydrachna skorikowi specimens from the Netherlands (Davis 1972) indicates similarities and some difference between material examined in the current study and Davis' measurements ( Table 1). Based on our three years' collection information from light traps in Guilan province, Iran, infection of water boatmen ( Corixidae ) specimens by larvae of H. skorikowi is started in May. In middle of May and July maximum infection is observed. The infection of bugs continues to September. Unfortunately, we did not continue sampling in the fall season, because for seasonal rainfall in Guilan province. Maximum intensity projection in parasitizing larvae were 720 (600–870) μm ( Fig. 3B ). The larvae of H. skorikowi were found on the legs I-III infected water boatmen ( Fig. 8 ).

Figures

Figure 2. Larva of Hydrachna skorikowi – A. Ventral view of body; B. Dorsal view of body. Scale bar: 100 μm.

Figure 3. Larva of Hydrachna skorikowi (mounted specimens) – A. Dorsal habitus of newly emerged larva; B. Dorsal habitus of parasitizing larvae. Scale bars: 100 μm.

Figure 4. Larva of Hydrachna skorikowi (mounted specimens) – A. Ventral view of body; B. Ventral view of coxal plates. Scale bar: 100 μm for A, 40 μm for B.

Figure 5. Larva of Hydrachna skorikowi (mounted specimens) – A. Ventral view of gnathosoma; B. Dorsal view of gnathosoma. Scale bar: 50 μm for A, 40 μm for B.

Figure 6. Larva of Hydrachna skorikowi (mounted specimens) – A. Chelicerae; B. Pedipalp. Scale bar: 15 μm for A, 13 for B.

Figure 7. Larva of Hydrachna skorikowi (mounted specimens) – A. Legs I-III; B. Legs II-III. Scale bar: 50 μm for A and B.

Figure 8. Corixa punctata and Sigara sp. infected with larvae of Hydrachna skorikowi – A & B. Infected fore legs of Corixa punctata; C & D. Infected middle leg of Sigara sp.