Hydryphantes clypeatus (Thor, 1899)

Tuzovskij, Petr V., 2014, Larval morphology of Hydryphantes clypeatus Thor, 1899, H. dispar Schaub, 1888 and H. planus Thon, 1899 (Acari, Hydrachnidia: Hydryphantidae), Zootaxa 3869 (2), pp. 131-142 : 132-135

Hydryphantes clypeatus (Thor, 1899)

( Figs 1–16 )

Material examined. Larvae (n = 26) were reared from four females collected in a sedge bog near village Postyltsevo, Nekouz District, Yaroslavl Province: two females 25 May 2000, one female 1 June 2002 and one female 10 June 2004. The duration of the embryonic period was 12–15 days.

Diagnosis. Larva. Distance between bases of trichobothria Oi larger than their length; all dorsal hysterosomal setae subequal; excretory pore plate wider than long; urstigma wider than long; posterior margin of coxal plate II convex; P-5 with long solenidion; I–II-Leg-4 solenidia 2.0–2.5 times longer than eupathidia; I–II-Leg-5 with unequal solenidia; I-Leg-6 de shorter than ds.

Description. Colour red. Anterior pair of platelets small, more or less triangular, posterior plate relatively large, anteriorly narrow, posteriorly widening; median eye weakly developed and situated between setae Vi ( Fig. 1 ). Both pairs of trichobothria thin, Fp very long, Oi short. Distance between bases of trichobothria Oi larger than their length. Simple proterosomal setae (Fch and Vi) thick, but Fch slightly shorter than Vi. Other dorsal setae (Oe, Hi, He, Sci, Sce, Li and Le) thick and approximately equal in length. lateral eyes with anterior lenses large and circular, posterior lenses elongate.

Coxal plates II triangular, coxal plates I and III more or less trapezoidal and rounded medially ( Fig. 2 ); all coxal setae relatively short and subequal. Urstigma rather large, wider than long. Setae Si slightly longer than other ventral idiosomal setae. Setae Se, Ci, Pi and Pe subequal and slightly longer and thicker than both pairs of anal setae. Excretory pore plate small and usually wider than long (Figs 3, 5). Bases of setae Ae near middle or in posterior portion of excretory pore plate.

Chelicera (Fig. 6) with large basal segment and small stylet. Basal segment of chelicera with rather wide strips.

Pedipalps stout (Fig. 7): P-1 short, without seta; P-2 large with convex dorsal margin and a single dorsal seta in proximal part; P-3 with two subequal setae (proximal and distal); P-4 with three thin subequal setae and large dorsodistal claw; P-5 small conical, with a single moderately long solenidion and seven setae, five long and thick, two short and thin.

Legs 6-segmented. Shape and arrangement of specialized setae on terminal leg segments as shown in Figs 8– 10. I–II-Leg-4 solenidia 2.0–2.5 times longer than eupathidia; I-Leg-5 and II-Leg-5 with two proximal unequal solenidia; I-Leg-6 de shorter than ds; II-Leg-6 solenidion in proximal, eupathidium in submedial position. Claws of legs III slightly larger than claws of legs I and II. Lateral claws shorter and thinner than the strong empodial claw (Fig.11).

Measurements, n=10. Dorsal plate L 45–48, W 41–44; setae Fch L 21–23, setae Fp L 62–69, setae Vi L 28–32, setae Oi L 8 –10, setae Oe, Hi, He, Sci, Sce, Li, Le and Si L 26–28; setae Se, Ci, Pi and Pe L 16–18, setae Ai and Ae L 13–14; distance between setae Vi– Vi 31–35, distance between setae Oi-Oi 17–20; excretory pore plate L 6–9, W 10–12; basal segments of chelicera L 68–73, cheliceral stylet L 13–14; strips on basal segment of chelicera W 0.5 –0.7; pedipalpal segments (P-1–5) L: 6–7, 27–29, 22–25, 15–19, 10–11; leg segments L: I-Leg-1–6: 23–27, 18–24, 15–19, 25–28, 32–37, 62–65; II-Leg-1–6: 22–25, 17–19, 11–13, 16–19, 30–32, 46–50; III-Leg-1–6: 22–25, 17–23, 12–15, 20–23, 33–37, 45–48.

Female. Integument soft with rather long rounded papillae ( Fig. 12 ). Frontal plate ( Fig. 13 ) compact and nearly quadrate, anterior margin slightly convex or obtuse-angled, lateral margins concave, posterior margin straight, lateral and posterior extensions short. Median eye small and situated slightly posterior to anterior setae.

Capitulum ( Fig.14 ) with equally S-shaped ventral margin and rather long rostrum (base of capitulum/rostrum L ratio 4.4–5.1). Chelicera ( Fig.15 ) slender, basal segment with obtuse-angled hump near middle, cheliceral stylet moderate in length.

Pedipalp slender ( Fig. 16 ): P-1 with 3–4 dorsodistal setae; P-2 with 10–13 setae; P-3 usually with two long dorsodistal setae (occasionally an additional short one); P-4 slender with three thin distal setae and a short, thick dorsodistal spine.

Measurements, n=5. Idiosoma L 1100–1400; dorsal plate L 360–400, W 360–390; genital flap L 235–250, W 110–125; genital acetabula (ac.1–ac.3) L 35–42, 25–30, 55–63; capitulum L 275– 290, rostrum L 55–63, chelicera L 360–375, cheliceral stylet L 120–125; pedipalpal segments (P-1–5) L: 62–75, 110–120, 60–90, 185–200, 25–30; leg segments L: I-Leg-1–6: 75–90, 110–135, 135–140, 210–220, 235–250, 250–265; II-Leg-1–6: 100–105, 125–140, 160–175, 275–290, 325–340, 325–350; III-Leg-1–6: 95–105, 125–140, 170–180, 385–300, 325–340, 330–340; IV-Leg-1–6: 180–190, 185–200, 250–265, 400–415, 285–400, 335–350.

Remarks. Lundblad (1962) considered H. clypeatus , as well as the species and subspecies H. bayeri Pisarovic, 1896 , H. bayeri nonundulatus Viets, 1919 , H. affinis Sokolow, 1931 and H. ruber tuxeni Motas, 1961 , as junior synonyms of H. planus . However, clear differences can be found both in the larvae and females of H. clypeatus .

The larva is similar to the larva of H. planus (see description of this species). However, the latter differs from H. clypeatus in: (1) the posterior margin of the coxal plate II straight ( Fig. 33 ), not convex; (2) the excretory pore plate is longer than wide ( Fig. 34 –55); (3) P-5 with short solenidion ( Fig. 37 ); (4) I-Leg-4 solenidion slightly shorter than eupathidium ( Fig. 38 ), I-Leg-6 de as long as ds.

Figures

FIGURES 1 – 2. Hydryphantes clypeatus Thor, 1899, larva: 1, dorsal view; 2, ventral view. Scale bar: 20 µm.

FIGURES 12 – 16. Hydryphantes clypeatus Thor, 1899, female: 12, fragment of integument; 13, frontal plate; 14, capitulum; 15, chelicera; 16, pedipalp. Scale bars: 12, 16 = 50 µm, 14 – 15 = 100 µm, 13 = 200 µm.

FIGURES 32 – 33. H. planus Thon, 1899, larva: 32, dorsal view; 33, ventral view. Scale bar: 50 µm.

FIGURES 34 – 41. H. planus Thon, 1899, larva: 34 – 35, excretory pore plate; 36, chelicera, dorsal view; 37, pedipalp, ventrolateral view; 38, I-Leg- 4 – 6; 39, II-Leg- 4 – 6; 40, III-Leg- 4 – 6; 41, claws of leg III. Simple setae on I – III-Leg- 4 – 6 are not shown. Scale bars: 34 – 35, 37, 41 = 20 µm, 36, 38 – 40 = 50 µm.