Amphialycus (Orthacarus) oblongus (Halbert, 1920)

Uusitalo, Matti, Ueckermann, Edward A. & Theron, Pieter D., 2020, A review of the family Alycidae (Acari, Acariformes) from South Africa, Zootaxa 4858 (3), pp. 301-340 : 321-323

Amphialycus (Orthacarus) oblongus (Halbert, 1920)

( Figs. 76–89 )

Alicus oblongus Halbert, 1920: 140 , pl. 23, figs. 23a–c, erroneous orthography of Alycus C.L. Koch ; holotype from Malahide , Ireland, from orange lichen zone at NMI ( National Museum of Ireland) .

Pachygnathus oblongus: Thor & Willmann 1941: 138 ; Baker & Bayliss 2005: 288.

Amphialycus (Orthacarus) oblongus: Uusitalo 2010: 58 , figs. 82–87.

Alycus? roseus Womersley, 1944: 139 .

Orthacarus tremli Zachvatkin, 1949: 292 , figs. 1–5.

Description. Dorsum ( Figs. 76, 77 ). Length 300–500 μm; neotrichous setal pattern dorsally and on ventral side; naso absent, prodorsal setae vi, sce and exp sparsely ciliated (reduced), sensilla ve and sci filamentous, distances between counterparts of setae vi and anterior bothridial sensilla ve less than distance between setae in.

Venter ( Figs. 77–79 ). Genital valves each with 12–18 genital setae; anal valves terminally with 7–8 setae.

Gnathosoma ( Figs. 76, 80–82 ). Pair of smooth cheliceral setae abaxially; rutella widening to apical lobes and a pointed process, one pair of adoral setae; distally narrow palpal tarsi with four basally fused, microtrichous eupathids.

Legs ( Fig 83 ). Claw-like empodium multisetulate; solenidial formula for tarsi, tibiae, genua and femora on legs I, II, III and IV, respectively: 2-1-0-0, 2-2-2-0, 3-2-0-1, 1-0-0-0.

Larva (n=5, Figs. 88, 89 )

Dorsum. Length 200 μm; holotrichous; sensilla ve and sci filamentous.

Venter. Holotrichous; genital valves absent.

Gnathosoma . One pair of fused palpal eupathids.

Legs. Solenidial formula for tarsi, tibiae, genua and femora on legs I, II and III, respectively: 1-1-0, 2-2-2, 3- 2-0, 1-0-0.

Other life stages:

Protonymph (n=6, Fig. 87 ), 1 genital seta per valve.

Deutonymph (n=8, Fig. 86 ), 4 genital setae per valve.

Tritonymph (n=6, Fig. 85 ), 11 genital setae per valve.

Adult male (n=9, Fig. 84 ), 12–18 genital setae setae, 7 pairs of eugenital setae.

Adult female (n=18, Figs. 78, 79 ), 12–18 genital setae per valve, 1 pair of eugenital setae.

Material examined. Eighteen females, 9 males, 6 tritonymphs, 8 deutonymphs, 6 protonymphs and 5 larvae from Themeda triandra -biotope, Potchefstroom, NORTH-WEST PROVINCE, 25 March 1969, P.D. Theron. Deposited at ARC-Plant Health and Protection, Pretoria, South Africa .

Differential diagnosis. This species easily differs from other neotrichous species of Amphialycus by having character states typical to the subgenus Orthacarus : without naso, prodorsal setae reduced in size, counterparts of setae vi inserted exceptionally closely to each other, basally fused palpal eupathids, short and bent legs and caudal anus ( Figs. 76, 77, 82 ). From other (still undescribed) species of the subgenus Orthacarus , this species differs by having both pairs of prodorsal sensilla (ve and sci) filamentous, abaxially inserted cheliceral setae and a typical solenidial pattern.

Figures

FIGURES 76−83. Amphialycus (Orthacarus) oblongus (Halbert). 76—Prodorsum, naso missing, distance between counterparts of setae vi and sensilla ve smaller than between setae in, setae vi, sce and exp reduced; 77—Dorsal habitus, neotrichy; 78—Ventral habitus, 17 genital setae per valve, 8 anal setae per valve (cf. Fig. 77); 79—Genital valve of female, 16–18 genital setae, 1 pair of eugenital setae; 80—Subcapitulum, 1 pair of adorals; 81—Rutellum; 82—Palp, tarsus with 4 barbed and basally fused eupathids; 83—2 slightly bent claws and densely setulated, claw-like empodium.

FIGURES 84−89. Amphialycus (Orthacarus) oblongus (Halbert). 84—Genital valve of male, 12 genital setae per valve, 7 pairs of eugenital setae; 85—Tritonymph, venter, 11 genital setae per valve; 86—Deutonymph, venter, 4 genital setae per valve; 87—Protonymph, venter, 1 genital seta per valve; 88—Larva, ventral habitus, holotrichy, genital valves absent; 89—Larva, dorsal habitus, holotrichy. 76−89 from RSA, near Potchefstroom.