Thinoseius peltatus, Halliday, 2010

Halliday, R. B., 2010, Revision of the Australian Eviphididae (Acari: Mesostigmata) 2596, Zootaxa 2596 (1), pp. 1-60 : 48-51

Thinoseius peltatus sp. nov.

( Figs 95–99 , 102, 103 )

Material examined. Holotype. Female, New South Wales, Durras , 17 April 1985, E. Holm coll., in seaweed (in ANIC) . Paratypes. New South Wales. 3 females, same data as holotype ; 1 female, Broulee , 7 May 1986, W. Nicholas coll., seaweed on beach ; 12 females, Malonys Beach, near Batemans Bay , 35°43'S 150°11'E, 7 May 2008, R. B. Halliday coll., seaweed on beach . South Australia. 11 females, Nora Creina Bay , 37°20'S 139°51'E, 26 March 2008, R. B. Halliday coll., seaweed on beach ; 2 females, Robe, southern end of Long Beach , 37°46'48"S 139°46'48"E, 26 March 2008, R. B. Halliday coll., seaweed on beach . Victoria. 6 females, Mallacoota, Betka Beach , 37°34'S 149°45'E, 4 August 2007, J. Błoszyk and S. Konwerski coll., seaweed on beach. (all in ANIC) .

Description. Female. Dorsal idiosoma ( Fig. 95 ). Dorsal shield length 554–592 µm, width 315–382 µm (n=5), not completely covering dorsal idiosoma, shield surrounded by unsclerotised striate cuticle postero-laterally and posteriorly ( Fig. 103 ); margins of shield irregular and eroded, surface with polygonal ornamentation throughout, with 13 pairs of setae and ca. six pairs of minute pores. Setae z 1 minute, fine and pointed, j 2 short, fine, needle-like, other podonotal shield setae thick, parallel-sided, with blunt tips, often curved and directed forward; s 2, s 5, s 6, r 2, r 3, r 5 thick and spine-like, inserted in soft skin outside shield. Opisthonotal setae J 5 minute, fine and pointed, J 1, J 2, J 3 short, curved and directed forward, other opisthonotal setae thick and spine-like, inserted in soft skin outside shield.

Ventral idiosoma ( Fig. 96 ). Tritosternum with elongate base and very long delicate finely pilose laciniae. Sternal shield absent; sternal setae st 1, st 2, st 3, st 4, lyrifissures stp 1, stp 2, and minute circular metasternal pores stp 3, all inserted in unsclerotised striated skin. Metasternal setae st 4 (20 µm) ca. half as long as st 1, st 2, st 3 (40 µm). Endopodal plates I–II large, triangular, sometimes with long narrow projection extending outward between coxae I–II; endopodal plates II–III and III–IV fused to form elongate plates extending from mid-level of coxae II to mid-level of coxae IV, posterior end sometimes partly overlain by epigynal shield. Epigynal shield with rugose surface, outer edges weakly sclerotised, with a pair of fine needle-like setae inserted in lateral weakly sclerotised area. Anal shield oval, slightly wider than long, surface with irregular lines of ornamentation, cribrum large and conspicuous, para-anal setae fine and needle-like, post-anal seta shorter, thicker, blunt-tipped. Anal shield surrounded by a large area of sclerotised skin resembling a ventrianal shield ( Fig. 102 ), anterior margin abutting posterior margin of epigynal shield and coxae IV; central part of this area with strong rectangular to polygonal ornamentation, polygons separated by prominent ridges; lateral and posterior margins of sclerotised area irregular, grading into unsclerotised striate opisthogastric integument ( Fig. 103 ). Opisthogastric area with six pairs of short setae, the posterior two pairs thick, with blunt tips. Exopodal platelets between coxae I–II and II–III free, triangular, exopodal plates III–IV fused but free from peritrematal shield, anterior end at mid-level of coxa III, posterior end embracing posterior margin of coxae IV. Anterior ends of peritrematal shields anterior to coxa I, extending beyond stigmata, with two pairs of post-stigmatal pores, and a prominent pore on outher margin of shield at level of coxa III. Anterior end of peritremes at mid-level of coxae I.

Gnathosoma . Surface of hypostome rugose, with irregular linear markings. Rostral setae h 1 and internal setae h 3 subequal in length, 60 µm, external setae h 2 shorter, 45 µm, palp coxal setae shortest, 30 µm, all fine and needle-like ( Fig. 97 ). Deutosternal groove with five transverse rows of denticles, ca. eight denticles per row, and a curved smooth anterior line; corniculi robust, outer margin slightly sinuous; internal malae with very long conspicuous fringes. Seta av on palp trochanter shorter and thicker than pv, al on femur, genu and tibia shorter and thicker than pl, tarsus without long sensory seta, palp tarsal claw with two subequal spatulate tines. Epistome with 8–10 long anterior points, central point longest (ca. 40 µm), some points distally bifurcate or subdivided ( Fig. 98 ). Cheliceral digits long and slender, fixed digit with a triangular distal tooth and a second smaller blunt distal tooth, pilus dentilis short and robust, dorsal seta long, robust, semi-erect ( Fig. 99 ); movable digit with two triangular teeth, arthrodial membrane a small rounded flap.

Legs. Chaetotaxy: Leg I. Coxa 0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 2 3/1 2/2 2, genu 1 3/2 2/1 2, tibia 1 3/2 2/1 2. Leg II. Coxa 0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 1 3/1 2/2 1, genu 1 3/1 2/1 2, tibia 1 2/1 2/1 2, tarsus 3 3/2 3/2 3 + mv, md. Leg III. Coxa 0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 1 2/1 1/1 1, genu 1 2/1 2/0 1, tibia 1 1/1 2/1 1, tarsus 3 3/2 3/2 3 + mv, md. Leg IV. Coxa 0 0/0 0/1 0, trochanter 1 0/1 0/2 1, femur 1 2/ 1 1/0 1, genu 1 2/1 2/0 1, tibia 1 1/1 2/1 1, tarsus 3 3/2 3/2 3 + mv, md. All leg setae smooth and pointed, most dorsal setae thickened, ventral and lateral setae fine and needle-like. Pre-tarsi as for T. papillatus . Coxae I with two pairs of conspicuous coxal glands.

Genital structures. Sacculus indistinct and apparently unsclerotised, sections of insemination ducts occasionally visible, originating from posterior margin of coxa III. Some specimens contain a single large egg, 290 x 240 µm.

Etymology. The name of this species is the Latin word peltatus , armed with a shield, referring to the large area of opisthogastric sclerotisation, resembling a ventri-anal shield.

Notes. Two Australian species of Thinoseius have a large area of opisthogastric sclerotisation resembling a ventri-anal shield in the female, T. papillatus and T. peltatus . Both these species also lack seta pv on genu III. They have been collected together at the same site (Robe, South Australia), but are easily distinguished. In T. papilllatus , the first pair of sternal setae are inserted in a distinct sclerotised shield fragment, there is a large endopodal plate adjacent to coxae II, a wide endopodal plate extending from the mid-level of coxae II to beyond the mid-level of coxae IV, and the opisthogastic skin surrounding the posterior half of the dorsal shield is sclerotised and strongly papillate. In T. peltatus , the sternal skin surrounding setae st 1 is unsclerotised and smooth to very slightly granulate, endopodal plates between coxae II–IV are much narrower, and the skin surrounding the posterior half of the dorsal shield is unsclerotised and striate.

Thinoseius ramsayi also has a strongly sclerotised area of skin surrounding the anal shield, resembling a ventri-anal shield. Thinoseius peltatus may be easily distinguished from T. ramsayi because the latter has sternal setae st 1 and the first pair of sternal lyrifissures inserted in a sclerotised plate, while in T. peltatus these setae and lyrifissures are inserted in soft skin. Also, the area of opisthogastric sclerotisation in T. peltatus is bigger than that in T. ramsayi , big enough to capture the metapodal plates, and often extending around the posterior end of the opisthosoma to meet the dorsal shield. In both species the anal shield is clearly demarcated from the surrounding “ventri-anal” area of sclerotisation. In T. ramsayi , the surrounding sclerotised area has a uniform finely granular texture, while that of T. peltatus is very strongly ornamented in a rectangular brickwork pattern, in which each rectangle encloses a few grooves or dimples. (holotype of T. ramsayi examined, in NZAC).

Figures

FIGURES 95–99. Thinoseius peltatus, female. 95, dorsal idiosoma; 96, ventral idiosoma; 97, hypostome; 98, epistome, three different specimens; 99, chelicera. Scale bar = 100 µm for 95, 96; 50 µm for 97, 98, 99.

FIGURES 100–103. Thinoseius spp., females. 100, T. papillatus, anal shield and surrounding opisthogaster; 101, T. papillatus, postero-dorsal opisthosomal skin; 102, T. peltatus, anal shield and surrounding opisthogaster; 103, T. peltatus, postero-dorsal opisthosomal skin. Scale bar = 100 µm for 100, 102; 50 µm for 101, 103.