Cheiroseius rajasthanicus, Bhattacharyya & Bhattacharyya, 2004

Bhattacharyya, Asit K. & Bhattacharyya, Sisir K., 2004, Two new species of the genus Cheiroseius Berlese, 1916 (Ascidae: Mesostigmata) from the Indian Thar Desert, Zootaxa 403 (1), pp. 1-11 : 7-10

Cheiroseius rajasthanicus sp. nov. ( Figs. 9–20 )

Diagnosis: Dorsal shield with 36 pairs of setae; nine pairs of dorsal setae on tubercles; setae J5 serrated; ventri­anal shield broadly triangular, with 9 setae; seven rows of deutosternal denticles, each row with 7–16 denticles; sterniti­genital shield in male with four pairs of setae.

Female: Dorsal shield (341µ long, 157µ wide) heavily sclerotized, with reticulated ornamentation and 36 pairs of setae; setae j1–j6, z1–z6, s1–s6 and r2–r4 placed on anterior region of the shield; setae r5 occur on the lateral interscutal membrane; posterior region of the dorsal shield complete with 15 pairs of setae; setae R1–R7 occur on the lateral interscutal membrane posterioly; nine pairs of setae borne on raised tubercles; excepting serrated J5 setae (7µ), all setae simple, thornlike, abruptly tapering at tips; setae J1–J4 20µ long, Z5 and S5 are 22µ and 31µ long respectively ( Fig. 9 ).

Tritosternum long, with moderately pilose lacinae. Sternal shield (55µ long along midline, 98µ wide between two anterolateral corners) finely granulated, slightly concave medially; semicircular structures present at level of first pair of sternal setae; setae st1–st2 and st4 subequal (7µ) but shorter than setae st3 (12µ); sternal shield convex posteriorly; metasternal shields irregular in shape, with metasternal setae; remnants of endopodal shield present between coxae II­IV. Peritreme moderately wide; post­stigmatal prolongation of peritrematal shield encircling coxae IV, divided into several small platelets. Genital shield with genital setae; ventral membrane posterior to genital shield with two pairs of setae (Jv1 and Zv1) and two pairs of post­genital scutellae. Metapodal shields small, present laterally. Ventri­anal shield (78µ long, 87µ wide) roughly triangular in outline, with three pairs (Jv2–Jv3 and Zv2) of setae, excluding a pair of para­ and a post­anal seta; post­anal seta (12µ) shorter than para­anal setae (20µ); anal opening large, placed at the middle of ventri­anal shield; setae Jv4 and Jv5 placed on ventral membrane and borne on raised tubercles; lineation of ventral membrane around ventri­anal shield depicted in fig. 10.

External malae relatively short, stout ( Fig. 11 ); internal malae shorter than external malae, tips curved, slightly outward, outer margin finely fringed laterally; salivary styli arch­shaped anteriorly; anterior hypostomatic setae and V2 (situated on palp trochanter) almost subequal (50µ – 51µ) but almost double length of posterior one (25µ). Ventrally seven rows of deutosternal denticles present, with 7–16 teeth in each row, fifth row widest; lateral margin of deutosternal groove not clearly discernible, rounded structures present in the distal half of lateral groove. Palp apotele two­tined; epistome tripartite, all tips with minute denticulate projection ( Fig. 12 ). Chelicerae well­developed, movable digit bidentate, fixed digit tridentate, pilus dentilis simple ( Fig. 13 ).

All legs provided with well­developed ambulacra and paired claws; tarsus I slightly longer (160µ) than tibia I (150µ); length of legs I–IV are 590µ, 500µ, 450µ and 610µ respectively; tarsus I distally provided with paired claws, 3­pointed lobes and sensory setae ( Fig. 14 ); tarsus II as figured ( Fig. 15 ); some setae on legs II–IV relatively short, spine­like ( Fig. 16 ); leg chaetotaxy normal for the genus.

Male: Holodorsal shield 284µ long, 182µ wide; anterior region of the dorsal shield with 19 pairs of setae; posterior region of the dorsal shield with 14 pairs of setae; setae J5 serrated; in both the paratypes, setae J3 unpaired and present on the right aspect only ( Fig. 17 ).

Tritosternum normal for the genus. Sterniti­genital shield (118µ long, 100µ wide) lineated, with 4 pairs of setae ( Fig. 18 ), setae st4 absent; anal orifice at the anteromedian portion of sterniti­genital shield. Ventri­anal shield (118µ long along midline, 175µ wide between two anterolateral corners) with four pairs of setae, excluding a pair of para­ and a post­anal setae; exopodal and peritrematal shield fused; peritreme moderately wide, stigmata placed at anterior level of coxae IV.

Tectum as in female. Five rows of deutosternal denticles, with 16–30 denticles in each row ( Fig. 19 ). Movable cheliceral digit tridentate, fixed cheliceral digit with several small teeth ( Fig. 20 ); spermadactyl process not clearly discernible.

All legs with well­developed ambulacra and claws; excluding ambulacra, length of legs I–IV as follows: 510µ, 320µ, 320µ and 390µ; no sexual dimorphism has been observed.

Types: Holotype female, Jaliwada, Jodhpur , Rajasthan; ex. soil beside kitchen drainage; 15 January 2001 . Paratypes: 2 females, Zoological Survey of India compound, Jodhpur , Rajasthan; ex. decomposed grass litter collected from semi­dried drainage system; 2 July 2003; A.K. Bhattacharyya coll. 4 females, 1 male, 23 March 2003, collection details same; 5 females, 1 male, 27 March 2003; collection details same; 1 female, 4 April 2003; collection details same.

Distribution: INDIA: Rajasthan.

Differential diagnosis: The new species, Cheiroseius rajasthanicus superficially resembles C. indicus ( Pramanik and Raychaudhuri, 1977) in having similar type of dorsal reticulation, shape and reticulation of sternal shield as well as the presence of sclerotized platelets between genital and ventri­anal shield. However, the new species differs from indicus in the following aspects: nature of dorsal setae, serrated J5 seta, shape of metasternal shield and chelicerae.

Lack of congruence between ventral setation of male and female in ascids and their relatives is unusual rather than unknown. Evans and Hyatt (1960) mentioned the absence of setae st4 among adult males of all species of Platyseius but not in any male of the three Cheiroseius species described therein. In his personal communication, Lindquist informed us that some unidentified species of Cheiroseius in the Canadian National Collection also show the absence of setae st 4 in male specimens. It is considered that in Dermanyssina setae st1–st5 are the most highly conserved chaetotactic series. Since seta st4 is the last one to be added in the deutonymphal stage, it is likely probable that it will be lost later in course of further development i.e., adult. However, in the absence of any detailed further study on different developmental stages, the ontogenetic sequence and mechanism for this type of dimorphic suppression will remain uncertain.

Etymology: The species has been named after the name of the state i.e., Rajasthan to which the type­locality belongs.

Figures

FIGURE 9–10: Cheiroseius rajasthanicus sp. nov., female. 9. Dorsum, 10. Venter. Scale bar: 50µ.

FIGURE 11–16: Cheiroseius rajasthanicus sp. nov., female. 11. Gnathosoma, 12. Tectum, 13. Chelicera, 14. Tarsus I, 15. Tarsus II, 16. Leg IV. Scale bar: Figs. 11, 12, 14, 15, 16, 50µ; Fig. 13, 39µ.

FIGURE 17–20: Cheiroseius rajasthanicus sp. nov., male. 17. Dorsum, 18. Venter, 19. Gnathosoma, 20. Chelicera. Scale bar: Figs. 17, 18, 19, 50µ; Fig. 20, 38µ.