Neocaeculus nudonates, Taylor, 2014

Taylor, C. K., 2014, Two Further Neocaeculus Species (Acari: Prostigmata: Caeculidae) From Barrow Island, Western Australia, Acarologia 54 (3), pp. 347-358 : 353-356

Neocaeculus nudonates new species

( Figures 4-5 )

Holotype — Female, Barrow Island , Western Australia, 20°47’39"S 115°27’15"E, 19-30 March 2012, N. Gunawardene, C. Taylor, pitfall trap ( WAM T132732 ; slide-mounted).

Paratypes — 4 females, as for holotype ( WAM T132733 [1 specimen, slide-mounted]; WAM T132734 [remaining specimens, in ethanol]) .

Etymology — Noun in apposition, from the Latin nudus, uncovered or exposed, and nates, buttocks, in reference to the small posterior sclerites.

Diagnosis — In the key to Australasian Caeculidae provided by Taylor et al. (2013), Neocaeculus nudonates would key out with Neocaeculus imperfectus , N. luxtoni and Microcaeculus pica . It differs from N. imperfectus in having the enlarged setae on femur I clavate rather than spinose, and from N. luxtoni and M. pica in lacking seta es. It also differs from M. pica in the lower number of setae on the legs and epimeres, in having the setae Pa located on the anterior edge of the aspidosomal sclerite rather than ventral to the anterior edge, and in lacking the strikingly contrasting coloration of M. pica ( Otto 1993) . It differs from N. knoepffleri , N. bornemisszai , N. johnstoni and N. womersleyi in having the bothridial setae bo globose-capitate.

Dorsum — Idiosoma length 608-667; width 358- 400. Dark brown sclerites separated by light brown striated integument. Aspidosomal sclerite with median depression poorly demarcated; setae Pa situated at anteriormost corners of sclerite; setae Pm at 0.3 on anterior lateral corners of sclerite; setae Pp at about 0.7 towards posterior lateral margins of sclerite, which are distinctly rounded rather than angular; aspidosomal sclerite length 192-249, width 166-177. Two pairs of eyes on accessory sclerite lateral to rear of aspidosomal sclerite; anterior margin of anterior eyes roughly level with setae Pp. Centrodorsal sclerite with paired setae a1, b1, c1 present; posterior margin of centrodorsal sclerite distinctly emarginate; centrodorsal sclerite length 196-276, width 185-223. Lateral sclerites not distinctly subdivided by emarginations; paired setae a2, b2, c2 present roughly level with corresponding setae on centrodorsal sclerite; lyrifissure ia angled slightly laterally forwards, about one-fifth width of lateral sclerite, placed about midway between setae a2 and b2; lyrifissure im angled laterally rearwards, similar in size to ia, placed at about 0.6 between setae b2 and c2. Opisthosoma with broadly separated medial sclerites bearing setae pairs d1, d2, with unpaired seta ds present medially on soft integument; broadly separated posterior sclerites bearing setae pairs e1, e2; and two lateral pluriposterior sclerites bearing seta h medially, together with single median pluriposterior sclerite bearing seta hs. Seta es absent. Lyrifissure ip oval in shape, positioned on side of body in line with division of medial and posterior sclerites.

Venter — Epimeres dark brown; surrounded by darker cream integument; venter of idiosoma largely darker cream except sclerites dark brown. Median eye present below anterior projection of aspidosomal sclerite, seta Po reduced to minute spine above median eye; bothridial setae bo lateral to median eye globose-capitate. Infracapitulum bearing two pairs of setiform setae, median pair slightly anterior to lateral pair. Epimeres I and II fused; epimere I bearing four elongate setae; epimere II bearing one elongate seta. Epimeres III and IV fused, each bearing one elongate seta. Genital valves with six pairs of setiform setae; genital opening length 76-104. Nine pairs of clavate aggenital setae present, four pairs on aggenital sclerites; anteriormost pair level with epimere IV; one pair just anterior, two pairs exterior and one pair just posterior to aggenital sclerites. Adanal setae absent; pseudanal sclerites with three pairs of clavate setae; anal opening length 95-138.

Gnathosoma — Gnathosoma uniformly dark brown. Palp with four segments; fused femur-genu with three dorsal barbed setae; tibia with one prolateral setiform seta, and three dorsal and one terminal barbed setae; tarsus with recessed solenidion proximodorsally, three setiform setae around halfway, and paired eupathidia terminally.

Legs — Legs black bearing white clavate setae. All femora undivided. All legs with anterior tarsal claw much smaller than posterior claw. Elongate bothridial seta bt absent on legs I and II, present dorsally at about 0.6 on tarsi III and IV. Clavate setae present dorsally on all legs. Trochanter I with elongate prolateral tubercle bearing clavate seta; femur I with large proventral and retroventral seta, paired dorsolateral eupathidia present distally; genu I with two large proventral and one retroventral spinose setae, paired dorsolateral eupathidia present distally; tibia I with two proventral and two retroventral spinose setae, retrodorsal eupathidium present distally with recessed solenidion and seta k" slightly more ventrodistal; tarsus I with recessed prolateral solenidion at about halfway, setae er claw-like and directed parallel to tarsus. Leg II with large proventral clavate setae on femur and genu, remaining ventral setae not enlarged; arrangement of eupathidia as for leg I; prolateral solenidion also present at about halfway on tarsus.

Comments — Other species of Caeculidae with clavate rather than spinose enlarged leg setae are known to be diggers in sandy substrates (Coineau and Enns, 1969; Coineau, 1974a; Otto, 1993), and it seems likely that Neocaeculus nudonates is similar in habits. Barrow Island is therefore inhabited by two likely fossorial species, N. nudonates and N. bornemisszai . Data are currently inadequate to determine whether these two species exhibit any differences in habitat preference, though it may be noted that N. bornemisszai is more heavily sclerotised than N. nudonates .

The reduced opisthosomal sclerotisation of N. nudonates immediately distinguishes it from all other Australasian caeculids, most of which have the posterior sclerites in particular tending to become fused into a single transverse sclerite (as in Fig. 2a ). The species most similar to N. nudonates in this regard is Microcaeculus pica which, as noted by Taylor et al. (2013), may prove more closely related to Neocaeculus once the relationship of this genus with Microcaeculus is better established.

Together with Microcaeculus pica , Neocaeculus luxtoni and N. imperfectus , N. nudonates is part of a group of species that are distinctive in the possession of a strongly globose-capitate bothridium bo. Taylor et al. (2013) believed that this bothridial morphology had not been recorded outside Aus- tralasian species; however, AndrØ (1936) illustrated a similar bothridium for the Italian species Microcaeculus pisanus ( AndrØ, 1936). Unfortunately, M. pisanus was described (in the genus Caeculus ) from the larva only, and Coineau (1974a) listed it as a species of Microcaeculus without further comment. Its relationship with other caeculid species therefore remains uncertain.

Figures

FIGURE 4: Neocaeculus nudonates, labels as for figure 2: A – Dorsal view; B – diagram of dorsum of idiosoma; C – venter of idiosoma; D – lateral view of anterior of idiosoma.

FIGURE 5: Legs of the left side of Neocaeculus nudonates in dorsal view; labels as for figure 3.

FIGURE 2: Neocaeculus kinnearae: A – Dorsal view; B – diagram of dorsum of idiosoma showing positions of setae and lyrifissures; le = lateral eyes; C – venter of idiosoma: AD = adanal sclerite, AG = aggenital sclerite, G = genital sclerites, PS = pseudanal sclerite; D – lateral view of anterior of idiosoma, showing palp and anterior bothridial seta bo. Solenidion indicated by ω; eupathidia indicated by ζ; me = median eye.