Neocaeculus kinnearae, Taylor, 2014

Taylor, C. K., 2014, Two Further Neocaeculus Species (Acari: Prostigmata: Caeculidae) From Barrow Island, Western Australia, Acarologia 54 (3), pp. 347-358 : 348-352

Neocaeculus kinnearae new species

( Figures 2-3 )

Holotype — Female, Barrow Island , Western Australia, 20°41’30"S 115°25’09"E, 19-30 March 2012, N. Gunawardene, C. Taylor, pitfall trap ( WAM T132729 ; slide-mounted).

Paratypes — 1 female, Barrow Island , Western Australia, 20°49’37"S 115°26’48"E, 19-30 March 2012, N. Gunawardene, C. Taylor, pitfall trap ( WAM T132730 ; in ethanol) ; 1 female, Barrow Island , Western Australia, 20°41’26"S 115°25’01"E, 17-29 March 2013, N. Gunawardene, C. Taylor, pitfall trap ( WAM T132731 ; in ethanol) .

Etymology — Named for Adrianne Kinnear, who identified many of the mites from Barrow Island and incited my own interest in mites.

Diagnosis — In the key to Australasian Caeculidae provided by Taylor et al. (2013), Neocaeculus kinnearae would key out to N. knoepffleri , to which it is very similar. It differs from N. knoepffleri in its smaller size (about 1.1-1.2 mm in idiosoma length vs 1.5-1.6 mm in N. knoepffleri ) and lack of a retroventral spinose seta on femur I. Neocaeculus kinnearae also has the major setae less sharply spinose than those of N. knoepffleri , with the tips baculate rather than acute. Neocaeculus bornemisszai has shorter, more clavate major setae on the legs (Coineau andEnns, 1969). Neocaeculus kinnearae differs from N. luxtoni Coineau, 1967 , N. imperfectus and Microcaeculus pica in having bothridial seta bo elongate and non-capitate. It differs from N. johnstoni Coineau, 1974b and N. womersleyi Coineau, 1974b in having femur I undivided.

Dorsum — Idiosoma length 1130-1179, width 645-686. Cream-coloured sclerites divided by darker striated integument. Dorsal setae small, can be difficult to distinguish. Aspidosomal sclerite with median rectangular area outlined by darkpigmented grooves; sclerite length 355-445, width 316-415; setae Pa situated at anteriormost end of sclerite; setae Pm at 0.2 on anterior lateral corners of sclerite; setae Pp at 0.7 towards retrolateral corners of sclerite. Accessory sclerite bearing two pairs of eyes fused to lateral margin of rear of aspidosomal sclerite; anterior margin of anterior eyes roughly level with setae Pp. Centrodorsal sclerite with paired setae a1, b1, c1 present; centrodorsal sclerite length 413-549, width 315-378. Lateral sclerites each subdivided by two mediolateral indentations; paired setae a2, b2, c2 sequentially placed with one seta on each sub-region of sclerite demarcated by indentations; lyrifissure ia angled laterally rearwards, placed at about 0.7 between setae a2 and b2; lyrifissure im angled laterally rearwards, placed about halfway between setae b2 and c2. Opisthosoma with broadly separated medial sclerites bearing setae pairs d1, d2; one transverse posterior sclerite bearing setae pairs e1, e2, and unpaired median seta es; and two lateral pluriposterior sclerites bearing seta h medially together with single median pluriposterior sclerite bearing seta hs. Seta ds absent.

Venter — Epimeres dark brown; surrounded by darker cream integument; venter of idiosoma largely darker cream except genital and adanal sclerites dark brown, aggenital and pseudanal sclerites grey-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 elongate, distally fusiform but not distinctly capitate. Infracapitulum with two pairs of setae arranged in a transverse line. Epimeres I and II fused; epimere I with six elongate setae; epimere II with one elongate seta. Epimeres III and IV fused, each with one elongate seta. Genital valves with five to seven pairs of setiform setae; genital opening length 173-193. Eight pairs of aggenital setae present, with four pairs of setiform setae on aggenital sclerites; anteriormost clavate aggenital seta close to level of anterior of epimere IV; one pair each of clavate setae present just anterior to genital opening, exterior to aggenital sclerite and posterior to genital opening. Adanal sclerites with one pair of clavate setae; pseudanal sclerites with three pairs of clavate setae; anal opening length 152-173.

Gnathosoma — Gnathosoma uniformly black. Palp with four segments; fused femur-genu with four dorsal barbed setae; tibia with three dorsal barbed setae and one large barbed seta distally; tarsus with recessed solenidion proximodorsally, four setiform setae around halfway, and four eupathidia with two paired eupathidia terminally and two separated eupathidia close to distal end.

Legs — Legs black with white setae. All legs with femora undivided. All legs with anterior tarsal claw much smaller than posterior claw. Prodorsal, dorsal and retrodorsal rows of clavate setae present on all legs. Elongate bothridial seta bt absent on legs I and II, present dorsally at about 0.6 on tarsi III and IV. Trochanter I with four elongate prolateral tubercles each bearing rounded terminal seta; femur I proventrally with one elongate clavate seta at about 0.6, retroventrally with five clavate setae on raised tubercles, paired dorsolat- eral eupathidia present distally; genu I proventrally with two or three elongate clavate setae, retroventrally with one elongate clavate seta, paired dorsolateral eupathidia present at about 0.3 and distally; tibia I proventrally with three spinose setae, retroventrally with two spinose setae; paired dorsolateral eupathidia present at about 0.3; retrodorsal eupathidium present distally with recessed solenidion and seta k" slightly more ventrodistal; tarsus I with proventral and retroventral rows of spinose setae, paired dorsolateral eupathidia at about 0.3 and distally, recessed prolateral solenidion at about halfway, setae er claw-like and directed parallel to tarsus. Leg II with elongate spinose setae on genu and tibia, remaining ventral setae not enlarged; arrangement of eupathidia as for leg I; prolateral solenidion also present at about halfway on tarsus.

Comments — The life habits of Neocaeculus kinnearae are unknown, but its collection from pitfall traps rather than on vegetation suggests it is probably terrestrial rather than scansorial as has been suggested for N. imperfectus ( Taylor et al., 2013) . Its elongate major leg setae suggest that it is probably an epigean species like N. knoepffleri (see above) rather than a burrower in the likely manner of N. bornemisszai and N. nudonates . The blunter major leg setae of N. kinnearae than those of N. knoepffleri may indicate that these species differ in microhabitat; N. kinnearae may prefer a coarser substrate than the clay or rock from which N. knoepffleri has been collected (Coineau and Enns, 1969, and above).

Neocaeculus kinnearae is similar in overall morphology to Neocaeculus knoepffleri , and the two species seem likely to be closely related. However, while the anterior section of the aspidosomal sclerite of N. knoepffleri is strongly downturned above the gnathosoma (Coineau and Enns, 1969: Fig. 2 therein), that of N. kinnearae is less downturned and projects slightly forwards ( Fig. 2D ). This is problematic, as the anterior projection of the aspidosomal sclerite has previously been used to distinguish Neocaeculus from the genus Microcaeculus ( Taylor et al., 2013) .

Further consideration has convinced me that distinguishing these two genera by this character alone is untenable, as it is unclear whether it can be consistently applied. The aspidosomal sclerite of Microcaeculus sabulicola Franz, 1952 (Coineau, 1969: Fig. 3 therein) is only a little more produced than that of Neocaeculus luxtoni Coineau, 1967 (Fig. 6 therein), and less expansive overall than that of N. knoepffleri . The anterior part of the aspidosomal sclerite of the latter species is in fact relatively elongate despite being downturned. This stands in contrast to N. johnstoni Coineau, 1974b , whose ’ Neocaeculus ’ profile is due to direct truncation of the aspidosomal sclerite itself, and not due to a downturn of the anterior portion (indeed, Coineau, 1974b, made no mention of the aspidosomal sclerite in his list of characters associating the latter species with Neocaeculus ). Nor is any distinct downturn of the aspidosomal sclerite evident in the profiles of N. imperfectus ( Taylor et al., 2013: Fig. 2 therein) or N. nudonates ( Fig. 4D ), despite the truncate profiles of both.

Nevertheless, it remains premature at this point to synonymise the two genera. Taylor et al. (2013) noted characters that may be synapomorphic for Neocaeculus , including fusion of the basifemur and telofemur of leg I into a single segment (absent in N. johnstoni and N. womersleyi Coineau, 1974b ) and reduction of the adanal setation to a single seta (lost entirely in N. nudonates ). Also noteworthy is that the four-segmented palp of Neocaeculus species (with femur and genu fused) contrasts with the five-segmented palp of many Microcaeculus species (e.g. Coineau, 1968, 1969; Coineau and Haupt, 1977; Piffl, 1965), though the type species of that genus, M. austriacus Franz, 1952 , was originally illustrated with a four-segmented palp (a detail that requires confirmation).

Unfortunately, many Microcaeculus species (in particular M. austriacus ) have not been described in detail and would benefit from further investigation. For instance, species of Microcaeculus described from South America by Franz (1962, 1964) may be better placed in Andocaeculus (A. Porta, pers. comm., 2014).

Figures

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.

FIGURE 3: Legs of the left side of Neocaeculus kinnearae in dorsal view. Selected proventral setae v’ marked on legs I and II to facilitate orientation. Eupathidia marked with ζ; tibial solenidia marked with ’; tarsal solenidia marked with ω.

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.