Neocaeculus imperfectus, Taylor & Gunawardene & Kinnear, 2013

Taylor, C. K., Gunawardene, N. R. & Kinnear, A., 2013, A New Species Of Neocaeculus (Acari: Prostigmata: Caeculidae) From Barrow Island, Western Australia, With A Checklist Of World Caeculidae, Acarologia 53 (4), pp. 439-452 : 440-445

Neocaeculus imperfectus n. sp. Figures 1-3

Holotype — Adult female, gas treatment plant site, Barrow Island , Western Australia, N. Gunawardene, C. Taylor, 14-24 March 2011, suction ( WAM).

Paratypes — Numerous adults and nymphs, as for holotype ( WAM) .

Other material — Specimens of this species have been collected in numerous samples over several years on Barrow Island, Western Australia. The greater number of specimens have been collected via suction of vegetation; smaller numbers of specimens have been collected in pitfall traps.

Etymology — Latin imperfectus , incomplete, referring to the retention of juvenile characters (particularly the lower number of setae) into maturity by this species.

Dorsum ( Figures 1 A-B) — Idiosoma length 1036 (885 – 1147), width 599 (525 – 663). Cream-coloured sclerites divided by black striated integument. All sclerites with reticulate ornamentation of raised ridges. Aspidosomal sclerite with median rectangular area outlined by dark-pigmented grooves; aspidosomal sclerite length 325 (268 – 375), width 342 (287 – 370); setae Pa situated at anteriormost corners of sclerite; setae Pm at 0.2 on anterior lateral corners of sclerite; setae Pp at 0.7 towards posterior lateral corners of sclerite. 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; centrodorsal sclerite length 452 (404 – 515), width 333 (303 – 363). Lateral sclerites

Taylor C.K. et al.

each subdivided by two transverse pigmented depressions; paired setae a2, b2, c2 sequentially placed with one seta on each sub-region of sclerite demarcated by depressions; lyrifissure ia transverse, about one-sixth width of lateral sclerite, placed roughly two-thirds of distance posteriad between a2 and b2; lyrifissure im angled laterally rearwards, similar in size to ia, placed about two-thirds of distance posteriad between b2 and c2. Idiosoma with broadly separated medial sclerites bearing setae pairs d1, d2, two separated or one transverse posterior sclerites bearing setae pairs e1, e2, and pluriposterior accessory sclerite bearing upaired seta hs with paired setae h on striated cuticle lateral to hs. Setae ds and es absent. Venter ( Figures 1 C-D) — Epimeres grey-brown;

epimeres I separated from gnathosoma by cream collar with cream stripes internal to epimeres I and II, median integument between epimeres I and II and entire integument between epimeres III and IV grey-brown; venter of idiosoma largely cream ex- cept genital valves dark brown, black stripe external to pseudanal sclerites. Median eye present just behind underside of anterior projection of aspidosomal sclerite; large bothridial setae bo present lateral to median eye, with nodulose pyriform caput. Epimere I fused with II, epimere I with four anterior barbed setae with basalmost seta placed close to junction between epimeres I and II, epimere II with one anterior barbed seta close to base; epimere III fused with IV, epimere III with one barbed seta close to anterior medial corner, epimere IV with one barbed seta close to base. Genital valves with six to eight pairs of setiform setae, with setae on each valve somewhat staggered; genital opening length 151 (119 – 163). Eight pairs of aggenital setae present, with one pair of setiform setae on aggenital sclerites; anteriormost pair of clavate aggenital setae ag1 close to level of anterior of epimere IV; one pair of setiform setae directly anterior to aggenital sclerites; two pairs of barbed setae roughly lateral to anterior ends of aggenital sclerites; remaining four pairs of barbed or clavate setae forming series running from about level of midline of aggenital sclerites to near posterior ends of aggenital sclerites, with anteriormost pair furthest laterad from aggenital sclerites and posteriormost pair close to aggenital sclerites. Anal valve with one pair clavate setae; pseudanal sclerites with one to three pairs clavate setae; anal opening length 145 (135 – 168).

Gnathosoma ( Figure 2 ) — Gnathosoma uniformly dark brown. Gnathosoma base with two pairs of setiform setae, with median pair placed slightly anterior of lateral pair. Rostral lobes each with distal pair of small setiform setae. Palp with four segments; fused femur-genu with three dorsal barbed setae; tibia with five setae (three dorsal spiniform setae at about mid-length; one proximal anterior ventrolateral setiform seta and one terminal spiniform seta); tarsus with three ventral spinose setae at about 0.5, one dorsal solenidion at about 0.5, and four eupathidia (two paired eupathidia at distal end, two separated dorsal eupathidia close to distal end).

Legs ( Figure 3 ) — Legs black with white setae. Setae of all legs (from the femur onwards) are arranged more or less into five rows that are referred to here as the anterior dorsolateral, median dorsal, posterior dorsolateral, anterior ventrolateral and posterior ventrolateral rows; the median dorsal row on each leg generally only reaches to about halfway along the tibia, so the distal half of the tibia and the tarsus only bear four rows of setae. Dorsal setae are generally short clavate from the trochanter to the genu, becoming more elongate and spinose on the tibia and tarsus. Leg I with anterior ventrolateral and posterior ventrolateral setae borne on long tubercles; femur I with one proximal elongate clavate and one medial spinose seta in each of anterior ventrolateral and posterior ventrolateral rows; genu I with three pairs of anterior ventrolateral and posterior ventrolateral spinose setae, distal two anterior ventrolateral setae longer than proximalmost seta, posterior ventrolateral setae with median seta longer than distal seta which is in turn longer than proximal seta; tibia I with three pairs of anterior ventrolateral and posterior ventrolateral spinose setae, with distal setae longer than proximalmost seta in both anterior ventrolateral and posterior ventrolateral rows, hidden solenidion present distal to eupathidium at distal end of posterior dorsolateral row, with regressed seta k" immediately dorsal to solenidion; tarsus I with three pairs of anterior ventrolateral and posterior ventrolateral small spinose setae, anterior lateral solenidion present at 0.5 below distal anterior dorsolateral eupathidium, distal end of tarsus with three anterior lateral, one posterior dorsolateral and one posterior ventrolateral small solenidion, and one posterior lateral cone-shaped seta; claws unequal with anterior claw smaller. Femur II with two large anterior ventrolateral clavate setae (distal seta longer than proximal), one posterior ventrolateral short spinose seta at 0.5; genu II with two anterior ventrolateral spinose setae, two posterior ventrolateral small spinose setae; tibia II with four anterior ventrolateral spinose setae, five posterior ventrolateral small spinose setae, posterior dorsolateral distal hidden solenidion; tarsus II with five anterior ventrolateral and posterior ventrolateral small spinose setae, anterior lateral hidden solenidion at 0.5, distal end of tarsus with one anterior dorsolateral cone-shaped seta; claws unequal with anterior claw smaller. Femur III with two anterior ventrolateral clavate setae, one posterior ventrolateral small spinose seta; genu III with three anterior ventrolateral clavate setae, two posterior ventrolateral small spinose setae; tibia III with five anterior ventrolateral clavate setae, five posterior ventrolateral small spinose setae; tarsus III with four anterior ventrolateral and posterior ventrolateral spinose setae, distal end of tarsus with two ventral and one posterior lateral horn-shaped setae, one anterior dorsolateral spinose seta, elongate dorsal bothridial seta bt slightly behind distal anterior dorsolateral seta; claws subequal, anterior claw only slightly smaller. Femur IV with two anterior ventrolateral clavate setae, one posterior ventrolateral small spinose seta; genu IV with one anterior ventrolateral clavate seta, one posterior ventrolateral small spinose seta; tibia IV with five anterior ventrolateral and posterior ventrolateral spinose setae, one distal posterior lateral hidden solenidion; tarsus IV with four anterior ventrolateral and posterior ventrolateral spinose setae, distal end of tarsus with two ventral large cone-shaped setae, one posterior

Position of eupathidium marked with ζ; ’ marks position of hidden tibial solenidion; ω marks position of hidden tarsal solenidion; bt marks tarsal bothridium. The first visible ventrolateral spine is marked on each leg to facilitate orientation; v’ indicates the anterior ventrolateral row, v" indicates the posterior ventrolateral row.

lateral cone-shaped seta, elongate dorsal bothridial seta bt about halfway between level of third and fourth anterior dorsolateral setae.

Nymphal stages — Dorsal setation as for adult female. Genital and anal openings successively smaller and less sclerotised; fewer aggenital setae. Epimere I with four setae in tritonymph, three setae in deutonymph and protonymph. Enlarged ventrolateral leg setae similar to adult in tritonymph and deutonymph, though proximal anterior ventrolateral clavate seta on femur I successively smaller in each instar; protonymph leg I with one anterior ventrolateral and posterior ventrolateral large spinose seta on femur I; two anterior ventrolateral and one posterior ventrolateral large spinose seta on genu I; two anterior ventrolateral and two posterior ventrolateral large spinose setae on tibia I.

Variation — Variation in dorsal setation was very uncommon. A single tritonymph was observed with a second slightly smaller pair of setae Pp behind the usual pair on the aspidosomal sclerite. Two individuals were also observed in which the setal pair d2 was doubled (in one of these individuals, on one side only). Variation in ventral and leg setation was more common. At least one larger individual was found with five rather than four setae on epimere I; epimere setae could also vary noticeably in length, being short clavate in some individuals and more elongate in others. Dorsal leg setae could vary in number between individuals. Supernumerary accessory dorsal setae were not uncommon, but the number and arrangement of the larger ventral setae were mostly consistent with variants being very rare.

Comments — Compared to other species in Caeculidae (reviewed by Coineau, 1974a), Neocaeculus imperfectus is remarkable in the relative constancy of its setation between instars and can be described as a true neotenous form. Despite the observation of specimen numbers probably into the hundreds, no males have been identified, and the species is probably parthenogenetic.

Neocaeculus imperfectus can be assigned to Neocaeculus by the features given in the key to caeculid genera below. Among other Australasian species of Caeculidae , it differs from N. bornemisszai and N. knoepffleri in the shape of bo (globose-capitate vs brush-like and non-capitate; Coineau and Enns 1969). Neocaeculus imperfectus can be distinguished from N. luxtoni and Microcaeculus pica by the absence of the dorsal median accessory setae ds and es, and in the presence of large spinose setae on trochanter and femur I ( Coineau 1967a; Otto 1993). It differs from N. johnstoni and N. womersleyi in having femur I undivided ( Coineau 1974b).

Coineau (1974a) assigned two species from outside Australasia to Neocaeculus , the southern African N. lamorali and the South American N. bruchi (miscited by Coineau, 1974a, as ’ N. brucki ’). Both these species have, to date, received only brief descriptions, and potentially important features such as bothridial morphology remain undescribed for both. Neocaeculus lamorali may be distinguished from Australasian species by the presence of two pairs of setae Pp and the presence of paired setae instead of a single seta es ( Coineau, 1974a). The initial description of ’Caeculus’ bruchi by Berlese (1916) is probably inadequate for its identification, and it was listed as a species incertae sedis by Franz (1952). Coineau (1974a) referred to it as a Neocaeculus species without redescribing it in detail, commenting only on a single aspect of this species’ setal morphology. The distal setae er on the leg tarsi of N. bruchi are rounded, divergent from the tarsus, and enlarged to a diameter half that of the tarsus, rather than being flattened, distally directed, and relatively smaller in most other species ( Coineau, 1974a).

Figures

FIGURE 1: Neocaeculus imperfectus, idiosoma: A – photograph of dorsum; B – schematic drawing, with representative seta and lyrifissure labels; C – photograph of venter; D – schematic drawing (locations of smaller setae marked with black dot), with labels showing position of setae ag1 and adanal setae (ad), aggenital sclerite (AG) and pseudanal sclerite (PS).

FIGURE 2: Neocaeculus imperfectus, gnathosoma, lateral view: A – photograph; B – schematic drawing, with representative seta labels: eupathidia marked with asterisk (*), position of solenidion marked with ’.

FIGURE 3: Neocaeculus imperfectus, legs. A – Leg I in anterior dorsolateral view; B – Leg II in dorsal view; C – Leg III in anterior dorsolateral view; D – Leg IV in posterior dorsolateral view.