Pseudachorutes morulifer Babenko & Nakamori, 2021

Babenko, Anatoly, Kuznetsova, Natalia, Nakamori, Taizo & Shveenkova, Yulia, 2021, A review of Pseudachorutes Tullberg, 1871 (Collembola, Neanuridae) from the East Asia, with description of six new species, Zootaxa 4938 (4), pp. 351-391 : 366-368

Pseudachorutes morulifer Babenko & Nakamori sp. nov.

Figs 47–52 , Table 1

Type material. Japan: holotype, female, Honshu Island, near Nara, Nara Park (forest-park), debris on river bed, 34°41.17’ N 135°51.42’ E, 25 August 2016 , N. Kuznetsova leg. [ MSPU collection]. Paratypes, 2 females and 1 male, Kyushu Island, Miyazaki Prefecture, Ohkawauchi, Shiiba Village , «Mt. Tsunodake», Yatate , 32°22.25’N 131°5.13’E, ~ 1200 m alt., shadow beech forest, rotten wood, 05 August 2016 ; 1 female, same area, but Cryptomeria plantation; 1 male, same area, but « Maruju », mixed forest on slope, litter, 04 August 2016. All T. Nakamori, S. Saitoh, M. Potapov & N. Kuznetsova leg. [3 ind.–– MSPU collection, 2 ind.–– TRPM collection]

Diagnosis. Medium sized species. Ant. IV with clear «ventral file». PAO with complex lobes divided into several branches. Main part of labium with 3 proximal setae, seta L and two organites, both its basomedial and basolateral parts with 4 setae. Mandibles with four strong apical teeth. Dorsal chaetotaxy with short ordinary setae and usual number of long differentiated sensilla, head with both a0 and d0, Th. I with 4+4 setae, Th.II–III with 4 ordinary setae (a3, a4, m4 and p4) in dorso-external group additionally to S, Abd. I–III with 4+4 p-setae between sensilla. Mucro with basal «swelling». Each anal valve with 3 hr-setae.

Description. Habitus typical of genus, rather wide and somewhat flattened ( Fig. 47 ). Length of adults (without antennae) from 0.85 to 1.38 mm. Colour unknown (only cleared specimens available). Tegument granulation rather coarse, especially on Abd. VI.

Antennae slightly shorter than head, Ant. III–IV fused dorsally, ventral separation well marked. Ant. IV with trilobed apical vesicle, external ms, subapical or and seta i present; sensilla (S1–S4, S7–S8) on dorsal side of Ant. IV clearly differentiated, S1 and S2 somewhat slender, ventral side with about 30 truncate or slightly clavate sensilliform setae around longer one. Antennal organ of Ant. III typical, inner sensilla small, inclined to one side and located in cuticular fold, sgv only slightly longer than sgd, ventral ms present. Ant. I–II with 7 and 12–13 setae, respectively.

Head with 8+8 subequal ocelli. PAO elliptic, consisting of 10–14 compound vesicles, divided into 2–6 branches, ratio of its longer diameter to ocellus B as 1.4–1.6: 1 ( Figs 51–52 ). Buccal cone elongated ( Fig. 48 ). Maxilla styliform, with several tiny apical teeth ( Fig. 50 ), number of lamellae uncertain. Mandible triangular at apex with four strong teeth ( Fig. 49 ). Distal edge of labrum truncate, number of labral setae as: 4/2334. Main part of labium with three proximal ordinary setae, seta L and two small labial organites ( Fig. 48 ); submentum and mentum with usual set of four setae each, i.e. 4+4. Perilabial area with 5+5 setae.

Dorsal setae short and smooth, sensilla clearly longer, about as 2.5–3.5 times longer than ordinary setae, their number as usual: 22/1111. Chaetotaxy stable, asymmetrical abnormalities not frequent ( Fig. 47 ). Main characteristics: head with both a0 and d0 present, Th. I with 4+4 setae, Th. II with a2-seta and lateral ms present, dorso-external group with three setae (a3–a4, m4) in front of p3–p4. Th. III identical but without a2 and ms. Abd. I–III with 1+1 extra setae in p-row between sensilla p4, i.e. 4+4 p-setae, totally, and 3 setae (a3, m3–m4) in front of p3–p3’–p 4 in dorso-external group. Abd. IV with more setae in a-row, some m-setae laterally, extra p-seta between sensilla present or absent. Abd. V without p2 as usual.

Thoracic sterna without setae. Ventral tube with 4+4 setae, no seta on sternum of Abd. I, Abd. II with 5(6)+5 sternal setae, Abd. III with 10–13 such setae on each side. Tenaculum with 3+3 teeth as usual. Furca complete, manubrium with 10+10 setae on main part, 4 setae on each basolateral lobe and 2 basal setae in line. Dorsal side of dens with six setae, hyaline field on its ventral side about as large as mucro length. Mucro curved, lateral lamella high but short forming basal «swelling». Each anal valve with three tiny hr-setae.

Legs I–III with typical number of setae: 1, 2, 2 setae on upper subcoxae, 0, 3, 2–3 setae on lower subcoxae, 3, 7–8, 7–8 setae on coxae, 6, 6, 6 on trochanters, 13, 12, 11 setae on femora and 19, 19, 18 setae on tibiotarsi. Unguis with strong basal tooth on inner edge, lateral teeth invisible.

Etymology. The name of the new species reflects its most characteristic feature—the morula-like shape of its PAO.

Affinities. The new species possess two unique characters, which are very rare for the genus, namely, compound vesicles in the PAO and 4+4 setae of the p-row between sensilla on Abd. I–III. The only other known congener shared both these characters is P. prosimplex Weiner & Najt, 1985 described from North Korea. The difference of these two forms is limited by the shape of the mandibles: P. morulifer sp. nov. has 4, but not 2 mandibular teeth as described for Korean type of P. prosimplex . Initially we believed that our Japanese specimens are conspecific to the true P. prosimplex and two additional teeth on mandibles have been missed during the original description. Fortunately, the holotype of P. prosimplex is still kept in the ISEA collection ( Poland) and was studied again by W.M. Weiner and G. Paśnik at our request. This study unambiguously confirmed the correctness of the initial description of the mandibular shape in P. prosimplex (W.M. Weiner, person. comm.). Thus, despite the obvious close relationship between P. prosimplex and P. morulifer sp. nov., they may well be considered independent species, at least until the variability of this usually very stable structure is established.

It should also be noted that this study revealed additional similarities between these two species. In particular, chaetotaxy of Abd. IV in P. prosimplex appeared to be more usual and devoid of setae m1 (as in P. morulifer sp. nov. and contrary to fig 15A in Weiner & Najt 1985), sensilla S1 and S2 on Ant. IV in both species are slender than S3 and S4 and both species have three hr-setae on each anal valve.

There is another species in the fauna of Japan, namely P. insularis Yosii, 1965 , whose PAO is comparable to those of P. prosimplex and P. morulifer sp. nov. It has been described as being composed of ca. 16 peripheral and 20 central elements, and, judging from the fig.5 G & H in Yosii (1965), is similar in general appearance to that of P. morulifer sp. nov. According to existed descriptions, there are many formal differences between P. insularis and P. morulifer sp. nov. (and P. prosimplex as well). Pseudachorutes insularis is smaller (0.6 mm vs 0.9–1.4 mm in P. morulifer sp. nov.), appears to have no ventral file on Ant. IV, its mandibles have only two teeth as in P. prosimplex, VT with 2+2 setae, only 3+3 setae on Th. I present, some other peculiarities in chaetotaxy also exist. However, most of these differences can be related to the size/age of the types or be a result of misinterpretation. In fact, P. morulifer sp. nov. may probably be a junior synonym for P. insularis , but this assumption is difficult to prove or disprove without studying the types of the latter species. Unfortunately, we could not find them.

Distribution. The species is known only from two Japanese Islands: Honshu and Kyushu.

Figures

FIGURES 47–52. Pseudachorutes morulifer sp. nov.: 47, dorsal chaetotaxy; 48, labium; 49, mandible; 50, maxillae; 51–52, PAO. Scales: Figs 47–48 = 0.1 mm, 49–52 = 0.01 mm.