Plutomurus shurubumuensis Barjadze, Jordana & Soto-Adames, 2018

Barjadze, Shalva, Jordana, Rafael, Baquero, Enrique, Giordano, Rosanna & Soto-Adames, Felipe N., 2018, Two new species of Plutomurus Yosii (Collembola, Tomoceridae) from the Caucasus, Zootaxa 4526 (1), pp. 29-40 : 32-36

Plutomurus shurubumuensis Barjadze, Jordana & Soto-Adames sp. nov.

Figs 4–22

Type locality. GEORGIA, Samegrelo– – Zemo Svaneti region , Chkhorotsku district , 3 km from Mukhuri , Migaria karst massif, Shurubumu Cave, 4239'5.71"N, 4213'44.58"E, 464 m alt .

Type material. Holotype, female on slide: dark zone, 03.x.2014, leg. Sh. Barjadze (code GEOShu20141003– 04). Paratypes (same data as holotype): four females on slides (code GEOShu20141003–01, 02, 03 and 05). Three specimens mounted on SEM stubs (GEOShu20141003–06, 07 and 08). Seven specimens in ethyl alcohol (GEOShu20141003–09–15); Paratypes (same data as holotype but 28.ix.2017) one male (GEOShu20170428–01) and one female (GEOShu20170428–02) on slides, leg. Sh. Barjadze ; three additional females with same date as holotype but 28.ix.2017, leg. Sh. Barjadze. Holotype and paratypes 01, 02, 06, 07 and 08 deposited at MZNA ; paratypes GEOShu20141003–03 and 05, GEOShu2017040328–01 and 02 deposited at IZISU; 3 female paratypes deposited at FSCA ( N105–107 ) .

Description. Body length up to 3.36 mm, excluding antennae and furcula.

Color pattern. Habitus and grey pigment distribution as in P. pichkhaiai sp. nov. ( Fig. 23 ).

Scale distribution. Dorsally on Ant. I–II, head, body, all legs segments, both faces of collophore and ventral face of furcula. Postlabial region of head with few or no scales.

Head. Ratio body length to antennae length up to 1.09. Number of eyes unclear, apparently 6, but all cornea reduced and actual number difficult to determine in most specimens; under light microscope eye number appears to vary from 3 to 6, whereas the single individual evaluated using SEM clearly shows 6 eyes ( Fig. 4 ). Head dorsally ( Fig. 7 ) with one unpaired (A 0), and 6 (7) paired Mc: 2 anterior (A 2, A 3), 2 interocular (Ps 2, Ps 3) and 2(3) postocular ((Pa 2), Pa 3, Pa 5) (supplementary Mc represented by dotted line in Fig. 7 ). Prelabral and labral chaetae smooth ( Fig. 11 ): prelabral chaetae 6 (3+3); labrum with 554 papillate chaetae as typical for genus; distal margin of labrum with 4 elongate, thin-walled, curved papillae. Outer maxillary lobe trifurcate ( Fig. 12 ), basal chaetae shorter than apical process; sublobal plate with 4 processes each one resting on a short papilla. Sclerotized head of maxilla ( Fig. 13 ) with 3 large and 1 small teeth; maxillary lamella 1 ( Fig. 6 ) evidently longer and more slender than others, with a small posterior basal brush and better developed anterior medial brush, ventral margin with long cilia; lamella 2 ( Fig. 6 ), and 4 (not shown) wide, densely covered with denticles and hooks; lamella 3 ( Fig. 6 ) short, somewhat ellipsoidal, with cilia regularly distributed along its entire margin; lamella 5 ( Fig. 14 ), sinuous but variable in shape, basal beard absent (i.e., prostheca not developed); lamella 6 narrow, comb-shaped, with short processes ( Fig. 15 ). Labial papilla E with 6 guard processes; lateral modified process thin-walled, tapering and surpassing tip of papilla ( Fig. 16 inset). Labium with 16–17 proximal chaetae ( Fig. 16 ). Basomedial field (i.e., labial triangle) without scales, with 22–23 smooth chaetae; basolateral field with 5 chaetae (A3–A5 and L1–L2), chaetae on anterior row slightly longer than those on posterior row.

Body. Dorsal bothriotrichal formula 2,1//0,0,1,2,0 ( Figs 8–9 ). Dorsal Mc formula 4,2//3,3,4,1(2),4 ( Figs 8–10 ). Thorax macrochaetotaxy as in Fig. 8 : Th. II with 2 medial and 2 posterior Mc; Th. III with 2 posterior Mc. Abdominal macrochaetotaxy as in Figs 9–10 : Abd. I– –II each with 3 posterior Mc; Abd. III with 2 anterior and 2 posterior Mc as typical for genus; Abd. IV with 7 enlarged chaetae (labeled 1–7 in Figs 9–10 ), chaeta N7 always largest Mc, chaeta N2 a small Mc in 1 out of 6 individuals examined, all other differentiated posterior chaetae clearly enlarged, but sockets always small, mesochaeta-like; Abd. V with 4 posterior Mc, 1 additional lateral Mc always present, but often hidden by slide mounting induced deformation of cuticle, and segment appears as having 4 Mc.

Legs. Hind legs with well-developed trochanteral (18–35 chaetae) and femoral organs (20–44 chaetae) (n=9) ( Fig. 17 ). Posterior face of hind tibiotarsus with 2 outstanding pointed spine-like chaetae, one basal and one distal, resulting in a 002 tibiotarsal spine formula ( Fig. 20 ). Tenent hair acuminated, thinner and shorter than flanking chaetae, and inserted in a well-developed depression ( Fig. 18 ). Ratio hind unguis: unguiculus: tenent hair as 1.54– 3.55: 0.92–2.48: 1 (n=11). Inner edge of unguis on all legs with one minute proximal unpaired tooth (a in Figs 5 and 18 ), and 1 larger distal unpaired tooth (b in Figs 5 and 18 ). Unguis with lateral teeth 0.42–0.86 as long as length of inner edge (n=9), reaching proximal minute inner tooth. Unguiculus lanceolate, tapered, with 2 internal lamellae bearing 0–6 teeth ( Fig. 18 ).

Collophore. Anterior, posterior and distal faces with 27, 45 and ca. 65 smooth chaetae, respectively.

Tenaculum. Corpus with 1 smooth chaeta; rami with 4 + 4 teeth ( Fig 19 ).

Furcula. Ratio manubrium: dens: mucro as 3.83–6.00: 4.80–8.75: 1 (n=8, including holotype). Outer margin of basal segment of dens with 3(4) apically acuminate macrochaetae, distal macrochaeta largest, proximal shortest ( Fig. 22 ). Inner edge of dens basally with well differentiated spine-like chaetae; spines on basal segment of dens forming 2–3 short and poorly organized rows, upper row usually formed by 2 large, well-differentiated spines; spines on distal segment forming a single row extending distally between 35–43% of dens length; 3 proximal spines always small, terminal spine always largest in row; with long spines intercalated between short spines ( Fig. 22 ), but always with at least 2 (sometimes 3) distinctly larger distal spines; total dental spines formula variable as 9–13 II–IV /10–13 III–IV. Mucro with 2 proximal and 2 distal teeth (202 formula): proximal teeth fused throughout most of their length, separated only at tip. ( Fig. 21 ).

Variation. The actual number of eyes is difficult to ascertain using light microscope preparations. The dorsal cephalic and Abd. IV chaetotaxies are variable: one individual has three posterior Mc on the head instead of the two normal Mc; several individuals have a distinctly enlarged dorsal posterior chaeta N2 on Abd. IV. The number of teeth on the inner lamellae of the unguiculus varies from 0 to 6. The total number of dental spines also varies as reported above. Ratio of unguis III: unguiculus III: tenent hair and ratio of manubrium: dens: mucro are variable characters.

Discussion. Among members of the genus Plutomurus , only P. shurubumuensis sp. nov. has eyes, 3+3 prelabral chaetae, 2 spines on the inner edge of metathoracic legs, and 1 (sometimes 2) posterior Mc on Abd. IV. The new species is most similar to P. pichkhaiai sp. nov., and P. kelasuricus . The new species differs from P. pichkhaiai sp. nov., in the number of posterior Mc on Abd. IV (1–2 in P. shurubumuensis sp. nov., 3 in P. pichkhaiai sp. nov.) a p-distance of at least 13.7% in the 3’ half of the COI mitochondrial gene, which results in reciprocally exclusive monophyletic sister groups in a Bayesian analysis (cf. Barjadze et al. 2016), and in that they occupy different cave formations (see Materials & Methods) isolated by a fault. From P. kelasuricus the new species differs in having 2 inner spine–like chaetae on the inner edge of the hind tibiotarsus (only 1 in P. kelasuricus ) and in occupying different, isolated cave formations separated by a geographic distance of nearly a 100 km ( Fig. 1 ).

Plutomurus shurubumuensis sp. nov. is also very similar to P. revazi , which has a capitate tenent hair (acuminate in the new species), and 5 (medial and posterior), 3 Mc on Th. II and Abd. V, respectively (4, 4 Mc in the new species). All other seven species of Plutomurus with 3+3 prelabral chaetae ( P. ehimensis Yosii, 1956 , P. eristoi , P. gul ( Yosii, 1966) , P. grahami , P. iwatensis Yoshii, 1991 , P. kawasawai Yosii, 1956 , and P. ortobalaganensis ) are blind and easily distinguished from P. shurubumuensis sp. nov.

Etymology. The species is named after the cave in which it was collected.

Ecology. The body and eye patch pigmentation, together with the thick, toothed unguis suggest this is a troglophilous species. The small number and size of the inner ungual teeth and presence of an acuminate tenent hair place it in the early stages of troglomorphy.

Figures

FIGURE 1. Distribution of Plutomurus species reported from Georgia.

FIGURE 23. Plutomurus pichkhaiai sp. nov. Habitus, from Letsurtsume Cave (bar: 0.5mm).

FIGURES 4–6. Plutomurus shurubumuensis sp. nov. 4, Right eye patch (bar: 0.04 mm); 5, Hind unguis. a: basal tooth; b: distal tooth (bar: 0.006 mm); 6, Maxilla, showing lamellae N1, N2 and N3 (bar: 0.02 mm).

FIGURE 7–10. Generalized maps of dorsal chaetotaxy in Plutomurus shurubumuensis sp. nov.: 7, Head macrochaetae. A: Anterior; B: interocular; C: postocular; 8, Thoracic segments II–III, mesothoracic collar omitted; 9, Abdominal segments I–V, arrow points at element transformed into macrochaeta in one paratype; 10, Detail of differentiated chaetae on abdominal segment IV. Large black circle represents macrochaeta; empty circles represent mesochaetae; hatched circle (chaeta N2) represents variable meso– or macrochaeta; squares with circles represent bothriothricha; circles with a slash represent pseudopores.

FIGURES 11–22. Plutomurus shurubumuensis sp. nov. 11, Labrum and prelabral chaetae (bar: 0.04 mm); 12, Outer lobe of maxillary palp (bar: 0.02 mm); 13, Sclerotized portion of maxillary head (bar: 0.02 mm); 14, Maxillary Lamella N5 (bar: 0.01 mm); 15, Maxillary Lamella N6 (bar: 0.01 mm); 16, Labial palp (bar: 0.02 mm); 17, Trochanteral and femoral organs (bar: 0.06 mm); 18, Hind claw complex (bar: 0.02 mm); 19, Tenaculum (bar: 0.06 mm); 20, Hind tibiotarsus, showing location of spinelike chaetae (bar: 0.06 mm); 21, Mucro without chaetae and chaetal sockets (bar: 0.025 mm); 22, Dental spines (bar: 0.05 mm).