Siliquobolellus, Pimvichai & Enghoff & Panha & Backeljau, 2022

Pimvichai, Piyatida, Enghoff, Henrik, Panha, Somsak & Backeljau, Thierry, 2022, A new genus of Pseudospirobolellidae (Diplopoda, Spirobolida) from limestone karst areas in Thailand, with descriptions of three new species, Zoosystematics and Evolution 98 (2), pp. 313-326 : 313

Genus Siliquobolellus gen. nov.

Fig. 2

Etymology.

From Latin siliqua = pod, and referring to the podlike shape of the gonopod telopodite.

Type species.

Siliquobolellus prasankokae gen. et sp. nov.

Other included species.

Siliquobolellus amicusdraconis gen. et sp. nov. and Siliquobolellus constrictus gen. et sp. nov.

Diagnosis.

Siliquobolellus species are characterised by (1) the unique shape of the telopodital part of their posterior gonopod, which forms a deep concavity. In contrast, the telopodital part of the posterior gonopod is extremely slender and sickle-shaped in Pseudospirobolellus , does not form a deep concavity in Coxobolellus , or is slender with a broad apical canopy in Benoitolus ; (2) the telopodite of anterior gonopod (at) simple, directed distad, not reaching tip of coxal part of the anterior gonopod (cx). In contrast, the telopodite of anterior gonopod (at) is overreaching coxa in the other three genera; and (3) tip of anterior gonopod coxa narrowed, curving mesad. In contrast the tip of the anterior gonopod coxa directed distad in Coxobolellus , or is rounded in Pseudospirobolellus and Benoitolus .

General description.

Head capsule smooth. Occipital furrow extending down between, but not beyond eyes; clypeal furrow reaching level of antennal sockets. Area below antennal sockets and eyes impressed, forming part of antennal furrow. Incisura lateralis (IL) open (Fig. 2A ). 2+2 labral teeth, a row of labral setae, 3+3 supralabral setae. Diameter of eyes ca half of interocular space; 7 vertical rows of ommatidia, 4 horizontal rows, 24-26 ommatidia per eye. Antennae short, not reaching beyond collum when stretched back, accommodated in a shallow furrow composed of a horizontal segment in the head capsule and a vertical segment in the mandibular cardo and stipes. Antennomere lengths 2> 6> 1> 5> 3 = 4> 7 in Siliquobolellus amicusdraconis gen. et sp. nov. and S. constrictus gen. et sp. nov. and 2> 1> 6> 5> 3 = 4> 7 in S. prasankokae gen. et sp. nov.; antennomere 1 glabrous, 2 and 3 with some ventral setae, 4, 5 and 6 densely setose; 4 apical sensilla. Mandibles: stipes (Mst) broad at base, apically gradually narrowed, triangular. Gnathochilarium (Fig. 2B ): each stipe (Gst) with 3 apical setae; each lamella lingualis with 2 setae, one behind the other. Basal part of mentum (Me) transversely wrinkled; basal part of stipites longitudinally wrinkled.

Collum smooth, with a marginal furrow along lateral part of anterior margin; lateral lobes narrowly rounded, extending as far ventrad as the ventral margin of body ring 2.

Body rings 2-3 ventrally concave, hence with distinct ventrolateral “corners”. Body rings very smooth, parallel-sided in dorsal view. Prozona smooth. ‘Tergo-pleural’ suture visible on pro- and mesozona; mesozona ventrally with fine oblique striae, dorsally punctate; metazona ventrally with fine longitudinal striae, otherwise smooth. “Pleural” parts of rings with fine oblique striae. Sterna transversely striate. Ozopores from ring 6, situated in mesozona, ~1/2 pore diameter in front of metazona.

Telson smooth; preanal ring (Pre) with slightly recurved dorsal profile, with short process protruding to vertical tangent to anal valves or slightly beyond (Fig. 2C-E ). Anal valves (Av) smooth, rounded (Fig. 2C-E ). Subanal scale (Sub) broadly triangular (Fig. 2F ).

Legs (Fig. 2G, H ): length of midbody legs 55-60% of body diameter in males, 40-48% of body diameter in females. Prefemur basally constricted and longer than other podomeres. First and second legs with 2 or 3 prefemoral, 2 or 3 femoral, 2 or 3 postfemoral, and 2-4 tibial setae, and 4 or 5 ventral and 1 dorsal apical setae on tarsi, numbers of setae reaching constancy from pair 3: in males each podomere from postfemur to tibia with 1 seta; tarsi with 1ventral apical and 1 dorsal apical seta; in females each leg podomere from coxae to tibia with 1 seta, tarsi with 1-3 ventral and 1 dorsal apical setae. Claw slender and sharp.

Male sexual characters. Apical part of coxa and entire ventral surface of prefemur from third to the last body rings with large ventral soft pad. Body ring 7 entirely fused ventrally, no trace of a suture. Tip of anterior gonopods visible when the animal is stretched out (not when it is rolled up).

Anterior gonopods (Figs 3 - 5A, B, D, E ) with a fairly small triangular mesal sternal process (st). Coxa broad at base, apically gradually narrowed, curving mesad, posterior surface folding over telopodite, for accommodation of telopodite. Telopodite gradually narrowed towards tip, directed distad, not reaching tip of anterior gonopod coxa (cx).

Posterior gonopods (Figs 3 - 5C, F ) simple, rounded, with short, smooth coxal part (pcx); with prominent opening of efferent groove (oeg) distomesally of pcx; telopodital part (pt) twice the length of the pcx, lateral margin folding mesad, forming a deep concavity.

Female vulvae (Figs 3L , 4K , 5K ) simple, valves prominent.

Species descriptions

Figures

Figure 2. External morphology of Siliquobolellus gen. nov. A - C. S. amicusdraconis gen. et sp. nov. A. Head, lateral view; B. Head, ventral view; C. Posterior end, lateral view; D. Posterior end, lateral view (S. prasankokae gen. et sp. nov.); E. Posterior end, lateral view (S. constrictus gen. et sp. nov.); F-I. S. prasankokae gen. et sp. nov.; F. Posterior end, ventral view; G, H. Male leg, latero-ventral view; I. Body rings, dorsal colour pattern; J. S. constrictus gen. et sp. nov., body rings, dorsal colour pattern. Av = anal valves; Gst = gnathochilarial stipes; IL = incisura lateralis Me = mentum; Mst = Mandibular stipes; Pre = preanal ring; Sub = subanal scale.

Figure 3. Siliquobolellus amicusdraconis gen. et sp. nov., holotype, gonopods (specimen from Hub Pa Tard, CUMZ-D 00149 - 1). A. Anterior gonopod, anterior view; B. Anterior gonopod, posterior view, arrow indicates a thumb-like process; C. Right posterior gonopod, lateral view; D. Anterior gonopod, anterior view; E. Anterior gonopod, posterior view; F. Right posterior gonopod, lateral view; G. SEM, Right posterior gonopod, latero-mesal view; H. SEM, Mesal part of right posterior gonopod, lateral view; I. SEM, Right posterior gonopod, latero-mesal view; J. SEM, Tip of right posterior gonopod, latero-mesal view, arrow indicates a canopy; K. SEM, lateral part of pt, latero-mesal view; L. SEM, left female vulva, posterior mesal view. at = anterior gonopod telopodite; cx = coxa; oeg = opening of efferent groove; op = operculum of vulva; pcx = coxal part of the posterior gonopod telopodite; pt = telopodital part of the posterior gonopod telopodite; st = sternal process.

Figure 4. Siliquobolellus constrictus gen. et sp. nov., holotype, gonopods (specimen from Ban Yang Chum, CUMZ-D 00150 - 1). A. Anterior gonopod, anterior view; B. Anterior gonopod, posterior view, arrow indicates a thumb-like process, with longitudinal ridge; C. Right posterior gonopod, lateral view; D. Anterior gonopod, anterior view; E. Anterior gonopod, posterior view; F. Right posterior gonopod, lateral view; G. SEM, Left posterior gonopod, lateral view; H. SEM, Left posterior gonopod, latero-mesal view; I. SEM, tip of left posterior gonopod, latero-mesal view; J. SEM, Mesal part of left posterior gonopod, lateral view; K. SEM, left female vulva, posterior mesal view. at = anterior gonopod telopodite; cx = coxa; oeg = opening of efferent groove; op = operculum of vulva; pcx = coxal part of the posterior gonopod telopodite; pt = telopodital part of the posterior gonopod telopodite; st = sternal process.

Figure 5. Siliquobolellus prasankokae gen. et sp. nov., holotype, gonopods (specimen from Pha Thai, CUMZ-D 00148 - 1). A. Anterior gonopod, anterior view; B. Anterior gonopod, posterior view, arrow indicates a a thumb-like process with strong ridge distomesally; C. Right posterior gonopod, lateral view, arrow indicates a short, sharp protrusion; D. Anterior gonopod, anterior view; E. Anterior gonopod, posterior view; F. Right posterior gonopod, lateral view; G. SEM, Right posterior gonopod, lateral view, arrow indicates a short, sharp protrusion; H. SEM, Mesal part of right posterior gonopod, lateral view; I. SEM, Right posterior gonopod, mesal view, arrow indicates a canopy; J. SEM, Tip of right posterior gonopod, mesal view; K. SEM, left female vulva, posterior mesal view. at = anterior gonopod telopodite; cx = coxa; oeg = opening of efferent groove; op = operculum of vulva; pcx = coxal part of the posterior gonopod telopodite; pt = telopodital part of the posterior gonopod telopodite; st = sternal process.