Phymatodesmus sakalava ( de Saussure & Zehntner, 1897 )

Wesener, Thomas, Akkari, Nesrine & Golovatch, Sergei I., 2025, Revision of the millipede family Dalodesmidae in Madagascar, with descriptions of two new Malagasy species of Dalodesmus Cook, 1896 (Diplopoda, Polydesmida), ZooKeys 1223, pp. 185-220 : 185-220

Phymatodesmus sakalava ( de Saussure & Zehntner, 1897)

Figs 1 , 2 , 3

Polydesmus sakalava de Saussure & Zehntner, 1897 : plate 5, fig. 22 (figure and caption only).

Polydesmus (Phymatodesmus) sakalava – de Saussure and Zehntner 1902: 95 (D).

Eutubercularium sakalava – Brölemann 1916: 605 (D); Hollier and Wesener 2017: 62 (L).

Dalodesmus sakalava – Jeekel 1965: 238 (L); Hoffman 1974: 230 (L); Golovatch and Hoffman 1989: 162 (L).

Phymatodesmus sakalava – Attems 1940: 490 (L); Enghoff 2003: 623 (L); Mesibov et al. 2018: 389 (N); Wesener and Enghoff 2022: 926 (L).

Dalodesmidae sp. – Spelzhausen et al., 2020: 4 (L).

Note.

As iterated above, the confusion de Saussure and Zehntner (1897, 1901, 1902) created by the initial usage of the specific epithet sakalava for two species of Polydesmus Latreille, 1761 has been resolved only recently ( Mesibov et al. 2018). While the original type locality of the species is unknown, Franz Sikora is known to have collected mainly around the capital, Antananarivo. The freshly collected male specimen comes from Andasibe ( Spelzhausen et al. 2020), one of the largest remaining blocks of natural vegetation, on the old way from the coast to the capital.

Material examined.

• ♀ holotype, fragmented ( MHNG), ‘ Madagascar’, coll. Sikora • 1 ♂, ZFMK MYR 12217 ; Madagascar, Moramanga District , Andasibe National Park (= Périnet), Analamazaotra Forest Station, secondary forest, Eucalyptus 1909 plantation, sifted leaf litter, IV. 2017, L. Spelzhausen and G. Rakotonirina leg.

Brief description.

(After de Saussure and Zehntner 1897, 1902.) A single line drawing (Fig. 1 G ) and its caption reading “ Polydesmus sakalava ” in de Saussure and Zehntner (1897) serve as the original description. Combined with a later verbal description of the adult ♀ holotype, by de Saussure and Zehntner (1902), the following relevant information can be obtained: body pale reddish, subcylindrical, 10 mm long, 1 mm wide, with a strongly convex dorsum and very narrow, declivous, and subrectangular paraterga.

Phymatodesmus s akalava can be readily distinguished from other known Malagasy Dalodesmidae : the small size, a subcylindrical body, the mostly small, conical, and sharp tuberculations on midbody metaterga arranged in four unusually regular transverse rows, and strikingly small, narrow, and rectangular paraterga.

First description of the male.

Length ca 10 mm, width of midbody pro- and metazona 0.75 and 1.05 mm, respectively.

Colouration (freshly preserved in ethanol) brown; prozona, basal parts of legs, mandibles, and paraprocts paler. Epicranium grey, antennae and apical parts of legs faded grey.

Body with 20 rings. Tegument mainly dull (Fig. 1 A – F ), microgranulate to microtuberculate throughout (Fig. 1 G, H ), even surfaces of prozona and of metazona below paraterga finely microgranulate, sterna granulate.

Head also densely microtuberculate or granulate throughout, micropilose; epicranial suture thin, but distinct; genae squarish, set off ventrally from gnathochilarial stipes by a small, but evident ridge. Interantennal isthmus ~ 2 × diameter of antennal socket (Fig. 1 C ).

Antennae very short and rather clavate, in situ reaching back past ring 2 when stretched dorsally, very densely setose and microgranulate. In length, antennomere 6> 5 = 3> 4> 2> 1 = 7; antennomere 6 the largest and the highest, antennomeres 5 and 6 each with a small, round, distodorsal knob, most likely beset with sensory cones.

In width, collum = head <ring 2> 3 = 4–16; thereafter body gradually tapering towards telson (Fig. 1 A – C ). Collum transversely suboval, regularly and broadly rounded laterally, densely tuberculate, most tuberculations being circular, evident, equipped with very short, mostly subclavate setae and arranged in 15–17 lateral, 8–9 transverse, rather irregular, arcuated rows. Metaterga 2–4 narrow, each with four, similar, transverse, arcuated, circular rows of setigerous tubercles, following metaterga each largely with five such rows (Fig. 2 A, B ). Paraterga short, rectangular, strongly declivous, posterior margin straight (Fig. 2 B, C ). Lateral margin of paraterga beset with 5–6 similarly circular, setigerous (Fig. 2 D ) tubercles / lobulations. Ozopores inconspicuous, opening laterally near penultimate lateral lobulation on pore-bearing rings 5, 7, 9, 10, 12, 13, 15–19. Strictures between pro- and metazona narrow and rather deep, nearly smooth (Fig. 2 E ).

Telson: Epiproct small, conical, and subtruncate at tip. Hypoproct trapeziform, with 1 + 1 setae borne on distinct oblong knobs at caudal margin. Paraprocts with 2 + 2 setae on triangular and projecting knobs (Fig. 2 C ).

Limbus very thin, small, and entire. Neither an axial line nor pleurosternal carinae (Fig. 1 A – C ). Posterior margin of metazona a row of dense, elongate, apically microdenticulate (with 6–9 indentations (Fig. 2 F ), subrectangular projections (Fig. 2 F )).

Gonopodal aperture roundly pentagonal, large, taking up ~ 2 / 3 width of metazonum 7, clearly open and drawn into metazonum 6 (Fig. 1 I ).

First two leg pairs shorter and thicker than other legs. Midbody legs incrassate, medium in length, as long as body height, with small, stout, abundant, and usually curved setae with admixture of sphaerotrichomes ventrally on all podomeres; gonopores on coxae 2 inconspicuous, prefemora not bulged laterally; claws simple, very small; in length, tarsus> femur> prefemur> coxa> tibia = postfemur.

Gonopods (Figs 1 I , 3 A – F ) relatively simple. Both coxite and prefemorite very short, fused medially, prefemorite setose. Femorites (fe) contiguous medially, densely setose both ventrally and laterally, rather stout (~ 2 × as long as acropodites), suberect and clearly flattened dorsoventrally. Acropodite tripartite, divided into a dorsomedial, long, simple and subsecuriform solenomere (sl), a simple and subspiniform lateral branch (lb), both sl and lb being subequal in length, but clearly shorter than the longest, simple, rather finger-shaped, apically roundly and irregularly trifid, mesal branch (mb).

Remarks.

Aside from the very obvious differences between Phymatodesmus and Dalodesmus in the development and shape of paraterga, clear-cut discrepancies also concern leg lengths (in Phymatodesmus , the whole legs, especially both postfemora and tibiae are shorter), the antennae are also shorter, the collum is as wide as the head, the head is completely micropilose, including the epicranium (vs glabrous in Dalodesmus ), the paraprocts of the telson lack triangular setiferous knobs / projections (vs 2 + 2 setae borne on knobs on the paraprocts), and the 1 + 1 setae on the hypoproct are borne on prominent knobs and better separated (vs placed closer to one another in Dalodesmus ).

Figures

Figure 1. Phymatodesmus sakalava (de Saussure & Zehntner, 1897), ♀ holotype MHNG (G, H), ♂ specimen (ZFMK MYR 12217). Multi-layer photographs and drawings A habitus, dorsal view B habitus, lateral view C habitus, ventral view D detail of midbody rings, dorsal view E detail of anterior body rings and gonopod, lateral view F detail of anterior rings and gonopods, ventral view G drawing from the original description in de Saussure and Zehntner (1897) H detail of body ring, ♀ holotype I gonopod still attached, ventral view. Abbreviations: lb = lateral branch; mb = mesal branch; sl = solenomere branch. Scale bar: 0.3 mm (H).

Figure 2. Phymatodesmus sakalava (de Saussure & Zehntner, 1897), ♂ specimen (ZFMK MYR 12217). SEM micrographs A midbody ring with pro- and metazonite, dorsal view B midbody ring, lateral view C midbody ring, paranota with ozopore D details of surface structures, dorsal view E detail of surface structures of prozonite and metazonite F endotergum. Scale bars: 100 µm (A – C); 10 µm (D); 20 µm (E); 10 µm (F).

Figure 3. Phymatodesmus sakalava (de Saussure & Zehntner, 1897), ♂ specimen (ZFMK MYR 12217). Multi-layered photographs and drawings, gonopod A posterior view B lateral and mesal view C lateral view D posterior view E anterior view F lateral view. Abbreviations: fe = femorite; lb = lateral branch; mb = mesal branch; sl = solenomere branch.