The first blind spirostreptid millipede, found in a cave in Morocco; with notes on the genus Odontostreptus Attems, 1914 (Diplopoda, Spirostreptida, Spirostreptidae)

. The first eyeless species of the suborder Spirostreptidea, Odontostreptus fadriquei sp. nov., is described from a cave in Morocco. The new species, which exhibits some troglomorphic traits, is compared with the highly variable O. maroccanus (Attems, 1914) of which new material is presented. The first blind spirostreptid millipede, found in a cave in Morocco; with notes on the genus Odontostreptus Attems, 1914 (Diplopoda, Spirostreptida, Spirostreptidae).


Introduction
Millipedes of the family Spirostreptidae have frequently been found in caves, but with one exception, they do not present troglomorphisms (Krabbe 1982: 81). The exception is Orthoporus kiemi Loomis, 1962, described from a cave in the Yucatan Peninsula, Mexico.
The family Spirostreptidae counts around 275 described species of medium-sized to very large millipedes. They are distributed mainly in the Afrotropical (including Madagascar) and Neotropical regions, with a few marginal occurrences in southern North America, North Africa and the Middle East (Enghoff et al. 2015). Two genera of Spirostreptidae occur in the southernmost fringe of the Palaearctic subregion: Archispirostreptus Silvestri, a mainly Afrotropical genus, is represented by A. syriacus (Saussure, 1859) in Israel, Syria, and the Arabian Peninsula, and (stretching the delimitation of the Palaearctic) by A. lugubris (Brölemann, 1901) ssp. villiersi (Schubart, 1951) in the Aïr Mts in Sahara (Mwabvu et al. 2010); in addition, fragments of an unidentified species of Archispirostreptus have been found in Libya (Enghoff & Van Neer submitted). In the western part of North Africa, in Morocco, spirostreptids of the genus Odontostreptus Attems, 1014, are not uncommon. Odontostreptus currently includes 13 species, most of which occur in Central and Western Africa, but O. maroccanus (Attems, 1914)

R e s e a r c h a r t i c l e
urn:lsid:zoobank.org:pub:C439FA30-349D-44FC-9600-87E62F87E7AD (Verhoeff, 1938) are restricted to Morocco (Krabbe 1982), isolated from their congeners by the Sahara desert. Here

Material and methods
Specimens were obtained from the collection of the Zoological Museum of Barcelona (MZB) and the Natural History Museum of Denmark (NHMD, formerly ZMUC).
Specimens were examined under a binocular stereo microscope Leica M165C, and measurements were made with the software Leica Application Suite ver. 4.12. Habitus were photographed with a Cannon 6D equipped with a macrolens. The gonopods were dissected and mounted on temporary slides in lactic acid or glycerine for study under light microscopy in a Leica DM2500 microscope. For scanning electron microscopy (SEM) specimens were mounted on aluminium stubs, coated for 110 seconds with platinum/ palladium, and studied in a JEOL JSM-6335F microscope. The background of some SEM images was processed with Adobe Photoshop CS6. Genus Odontostreptus Attems, 1914 Diagnosis (based on Krabbe 1982) Differs from other genera of Spirostreptidae by having a gonopod telopodite with an antetorsal process and a terminal, large, ladle-like lamella protecting an unbranched solenomere, in combination with having a simple gonopod coxal metaplica without terminal lamellae, moderately developed prefemoral processes on the first pair of male legs, a dorsally smooth preanal ring, and body rings without longitudinal keels.

Class
Of the 13 included species (Krabbe 1982), two are restricted to Morocco, viz., O. maroccanus (Attems, 1914) and O. lepineyi (Verhoeff, 1938). The latter is very poorly known; it was described from a female and according to Schubart (1960) may be a synonym of O. maroccanus tidsiaccola. In contrast, O. maroccanus has been collected frequently. In its present concept it is quite a variable species; the following forms have been described: -O. maroccanus tidsiaccola (Brolemann, 1928) -O. maroccanus ahmedensis (Brolemann, 1928) -a form of ahmedensis with particularly many body rings (Schubart 1960) -a form of ahmedensis ("Rif-Form") with ozopores on body ring 5 (Schubart 1960) Schubart (1952Schubart ( , 1960 considered the possibility that ahmedensis could be a separate species. We here present some notes and illustrations of O. maroccanus s. lat., but a clarification must await a study of a much more comprehensive material. On the other hand, we are confident in describing the new eyeless Odontostreptus as a separate species. Colour. Uniform pale yellowish-whitish, faint dark shadows posteriorly on some metazonites.
Body ringS. Very faintly constricted between pro-and metazonite. Prozonites without concentric furrows; metazonites dorsally smooth, laterally (from well above ozopores) and ventrally with regular, fairly dense longitudinal striae. Ozopores starting on body ring 6, situated ca in middle of metazonites.
oTHer nonSexual CHaraCTerS. As in male, except for relatively shorter appendages.

Remarks
On the head, antennae and legs of both specimens, thalli of a very conspicuous amphoromorph fungus were seen (Fig. 1E), similar to those reported from other species of millipedes by Enghoff & Reboleira (2017).

Descriptive notes
The studied specimens show a great deal of variation in size, colour, and sculpture. Thus, the specimens in samples NHMD 52999 and 53000 lack prozonital ring furrows (character of ssp. tidsiaccola), and the ones in samples NHMD 53001 and NHMD 53002 have the metazonites clearly vaulted and deeply furrowed even dorsally (character of ssp. ahmedensis). Figure 3 indicates the colour variation (the difference does not seem to be due to preservation), and Figs 4-5 show gonopods of two males, illustrating the variation in, e.g., the distal margin of the proplica (pp) and the shape of the lateral metaplical process (lap).

Discussion
Odontostreptus fadriquei sp. nov. shows some troglomorphic characters, notably lack of eyes and pigment. Compared to other spirostreptids, the only other known troglomorphic spirostreptid, Orthoporus kiemi Loomis, 1962, is paler ("nearly white throughout, the only exception being an internal dark spot beneath each pore, doubtless the repugnatorial gland") has smaller eyes, and longer legs (leg span 13 mm, compared with body width 4.5 mm) (Loomis 1962 The presence of two apodous rings in front of the telson in the holotype is noteworthy. In Spirostreptidae as a rule, there are no such apodous rings, even in larger juveniles, meaning that the full number of body rings is attained before maturity is achieved, a process known as hemianamorphosis, cf. Enghoff et al. (1993). The holotype of O. fadriquei sp. nov., although mature, thus has retained the potential of adding further body rings, but the significance of this cannot be assessed. (Attems, 1914). A. ♀ from the Asni area (NHMD 52994). B-C. ♂, from 10 km before Ouzzane (NHMD 53001). Scale bars = 5 mm.   Schubart 1960). The variation in the gonopods is apparently uncorrelated with the non-gonopodal characters. Neither Brolemann (1928) nor Schubart (1960) found useful differences between maroccanus s. str., tidsiaccola and ahmedensis in gonopod characters, and the material we have seen supports the conclusion of these authors. The Moroccan Odontostreptus definitely invite a comprehensive analysis which will presumably lead to the recognition of several species, in addition to O. maroccanus and O. fadriquei sp. nov.