Rickia obelostrepti Santam., Enghoff, & Reboleira, 2016

Santamaria, Sergi, Enghoff, Henrik & Reboleira, Ana Sofia P. S., 2016, Hidden biodiversity revealed by collections-based research-Laboulbeniales in millipedes: genus Rickia, Phytotaxa 243 (2), pp. 101-127 : 114

Rickia obelostrepti Santam., Enghoff, & Reboleira , sp. nov. (Figs 30–35)

Mycobank MB 815406

Diagnosis:—Receptacle triseriate, a: 3, m: 1(–3), p: 1–2 (+ 5 of lateral branch). Posterior series extending in a free, lateral branch of 5 cells. Antheridia always paired and only on immature thalli. Perithecial apex with two protuberant lobes and two short lips. Dark brown color only in foot and septa separating the appendiculate cells from appendages and antheridia.

Type: — TANZANIA. Uluguru Mts, Lupanga East, on Obelostreptus cf. proximospinosus Krabbe, 1983 ( Spirostreptida , Spirostreptidae ), 19 July 1981, M. Stoltze & N. Scharff leg., C-F-95087, C-F!, holotype designated here; BCB-SS ·E579bc, BCB!, isotypes designated here.

Etymology:— obelostrepti , referring to the host.

Thallus hyaline except for the dark brown foot and the septa separating the appendiculate cells from appendages and antheridia. Total length 172–204 μm. Receptacle triseriate. Basal cell 2–3 times as long as broad. The basal cell borders distally on the two lower cells of the marginal series or only to the lower cell of the anterior series.

Anterior series consisting of 3 superposed cells (Fig. 35). Cell a 3 developing the perithecium, bearing a big appendiculate cell and a secondary appendage; in immature thalli this cell gives rise to a set of paired antheridia together with the appendiculate cell. Exceptionally cell a 2 supports a group of paired antheridia, and the cell a 1, one appendage.

Median series consisting of 1(–3) cells, not bearing any appendage, antheridia or perithecial initial.

Posterior series consisting of a basal part with 1–2 cells, extending in a free lateral flat branch 73–101 μm long,

which consists of an isodiametric basal cell, narrower than the 5 cells above, which are more or less strongly flattened

(Figs 30, 35). Each cell of the free branch bearing one appendage on each side. Rarely, the second cell of this branch with one appendage only on the ventral side. The distal cell of the branch with 3 appendiculate cells supporting secondary appendages, probably the one in the center is the primary appendage.

Antheridia 12–15 × 3–4 μm, only seen in immature thalli, arising from cell a 3 and from the cells 3–4 of the free branch of the posterior series, always paired above a trapezoidal stalk cell, entirely hyaline except for the darkened basal septum which separates the set of two antheridia and its stalk cell from the appendiculate cell (Figs 32–33).

Secondary appendages 12–40 μm, soft, delicate, easily deteriorating when ageing, with an obtuse apex, hyaline,

except for the darkened basal septum above the appendiculate cell (Fig. 34).

Perithecium 89–101 × 32–36 μm, solitary, formed from the apex of the anterior series. Body subcylindrical, with subparallel sides, abruptly differentiated into a neck at cells w 2 and w 3 level (Fig. 31). Apex symmetric in front view, with two outer lobes contiguous with the two lips which form the tip (Fig. 31). Perithecial stalk cell ( VI) triangular in section, minute, located in the corner of cell a 3, above cell m 1, and side by side with cell m 1 or m 2 (Fig. 35, VI).

Position on host:— Thalli are found on the ventral part of the body, directly on legs or among them.

Discussion:— This species may be considered the most reduced in the group including R. gigas , R. lophophora and R. odontopygiidarum . Besides the small size, its pale color and the lateral branch composed of a squarish basal cell, plus no more than 5 cells, separates this species from the other three. This species and R. lophophora parasitize the same host and have been found in the same locality, R. obelostrepti lives on and between legs whereas R. lophophora grows only on the posterior edges of body rings. Neither species coexist on the same individual host and have been found only on the parts of body indicated.

For notes on the host see under R. lophophora .