Rickia lophophora 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 : 112-114

Rickia lophophora Santam., Enghoff, & Reboleira , sp. nov. ( Figs 24–29 )

Mycobank MB 815405

Diagnosis:—Receptacle triseriate, a: 3, m: 3, p: 1–3 (+ 5–8 of lateral branch). Posterior series extending in a free, lateral branch of 5–7 cells. Antheridia solitary or in pairs scattered on the thallus. Perithecia elongate subfusiform. Perithecial apex bearing two small lobes and two short lips. Secondary appendages and antheridia with a strongly constricted and dark brown base.

Type: — TANZANIA. West Usambara, Mts. Mazumbaion, on Spirostreptidae indet. (new genus near Trachystreptus or Attemsostreptus ), 1 August 1980, M. Stoltze & N. Scharff leg., C-F-92260, C-F!, holotype designated here; BCB-SS ·E573bc, BCB!, isotypes designated here.

Etymology:— lophophora , from the Greek “lophos” crest, and “phoros” bearing. Referring to the crest-like lateral branch.

Thallus hyaline except for the dark brown foot, the trichogyne scar, and the lower portion of the secondary appendages and antheridia. Total length 177–254 μm. Receptacle triseriate. Basal cell twice as long as broad.

Anterior series consisting of 3 superposed, variably shaped cells ( Fig. 27 ). Cell a 2 with two secondary appendages on the outer, upper corner. Cell a 3 bearing three appendiculate cells, superposed in a vertical row, each giving rise to secondary appendages or to 1–2 antheridia on the distal one ( Fig. 29 ).

Median series consisting of 3 cells, topped with 1–2 antheridia, secondary appendages, or not rarely with one perithecium ( Fig. 29 ).

Posterior series consisting of a basal part with 1–3 cells, each bearing 1–3 secondary appendages and/or single to paired antheridia. Rarely, cells p 2–3 may develop a perithecium ( Fig. 29 , arrow). The series extends in a free lateral flat branch 68–119 μm long, consisting of a basal trapezoidal cell, and 5–8 superposed, flattened cells. There are neither appendages on the basal cell of this branch nor on the ventral side of the lowermost 3 cells. Remaining cells of this branch bear 1–2 appendages or, less commonly, single antheridia. When two appendiculate cells are borne by the same cell, they appear more or less overlapped, especially those on the upper cells of the branch. The uppermost cell is terminated by the short and rounded primary appendage which is flanked by secondary appendages with their respective appendiculate cells.

Antheridia 19–29 × 4–7 μm, single ( Fig. 26 ) or paired ( Fig. 25 ) above the elongated stalk cell which is similar in shape to the lower segment of secondary appendages, above the septum which separates them from the appendiculate cells. Each antheridium with a more or less laterally curved, brownish, short efferent neck.

Secondary appendages 26–33 μm, rounded and broadened distally, deteriorate with ageing, hyaline at the distal end and reddish deep brown at the basal 2/3 of their total length; abruptly narrowing towards the constricted septum which separate them from the appendiculate cells ( Fig. 24 ).

Perithecia 97–150 × 21–32 μm, up to three on the same thallus, formed primarily from the anterior series as usual,

but also from the median and even, although rarely, from the posterior series. Perithecium body long and narrow,

fusiform to cylindrical, with a slightly inflated venter, gradually tapering or broadening towards the apex and at the level between cells w 2 and w 3, then abruptly differentiated in a neck right under the asymmetrical tip which bears 4 protuberances, i.e. two outer lobes and two inconspicuous inner lips ( Fig. 28 ). A persistent trichogyne brown scar is found at upper outer margin of the neck ( Fig. 29 , trs). Perithecial basal cells very flattened and inconspicuous.

Perithecial stalk cell ( VI) very small, variable.

Position on host:— Thalli are found on the body rings, along the trunk, mainly seated at the limbus, with some also in the suture of the prozone and metazone. This species forms conspicuous infections on its hosts with thalli growing typically on the posterior edges of the body rings.

Notes on hosts:— Spirostreptidae is a large family of mainly tropical millipedes. Obelostreptus proximospinosus has been recorded from several mountain blocks in the Eastern Arc system (Enghoff et al. in press).

Discussion:— The examined material is quite uniform; only the thalli found on Obelostreptus (cf.) proximospinosus

Krabbe 1982 (BCB-SSE574ac) are distinctly larger, with lateral branches of the posterior series with up to 12 cells,

whereas typical thalli have 5–8 cells.

Rickia lophophora belongs to the same group of species as R. gigas , R. obelostrepti and R. odontopygiidarum ,

sharing with these the free lateral branch of the posterior series of the receptacle and the morphology of the perithecial apex. It differs from R. gigas and R. odontopygiidarum for the fusiform perithecia, inconspicuous protuberances on the perithecial tip, secondary appendages with a strongly constricted and dark brown base, and stockier antheridia with less differentiated efferent necks. It can be easily distinguished from R. obelostrepti by the pale and simple lateral branch of the posterior series of the latter.

Additional collections examined: — TANZANIA. Iringa region /district, New Dabaga/Ulangambi F.R., 1908 m, 08°00’26.6’’S 35°56’06.1’’E, on Spirostreptida indet., 19–26 October 2000, BCB-SS·E572ac (BCB!). Uluguru Mts., Lupanga West, 1900 m, on Obelostreptus (cf.) proximospinosus Krabbe, 1982 ( Spirostreptida , Spirostreptidae ), 1 July 1981, BCB-SS·E574ac (BCB!). Uluguru Mts., Lupanga East, 1600 m, on Eiphorus sp. ( Spirostreptida , Spirostreptidae ), 10 July 1981, BCB-SS·E599 (BCB!), C-F-9509 and C-F-95110 (C-F!).

Figures

FIGURES 24–29. Rickia lophophora. Fig. 24. Detail of a secondary appendage. Fig. 25. Detail of a set of paired antheridia. Fig. 26. Detail of a solitary antheridium. Figs 27, 29. Mature thalli. In Fig. 29, a young, probably aborted perithecium is indicated with an arrow. Fig. 28. Perithecial apex. (Figs 24–28, SS·E572a; Fig. 29, C-F-92260.). FIGURES 30–35. Rickia obelostrepti. Figs 30, 35. Mature thalli. Fig. 31. Perithecial apex. Figs 32–33. Detail of paired antheridia. Fig. 34. Detail of secondary appendages. (All Figs from slide SS·E579b.) (For interpretation of abbreviations see under materials and methods.) Scale bars for Figs 24–26, 28, 31–34 = 10 μm; for Figs 27, 29, 30, 35 = 50 μm.