Rickia galatheae 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 : 107-109

Rickia galatheae Santam., Enghoff, & Reboleira , sp. nov. (Figs 11–15)

Mycobank MB 815403

Diagnosis:—Receptacle triseriate, a: 4, m: (7–)9, p: (8–)10(–12). Uppermost cell of anterior series (a 4) bearing a single antheridium, without a stalk cell, terminating in a brownish, outwardly curved, efferent neck. Median series flanking the dorsal side of the perithecium, consisting of subequal cells, with approximately parallel sides.

Type: — NEW ZEALAND. Wellington Porirua PA, on Eumastigonus distinctior Chamberlin 1920 ( Spirostreptida , Cambalidae ), 14 December 1951, Galathea II expedition, C-F-95088, C-F!, holotype designated here; BCB-SS ·E598a, c, BCB!, isotypes designated here.

Etymology:— galatheae , named after the “ Galathea II ” expedition ( Bruun et al. 1956) during which part of the host material was collected. We wish to emphasize these interesting finding sponsored by the Danish government through the important Galathea expeditions.

Thallus hyaline except for the dark brown foot, the trichogyne scar, the septa separating the appendiculate cells from appendages and often, the pale brown efferent necks of antheridia located along the perithecium on a 4 (Figs 11–12, 14, an). Total length 112–133 μm. Receptacle triseriate. Basal cell 1.5 times as long as broad, base cylindrical,

upper part acute, embedded between a 1 and p 1, reaching about the middle of these cells, or higher (Fig. 11, I).

Anterior series consisting of four cells (Fig. 12). Cell a 4 subtending perithecium, narrow and elongate, reaching half of the perithecium length, supporting an appendiculate cell giving rise to an antheridium (Fig. 11–12, an). Cell a 3 with a secondary appendage (Fig. 12, sa), which rarely may be replaced by an antheridium (Fig. 14, an). The septum under the antheridia is neither constricted nor darkened, in contrast to septa below the secondary appendages. Cells a 1–2 may support a secondary appendage each, although this is very variable, being more common on a 2.

Median series consisting of (7–)9 cells, forming a row lining the margin of the perithecium as far as to leave free only its tip. The cells of this series are rather similar in length and breadth—an outstanding feature for this species. The upper cell of the series bears a secondary appendage with an appendiculate cell. The series (m 1) begins just above a 1 and p 1.

Posterior series consisting of (8–)10(–12) cells. Upper cell of the series bearing the primary appendage, which consists of a dome-shaped basal cell and a distal filamentous cell separated by a brown constricted septa (Fig. 12, pa).

The primary appendage is similar to the secondary appendages. Appendages may be present on any of the cells of the series, but are most common on the distal cells, i.e., those above p 3.

Antheridia 12–15 × 3–6 μm, usually a single one for any mature thallus, rarely two (Fig. 14, an) (see above the description for the anterior series), borne on cell a 4, above an appendiculate cell, without a stalk cell, with a conspicuous efferent neck, straight to variably curved, outwardly directed, more or less suffused with brown (Fig. 15).

Secondary appendages 11–30 μm, entirely hyaline, soft, delicate and easily deteriorating, with a constricted brownish septum which separate them from appendiculate cells.

Perithecium 58–80 × 22–28 μm, solitary, ovoid to broadly fusiform, hyaline, except for the tan trichogyne scar present on the outer side, where the slightly differentiated and short neck begins (Fig. 11, trs). Apex blunt, slightly bent towards the ventral side. Stalk and basal cells of the perithecium indistinguishable.

Position on host:— Thalli are mostly located on the posterior margin of the body rings, the so-called limbus, and also on some legs, as well as on the head, including the clypeus and the antennal insertion.

Discussion:— This small, beautiful new species is distinct from all others included in this study, although R.

appendicifera and R. candelabriformis were also found to parasitize millipedes of the family Cambalidae (see under

R. candelabriformis for notes on the host). The antheridium, sometimes two, located on the ventral margin, bearing a conspicuous brown efferent neck, and the median series of cells, reminiscent of a backbone, are two characters that very easily distinguish this species from others in the genus.

We found a gross resemblance to R. spathulata Thaxt. , a species described from a mite of the genus Celanopsis from the Amazon ( Thaxter 1926). The number of cells in each series is similar except for the anterior series where R.

galatheae has fewer cells. The presence of a single antheridium in front of the perithecium is a character shared by both species but, despite this, the relation of these species seems unlikely based on hosts and geographical distribution.

Moreover, from the morphological point of view there are some important differences such as the shape of the secondary appendages, the location and orientation of perithecium, and the shape of the uppermost cell of the posterior series subtending the primary appendage.

Additional collections examined: — NEW ZEALAND. South of the Island, Tasman Dist., Kahurangi N.P., Flora

Saddle, 4º11’24.3”S 172º44’28.8”E, 970 m. a.s.l., litter and logs, on Eumastigonus sp. ( Spirostreptida , Cambalidae ), 7

March 2010, N. Scharff & G. Hormiga leg., BCB-SS·E587 (BCB!). Milford Sound, 44º40’S 167º56’E, on Eumastigonus

cf. insulanus ( Spirostreptida , Cambalidae ), 16 January 1952, Galathea II expedition leg., BCB-SS·E595ab (BCB!).