Troglomyces dioicus Santam., Enghoff & Reboleira, 2018

Santamaría, Sergi, Enghoff, Henrik & Reboleira, Ana Sofía P. S., 2018, New species of Troglomyces and Diplopodomyces (Laboulbeniales, Ascomycota) from millipedes (Diplopoda), European Journal of Taxonomy 429, pp. 1-20 : 11-13

Troglomyces dioicus Santam., Enghoff & Reboleira sp. nov.

MycoBank No: MB824139

Fig. 4

Diagnosis

First dioecious species in the genus, with female thalli characterized by a very short cell III and a septum II-III placed under the level of the perithecial base, whereas in the other species cell III is taller and the septum II-III is clearly higher up.

Etymology

Self-defined by its species epithet, meaning “two households”.

Material examined

Holotype

MYANMAR: Mandalay Division, 7 km NW Mogok, above road Mogok-Bemardmyo, S. Panlin village, west slope of Mt. Taung Mae , 22º58′09″N 96º27′13″E, 1710‒1750 m a.s.l., on Nepalmatoiulus sp. ( Julida ), 10‒18 Jun. 2014, Brunke & Schillhammer leg., slide C-F-92269 .

Isotypes

MYANMAR: Same data as holotype. Slides SS E617a , SS E617c , SS E617d and SS E617e ( BCB- Mycotheca).

Description

Dioecious. Both male and female thalli are hyaline except for the darkened feet.

Male thalli. Consisting of six superposed cells. Basal cell (I) about 3 times as long as broad. Suprabasal cell (II) small and squared. Cell III 1.5 times as long as broad. Primary septum well distinguished. Fourth cell 1.5 times as long as broad. Fifth cell squared, very small, bearing the single, apical, bottleshaped antheridium. No spiny remains of spore apex because it is coincident with the apex of efferent tube, i.e., where the discharging pore is found.

Female thalli. Basal cell (I) twice or more as long as broad, enlarged distally, slightly constricted at the base. Suprabasal cell (II) as long as broad, laterally adnate to cell VI, broadened at base where in contact with cell I, narrowed toward distal end. Cell III very narrow, 3 times as long as broad, laterally adnate to perithecium. Septum I-II horizontal. Septum II-III horizontal or slightly oblique, below the level of septum VI-VII.

Primary appendage unbranched, forming an angle of almost 90º with main axis of thallus, consisting of up to 4 cells, of which the lower is about 4 times as long as broad, the others gradually shorter and tapering distally. Spiny remains of spore apex (sx) difficult to see in mature thalli ( Fig. 4A ), but well visible in very young thalli ( Fig. 4D ).

Perithecial stalk cell (VI) triangular, as long as broad, resting in the concave apico-ventral side of cell II. Secondary stalk cell (VII) wedge-shaped, resting on the outer (ventral) corner of cell VI. Perithecium fusiform, stout, with broad venter, maximum width near lower 1/4‒1/5th, gradually tapering upwards, more abruptly upwards from w2-w3 septa. The tip is asymmetric, slightly bent dorsally, forming first a neat constriction, followed by a bulge and ending with four small lips. Dorsal side rather straight, ventral side convex.

Length of male thalli from foot to apex of antheridium 88–93 µm. Antheridium 21–26 × 5–6 µm. Length of female thalli from foot to apex of perithecium 159‒201 µm. Perithecium (including basal cells) 91‒117 µm. Primary appendage (from primary septum to apex, undamaged) 50‒70 µm.

Remarks

This species is unique among the species of Troglomyces for its dioecism and because cell III, although adnate to perithecium (a characteristic of the genus) is located much lower than in other forms.

Male and female thalli are paired, as it is usual in dioecious Laboulbeniales . However as can be seen in Fig. 4A we have found a pair of females without any trace of antheridia or paired males (often seen as remains of the darkened feet, e.g., Fig. 4B ).

The species seems very rare and the thalli were scarce on legs 2, 3 and several anterior post-gonopodal legs. Undamaged mature male thalli with spermatia present in the efferent neck have been seen only twice ( Fig. 4C ); immature thalli are more common and help us to understand that the efferent neck and pore (through which spermatia discharge) coincide with the original acute ascospore apex ( Fig. 4D , arrow), an unusual feature among Laboulbeniales .

Dioecism is not unusual among genera of Laboulbeniales although most species are monoecious. A good example is the genus Laboulbenia Mont. & C.P.Robin , with more than 600 species, only three were demonstrated to be dioecious ( Santamaría 1998).

The host belongs to the large Southeast Asian genus Nepalmatoiulus Mauriès, 1983 , which are mainly inhabitants of forest litter ( Enghoff 1987).

Figures

Fig. 4. Troglomyces dioicus Santam., Enghoff & Reboleira sp. nov. A–B. Mature female thalli with labelling of cells and other elements. C. Mature male thallus with labelling of cells and other elements. D. Paired immature thalli where original spore apex are labelled (sx for female at left; arrow for male at right). Scale bars: 50 µm (A‒B, D), 25 µm (C). Photographs from: SS E617a (A), SS E617c (B, D) and C-F-92269 (C).