2.5.1 Asteromyces cruciatus

Asteromyces cruciatus was introduced by Moreau and Moreau (1941) from sand dunes of the Atlantic Coast of France. This species has a worldwide distribution and reported from a wide range of substrata (Jones and Ward 1973). Despite its profuse growth in culture and its wide occurrence in the marine milieu, its taxonomic position has remained unresolved. Asteromyces cruciatus was classified as incertae sedis in Index Fungorum and Species Fungorum, while Mycobank classified it under the old family name Dematiaceae . In a new study, Torres-Garcia et al. (2022) placed A. cruciatus in the Pleosporaceae based on a phylogenetic analysis of five gene markers (ITS, LSU, gapdh, rbp2, and tef1-α). Asteromyces is in a well-supported distinct clade with two marine Paradendryphiella species as its sister taxa, and closely related to both Paradendryphiella and Stemphylium, but they are markedly different in morphology. Brown (1958), Hennebert (1962), Kohlmeyer and Kohlmeyer (1964 – 1969), and Jones (1968), all report the conidia of A. cruciatus as ovoid or pyriform, smooth, thin-walled, one-celled without germ slit or pore, 10 – 20 × 4 – 9 µm, with up to 13 µm conidia developing in basipetal succession, singly on cylindrical denticles 3 – 6 × 0.5 – 1 µm. The first formed conidium is apical and retains this position. On germination, conidia often become 1-septate and these have been illustrated by Kohlmeyer and Kohlmeyer (1964 – 1969), Hennebert (1962), and Nolan (1972), who also reports 2-septate conidia. Jones and Ward (1973) investigated the effect of light on the sporulation of A. cruciatus: continuous illumination and in total darkness when conidia were unicellular. However, when subjected to black light (fluorescent lamp with a continuous spectrum maximum at 360 nm, 18 in. above plates), 1 – 6-septate conidia were formed depending on the growth media. Asteromyces cruciatus is also of interest because it can tolerate concentrations of up to 2.0 M NaCl in liquid media (Jones and Jennings 1965), with tolerance increased to 2.5 M NaCl with the addition of 0.05 M CaCl 2. Asteromyces cruciatus is beautifully illustrated in Kohlmeyer and Kohlmeyer (1964 – 1969).