Autoicomyces humilis (Thaxt.) Thaxt.

Santamaria, Sergi & Pedersen, Jan, 2021, Laboulbeniomycetes (Fungi, Ascomycota) of Denmark, European Journal of Taxonomy 781, pp. 1-425 : 28

Autoicomyces humilis (Thaxt.) Thaxt.

[not registered in MycoBank]

Fig. 2E

Memoirs of the American Academy of Arts and Sciences 16: 359 ( Thaxter 1931). – Basionym: Ceratomyces humilis Thaxt., Proceedings of the American Academy of Arts and Sciences 29: 94 ( Thaxter 1894) [MB#227550]. –

Type: “ On legs and at the edges of the elytra of Berosus striatus Say. Kittery Point , Maine ”; FH. [ USA]

Autoicomyces anaceros Speg. ( Spegazzini 1915b: 38) [MB#159363]

Diagnostic features

Thallus uniformly hyaline to pale yellow. Receptacle two-celled. Perithecium with a rather welldistinguished neck and a truncate apex. [Detailed descriptions: Sugiyama & Hayama 1981]

Distribution and hosts

Grows between the claws of its hosts. Described from Berosus Leach, 1817 (Col. Hydrophilidae ) from USA, it has been reported on the same host genus from Sumatra and Philippines ( Thaxter 1931), Taiwan ( Sugiyama & Hayama 1981) and China ( Shen & Ye 2006). Also on Regimbartia Zaitzev, 1908 (Col. Hydrophilidae ) from Sumatra, China ( Thaxter 1931), and on Hydrochus (Col. Hydrochidae ) from Cuba and USA ( Thaxter 1931). Autoicomyces anaceros , accepted as a synonym, was described on Laccobius Erichson, 1837 from Italy, but this may be a growth form of A. crassus Speg. ( Santamaria 2003: fig. 11e– h). Santamaria (2003) reported it from Spain as a growth form of A. aquatilis .

Collections examined from Denmark

On Hydrochus crenatus (Fabricius, 1792) (Col. Hydrochidae )

DENMARK – Nordøstsjaelland (NEZ) • Heatherhill ; 56°5.240′ N, 12°8.611′ E; UC21; 22 May 2016; JP 91; JP det.; ZMUC C-F-122566 .

Remarks

First record from Denmark. The status of this taxon as a separate species has been the subject of debate. According to some authors it should be considered a growth form found between the claws of male hosts, therefore related to sex-host specificity and mating behaviour. However, in our sample the same individual host bears the normal ‘horned’ form known as A. aquatilis on the elytra and the reduced form known as A. humilis between the claws. Moreover, Thaxter (1894) described this species growing on legs and elytral margins, which is contradictory with the ‘concept’ of growth form.

Figures

Fig. 2. A–C. Helodiomyces elegans F.Picard. A. Mature thallus with labelling of cells VI, VI’ and VII. B–C. Details of perithecium, including ligules (li) in C. – D. Autoicomyces aquatilis (F.Picard) I.I.Tav.; mature thallus showing the perithecial outgrowth (arrow). – E. Autoicomyces humilis (Thaxt.) Thaxt.; mature thallus at the base of a host claw, and a sporeling on the right. – F–H. Ceratomyces pyrenaeus Santam.; mature thalli showing labelled perithecial excrescences (arrows in G). Scale bars: 50 µm. Photographs from slides ZMUC C-F-122583 (A–C), ZMUC C-F-122567 (D), ZMUC C-F-122566 (E), ZMUC C-F-123551 (F), and ZMUC C-F-123550 (G–H).