Stigmidium ascophylli

Stigmidium ascophylli (Cotton) Aptroot, CBS Biodivers. Ser. 5: 41. 2006 [pdf]

MycoBank MB500377

AUTHOR: Olariaga I.


Mycosphaerella ascophylli Cotton, Trans. Br. Mycol. Soc. 3(2): 96. 1909. [1908]. [pdf]
Sphaerella ascophylli (Cotton), Sacc. & Trotter, Syll. fung. 22(1): 147. 1913. [pdf]
Mycophycias ascophylli (Cotton), Sacc. & Trotter, Kohlm. & Volkm.-Kohlm., Syst. Ascomycetum 16(1-2): 3. 1998.

= Mycosphaerella pelvetiae G.K. Sutherl., New Phytol. 14: 34. 1915. [pdf].
= Sphaerella pelvetiae (G.K. Sutherl.) Trotter, Syll. fung. 24(2): 849. 1928. [“Sphærella pelvetiæ][pdf]


Taxonomic Classification

phy Ascomycota

sbp Pezizomycotina

cls Dothideomycetes

sbc Dothideomycetidae

ord Mycosphaerellales

fam Mycosphaerellaceae

gen Stigmidium

sp Stigmidium ascophylli


Pseudothecia 60-120 × 55-90 µm, embedded in the thallus cortex, with only the ostiole protruding, black. Pseudothecial wall hyaline and thin except in the ostiole region, carbonized, 12-15 µm thick. Asci octosporic, fusiform to clavate, initially with a thick-walled apical canal, bitunicate, 59-65 × 26-29 µm. Ascospores fusiform, hyaline, uniseptate, not constricted at the septum, (15)23-30 × (4.5)6.5-8 µm, with a supra-median septum and 1-5 large guttules when alive. Paraphyses absent. Periphyses present in the ostiolar zone, cylindrical, hyaline, 9-15 × 3-3.5 µm.

Habitat and Distribution: Pyrenomycete that inhabits receptacles of living Pelvetia canaliculata and Ascophyllum nodosum. Although currently Stigmidium ascophylli, based on material collected on Ascophyllum nodosum, and Mycosphaerella pelvetiae, described on Pelvetia canaliculata, are considered synonymous (WoRMS 2023), Sutherland (1915) argued that M. pelvetiae differed from S. ascophylli (as Mycosphaerella ascophylli) in their hyphae, asci, and spores, although without providing more specific details. Due to the high specificity shown by many symbiotic fungi, and considering the different ecology of P. canaliculata (supralittoral) and A. nodosum (intertidal), we believe that a critical comparison, including molecular studies, could question this synonymy. In the meantime, we follow the synonymy that appears to be currently accepted. Almaraz & al. (1994) first cited S. ascophylli (as Mycosphaerella ascophylli) in the Iberian Peninsula, on P. canaliculata, although they did not specify the locality as the specimens were washed ashore. This material was possibly collected in the province of La Coruña, like the rest of the material of other species cited in the article. In any case, the two collections cited here are the first Iberian records with precise locality. The spores and asci of our material are larger than those mentioned by Almaraz & al. (1994). This may be because immature pseudothecia with immature ascospores are frequently found. Sp: C(?), O.

Species References in the Territory
  • Almaraz T., Checa J. & Gallardo T. 1994. Ascomycetes associated with Pelvetia canaliculata Decne. & Thur. (Fucales, Phaeophyta). Anales Jard. Bot. Madrid 52(1): 4. (Sp: C?) (as Mycosphaerella ascophylli) [pdf]
Specimens in Scientific Collections

Reference specimen marked in bold

C?: MA-Fungi 32024
O: ARAN-Fungi 17031, ARAN-Fungi 16988

Fig. 1. Known distribution of Stigmidium ascophylli. Source: SIM-SEL database.

Sequences in Public Databases and Obtained from Territory Material



Fig. 2. Colony of Pelvetia canaliculata in the supralittoral, on which Stigmidium ascophylli was collected (ARAN-Fungi 17031, Güelgues Beach, Carreño, Asturias).


Fig. 3. Colony of Pelvetia canaliculata in the supralittoral, on which Stigmidium ascophylli was collected (ARAN-Fungi 16988, La Franca Beach, Ribadedeva, Asturias).


Fig. 4. Thalli of Pelvetia canaliculata, with a more yellowish conceptacle in the center, on which Stigmidium ascophylli (ARAN-Fungi 16988) fruited.

Fig. 5. Thalli of Pelvetia canaliculata, with a more yellowish conceptacle in the upper part of the image, on which Stigmidium ascophylli (ARAN-Fungi 16988) fruited, visible as tiny black dots in the image.


Fig. 6. Conceptacle of Pelvetia canaliculata, in which tiny black dots corresponding to Stigmidium ascophylli (ARAN-Fungi 16988) ascomata can be seen.

Fig. 7. Section of a pseudothecium of Stigmidium ascophylli (ARAN-Fungi 16988), immersed in the thallus of Pelvetia canaliculata. Scale bar 50 µm.

Fig. 8. Section of the upper side of a pseudothecium of Stigmidium ascophylli (ARAN-Fungi 16988), in which periphyses are observed. Scale bar 10 µm.

Fig. 9. Ascus of  Stigmidium ascophylli (ARAN-Fungi 16988) in water. Scale bar 10 µm.

Fig. 10. Hymenium of Stigmidium ascophylli (ARAN-Fungi 16988) in SDS-congo red, showing asci and uniseptate hyaline spores. Scale bar 10 µm.

How to cite this sheet:

Olariaga I. 2023. Stigmidium ascophylli (Cotton) Aptroot. Fichas SIM 41 (Updated on 30-VII-2023). DOI:
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