Diderma effusum (Schwein.) Morgan (Amoebozoa): a new record of a myxomycete from Antarctica

ISSN 2215-650X Slime Molds 6 (2026) V6A3 https://doi.org/10.5281/zenodo.17266105 1 © 2026 Slimemolds.org Diderma effusum (Schwein.) Morgan (Amoebozoa): a new record of a myxomycete from Antarctica Steven L. Stephenson1 1 Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701 E-mail: [email protected] Received: 10 September 2025 Accepted for publication: 4 October 2025 Published: 10 October 2025 Editor: Carlos Rojas Abstract: Myxomycetes have been recorded from virtually every type of terrestrial ecosystem. However, the number of species known from Antarctica is very low, with only nine species in six genera representing the total myxobiota prior to the three records of Diderma effusum reported herein. This species appeared in moist chamber cultures prepared with samples of bryophytes Keywords: bryophytes, moist chamber cultures, protists, slime molds This work is licensed under a Creative Commons Attribution 4.0 International License Introduction The limited availability of liquid water, low temperatures, low habitat heterogeneity, and the absence of woody substrates impose severe environmental restrictions on the presence of myxomycetes (slime molds or myxogastrids) in Antarctica. Velloso et al. (2024), who reviewed all reports of myxomycetes from Antarctica, listed only nine species representing six genera. Horak (1966) was the first to report a myxomycete from Antarctica, and additional species were added by Ing and Smith (1983), Arambarri and Spinedi (1989), Putzke et al. (2004), and Velloso et al. (2020). The nine species reported thus far from Antarctica include four (Leptoderma megaspora Aramb. & Spinedi, Oligonema dancoii Aramb. & Spinedi, Trichia antarctica Aramb. & Spinedi, and a species of Diderma, D. antarcticola Horak) that appear to be endemic. The remaining species are primarily associated with high-latitude ecosystems, with occasional reports from other ecosystems throughout the rest of the world. Diderma effusum is an exception to this general pattern since it is a widely distributed species worldwide (GBIF 2023). Myxomycetes are relatively more common in the subantarctic, with diversity increasing with decreasing latitude and increasingly less severe conditions (Stephenson et al. 1992, Stephenson et al. 2007, Stephenson 2011). For example, 26 species are known from subantarctic Macquarie Island, located at 54° S latitude (Stephenson et al. 2007). Methods In late December of 2004 and early January of 2005, Ina Timling a graduate student at the University of Alaska, visited the Antarctic as a tourist aboard one of the vessels that make the voyage from Slime Molds 6 (2026) V6A3 Stephenson 2 Ushuaia to the Antarctic Peninsula. During this visit, she collected samples of bryophytes from several different localities and then sent these samples to the author when she returned to the United States. Bryophytes commonly occur in areas of exposed rock in the localities from which the samples were collected (Fig. 1). These samples were processed in moist chamber cultures in the manner described by Stephenson and Stempen (1994). Figure 1. Bryophytes on rocky outcrops near the Almirante Brown Scientific Station on the Antarctic Peninsula. (Photo by Steve Stephenson) Results and Discussion Several moist chamber cultures yielded fruiting bodies of Diderma effusum (Fig. 2), a species not previously recorded from Antarctica. The purpose of this paper is to report this addition to the myxomycete biota of Antarctica. Collections listed below were deposited in the herbarium of the University of Arkansas (UARK). Diderma effusum (Schwein.) Morgan ANTARCTIC PENINSULA, Livingston Island, 62°41ʹ18ʺ S, 60°11ʹ38 ʺ W, specimens obtained in moist chamber cultures prepared with bryophytes, material collected on 29 December 2004, SLS 19816 and SLS 20797. ANTARCTIC PENINSULA, Almirante Brown Scientific Station, 64°53ʹ44ʺ S, 62°53ʹ15ʺ W, specimen obtained in a moist chamber culture prepared with bryophytes; material collected on 1 January 2004, SLS 20801 It is interesting that Diderma effusum is the fourth species of Diderma reported from Antarctica. Bryophytes do not represent the typical habitat of this species, which is more likely to occur on leaf litter and other types of dead material derived from herbaceous plants (Martin and Alexopoulos 1969). Slime Molds 6 (2026) V6A3 Stephenson 3 However, the occurrence of the fruiting bodies of D. effusum on mosses has been reported (e.g., Stephenson and Rojas 2020). Figure 2. Fruiting bodies of Diderma effusum appearing on samples of bryophytes in moist chamber culture. (Photo by Steve Stephenson) Acknowledgements Appreciation is extended for Jorge Velloso for his suggestions on an earlier version of this manuscripts. References Arambarri AM, Spinedi HA. 1989. Mixomicetes antárticos [Antarctic myxomycetes]. Buenos Aires: Instituto Antártico Argentino. GBIF. 2023. Diderma effusum (Schwein.) Morgan, 1894 in GBIF Secretariat [Internet]. Denmark: GBIF Backbone Taxonomy. [visited 7 September 2025] Available from: https://doi.org/10.15468/39omei Horak E. 1966. Sobre dos nuevas especies de hongos recolectados en el Antártico. Contr Int Antárt Argent. 104: 3-13. Ing B, Smith RIL. 1983. Further myxomycete records from South Georgia and the Antarctic Peninsula. BAS Bull. 59: 80-81. 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