Mucor harpali Hyang B. Lee, P.M. Kirk & T.T.T. Nguyen sp. nov.
Index Fungorum number: IF 557325; MycoBank number: MB 557325; Facesoffungi number: FoF 09209; Fig. 1
Etymology – Referring to the name of a bombardier beetle, Harpalus sp.
Holotype – CNUFC HT18012
Colonies on MEA at 25 °C in darkness moderate reddish-brown (8.1R/3.1), the central part with mature sporangia and the margin with immature sporangia, reaching 72‒75 mm diam. after 4 days incubation; reverse vivid yellow (1.3Y/7.3). Sporangiophores arising directly from the hyphae immersed in the substrate, tall, 8–19.5 μm diam., usually unbranched or with few secondary branches, septate or coenocytic; one or two septa may be formed below the columella; branches commonly bearing a sterile sporangium. Sporangia non-apophysate, hyaline to yellow when young, becoming reddish-brown, globose, subglobose, 36.5–103.5×35–100.5 μm, wall deliquescent. Columellae often globose to subglobose, but also obovoid with truncate base, 27.5–55.5×26.5–52.5 μm, with distinct colar; a few reniform columellae also found. Sporangiospores mostly ellipsoidal, subglobose, reniform, or some irregular, 5.5–11.5×3–5.5 µm, smooth-walled. Oidia often observed. Zygospores not observed. Substrate mycelium branched, containing inflated regions terminating in thin rhizoid-like filaments and yellow droplets.
Culture characteristics – The isolate grew over a wide range of temperatures with varying growth rates on SMA (synthetic mucor agar), PDA (potato dextrose agar) and MEA (malt extract agar) of 13 mm, 15 mm, and 18.5 mm per 24 h, respectively. Optimal growth was observed around 25 °C, and slow growth was observed at below 10 °C. Maximum growth temperature was 35 °C. The fungus did not grow at 36 °C.
Material examined – REPUBLIC OF KOREA, Jeonnam Province, garden of the Chonnam National University located in Gwangju (35°10′20.3″ N 126°53′56.9″ E), from head of a bombardier beetle (Harpalus sp.), 30 July 2018, collected by H.B. Lee (CNUFC HT18012, holotype), extype living culture (CNUFC ICT18001).
GenBank numbers – ITS = MT192528, MT192529, LSU=MT192532, MT192533.
Notes – Phylogenetic analyses (Figs. 2 and 3) clearly placed Mucor harpali among other Mucor species within the Mucor racemosus group previously suggested by Walther et al. (2013). Mucor harpali and Mucor sp. CBS 608.78 (former: M. circinelloides f. griseocyanus) are the phylogenetically nearest species in the ITS tree (Fig. 2). Mucor harpali (Fig. 1) shared some similarities with M. circinelloides f. griseocyanus (current name: Mucor griseocyanus) such as ellipsoidal sporangiospores, and maximum temperature growth (Schipper 1978; Wagner et al. 2019). However, sporangia (up to 60 μm) and collumella (38×35 µm) of M. griseocyanus reported in the literature (Schipper 1978; Wagner et al. 2019) were smaller than those of M. harpali. Mucor harpali can be distinguished from the other species in this group, including M. racemosus, M. plumbeus, M. racemosus f. sphaerosporus, M. brunneogriseus, and M. mousanensis. Schipper (1978) has mentioned that M. plumbeus produces columellae usually with apical projections, whereas in M. harpali apical projections are absent. Mucor racemosus f. sphaerosporus produces mainly subglobose sporangiospores (Schipper 1978), while M. harpali produces variable in shape, mostly ellipsoidal. Mucor mousanensis produces columellae applanate elongated conical (up to 70×50 µm) (Schipper 1978), while M. harpali does not produce this structure. Based on the phylogenetic analyses and morphological comparison with similar species of Mucor, M. harpali is a distinct species.
Figure 1 – Mucor harpali (CNUFC ICT18001, ex-type living culture). a A bombardier beetle of Harpalus sp. belonging to Coleoptera. b Colony on synthetic mucor agar (SMA). c Colony on potato dextrose agar (PDA). d Colony on malt extract agar (MEA). e, f Sporangiophores and sporangia. g Sterile sporangium. h–j Typical columellae. k Sporangiospores. l Rhizoids (Fig. e: observed under a stereomicroscope; Figs. f–l: light microscope). Scale bars: f–l=20 µm
Figure 2 – Phylogram generated from maximum likelihood analysis based on ITS sequence data for the species of Mucor. Bootstrap values equal to or greater than 70% for ML analyses is presented at the nodes. Mucor amphibiorum is used as the outgroup taxon. Type strains are in bold and newly generated sequences are in blue
Figure 3 – Phylogram generated from maximum likelihood analysis based on LSU sequence data for the species of Mucor. Bootstrap values equal to or greater than 70% for ML analyses is presented at the nodes. Mucor amphibiorum is used as the outgroup taxon. Type strains are in bold and newly generated sequences are in blue