After incubation at 21 degrees Celsius under ambient light, a colony with characteristics reminiscent of the order Entomophthorales emerged. It was subcultured and cryopreserved under accession number ARSEF 7942 at the USDA-ARS Collections of Entomopathogenic Fungal Cultures in Ithaca. Under the microscope, the isolate showed clear affinities with Basidiobolus: simple conidiophores tipped with bulbous swellings, and uninucleate conidia that are launched forcibly when pressurized cytoplasm inside the conidiophore is expelled.

Yet several features did not fit any known Basidiobolus species. Most strikingly, after discharge the conidium retains a basal membranous appendage derived from the conidiophore apex, which never separates from the spore. The circumscissile rupture line, the clean break that releases the spore, sits higher on the conidiophore than in Basidiobolus.

And in a feature never before recorded in this group, primary conidia can give rise directly to digitate, finger-like chlamydospores, thick-walled resting structures borne terminally on a single conidiophore. The concatenated alignment comprised 2,136 nucleotide positions, with 894 sites from 28S, 519 from ITS, and 723 from RPB2. The best-fitting models were GTR+F+R4 for 28S and RPB2 and TPM3u+F+R3 for ITS in the maximum likelihood framework, and TrNef+G for 28S and ITS and TIMef for RPB2 in the Bayesian analyses.

The results were unambiguous in one key respect. All recognized Basidiobolus species formed a strictly monophyletic clade with maximal support of 100 percent bootstrap and a Bayesian posterior probability of 1.0. The focal isolate ARSEF 7942, however, segregated entirely from that complex, forming a distinct lineage with support values of 54 percent bootstrap and 0.99 posterior probability.

The bootstrap figure falls below the conventional 70 percent threshold, but the authors note that the lineage's monophyly is corroborated by congruent topologies under both inference methods, by the isolate's clear morphological distinctiveness, and by the absence of shared derived characters with Basidiobolus species. Intriguingly, the still unpublished genus Schizangiella, represented by strains from snakes, emerged as a sister lineage to ARSEF 7942 with strong support of 86 percent and 0.99. On the strength of this combined molecular and morphological evidence, the team established Drechslerosporium as a new genus, named in honor of Charles Drechsler, the mycologist who described many American species of Conidiobolus and Basidiobolus.

The type species, D. cornellii, honors Ezra Cornell, founder of Cornell University. The formal description records slow-growing colonies that are initially pale brown and later fuzzy and white in the center, with colorless mycelium that shows little aerial growth. Primary conidiophores are unbranched, mostly 5.4 to 9.1 micrometers wide, extending 91 to 237 micrometers into the air and terminating in an elongated ellipsoidal propulsive distention 27.1 to 38.3 micrometers long.

The subspherical to obovoid conidia measure 22.2 to 36.3 by 17.3 to 29.2 micrometers and carry the empty membranous remains of the conidiophore apex, mostly cylindrical structures of 4.9 to 9.9 by 4.9 to 7.4 micrometers that stay attached. The discharge mechanism itself is the centerpiece of the taxonomic argument. In typical Basidiobolus species, the conidiophore breaks cleanly at a circumscissile zone at the base of the apical vesicle, and a pressurized blast of cytoplasm expels the conidium, which then separates from the propulsive remnants in flight through eversion of a basal papilla.

This classical mechanism is known as the sporophore rocket. In Drechslerosporium, the rupture occurs anomalously higher, near the top of the apical vesicle, so the discharged conidium permanently retains conspicuous membranous remnants of the conidiophore apex. The conidium lacks a true columella and is delimited by a basal septum that tethers it to those remnants after launch.

The authors designate this arrangement a modified sporophore rocket, one that lacks the papillar eversion seen in its relatives. Secondary conidia appear in two forms: smaller replicas of the primary conidia, discharged in the same violent manner, and elongated capilliconidia, prolate ellipsoids 43.2 to 56.8 micrometers long including an apical beak of 9.1 to 12.4 micrometers that is coated distally with adhesive material for passive dispersal. The digitate chlamydospores, which develop directly from primary conidia under suboptimal conditions within three to five days and measure 38 to 53 by 12.2 to 19 micrometers, represent an autapomorphy, a unique derived trait, unrecorded in any allied taxon.

The genus does share foundational characters with Basidiobolus, including uninucleate primary conidia, similar conidial wall ultrastructure, homologous conidiophore architecture, and the capacity to produce capilliconidia. But the divergent discharge mechanism, historically a key generic-level diagnostic trait among these fungi, together with the darkly pigmented colonies that contrast with the typically hyaline mycelia of all known Basidiobolus species, justified generic separation. The authors note a superficial convergence with Ballocephala, whose discharged propagules also carry the ruptured conidiogenous cell apex, but point out that Ballocephala builds a complex branched conidiophore and has been transferred out of the Entomophthorales to the Kickxellomycotina, whereas Drechslerosporium retains a simple, unbranched conidiophore.

The discovery has broader consequences for fungal classification. Basidiobolus, established in 1886 with the type species B. ranarum, comprises ecologically versatile fungi found in soil, decaying organic matter, and amphibian feces, often dispersed by arthropod vectors, and several species are known to cause subcutaneous and systemic infections in humans. Molecular studies have long complicated the picture: early rDNA analyses showed Basidiobolus diverging significantly from other Entomophthorales and grouping instead with chytrid representatives, while subsequent multilocus and phylogenomic studies produced inconsistent topologies, leaving the genus's higher-order placement unresolved even as its monogeneric family remained entrenched in taxonomy.

The formal recognition of Drechslerosporium required an emended diagnosis of Basidiobolaceae, now defined to include the conidial appendages and digitate chlamydospores. Zygospores, the resting spores characteristic of Basidiobolus, have not yet been observed in D. cornellii, leaving one chapter of its biology still to be written.

Subject of Research: Description of the new fungal genus and species Drechslerosporium cornellii within Basidiobolaceae, based on morphology and multilocus phylogenetics

Article Title: Drechslerosporium cornellii gen. et sp. nov. within the Basidiobolaceae exhibiting unique conidial discharge and digitate chlamydospores

Article References: Nie, Y., & Huang, B. (2026). Drechslerosporium cornellii gen. et sp. nov. within the Basidiobolaceae exhibiting unique conidial discharge and digitate chlamydospores. MycoKeys, 136, 177-191. https://doi.org/10.3897/mycokeys.136.200461

Image Credits: AI Generated

DOI: 10.3897/mycokeys.136.200461

Keywords: Drechslerosporium cornellii, Basidiobolaceae, Basidiobolus, fungal taxonomy, Entomophthorales, conidial discharge, chlamydospores, multilocus phylogeny, new genus, mycology, Cornell, plant detritus

The Entomophthorales and Neozygitales, the two orders that make up the phylum Entomophthoromycota, are dominated by arthropod-pathogenic species, although saprobiontic members also occur. Because they can decimate insect populations in outbreaks known as epizootics, they are regarded as important natural regulators of arthropod numbers and hold considerable potential for biological pest control. Despite this ecological significance, the group has never been the subject of dedicated large-scale survey work, which is why new national records continue to surface from ordinary field collections.

The Swiss material originated from several localities and collectors. At Bümpliz in the canton of Bern, a strikingly high number of infected bush-crickets turned up in a cemetery, on the underside of leaves of a southern catalpa, Catalpa bignonioides. Further samples came from Muttenz and Duggingen in Basel-Landschaft, where cadavers were found on catalpa and on European beech, Fagus sylvatica, and from Eschenz in Thurgau, where hazel, Corylus avellana, and a Prunus species served as collection substrates.

One bush-cricket was even recovered from the ceiling of a house entrance in Regensdorf in the canton of Zurich. The single infected cockroach was found on ivy, Hedera helix, in the city of Bern. Collections spanned September 2020 through September 2021, with the bulk made in August 2021.

Both host species are Mediterranean in origin but are spreading northwards. Ectobius vittiventris has colonized Germany as far as North Rhine-Westphalia and has been recorded in the Alps up to 1400 metres altitude, while Meconema meridionale has spread across western Europe to the North Sea, apparently avoiding higher elevations. The authors suggest that these expanding populations may be encountering fungal pathogens for the first time in their new ranges, a hypothesis that could explain the unusually severe infections observed in Switzerland.

Laboratory work followed classical mycological protocols. Selected infected bush-crickets and the dead cockroach were placed individually in small Petri dishes with water, and microscope slides suspended above the cadavers collected the primary conidia actively discharged by the fungus. Secondary conidia were picked from the water surface.

Fourteen bush-cricket cadavers and the single cockroach cadaver were then dissected, and the fungal material was mounted in lactophenol-cotton blue or lactophenol-aceto-orcein stains. Measurements were taken only from primary conidia lying with their axis parallel to the slide and with the entire spore outline in focus, with twenty-five structures measured per host individual as a standard series, and multiple series examined to capture variation. The fungus attacking Meconema meridionale proved to be Zoophthora giardii.

The host body was completely filled with hyphal bodies, and compound rhizoids anchored the cadaver firmly to the leaf surface. The conidiophores were branched, and their terminal portions, from which the primary conidia develop, detached before spore formation. The primary conidia were subcylindrical with the widest diameter in the middle, averaging 20.0 to 21.6 micrometres long by 6.8 to 7.2 micrometres wide, with a length-to-diameter ratio of 2.86 to 3.08.

These conidia germinated in two ways: some produced a capillary germ tube ending in a type II secondary conidium, or capilliconidium, while others formed a short thick tube giving rise to a type I secondary conidium resembling the primary spore. The fusiform, slightly bent capilliconidia averaged 20.1 to 20.8 by 5.7 to 6.0 micrometres and developed at the tips of capillary tubes averaging 75.1 to 92.4 micrometres in length. Resting spores were absent.

The identification was confirmed by comparison with the original description of Zoophthora giardii published by Bałazy in 1993, which reported primary conidia of 19.5 to 23.5 by 6 to 7 micrometres and capilliconidia of 21 to 25 by 5.5 to 6.5 micrometres. The minor differences in capilliconidium length between the Swiss material and the original account were judged small enough to be attributable to different preparation and staining methods. Zoophthora giardii was previously known from France, Germany and Poland, where Bałazy considered it rather rare, so its appearance in Switzerland is not unexpected.

What is striking, however, is that in Switzerland the fungus was found at several localities and occasionally reached epizootic levels, a contrast the authors attribute to a difference in host. Bałazy had found the fungus on the oak bush-cricket Meconema thalassinum, whereas the Swiss infections occurred on M. meridionale, a newly documented host. It is possible that this species never encountered the fungus within its original distribution area and is therefore more susceptible to infection.

The cockroach pathogen was identified as Conidiobolus gustafssonii. The diseased Ectobius vittiventris was fixed to an ivy leaf with compound rhizoids, wings slightly opened, and surrounded by a white halo of discharged conidia. Inside the body cavity, the hyphal bodies were irregularly rounded, occasionally composed of two or more rounded elements or short hypha-like structures.

In contrast to Zoophthora, the conidiophores were unbranched, each bearing a single conidium, and the primary conidia were round to slightly pyriform with the spore body merging smoothly into a rounded papilla. Conidia were measured three ways: projected conidia averaged 43.2 by 35.6 micrometres, conidia taken from the leaf 40.6 by 31.5 micrometres, and conidia prepared from host tissue 39.9 by 31.4 micrometres. The projected spores were slightly larger, an artefact of compression between slide and cover glass; the other two preparations contained non-fungal material that prevented compression and thus yielded more accurate values.

The authors therefore consider 40 to 41 by 31.5 micrometres, matching Bałazy's original description of 41 to 47 by 30 to 40 micrometres, as the reliable size for this material. Primary conidia germinated with a single short tube to form a secondary conidium resembling the primary one, though no fully developed secondary conidia were observed, and resting spores were again absent. Bałazy had described the species from Ectobius lapponicus, so E. vittiventris likewise constitutes a new host record.

Voucher material has been deposited at the United Herbaria Zurich under the accession numbers ZT Myc 66704 and 66705 for Zoophthora giardii and ZT Myc 66706 for Conidiobolus gustafssonii. With these additions, the number of entomophthoralean fungi known from Switzerland rises to ninety species, a diversity unmatched by any other country for classified arthropod-pathogenic Entomophthoromycota. Pre-alpine valleys have proven especially rich: more than a third of the species recorded in Switzerland originate from the headwaters of the rivers Murg in Thurgau and Töss in Zurich, where relatively undisturbed riverine forests harbour a rich insect fauna that evidently supports a correspondingly rich fungal fauna.

The authors expect a similar effect in alpine ecosystems, which remain unexplored with respect to insect-pathogenic fungi. They conclude that further species of Entomophthoromycota certainly await discovery, not only in Switzerland but worldwide, since the group has never been systematically studied, even though it plays an important role in regulating arthropod populations and carries substantial potential for pest control. The association of these first records with northward-expanding Mediterranean hosts also hints that range shifts may reshuffle host-pathogen relationships, with newly arrived insects potentially meeting pathogens they have never evolved defences against.

Subject of Research: First Swiss records of the entomopathogenic fungi Zoophthora giardii and Conidiobolus gustafssonii on newly documented insect hosts

Article Title:  Zoophthora giardii Bałazy and Conidiobolus gustafssonii Bałazy ( Fungi , Entomophthorales ), two entomopathogens new for Switzerland

Article References: Keller, S. (2022).  Zoophthora giardii Bałazy and Conidiobolus gustafssonii Bałazy (Fungi, Entomophthorales), two entomopathogens new for Switzerland. Alpine Entomology, 6, 19-23. https://doi.org/10.3897/alpento.6.83182

Image Credits: AI Generated

DOI: 10.3897/alpento.6.83182

Keywords: entomopathogenic fungi, Entomophthorales, Zoophthora giardii, Conidiobolus gustafssonii, Meconema meridionale, Ectobius vittiventris, Switzerland, new host records, insect pathogens, biological pest control, biodiversity, Zoophthora