Coemansia reversais a species of one of most commonly encountered genera of the Kickxellales, subphylum Kickxellomycotina. The genus is known for the intricacy and elegance of its microscopic reproductive branches called ‘sporocladia’ (Fig. 1a, b). With ~21 species,Coemansiais also one of the largest genera in this subphylum. Kickxellomycotina are saprobes, mycoparasites or symbionts of aquatic arthropods or aquatic stages of arthropods.Coemansiaspecies are most often collected on dung and soil but they have also been isolated from dead insects and other organic matter.
Kickellomycotina is one of the five subphyla formerly classified in Zygomycota. Current data support Kickellomycotina as a unique lineage among the early diverging fungi, distinct from the Mucoromycotina (e.g.,RhizopusandPhycomyces).As such, they likely represent a reservoir of unique genes and enzyme potential. (JGI-MycoCosm-2015)
C. reversa vegetative hyphae are covered with capitate ornaments (Moss, 2002). On reproductive hyphae, ornamentation changes to rod-shaped. From the reproductive hyphae, a conidiophore is formed that is ternately branched (Linder 1943). The branches, called sporocladia, form multiple tiersoff of the main conidiophore stalk, each branch having a downward curve (or reverse curve, thus the species name “reversa”). Each sporocladio bears multiple conidia in rows that hang perpendicular to the branch on the underside of the sporocladia. A merosporangial membrane envelopes each conidium and conidia are surrounded by fluid in this membrane when mature (Young 1968). This membrane appears to split from the bottom apex of the conidium, allowing the spore to be released. The conidium of C. reversa is elliptical in shape and around 10 microns in length. C. reversa conidia have a very distinct look, as they lack both a distal fin region and ornamentation, two conidia features commonly found in other Coemansia species.
Brief description of Coemansia genus. Species list with references.
The distribution of this fungus is seemingly widespread. Since its original discovery in France, it has been isolated from Ukraine, Africa, Central America, and various locations within the United States (Cholondny, 1935; Moss, 2002; Farrow, 1954; Linder, 1943). It is most commonly isolated from rat dung, accompanying the fungus Isaria felina. It is readily culturable in media, such as Malt Extract Yeast Extract (MEYE) agar (McLaughlin, 2015). Although this fungus may not be apparent in the original sample, when cultured it produces bright yellow colonies (Linder, 1943). To date, only asexual reproduction has been observed for C. reversa. Despite this, two different trophic modes have been described for the specie. One mode is as a mycoparasite on Isaria felina, the other as a saprophyte in pure culture. A more in-depth discussion of the trophic nature of C. reversa is provided in the "Parasitic and Saprophitic Growth" section.
Much study has also been done on spindle pole bodies involved in mitotic replication in C. reversa. The paragraph below by Healy et. al details these findings.
“The SPB [spindle pole bodies] duplicated early in mitosis and separated on the intact nuclear envelope. Short spindle microtubules formed within the nucleus beneath the extranuclear SPB. The nucleolus formed an extensive band along the nuclear envelope distant from the SPB early in mitosis. Nuclear division appears to be intranuclear with spindle and kinetochore microtubules interspersed with the condensed chromatin. A metaphase plate appears to be absent. The nucleolus retained a peripheral position within the nucleus or was in a pocket on the nucleus later in mitosis (Figure 1B). Late stages in nuclear division were not observed. The results in C. reversa indicate that it possesses a fourth type of zygomycetous SPB, and the third type that suggests a reduced centriolar component in zygomycetous fungi. The ring of nine microtubules in C. reversa closely parallels the centriolar structure of Chytridiomycota and Blastocladiomycota, but the nine microtubules are not paired and the central microtubule is absent in C. reversa.” (Healy et. al, 2014)
Much debate has surrounded the trophic function of C. reversa. It was originally reported to be growing on rat dung (van Tieghem and Le Monnier, 1873). Subsequently, Thaxter reported being able to grow C. reversa in completely pure culture, bring into question its mycoparasitic function (Thaxter, 1895). However, Banier then reported the fungi to be parasitic on Isaria felina culture by (Bainier, 1906). In 1943, Linder proposed that the fungus actually was mycoparasitic on Isaria in the original cultures (Linder, 1943). He based this on the observation that all the rat dung from which he obtained isolates of C. reversa also contained Isaria spp., especially Isaria felina. Following this Benjamin found that in a pure mixed culture C. reversa sporulated extremely well in the presence of an Isaria fungus (Benjamin, 1959). However he also noted that he was not able to show that C. reversa actually parasitized the Isaria specie via hyphae penetration. In addition, he successfully grew C. reversa in pure culture in which no Isaria spp. were present. These multiple reports suggest that C. reversa is possibly capable of at least two different “modes”, one presumably as a saprophyte, the other as a mycoparasite. However, the issue has yet to be clearly resolved.
For electron microscope photographs of conidia, please refer to figures provided in Young TWK. 1968. Electron microscopic study of asexaul spores in Kickxellaceae. New Phytologist 67: 823-836
For drawings of conidiophore structure please refer to Plate 1.A in Linder DH. 1943. The genera Kickxella, Martensella and Coemansia. Farlowia 1:49-77
Coemansia reversa was first described by Tieghem and LeMonnier in France, 1873. It was presented as the type species for its genus, Coemansia. Fungi in the genus Coemansia are commonly isolated from dung and other organic materials, either as saprobes or mycoparasites. (Kwansa et al., 1999). They also typically bear conidia on the underside of the sporocladia. C. reversa shares these characteristics but also has distinct microscopic morphological feature that distinguish it from other members of the genus. In addition,C. reversa has been reported as a mycoparasite on Isaria, although this relationship has been questioned.
Photo of sporophore bearing asexual spores
Photograph of Coemansia reversa conidiophore
