Kickxellales
Overview
Three genera were known, Coemansia, Kickxella, and Martensella, when Linder (1943) described the Kickxellaceae. These fungi were usually included in the Deuteromycetes by early mycologists (Benjamin, 1959—p.326). Linder (1943) included the Kickxellaceae in the Zygomycetes after observing a zygospore in Coemansia aciculifera Linder. The family has appeared in several treatments of the Mucorales or the Zygomycetes published since that time (Hesseltine, 1955; Benjamin, 1959, 1979; Milko, 1974; Zycha et al., 1969; Hesseltine and Ellis, 1973). In 1979 Benjamin validated the order Kickxellales, a classification also followed in the Dictionary of the Fungi (Kirk et al., 2001).
Recently, four new genera Mycoëmilia (Kurihara et al., 2004), Myconymphaea (Kurihara et al., 2001), Ramicandelaber (Ogawa et al., 2001), and Pinnaticoemansia (Kurihara and Degawa, 2006) were added to the Kickxellales.
Although Martensella spp. are parasitic, they are apparently nonhaustorial. Coemansia reversa van Tiegh. & Le Monn. has also been reported to be a parasite of Isaria spp. (Linder, 1943) but Benjamin (1959) has grown and sporulated C. reversa in pure culture without an Isaria isolate being present. Both Spiromyces minutus and Spirodactylon aureum grow slowly on ordinary laboratory culture media, but these fungi grow better on a medium containing glycerol, YGCH (O’Donnell et al., 1998) (yeast extract, 15 gm; glycerol, 15 ml; casein hydrolysate, 15 gm; K2HPO4, 1 gm; MgSO4.7H20, 0.5 gm; agar, 15 gm; distilled water, 1 liter). Both Spiromyces minutus and Spirodactylon also grow and sporulate better on a plate when another fungus is also present (Dr. R.K. Benjamin, pers. comm., 1985).
Several taxa grow well on YpSs agar including Dipsacomyces pterosporus, Linderina pennispora, Martensiomyces pterosporus, Spiromyces aspiralis, and several isolates of Coemansia. Kickxella alabastrina has grown well on MEYE and CMPY, many isolates of Coemansia also grow well on MEYE. These and other culture media and their formulations can be found in Benjamin (1958, 1959) and Krug et al. (2004). Kurihara et al. (2001, 2004) report that Myconymphaea grows and sporulates on one-half strength MEYE agar.
Twelve genera are now recognized in the Kickxellaceae (Benjamin, 1963; Kurihara et al., 2001, 2004; Ogawa et al. 2001; Kurihara and Degawa, 2006). Members of nine of the genera release their merosporangia in spore drops (they are wet-spored at maturity): Coemansia, Dipsacomyces, Kickxella, Linderina, Martensella, Martensiomyces, Mycoemilia, Myconymphaea, Pinnaticoemansia, and Ramicandelaber, whereas the remaining two genera are dry-spored at maturity: Spirodactylon and Spiromyces (Benjamin, 1966). The wet- and dry-spored taxa exhibit differing types of merosporangial ornamentation. The wet-spored forms produce a pattern apparently characteristic for each species, which is caused by the tips of spines that are attached to transverse bands of wall material embedded in the spore wall (Young, 1970). The spine apices protrude through the outer layer of the merosporangiospore wall and touch the inner side of the merosporangial wall leaving a slightly raised area visible on the latter structure in carbon replicas or freeze-fracture replicas (Young, 1968; Benny and Aldrich, 1975). In the dry-spored taxa the spines are apparently external and are readily visible on the merosporangiospore—merosporangium surface (Young, 1968).
Four sporocladial types were described by (Benjamin, 1966). Two genera form unispored sporocladia: the merosporangia are produced on pseudophialides which arise from the sporocladium in Linderina spp. whereas in Spiromyces spp. the sporocladium is constricted apically and the pedicellate sporangiola form on the bulbous apex; a pseudophialide is not produced by Spiromyces minutus Benjamin. In the remaining members of the Kickxellaceae the sporocladium is multicelled and the merosporangia arise from pseudophialides; i.e., in Kickxella alabastrina Coemans, the sporocladium is three-celled, and several are umbellately arranged on the slightly vesiculate sporophore apex, whereas in the other taxa the sporocladia arise laterally from the sporophore, Coemansia, Dipsacomyces, Martensella, Spirodactylon, or umbellately on a lateral branch of the sporophore as in Martensiomyces. Several taxa have been isolated exclusively from soil, Dipsacomyces, Linderina, Martensiomyces, Ramicandelaber and some Coemansia spp., one genus is presumably parasitic, Martensella, and the remaining members of the family are coprophilous: most Coemansia spp., Kickxella, Spirodactylon, Spiromyces, or they have been isolated from insect cadavers or feces in soil: Mycoëmilia, Pinnaticoemansia .
Zygospores of Kickxellales (Linder, 1943; Benjamin, 1958, 1959, 1963, 1966; Benjamin and Tucker, 1978a; Kurihara et al., 2004) are similar to those of the Dimargaritales (Benjamin, 1959, 1961, 1963, 1965, 1966, 1979; Benjamin and Tucker, 1978b) and have a smooth or ornamentated zygosporangial wall and undifferentiated suspensors.
Moss and Young (1979) indicate that the Kickxellales (Zygomycetes) and the Harpellales (Trichomycetes) have several characters in common, i.e., septal morphology, the coemansioid arrangment of the anamorph, similar wall structure, serological affinity, and possible homology between the “labryinthiform organelle” (Kickxellales) and the trichospore appendage (Harpellales) (Moss and Lichtwardt, 1975). Some spp. of both the Kickxellales (see above) and the Harpellales (Moss and Lichtwardt, 1977) are known to produce zygospores. Young (1999) discusses the phylogeny of the asexual reproductive structures and the taxonomy of the Kickxellales. O’Donnell et al. (1998) present the phylogeny of the Harpellales and Kickxellales based on the comparison of SSU sequences and morphology.
Classification
KICKXELLALES Kreisel ex R. K. Benjamin, 1979 (In Kendrick, The Whole Fungus, p. 610).
=Kickxellales Kreisel, 1969 (Grundzüge eines natürlichen Systems der Pilze, p. 65); nomen nudum, without a Latin diagnosis; Art. 36.1 of the ICBN (Greuter et al., 2000).
Mycelium regularly septate; septa with single lenticular cavities containing plugs lacking polar protuberances; plugs not dissolving in dilute KOH. Sporophore arising directly from somatic hyphae, regularly septate, simple or branched. Fertile branches (sporocladia) aseptate or septate, producing unispored merosporangia indirectly via an intermediate cell (pseudophialide), or several merosporangia arising from a bulbous extension of the sporocladium. Zygospores globose, smooth or ornamentated; zygosporangial wall thin, smooth; sexual hyphae undifferentiated, similar to somatic hyphae. Saprobes or rarely (?) nonhaustorial parasites.
Type family: Kickxellaceae Linder.
A single family recognized.
Kickxellaceae Linder, 1943 (Farlowia 1: 56)(Linder, 1943; Benjamin, 1958, 1959, 1963, 1966, 1979; Zycha et al., 1969; Ogawa et al., 2001; Kurihara et al., 2001, 2004, 2008; Kurihara and Degawa, 2006-key to genera).
= Coemansiacées Vuillemin, 1910 [Bull. Soc. Sci. Nancy, Sér. 3, 10: 172 (1909), nomen invalid., invalid vernacular name, Art. 18.4, Ex. 5 of the ICBN (Greuter et al., 2000)].
With the characteristics of the order.
Type genus: Kickxella Coemans.
Updated Jan 31, 2009