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Monacrosporium drechsleri was first described as Dactylella drechsleri and isolated from roots and soil obtained from a grapefruit grove in Florida in 1960 This fungi is currently known as Monacrosporium drechsleri and also referred to as Golovinia drechsleri. Monacrosporium belongs to a large group of nematode trapping hyphomycetes in the order Helotiales. There are thirty nine accepted species included in the genus Monacrosporium. Fungi in this genus can be identified by having differentiated organs for nematode trapping and having top, spindle or calvate conidia. Species identification is done primarily based on the type of trapping organ. Anamorphs of M. drechsleri have been found in subtropical to temperate regions as predators of nematodes.

Characters used in identification and differentiation
Nematode trapping fungi use different mechanisms to capture their nematode prey. This is governed by producing nematode-trapping structures. For example, Drechslerella anchonia and Drechslerella dactyloides produce constricting hyphal rings to capture the nematode. These rings act as bait loops to capture the free swimming nematodes, and after entrapment, digestion by the fungus occurs. Fungi in the genera Drechmeria, Arthrobotrys and Dactylella are capable of producing “adhesive hyphae”. These adhesive hyphae are differentiated into adhesive knobs or nets, which are derived from the hyphae. For Monacrosporium drechsleri, the nematode trapping is governed by specialized knobs derived from the adhesive hyphae. Before the isolation of Monacrosporium drechsleri by Tarjan in 1961, this species was thought to be identical with Dactylella ellipsospora due to the similarities in the conidium and the adhesive knob shape, as well as growth habit. Due to the morphological dissimilarities of Monacrosporium drechsleri, it has been described as a new nematode trapping fungal species. The unique characters of M. drechsleri are listed below. It has been described as having fine, profuse mycelium with septate hyphae. Conidiophores can be branched or unbranched. Conidia are predominantly triseptate and somewhat fusiform with a length of 22 - 48.7 µm and a width of 9.5 - 15.4 µm. Nematode trapping is governed by formation of terminal adhesive spherical to subspherical knobs which originate on a unicellular, long, straight stalk and develop perpendicular to the parent mycelium. According to the first report, the knob length was 8 - 10 µm and had a width of 7.2 - 9.6 µm. Incubation on corn meal agar at, a temperature of 70 - 75°F and a pH rage of 5.2 – 6 was identified as the best conditions for Monacrosporium drechsleri under laboratory conditions, showing a preference of cooler temperatures for predation when compared with Dactylella ellipsospora. The aforementioned morphological characteristics are different and unique to Monacrosporium drechsleri.

Phylogenetic Affinities and Modern phylogenetic research
Recent studies analyzing the ITS, LSU and Ef1-α genes, have shown that trapping devices are more important for species classification than other morphological characteristics of the fungi. According to Meyer et al. (2005), their phylogenetic analysis using ITS and Ef1-α indicated that M. drechsleri was most closely related to M. ellipsosporum. In this study, four different species of Monacrosporium were used. There are about 39 species included in this genus. Therefore, additional taxon sampling is needed to understand phylogenetic relationships among species of Monacrosporium and to determine which species is most closely related to M. drechsleri.

Nematode trapping fungi can be classified according to the type of trapping device they possess. Arthrobothrys is identified as having adhesive networks of hyphae, whereas Dactylellina and Drechslerella have adhesive knobs and constricting-rings respectively. Out of the three trapping devices, adhesive knobs are considered to be the primitive form and the other two types are derived from this structure. According to modern phylogenetic analysis, Monacrosporium is closely related to genus Arthrobothrys. Recent studies of ITS and 18s rDNA sequencing proposed that trapping devices are more reliable in classification than other morphological characters.

Ecology
Even though Monacrosporium drechsleri  was first isolated in grapefruit, most nematode trapping fungi inhabit the soil as predators of free living nematodes or survive mainly as saprophytes. This fungal predation is mainly an adaptation to low nutrient availability for the fungi. Fungi in a low nutrient environment tend to convert to predation more frequently than fungal species inhabiting a nutrient-rich environment. Fungi make inseparable attachments to the nematode through their adhesive knobs. After the attachment, a finger-like structure developed from the knob penetrates the cuticle of the nematode. This forms a circular structure, and the hyphae develop and absorb the nutrients from the nematode upon digestion. Within a short period of time, fungi assimilate all the nutrients from the nematode and appear as a tightly packed bundle of mycelia within the nematode.

Nematode identification by the fungi is mostly governed by chemotaxis. The chemicals produced by the nematode for communication and other physiological activities attract the fungi to initiate predatory behavior. A chemical known as ascarosides produced by the nematode is mainly used for recognition by the fungi. The trap formation is mainly governed by the amount of ascarosides present in the environment.

Dispersion of the fungi are similar to the dispersion of any other soilborne fungal species. This could be mainly governed by wind, water or by animals.

Reproductive Biology
Anamorphs, or the asexual reproductive stage of the fungi, are probably all predators on nematodes. Their sexual stages resemble one of the inoperculate discomycetes; they may not be closely related.