A New Species of Laboulbenia (Ascomycota) Parasitic on an African Fly (Diptera: Curtonotidae), with a Brief Review of Diptera-Associated Species of the Genus

ABSTRACT A new parasitic fungus, Laboulbenia curtonoti sp. n., associated with the endemic Madagascan fly Curtonotum balachowskyi Tsacas (Diptera: Curtonotidae), is described and figured. The new species is one of the very few Laboulbeniales which penetrate the insect's cuticle by means of more-or-less developed rhizoids. A brief review of the 23 species of the genus Laboulbenia associated with Diptera is presented in a tabulated form.


INTRODUCTION
Laboulbeniales is a large group of ascomycete fungi which complete their entire lifecycle on living arthropods. Most are found on insects, but a few are known to parasitise nearly 2,000 described species penetrate the insect's cuticle by means of more-or-less developed rhizoids.
With almost 600 described species, the genus Laboulbenia is by far the largest among the Laboulbeniales (Rossi 2011). The number of species of Laboulbenia parasitic on the Diptera is, however, relatively small, only 23 having been described to date. These are reported from the dipterous families Celyphidae, Curtonotidae (as Drosophilidae), Chloropidae, Diopsidae, Lauxaniidae, Psilidae, Richardiidae, Tephritidae and various previous records of Laboulbenia spp. associated with the Diptera is presented in tabulated form below (Table 1). Included names are updated, although some familial names were should be borne in mind that about half of the listed associations represent records from the African continent. It is also noteworthy that only a single fungal species, Laboulbenia diopsidis Thaxt., has subsequently been recorded after its original description. This does not represent evidence of rarity, but rather bears witness to the scarcity of research During the course of an ongoing revision of Madagascan Curtonotum by A. Kirk-Spriggs, numerous specimens of the Malagasy endemic species Curtonotum balachowskyi Further examination revealed that this parasite represents a new species of the genus Laboulbenia, which is described herein.

MATERIAL AND METHODS
Insects bearing Laboulbeniales were found in samples preserved in 95 % ethanol, resulting from Mike Irwin's Arthropod Survey of Madagascar's Protected Areas, on loan from the California Academy of Sciences, USA (CASC). Thalli were carefully removed from the hosts with a size 3 insect pin. Permanent microscope slides of fungi solution, which is a mixture of glycerol, phenol and lactic acid, as mounting medium; cover slips were ringed with transparent nail varnish.
Slides of the type series are preserved in the Botanical Museum of Florence, Italy (FI) except for the isotype, which is deposited at the National Museum, Bloemfontein, South Africa (BMSA).

Figs 1-5
curtonoti is derived from the name of the host insect (Curtonotum Cell I subspherical, partially to entirely inserted within host's integument; thallus penetrating beneath integument with large haustorium (rhizomycelium). Cell II subhyaline, forming elongated stalk of uniform diameter throughout, only slightly enlarged apically. Stalk-cell of appendage (cells III+IV+V) greyish, about 1.5× longer than broad, its upper third free, although often in contact with base of perithecium; surface of upper, outer cell of appendage. Outer appendage greyish, with large basal cell bulging externally, tuft of elongate, brownish antheridia on inner side. Inner appendage consisting of small basal cell giving rise on either side to very short branchlets, bearing apically crown of antheridia; in older specimens antheridia replaced by slender, hyaline, curved, sterile appendages, which barely reach half the height of perithecium. Stalk-cell of perithecium (cell VI) greyish, about as long as maximum width, its surface inconspicuously striate, separated from cell below by distinctly oblique septum. Perithecial venter free, blackish brown, ovoid, wall cells slightly twisted. Neck abruptly constricted, greyish, relatively short, distinctly curved, bearing two symmetrical, rounded prominences on inner (dorsal) side and smaller and paler bulge on outer side. Tip pale grey, also bearing three prominences positioned above those of neck; two inner ones hemispherical, surmounted rise to two large, hyaline, slightly diverging, pointed, horn-like lips. Total length (from

DISCUSSION
The small group of species of Laboulbenia parasitic on Diptera is paraphyletic. From the morphological standpoint it can be divided in three groups: one in which cells III, IV and V are distinct; one with these cells undivided; and one with a distinct cell V and cells III+IV fused together.
The very peculiar distal portion of the perithecium of Laboulbenia curtonoti sp. n., with the two large lips resembling the ears of a donkey, makes it possible to immediately distinguish it from all other species of the genus. The only species to which it can eventually be compared is L. dahlii (Thaxt.) Thaxt. (= Ceraiomyces dahlii Thaxt.), described also penetrates the host with a long haustorium and shares the undivided stalk cell of the appendage, but differs from L. curtonoti in almost every other respect.
Preservation for extended periods in 95 % ethanol, as these specimens had been, results in host insects becoming stiff and brittle, and as a result, it was not possible to extract the penetrating haustorium intact. It was possible, however, to observe that the basal portion of the haustorium is still quite large (diameter ca 30 μm) and undivided after in L. dahlii From preserved museum specimens it is also impossible to ascertain the degree of damage caused by the parasite to its host. Experimental studies undertaken with Stigmatomyces ceratophorus Fannia canicularis This example provides only limited evidence, however, as S. ceratophorus pressure or food shortages. It can be assumed in the present case that the presence of large haustoria of L. curtonoti sp. n. may be detrimental to the host, especially when