CORETHRELLIDAE (Wood, 1991)

Sinclair, Bradley J., Borkent, Art & Wood, D. Monty, 2007, The male genital tract and aedeagal components of the Diptera with a discussion of their phylogenetic significance, Zoological Journal of the Linnean Society 150 (4), pp. 711-742 : 731

CORETHRELLIDAE

Description ( Fig. 6B )

Testis: Each testis is an elongate spindle-shaped organ, similar to that of other groups, with internal zones organized into the various stages of spermatozoan growth and maturation ( McKeever, 1985).

Epididymis: Not differentiated.

Vas deferens: The vasa deferentia are a continuation of the outer walls of the testes, uniform and separate throughout their length, containing spermatozoa ( McKeever, 1985).

Accessory gland and seminal vesicle: The vasa deferentia unite with the accessory glands, at which point the ducts may be termed seminal vesicles due to the presence of a densely packed mass of spermatozoa. However, these ducts are not enlarged at this point ( McKeever, 1985). Each seminal vesicle terminates at a valve, at which point the duct continues and opens into the forked ejaculatory duct. The paired accessory glands are spherical and also open at the vasa deferentia – ejaculatory duct junction ( McKeever, 1985). These glands are lined with tall inner glandular cells.

Ejaculatory duct: The ejaculatory duct begins as a pair of ducts each continuous with the vas deferens, uniting distally ( McKeever, 1985). The duct is sheathed in circular muscle and is continuous posteriorly with the aedeagal sheath.

Ejaculatory apodeme, sperm pump, and aedeagus: There is no equivalent of the simuliid ventral plate in Corethrellidae ( Wood & Borkent, 1982; McKeever, 1985). As in other families of Culicoidea, the ejaculatory apodeme is absent. The aedeagus is membranous, tapered to a narrow opening ( McKeever, 1985). The only sclerotized structures that are readily observed are the fused parameres (penis valves) that form a Vshaped or tubular structure ( Belkin, 1968; McKeever, 1985).

Remarks: The internal male genital tract was detailed by McKeever (1985). In contrast to the Culicidae , the seminal vesicles of Corethrella Coquillett (the only genus in the family) are not enlarged and although spermatozoa are found throughout the vasa deferentia, they form a densely packed mass in the seminal vesicle. The structure and arrangement of the accessory glands, seminal vesicles (weakly differentiated from vasa deferentia), ejaculatory duct, and parameres are similar in Anopheles Meigen ( Lum, 1961a) and Corethrella ( McKeever, 1985) .

Figures

Figure 6. Male internal reproductive organs (dorsal view). A, Dixa yamatoma (Dixidae) (based on the specimen photographed in Fig. 5B). B, Corethrella sp. (Corethrellidae) [modified from McKeever (1985)]. C, Anopheles quadrimaculatus (Culicidae) [modified from Hodapp & Jones (1961)]. D, Ptychoptera nr japonica (Ptychopteridae) (scale bar = 0.1 mm). E, Ptychoptera lacustris (Ptychopteridae) [modified from Just (1973)]. acc gl, accessory gland; acc gl cplx, accessory gland complex; ej dt, ejaculatory duct; sem ves, seminal vesicle; tes, testis; vas df, vas deferens.