SCATOPSIDAE

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 : 724-725

SCATOPSIDAE

Description

Testis: Each testis is oval-shaped ( Loew, 1841).

Epididymis: Not differentiated.

Vas deferens: The ducts could not be traced in this study, but according to Loew (1841) a pair of rather long and convoluted ducts enters separately a small expanded region.

Accessory gland and seminal vesicle: A small oval expansion is present at the apex of the ejaculatory duct ( Loew, 1841) and may correspond to a seminal vesicle. The paired vasa deferentia enter this vesicle separately. This structure could not be confirmed in our dissections.

A pair of long tubular glands, with posteriorly recurved tips, dominates the posterior region of the genital tract. These thick-walled accessory glands lie dorsal to the sperm pump and rectum, arch anteroventrally and taper to narrow ducts that enter the sperm pump ventrally. The recurved tip appears to taper to a short nipple-shaped appendix. These glands are rather stout and the narrow extension of the gland to the sperm pump is also thick walled, with a narrow inner canal.

Ejaculatory duct: This duct could not be traced in the present study, but according to Loew (1841) the duct is similar in size to the vas deferens and extends from the expanded anterior sac (seminal vesicle?) to the sperm pump.

Ejaculatory apodeme, sperm pump, and aedeagus: The sperm pump and associated ejaculatory apodeme are clearly separated from the base of the external genitalia. The outer wall of the sperm pump is sclerotized and remains intact after being cleared in lactic acid. The pump bears stout opposing muscle sets and clearly functions to pump sperm to the aedeagus. The pump is connected to the aedeagus by a very narrow, clear tube (see Cook, 1981: fig. 20.18).

Remarks: The reproductive tract of Scatopse notata (L.) was described by Loew (1841). Unfortunately, we were not able to trace the configuration of the vasa deferentia in the material available and consequently cannot confirm the observations of Loew (1841). The most striking difference in Scatopsidae from other families is the apparent direct connection of the accessory glands to the sperm pump. Further study of the scatopsid male reproductive tract is required in order to confirm and interpret these observations.

Given the presence of the narrow tube connecting the sperm pump and the aedeagus and the robust sperm pump, an aqueous solution containing spermatozoa is probably pumped through this system.