Trichinella spiralis: morphological characteristics of male and female intestine-infecting larvae.

KOZEK, W. J. 1975. Trichinella spiralis: Morphological characteristics of male and female intestine-infecting larvae. Experimental Parasitology 37, 380-387. The sex of encysted and excysted intestine-infecting T. spiralis larvae can be distinguished by the following morphological characteristics: the male larva has a long (approx 50 pm) rectum, and the anterior part of the testis is curved posteriorly. The female larva has a shorter rectum (approx 25 pm), a telogonic ovary, coiled uterine and seminal receptacle primordia, and a vaginal primordium. In paraffin sections males can be recognized by the spermatocytes which are of the same size. The oocytes vary in size: the smallest are located in the ventral portion, the largest on the dorsal portion of the ovary. Sex of the larvae can be differentiated by the length of the rectum as early as the tenth day, by the curvature of the anterior part of the testis and by the uterine primordium by ,the eleventh day, and by the presence of the vaginal primordium by the thirteenth day of intramuscular development. Farm’s Organ is believed to be the primordium of the seminal receptacle. INDEX DESCRIPTORS: Trichinella spiralis; Intestine-infecting larvae; Morphological characteristics; Rectum; Testis; Spermatocytes; Ovary; Oocytes; Uterine primordium; Vaginal primordium; Seminal vesicle primordium; Intramuscular development; Farre’s Organ; Swiss female mice.