Embryonic and Post-Embryonic Development of Cylindrocorpus Longis'Toma (Nematoda: Cylindrocorporidae)

Abstract

Embryonic development in C. longistoma follows the general pattern of other nematode species. Embryonic development lasts 30-34 hours. The relationship between larval movement and the hatching mechanism is discussed. The proportional changes which occur in gross body form during postembryogenesis are studied through a biometrical analysis of morphometric and allometric characters. The greatest increase in body length occurs during the third stage, coinciding with the greatest increase in gonad length. Due to lack of allometry between pairs of morphometric characters, 'a', 'b', and 'c' ratios are unacceptable for taxonomic purposes pertaining to this species. Growth of the reproductive system is relatively stable and the use of 'V' and 'T' for taxonomic purposes is acceptable. The genital primordium of first- and second-stage larvae consists of two germinal and two somatic cells. Sexual differences are discernible during the second molt by the presence or absence of specialized ventral chord nuclei and differential development of the genital primordium. Specialized ventral chord nuclei take part in the formation of the vagina. A specialized somatic nucleus separates from the uterine wall and initiates the vaginal primordium. Specialized ventral chord nuclei are absent in male larvae. During the third molt the anterior portion of the male gonad turns posteriad and grows along the ventral side of the body. Primordia of spicules and gubernaculum begin development during the third molt and male accessory structures are completed during the final molt. Nuclear divisions in the reproductive system occur throughout molts and stages.