Effect Of Oxytocin On Growth And Reproductive Tract Development

Abstract

Development of fourth-stage larvae (L4) of Pseudoterranova decipiens appears to be arrested in the seal host during and post parturition. In view of the elevated level of oxytocin in mammals at parturition, it is hypothesized that oxytocin may be responsible, at least in part, for the arrested development of f. decipiens in seals. Third-stage larvae (L3) of f. decipiens dissected from the musculature of cod (Gadus morhua) were cultured in a two-step roller culture system. The medium API-l and API-l plus oxytocin were used for step 1. Fildes reagent was added to the medium and medium plus oxytocin in step 2. The gas phase consisting of 85% N2: 10% CO2: and 5% 02 was used. The worms were incubated at 35°C. Reproductive tracts were examined from male and female worms at days 7, 10, 15, 20, 25 and 30 and the developmental reproductive morphology was described. Whole worm lengths, reproductive tract length and the ratio of reproductive tract· length/whole worm length were calculated for 5 worms from each experimental set at each of the above days. Developmental changes such as times to moulting, first appearance of external sexual characteristics, appearance of first mature oocytes, first mating, and release of first eggs were advanced by oxytocin. The first appearance of fertilized eggs was observed 5 days earlier in oxytocin-treated worms than in the control worms Statistical analysis showed no significant difference between the growth (length) of male f. decipiens cultured in the oxytocin-treated medium and the growth of those in the control medium. Oxytocin significantly increased the length of female P. decipiens. The length of the reproductive tracts of both male and female f. decipiens was significantly increased by oxytocin as was the reproductive tract length/worm length ratio. Oxytocin at 2.2 x 10-6 mg/ml did not retard the growth and development of f. decipiens in vitro, but instead, enhanced the growth and development of the reproductive tracts in both males and females. The effect observed was more dramatic in female P. decipiens than in males.