Publication Date:
2021-07-16
Description:
The present study was firstly conducted to study the rate of sexual maturity in Nereis diversicolor under suitable conditions of temperature and photoperiod. The second objective was to determine the potential of artificial breeding in these worms for mass culture. Nereis diversicolor worms were collected from the Anzali lagoon in 4000 sampling operations during the year’s 2004 to 2006 using Ekman grab with a surface area of 400 cm2. The water salinity, temperature and total organic matter (TOM) of sediments in the sampling region was recorded. The worms were maintained in 0.5 tons (1 x 1 m^2) tanks containing clayey-muddy sediment to a height of 20 cm covered with 10 cm water (5 ‰) until they reached a weight of 200-300 mg. Sexual maturity in this species was attained at 4-6 ºC and spawning occurred at approximately 16 ºC. The first gametes were observed five weeks after the temperature increased from 6 to 16 ºC. Sexual maturity was studied at various salinities (0.5, 5, 12, and 15 ‰). Results indicate that these worms attained earlier sexual maturity at salinity of 15 ‰, compared to other salinities studied. No significant differences (P〉0.05) were observed between sexual maturity attained at 12 ‰ and 15 ‰. Stocking density (20, 50, 100, 150 worms) was studied in terms of sex and showed that number of females were higher than males and the ratio was 11:1 (female: male). No significant differences (P〉0.05) were observed between the various stocking densities and their replicates. The effect of light and photoperiod in synchronizing reproduction in male and female N. diversicolor was studied. It was evident that reproduction behavior in adult worms increased for a period of one week at the end of each month after they are exposed to a prolonged photoperiod (L:D=16:8) followed by a period of dim light (simulated using 1 W lamps). Feeding trials were carried out with Saccharomyces cerevisiae, formulated fish diets and humus. Results showed that this diet was effective in speeding up sexual maturity in worms and significant effect of treatment was observed (P〈0.05) in worms fed a diet of humus alone. Eggs and sperms were fertilized and worms developed from the young monotrochophore with jelly layer to the trochophore larvae.
Keywords:
Biology
;
Iran
;
Anzali Lagoon
;
Reproduction
;
Sexual Maturity
;
Fertilization
;
Nereis Diversicolor
;
Culture
;
Salinity
;
Temperature
;
Spawning
;
Female
;
Male
;
Larvae
;
Sacchromyces cerevisiae
;
Density
Repository Name:
AquaDocs
Type:
monograph
Format:
application/pdf
Format:
application/pdf
Format:
68
