Effect of Insect Growth Regulator Dimilin® (TH 6040) on Fecundity and Egg Viability of the Marine Copepod Acartia tonsa

Abstract

Studies of adult LD,, concentrations of Dimilin, an insect growth regulator which acts to inhibit chitin synthesis, are misleading when applied to arthropods which experience a terminal molt. The calanoid copepod Acartia tonsa Dana has a determinate number of molts after which no growth occurs and the necessity of chitin production is restricted. Survival of adult A. tonsa held for 5 d in concentrations as high as 1000 ppb Dimilin is not significantly (P < 0.05) different from the controls Fecundity of A. tonsa was not significantly (P < 0.05) altered by 1 to 4 d treatment with l , l 0 or 100 ppb Dimilin but the hatch of viable nauplii was reduced from 90+ % to less than 50 % in l ppb after 12 h of treatment and to less than 5 % in 10 ppb after 24 h of treatment. No viable n a u p l~i were produced by females held in either 1 or 10 ppb Dimilin for more than 36 h. When Dimil~n treatment ceased and the females were placed in seawater, the effect of Dimilin was not readily reversed No viable nauplii were produced by these females for at least the next 30 h after treatment ended

Effect of diflubenzuron on the maturation and reproductive success of the copepod Eurytemora affinis

“…Interestingly, in insects, DFB does not affect development of the larvae while in the egg, but they are unable to hatch and those that do hatch successfully often face high mortality rates of the first instar (Grosscurt and Jongsma 1987;Retnakaran and Wright 1987). DFB inhibited naupliar production in Tigriopus californicus (Antia et al 1985) and hatching success in Acartia tonsa (Tester and Costlow 1981). Lack of naupliar production following continuous (14 day) DFB exposure (Table 3) probably reflected the fact that this experiment was performed 1 week later than the early-versus lateexposure experiment.…”

“…Significant effects of DFB are found at concentrations less than 10 p.p.b, in most cases. Although some investigators have addressed the effects of DFB on copepods (Miura and Takahashi 1974;Mulla et al 1975;Colwell and Schaeffer 1980;Tester and Costlow 1981;Antia et al 1985), the only study specifically addressing larval survival has been that of Savitz et al (1994). In the current work we focused on the timing of exposure relative to the life stage of the copepod Eurytemora affinis and the effect of DFB on brood production.…”

Current practices in the chemotherapeutic control of sea lice infestations in aquaculture: a review

“…Not so surprisingly, adult crustaceans are more tolerant than larval forms. Tester & Costlow (1981) found no toxic effects in adult calanoid copepods, Acartia tonsa., exposed to 1000 ^/gp' for 5 days. However, a significant reduction in the number of viable nauplii was noted in addition to morphological abnormalities in surviving individuals.…”

Burrowing behavior by the fiddler crab Uca pugilator. Inhibition by the insecticide diflubenzuron

“…DFB has been found to disrupt development and reproduction in Crustacea (Costlow 1979, Christiansen & Costlow 1982. At concentrations as low as 0.5 pg I-', mysid and decapod larvae had increased malformations and mortality (Nimmo et al 1980, Tester & Costlow 1981. Mortality was associated with the inability to cast off the molt at ecdysis.…”