Tetraploid induction by meiosis inhibition with cytochalasin B in the dwarf surfclam, Mulinia lateralis Say: Effects of temperature

Tetraploidy, which is useful for the production of all-triploids, can be induced in marine bivalves by manipulating meiosis. In this study, we tested the effects of temperature on cytochalasin B (CB)-induced meiosis inhibition in a model bivalve, the dwarf surfclam, Mulinia lateralis Say. Newly fertilized eggs of the dwarf surfclam were treated with CB (0.75 mg/L) at proper times to block the release of polar body I (PB1) or polar bodies I and II (PB1&2) at 19°C, 24°C, and 28°C. Inhibition of PB1 produced largely triploid and aneuploid-tetraploid (3.7n to 3.8n) larvae, and sometimes small percentages of pentaploids. Inhibition of PB1&2 produced primarily pentaploids and occasionally triploids and aneuploid-tetraploids. Most of the larvae with ploidy levels higher than triploid developed as trochophores only and died a few days after fertilization. At Day 25 post-fertilization, four tetraploids (2%) were detected among 196 juvenile clams in one of the eight PB1&2 groups. No tetraploids were observed in the eight PB1 groups produced. In general, higher (28°C) temperatures did not improve tetraploid production measured as survival to juvenile stage. Low temperature (19°C) made CB treatment less effective, producing all diploid juveniles by Day 17. This work indicates that tetraploidy can be tolerated in M. lateralis and scope for further work on this species therefore exists.