SPERM MIXING IN THE COCKROACH DIPLOPTERA PUNCTATA.

Area of Science:

• Reproductive Biology
• Insect Behavior
• Evolutionary Biology

Background:

• Females of the viviparous cockroach Diploptera punctata exhibit sperm storage from their initial mating.
• Remating in this species occurs only after the first brood is delivered.

Purpose of the Study:

• To investigate sperm competition in Diploptera punctata when females are sequentially mated with normal and irradiated males.
• To determine the fertilization success of the second male in sequential matings.

Main Methods:

• Utilized the irradiated male technique to differentiate sperm from sequential matings.
• Analyzed the fertilization outcome of the second batch of eggs in females mated sequentially to normal and irradiated males.
• Examined oothecae for evidence of sperm mixing and differential fertilization.

Main Results:

• The second male to mate with a female fertilized approximately two-thirds of the eggs in the subsequent batch.
• Direct evidence of sperm mixing was observed, with undeveloped eggs (irradiated sperm) and developing embryos (normal sperm) found together.
• Sperm from both normal and irradiated males were released from the spermathecae during oviposition, indicating active competition.

Conclusions:

• Sperm from sequential matings in Diploptera punctata compete for fertilization.
• The second male has a significant fertilization advantage, fertilizing approximately 66% of the eggs in the second batch.
• The findings provide direct evidence for sperm mixing and competitive fertilization in this viviparous insect species.