Male choice and sexual selection in precopulatory mate-guarding marine gammarus species (Crustacea: amphipoda) found on the Avalon Peninsula of Newfoundland

Miller, Brenda Marie (1999) Male choice and sexual selection in precopulatory mate-guarding marine gammarus species (Crustacea: amphipoda) found on the Avalon Peninsula of Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Behavioural aspects of reproduction were studied on five species of mate-guarding Gammarus found on the Avalon Peninsula of Newfoundland. These species are Gammarus setosus, Gammarus oceanicus, Gammarus duebem. Gammarus lawrencianus, and Gammarus obtusatus. Males chose to form precopulas with females that were close to their next batch of eggs to be fertilized. Females sometimes exhibited reproductive choice by trying to escape the male's grasp. No interspecific precopulas were formed between G. setosus and G. oceanicus. Size assortative mating occurred in (G. setosus. The sequences of precopula formation behaviours differed in the successful and unsuccessful precopulas for all five species. Three takeovers by males were observed in (G. oceanicus, all with egg stage 4 females which are females which are closest to their next batch of eggs to be fertilized. The sequences of precopula formation behaviour contacts differed for successful and unsuccessful takeovers, and were also different from the normal behaviour sequences for G. oceanicus. Takeovers were considered to be male-male competition. However, female choice was observed as the females remained passive, which is considered a form of female choice, during both successful and unsuccessful takeovers. Two simultaneous assessments of females occurred with females that were both in the same egg stage (stage.4) in G. oceanicus. The sequences of precopula formation behaviour contacts differed for successful and unsuccessful simultaneous assessments and also differed from the normal behaviour sequences for (G. oceanicus. In the unsuccessful simultaneous assessments, the extra females sometimes resisted the male's grasp and escaped ( female choice) but the original females remained passive. In the successful simultaneous assessments, the original and extra females remained passive. There were successful precopulas formed with both stage 1 females with stage 4 eggs transplanted and with stage 4 females with eggs removed in G. oceanicus. The sequences of precopula formation behaviour contacts were different for successful and unsuccessful precopulas with egg manipulation females, and were different from the normal behaviour sequences for G. oceanicus. Female choice was observed with egg manipulation females as they sometimes kicked and escaped from the males.

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