Molecular ecology of mate recognition in the harpacticoid copepod Tigriopus: Antibody production, protein purification, and fitness consequences.

摘要

In the harpacticoid copepod Tigriopus, females mate once while males mate multiple times. To ensure successful reproduction, males pick up females as juveniles and guard them until their terminal molt. Tigriopus males discriminate among potential mate-guarding partners based on chemical signals displayed on the outer body surface of females that signal sex, species, and developmental stage. I used protease treatment to release mate-recognition proteins from the body surface of females, then developed an antibody to one of these proteins (Chapter II). This antibody recognized a protein that was expressed in a species-specific, stage-specific, and sex-specific manner. Females bound with the antibody were less attractive as mate-guarding partners. This antibody was used to isolate its cognate, mate-recognition protein (Ch III), 70 kD protein with sequence similarity to alpha2 -macroglobulin. A Western blot probed with anti-alpha2-macroglobulin recognized a 70 kD band expressed only in late-stage juvenile females of T. japonicus, and not two closely related species. A second, 36 kD band with sequence similarity to elastase, a cognate protein of alpha 2-macroglobulin, co-purified with the 70 kD band. Therefore, a 70 kD protein with sequence, structural, and functional similarity to alpha 2-macroglobulin may act as a mate-recognition protein in T. japonicus. I attempted to amplify the gene for the 70kD mate-recognition protein from T. japonicus using degenerate oligonucleotide primers for PCR (Chapter IV).; The fitness consequences of mate-guarding for females has not previously been studied. We determined that pre-copulatory mate-guarding increases the probability that females will bear offspring (Chapter V). Females that were mate-guarded prior to copulation were more likely to receive spermatophores than those raised in the absence of males. Therefore, pre-copulatory mate-guarding in Tigriopus plays an important part in reproduction for both males and females, and attractiveness as a mate-guarding partner may confer considerable selective advantage to copepods in the genus Tigriopus.