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Updated: Jul 15, 2026
06:49
Sperm Collection and Computer-Assisted Sperm Analysis in the Teleost Model Japanese Medaka (Oryzias latipes)
Published on: October 6, 2022
Reproductive-tactic-specific variation in sperm swimming speeds in a shell-brooding cichlid.
J L Fitzpatrick1, J K Desjardins, N Milligan
1Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1. fitzpajl@mcmaster.ca
Biology of Reproduction
|April 27, 2007
Summary
Males facing higher sperm competition produce faster-swimming sperm, supporting evolutionary theory. This study in cichlid fish found sneaker males, with intense sperm competition, had the fastest sperm, while pirates had the slowest.
Area of Science:
- Evolutionary Biology
- Animal Behavior
- Reproductive Strategies
Background:
- Sperm competition theory predicts increased investment in gonads and faster sperm with higher competition.
- While gonad investment is well-studied, the link between sperm swimming speed and sperm competition levels is less explored.
- Telmatochromis vittatus, a cichlid fish from Lake Tanganyika, presents a model system with distinct male reproductive tactics and varying sperm competition levels.
Purpose of the Study:
- To test predictions of sperm competition theory regarding sperm characteristics in Telmatochromis vittatus.
- To investigate the relationship between male reproductive tactics, levels of sperm competition, and sperm swimming speed.
- To determine if sperm size (tail length) is also affected by sperm competition.
Main Methods:
- Examined sperm characteristics of Telmatochromis vittatus males exhibiting four reproductive tactics: pirate, territorial, satellite, and sneaker.
- Assessed sperm swimming speed and sperm tail length.
- Correlated these sperm traits with the varying levels of sperm competition associated with each reproductive tactic.
Main Results:
- Sperm from sneaker males, facing the highest sperm competition, exhibited significantly faster swimming speeds.
- Sperm from pirate males, facing the lowest sperm competition, were the slowest swimming.
- No significant variation in sperm tail length was detected across the different reproductive tactics.
Conclusions:
- Sperm competition in Telmatochromis vittatus influences sperm energetics, leading to faster sperm in males with higher competition.
- The study supports the hypothesis that sperm swimming speed is an adaptive response to varying levels of sperm competition.
- Sperm size (tail length) does not appear to be a target of selection related to sperm competition in this species.
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