Bigger testes do work more: experimental evidence that testis size reflects testicular cell proliferation activity in the marine invertebrate, the free-living flatworm Macrostomum sp.
By L. Schärer, Peter Ladurner, R. Rieger. Behavioral Ecology and Sociobiology, 2004
84 citations recorded by the source corpus.
Evolutionary theory predicts that more resources are allocated to sperm production when sperm competition is high. This prediction is supported by both comparative and experimental data on static measures of male allocation, such as testis and ejaculate size. However, resource allocation is a dynamic process, and it is therefore important to evaluate if the static measures reflect this. Such an evaluation has to our knowledge never been done. Immunocytochemical labelling with bromodeoxyuridine (BrdU) allows visualisation of cells in S-phase. BrdU becomes incorporated into cells if, and only if, they are actively undergoing DNA duplication, which is a dynamic process. The number of BrdU-positive cells in the testis can hence serve as a dynamic measure of male allocation, i.e. testicular activity. We evaluate the relationship between testis size and testicular activity in the marine flatworm Macrostomum sp. In a previous study, we showed that testis size is phenotypically plastic in this species, and that worms make larger testes when they are raised in larger groups. We use this plasticity to experimentally produce variation in testis size, and demonstrate that larger testes are associated with higher testicular activity. Moreover, testis size and testicular activity were related linearly. We have thus, for the first time, shown that testis size is a good measure of resource allocation to the male function. Moreover, increased testicular activity is probably one of the first steps in the upregulation of sperm production. It is thus expected that testicular activity is a more sensitive measure of short-term variation in male allocation than the commonly used static measures.
Subfields: Ecology, Evolution, Behavior and Systematics, Genetics
View Paper: https://www.semanticscholar.org/paper/ac6080a2191ebab5ade60fde1565073b63899a1d
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Citations in the corpus
- Phenotypic plasticity in sperm production rate: there’s more to it than testis size (2007, methodology): “…induced to produce larger testes by raising them in groups instead of pairs (Schärer and Ladurner 2003; Schärer et al. 2005; Brauer et al. in press), and we have shown that this increase in testis size coincides with a higher cell proliferation activity in the testis (Schärer et al. 2004b).”
- A new model organism among the lower Bilateria and the use of digital microscopy in taxonomy of meiobenthic Platyhelminthes: Macrostomum lignano ,n . sp. (Rhabditophora, Macrostomorpha) (2005, background): “…under the name of Macrostomum sp.: shape of the copulatory organ and photomicrograph of stylet (Ladurner et al. 2000), socially induced changes in the allocation to male reproductive function (Schärer and Ladurner 2003; Schärer et al. 2004b, 2005), mating behaviour (Schärer et al. 2004a).”