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2. Phenotypic plasticity in sperm traits in scorpionflies (Mecoptera: Panorpidae): Consequences of larval history and seasonality on sperm length and sperm transfer
- Creator:
- Vermeulen, Andreas, Engels, Sierk, Engqvist, Leif, and Sauer, Klaus Peter
- Type:
- article, model:article, and TEXT
- Subject:
- Mecoptera, Panorpidae, ejaculate expenditure, larval rearing density, spermatogenesis, sperm competition, and sperm size
- Language:
- English
- Description:
- We examined effects of seasonality, larval food availability and larval rearing density on sperm length, sperm transfer rates and body size in the bivoltine scorpionfly Panorpa vulgaris. Males of the first annual generation were larger and had larger sperm. Comparing individuals of two summer generations showed that adult males resulting from group bred, ad libitum fed larvae were larger but had smaller sperm than males resulting from singly kept, food deprived larvae. Thus, sperm size is not a simple function of body size. Instead, we suggest that sperm size modification was caused by varying rearing densities. Group bred individuals produced smaller sperm but transferred at higher rate. This indicates a trade-off between sperm number and sperm size as predicted by evolutionary models of sperm production. Given the strong influence of larval history in our present work, we recommend that future studies investigating the consequences of varying sperm competition risk or intensity on male gametic strategies should also control for larval history in order to avoid distorting effects.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
3. Sexual activity in Coccinellidae (Coleoptera): a review
- Creator:
- Hodek, Ivo and Ceryngier, Piotr
- Type:
- article, model:article, and TEXT
- Subject:
- mating, preferential mating, sperm competition, dormancy, spermatheca, testes, Coccinellidae, Coccinella septempunctata, Ceratomegilla (syn. Semiadalia) undecimnotata, Adalia bipunctata, Harmonia axyridis, Cryptolaemus montrouzieri, and Epilachninae
- Language:
- English
- Description:
- Although there are few studies of the sexual life of coccinellids these phenomena have attracted the interest of isolated groups of coccinellidologists. Probably the most important finding is that at least some coccinellid species (Adalia bipunctata and Harmonia axyridis) do not mate at random with the females prefering certain males. This phenomenon was first observed in Adalia bipunctata by Lusis and then studied in detail by Majerus, O'Donald, de Jong and others. In Japan, Harmonia axyridis was similarly studied by Osawa and Ueno. While the former author found that in this species (as in A. bipunctata) the colour of the elytra is most important in mate choice by females, the latter stresses that size and activity are important. Sperm competition is another interesting phenomenon, most often the sperm of the last male fertilizes the eggs (Ueno, Katakura). Obata and Hidaka have contributed in an important way to elucidating the function of the spermatophore in mating. The studies by Hodek and Ceryngier recorded the maturation and regression of testicular follicles and the relation of mating activity to diapause in four coccinellid species. In contrast to females, where induction of diapause prevents maturation of ovaries, in diapausing males the tissue of testicular follicles remains active until the temperatures decrease in late autumn. Dissection of spermathecae revealed principal difference in autumn mating activity between Coccinella septempunctata, in which 40-60% of the beetles mated before hibernation and Ceratomegilla (syn. Semiadalia) undecimnotata, which does not mate in autumn.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
4. Sperm viability in the male accessory testes and female spermathecae of the bumblebee Bombus terrestris (Hymenoptera: Apidae)
- Creator:
- Freeff, Michael and Schmid-Hempel, Paul
- Type:
- article, model:article, and TEXT
- Subject:
- Apidae, sperm storage, sperm viability, sperm competition, accessory testes, spermatheca, Bombus terrestris, bumblebees, and colony cycle end
- Language:
- English
- Description:
- In many species sperm competition selects for large ejaculates while females eliminate or disable a high percentage of the spermatozoa in their storage organs in order to control paternity. Therefore, sperm viability is an excellent measure of the reproductive success of both males and females. Here we assess the viability of spermatozoa in males, freshly mated queens and old queens at the end of a colony cycle of the monandrous bumblebee Bombus terrestris. We found that the accessory testes of males contained a significantly lower percentage of dead sperm (i.e. higher average viability) than the spermathecae of both freshly mated and old queens. In each case, however, the percentage of dead spermatozoa was very small. No differences could be detected between sperm viability in freshly mated and old queens. To test for the possible incompatibility of the sperm and the environment provided by female spermathecae males and females either from different geographic regions (north and south of the Alps) or the same region were mated. We did not find any differences between matings of individuals from within or between regions. The mechanism that causes the lower sperm viability in females remains unknown.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public