Post-fledging body mass increase in Common Terns Sterna hirundo: influence of age, sex and year

We studied the inter-year and inter-sex variation of the post-fledging body mass development of Common Terns Sterna hirundo in 2000 and 2001 at the Banter See colony, northern Germany. Here, post-fledglings can be identified and weighed remotely and automatically by a transponder system that makes use of automated balances installed at the colony. Individuals were sexed with PCR amplification methods. After fledging, young generally continued to increase their mass. However, in 2000, the young did not significantly increase their mass during the post-fledging period. In 2001, conditions were more favourable and body mass increased continuously. Further, in 2001, male post-fledglings were significantly heavier than female post-fledglings. Once having left the colony area (on average 18–23 days after fledging in 2000, and 14–16 days after fledging in 2001), post-fledgling body mass had still not reached adult body mass. The longer a juvenile stayed at the colony, the higher was its final body mass, which if acting as a threshold level may control departure time. Neither brood size nor hatching order affected post-fledging mass or period. In the unfavourable year 2000, when many individuals were found dead after fledging, fledging age but not fledging mass was found to be a predictor of post-fledging survival before departure: individuals fledging when older had a lower survival probability. Our results stress the importance of the post-fledging period for body mass increase and survival prior to departure. The variation in post-fledging mass growth between years and between the sexes is discussed with respect to parental effort and a possible selective provisioning of sons over daughters.     

Female‐biased size dimorphism in a diapausing caddisfly,Mesophylax aspersus: effect of fecundity and natural and sexual selection

1. The effect of mating success, female fecundity and survival probability associated with intra‐sex variation in body size was studied in Mesophylax aspersus, a caddisfly species with female‐biased sexual size dimorphism, which inhabits temporary streams and aestivates in caves. Adults of this species do not feed and females have to mature eggs during aestivation. 2. Thus, females of larger size should have a fitness advantage because they can harbour more energy reserves that could influence fecundity and probability of survival until reproduction. In contrast, males of smaller size might have competitive advantages over others in mating success. 3. These hypotheses were tested by comparing the sex ratio and body size of individuals captured before and after the aestivation period. The associations between body size and female fecundity, and between mating success and body size of males, were explored under laboratory conditions. 4. During the aestivation period, the sex ratio changed from 1 : 1 to male biased (4 : 1), and a directional selection on body size was detected for females but not for males. Moreover, larger clutches were laid by females of larger size. Finally, differences in mating success between small and large males were not detected. These results suggest that natural selection (i.e. the differential mortality of females associated with body size) together with possible fecundity advantages, are important factors responsible of the sexual size dimorphism of M. aspersus. 5. These results highlight the importance of taking into account mechanisms other than those traditionally used to explain sexual dimorphism. Natural selection acting on sources of variation, such as survival, may be as important as fecundity and sexual selection in driving the evolution of sexual size dimorphism.     

Fossil water striders in Cretaceous French amber (Heteroptera: Gerromorpha: Mesoveliidae and Veliidae)

Fossil gerromorphan bugs from the Cretaceous (Albian–Cenomanian boundary) amber of Charentes, SW France, are reviewed. A larva described by Perrichot et al. (2005) as incertae familiae within the Gerromorpha is now placed in the Mesoveliidae. Three new genera and species are also described and illustrated: Emilianovelia audax Solórzano Kraemer & Perrichot, gen. et sp.n. , and Malenavelia videris Solórzano Kraemer & Perrichot, gen. et sp.n. , which are placed in the Mesoveliidae: Mesoveliinae; and Arcantivelia petraudi Solórzano Kraemer & Perrichot, gen. et sp.n. , which is the first Mesozoic member of the Veliinae. The relationships between these fossils and their palaeoecology are discussed. The new discoveries confirm the antiquity of the semi‐aquatic gerromorphans, particularly the clade (Veliidae + Gerridae). The habitat is described as aquatic and likely marine‐influenced, yet adaptation to a fully marine habitat in these gerromorphans remains difficult to establish. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:F8C034B8-7BD0-4C03-B8FC-CD81D75C7001 .     

Physiological factors regulating polyandry in Lobesia botrana (Lepidoptera: Tortricidae)

Abstract. The effects of several physiological factors related to female multiple mating in the monandrous Lobesia botrana Denis and Schiffermuller (Lepidoptera: Tortricidae) were studied under laboratory conditions. Polyandry was assessed observing the induction of re-calling in previously once-mated females. Female age at first mating had no effect on induction of re-calling during practically the whole of the female lifetime, but in older females it was significantly lower. The percentage of re-calling was negatively correlated with the volume of the spermatophore received, ranging from ≅ 23% with the largest spermatophores to ≅ 75% with the smallest ones. Furthermore, the smaller the spermatophore volume, the earlier the re-calling was induced, significantly reducing die female refractory period after the first mating. Heavy females showed a significantly higher rate of re-calling (52.8%) than light ones (37.0%), but no differences were observed when females received only small spermatophores. This finding was explained by die allometric relationship between me female weight and the size of its reproductive system that affects relative replenishment by the spermatophore. Females with a supply of water displayed a significantly higher rate of re-calling (41.2%) than control females (22.8%), highlighting the effect of adult feeding (or drinking) status on the re-calling behaviour. The short-distance presence of virgin males with once-mated females promoted a re-calling rate (and subsequent matings) close to 37%, significantly higher than that of isolated females (20%). It is concluded mat re-calling and polyandry in L. botrana are controlled, as expected, by a number of mating-derived stimuli, but also to a great extent by other physiological stimuli unrelated to mating. The reproductive strategies in relation to polyandry and the mechanisms controlling female sexual inhibition are discussed.