Strategic male mating effort and cryptic male choice in a scorpionfly.

In animal species with high male mating effort, males often find themselves in a dilemma: by increasing their mating effort, the gain from each copulation increases but simultaneously reduces available resources and, thus, the opportunity for future copulations. Therefore, we expect males to spend less reproductive resources on matings that provide low reproductive potential, thereby saving resources for future copulations, possibly with high-quality females, a sort of cryptic male choice. However, the strength of the trade-off between investment in a current mating and resources available for future matings must not be the same for all males. Males with relatively high mating costs should allocate their limited resources more cautiously than males with more plentiful resources. Here, we examine this prediction in the scorpionfly Panorpa cognata. Prior to copulation, males produce a large salivary mass on which females feed during copulation. We show that the production of larger salivary masses leads to longer copulations. Moreover, the size of the salivary gland and salivary mass increases with increasing male condition. However, males in poor condition make a relatively higher mating investment than males in good condition. We therefore expect male condition to influence cryptic male choice. In accordance with our hypothesis, only males in poor condition choose cryptically, producing larger salivary masses in copulations with females of high fecundity.

Gender differences and individual variation in the immune system of the scorpionfly Panorpa vulgaris (Insecta: Mecoptera).

From investigations of the vertebrate immune system gender specific differences in individual immunocompetence are well known. In general, females seem to possess more powerful immune systems than males. In invertebrates, the situation is much less clear. Therefore, we investigated the immune system of an invertebrate species, the scorpionfly Panorpa vulgaris. We found a high degree of individual variation in both traits studied, the lysozyme-like antibacterial activity of hemolymph and the capacity for in vitro phagocytosis of artificial particles. These two immune traits were positively correlated. As expected, hemolymph derived from females had higher lysozyme-like activity and hemocytes from females phagocytosed more particles. The difference in phagocytosis was mainly based on higher total hemocyte counts and higher proportions of phagocytically active cells in females, while the average number of ingested particles per active phagocyte was not significantly different. The observed gender differences are discussed in the context of reproductive strategies and parasite-mediated sexual selection.

Determinants of sperm transfer in the scorpionfly Panorpa cognate: male variation, female condition and copulation duration.

Recent studies suggest that sperm production and transfer may have significant costs to males. Male sperm investment into a current copulation may therefore influence resources available for future matings, which selects for male strategic mating investment. In addition, females may also benefit from actively or passively altering the number of sperm transferred by males. In the scorpionfly Panorpa cognata, the number of sperm transferred during copulation depended on copulation duration and males in good condition (residual weight) copulated longer and also transferred more sperm. Moreover, sperm transferred and stored per unit time was higher in copulations with females in good condition than in copulations with females in poor condition. Males varied greatly and consistently in their sperm transfer rate, indicative of costs associated with this trait. The duration of the pairing prelude also varied between males and correlated negatively with the male's sperm transfer rate, but no other male character correlated significantly with male sperm transfer rate. The results are consistent with strategic mating effort but sperm transfer could also be facilitated by the physical size of females and/or females in good condition may be more cooperative during sperm transfer.

[Evolution of the nervous system]. / Evolution des Nervensystems.

This review tries to establish a synthesis between the comparative/morphological approach and the molecular analysis of ontogenetic processes in development and evolution. We use the formation of the nervous system in metazoans as a paradigm to point out that highly conserved molecular mechanisms may be responsible to generate tissues and organ systems in bilateria. We discuss the conserved role of the Hox genes in anterior- posterior patterning, the function of the Achaete-scute genes and of the Notch/Delta signalling cascade in determining neural fates and the role of the BMP-4/Dpp-signalling pathway in positioning the neuroectoderm along the dorso-ventral axis of vertebrates and insects. We try to demonstrate that the evolution of complex body structures is based on modifying ontogenetic processes.

Mitochondrial gene fragments suggest paraphyly of the genus Panorpa (Mecoptera, Panorpidae).

Life history studies of scorpionfly species have been used to test predictions of evolutionary theory, but comparative analysis has been hampered by a lacking phylogeny of scorpionflies. We present a molecular phylogeny of selected panorpid scorpionflies inferred from mitochondrial 12S, 16S rRNA, and COI gene fragments, using parsimony and maximum-likelihood methods. Maximum-likelihood reconstructions depend on an explicit evolutionary substitution model; therefore, we estimated fit of substitution models to our data and used an optimal evolutionary substitution model in subsequent reconstructions. Both reconstruction methods converge on compatible trees with considerable statistical support for a majority of nodes. We performed parametric tests of most important phylogenetic conclusions employing the fitted GTR + %I + Gamma substitution model. Parametric bootstrapping allowed rejection of alternative explanations of the data set, where classical tests, like the KHY test, failed. Parametric bootstrapping confirmed that the association of Neopanorpa sp. with Asian Panorpa species is currently the superior explanation of the data set. Therefore, it is concluded that the genus Panorpa is most likely paraphyletic to the representative of the genus Neopanorpa. We conclude that the sequenced mitochondrial gene fragments appear to be well suited for future more comprehensive phylogenetic investigations of panorpid scorpionflies.

DNA preparation and efficient microsatellite analysis from insect hemolymph.

A simple and time-saving method for DNA preparation for efficient microsatellite analysis is described. The method is based on thermal treatment of only 1-5 microL of insect hemolymph in a Chelex 100-suspension. Since hemolymph withdrawal does not harm the insects, analysis of mating systems, population structure and phylogenetic reconstruction can be conducted with minimal experimental influence.

Phylogenetic signal and its decay in mitochondrial SSU and LSU rRNA gene fragments of Anisoptera.

The phylogeny of Anisoptera, dragonflies in the strict sense, has proven to be notoriously difficult to resolve. Based on morphological characters, several recent publications dealing with the phylogeny of dragonflies proposed contradicting inter- and intrafamily relationships. We explored phylogenetic information content of mitochondrial large-subunit (LSU) and small-subunit (SSU) ribosomal gene fragments for these systematic problems. Starting at published universal primers, we developed primer sets suitable for amplifying large parts of the LSU and SSU rRNA genes within dragonflies. These fragments turned out to harbor sufficient phylogenetic information to satisfyingly resolve intrafamily relationships, but they contain insufficient phylogenetic structure to permit reliable conclusions about several interfamily relationships. We demonstrate that decay of phylogenetic signal progresses from intrafamily to interfamily to outgroup relationships and is correlated with an increase of genetic distances. As expected, signal decay is most pronounced in fast-changing sites. Additionally, base composition among fast-changing sites significantly deviates from the expected homogeneity. Homogeneity of base composition among all included taxa was restored only after removing fast-changing sites from the data set. The molecular data tentatively support interfamily relationships proposed by the most recent publication based on morphological characters of fossil and extant dragonflies.