Sexual cannibalism by females and associated male behaviours may be driven by sexual conflict. One such male behaviour is the eunuch phenomenon in spiders achieved through total genital emasculation, a seemingly maladaptive behaviour. We provided the first empirical testing of an adaptive hypothesis, the remote copulation, in a highly sexually cannibalistic orb-web spider Nephilengys malabarensis. We demonstrated that sperm transfer continues from the severed male organ into female genitals after the male has been detached from copula. Remote copulation increased the total amount of sperm transferred, enhances paternity, and may thus counter sexual cannibalism and female-controlled short copulation duration.
COBISS.SI-ID: 33676845
Behaviour is generally plastic to some degree and allows an animal to react appropriately to changing and novel conditions. Consequently, degree of plasticity is predicted to be a key determinant of organisms' ability to cope with novel (e.g., urban) environments. . Yet, behavioural plasticity is often genetically determined and many animals exhibit personalities, i.e. consistent between-individual differences in behaviours. We explored the degree of behavioural plasticity versus personality in the bridge spider Larinioides sclopetarius, which occurs in extremely high-density in urban areas over the Holarctic. The spiders show extraordinary plasticity in life history. We investigated between- and within-individual variability, correlations and heritability for aggressiveness, boldness, behaviours in novel environment, and voracity towards prey. We predicted that these spiders either show high individual behavioural plasticity, or, that there is a mix of individuals with different personalities. We found temporal consistency and moderate heritability in intra-sex aggressiveness and boldness, whereas behaviours in novel environment were repeatable, but not heritable. Most behavioural traits showed high between-individual variability. We discuss that low heritability of behaviours related to foraging success and a lack of behavioural correlations may be due to developmental plasticity as a mechanism that promotes success in cities. In the next step, we experimentally tested whether composition of aggressiveness types affects spiders’ mass gain and survival in a high-density group. Groups of only aggressive types had highest mass but also showed highest mortality, though not significantly. Our results lend support to the hypothesis that living in high densities does not necessarily require a reduction of mean aggressiveness levels but that a polymorphism in aggressive personalities maintained by negative frequency dependent selection would be a possible scenario.
COBISS.SI-ID: 34213165
We found that in the giant wood spider (Nephila pilipes), the amorphous mating plugs are not produced by the males, that repeated copulations (most likely polyandrous) are necessary for egg fertilization and AP formation, and that the AP represents a female adaptation to sexual conflict through prevention of unwanted, excessive copulations. Considering the largely unknown origin of amorphous plugs in spiders, we predicted that a similar pattern might be detected in other clades, which would help elucidate the evolutionary interplay of various selection pressures responsible for the origin and maintenance of mating plugs.
COBISS.SI-ID: 34468141