Evidence of sperm removal behaviour in an externally fertilizing species and compensatory behaviour for the risk of self-sperm removal

The removal of rival sperm from a female's sperm storage organ acts as a strong sperm competition avoidance mechanism, which has been reported only in internally fertilizing species and not at all in externally fertilizing species. This study demonstrated for the first time that nest-holding males of Bathygobius fuscus , an externally fertilizing marine fish, remove the sperm of rival sneaker males from the spawning nest by exhibiting tail-fanning behaviour within the nest. Males showed tail-fanning behaviour when semen was artificially injected into the nest but not when seawater was injected, and in open nests this behaviour resulted in higher paternity rates for the focal male. The sperm removal behaviour entails the risk of removing their own sperm; therefore, additional sperm release behaviour is likely necessary to benefit from the sperm removal effect. Consistent with this, males increased post-fanning sperm release behaviour more in the semen than in the seawater injection treatment. Moreover, males who had removed sperm for a longer time spent more time releasing sperm after the removal, suggesting that the additional sperm release behaviour compensated for the loss of their own sperm. These results suggest that sperm removal behaviour is not restricted to internally fertilizing organisms and deserves further investigation in this and other species.

Parenting behaviour is highly heritable in male stickleback

Parental care is critical for fitness, yet little is known about its genetic basis. Here, we estimate the heritability of parenting behaviour in a species famous for its diversity and its behavioural repertoire: three-spined stickleback ( Gasterosteus aculeatus ). Male three-spined stickleback are the sole providers of parental care that is necessary for offspring survival; therefore, this system offers the opportunity to study the inheritance of parental behaviour when selection is primarily acting on males. Fanning behaviour is a conspicuous parental behaviour that is readily quantified in this species. We show that the heritability of fanning behaviour is ≥0.9 and significantly different from zero within a freshwater population. Moreover, there was abundant genetic variation for fanning behaviour, indicating that it could readily evolve. These results suggest that parenting behaviour is tractable for further genetic dissection in this system.

Fin size and associated fanning behaviour as indicators of reproductive status in male round gobies (Neogobius melanostomus)

Determination of male reproductive status in the round goby (Neogobius melanostomus) can be challenging because current metrics do not always reflect steroid production. In many fishes, fin size changes during the reproductive season; therefore, fins may provide additional information about reproductive status. In some species, fin size correlates with fanning behaviour; a trait common in fish species that exhibit male parental care as it is important for egg maintenance. Because male fanning begins before spawning, fanning also may play a role in pheromone dispersal and courtship, potential indicators of reproductive status. Initially, we examined which morphological metrics (head width, total length, condition, fin size) best delineated groups of reproductive and non-reproductive male gobies (determined using the gonadosomatic index, GSI). Surface areas of fused pelvic fins and caudal fins best separated these groups of males. Using video recordings of nest-guarding male gobies, we characterised both pectoral and caudal fanning behaviour. Rates of maximum caudal fanning (fin beats per minute) were higher than rates of pectoral fanning; however, caudal fanning overall was less frequent than pectoral fanning. Subsequently, we determined if fanning metrics were related to 11-ketotestosterone (11-KT), GSI and morphological traits. No relationship was found between any of the fanning or morphological metrics and GSI values or 11-KT. However, there was a significant relationship between the maximum pectoral fanning rate and condition factor of males. These findings suggest that relative fin size, but not fanning behaviours, may be useful metrics to measure reproductive status.

Sexual behaviour of Bosca's newt, Triturus boscai

The sexual behaviour of Bosca's newt, Triturus boscai is characterized by an extended phase of static display, during which tail fanning is the main display. This behaviour is similar to that of another species, T. italicus. During the static display phase males may also push the females' throat with the snout, and perform tail flicking movements. Unlike the other small-bodied Triturus species, T. boscai males receive very little or no indication on the part of the female signalling them to begin the spermatophore transfer phase, and do not perform retreat display. As in T. italicus, the tail-touch behaviour by the female of T. boscai appears to be less stereotyped than in the T vulgaris-helveticus-montandoni group. Spermatophore transfer success was highest at the beginning of the sexual encounters, the so-called early sequences. These sequences had little or no fanning behaviour before the spermatophore transfer. Luring behaviours are often performed, mainly during the spermatophore transfer phase.