Mating and mate choice in Pseudodiaptomus annandalei (Copepoda: Calanoida)

Copepod mating behavior can be broken down into several steps including search, encounter, pursuit, capture and copulation. Using optical systems, we examined the pre- and post-capture mating behavior for the little known subtropical species Pseudodiaptomus annandalei, living in the Danshuei estuary in northern Taiwan. During the mate-finding process, the male remotely located the female through water-born chemical signals released by the female. We found that, when placed into female-conditioned water, the displacement of males exhibited higher frequencies of swimming speeds over 20 mm s−1 and large displacements representing intensive search in restricted areas. Additionally, in presence of females, males responded to signals at a distance greater than 10 body lengths and raced up faithfully along diffusive chemical trails. P. annandalei males also used hydromechanical signals produced by females for close localization and final leap adjustment. The pursuits often resulted in encounters, but only a maximum of 50% of encounters led to copulation, due to rejection behavior by the females. To mate, males had to overcome intensely ‘shaky’ periods characterized by jumping alternating with strongly convoluted paths. Their chances to copulate increased with the time male maintained seizure of the female, which is helped by modified elements on both sides of the geniculation of their right antenna. Finally, copulation duration was estimated to last an average of 10 min. Rejection behavior by the female is another limitation in addition to the chance of an encounter in the success of the mating process. The possibility that females may perform rejection dance for mate choice is discussed.

Research highlights
► Pre and post-capture mating behavior of Pseudodiaptomus annandalei.
► Male remotely located the female through water-born chemical signals.
► Hydromechanical signals also used for close localization and final leap adjustment.
► Female exhibit rejection behavior characterized by intense ‘shaky’ periods.
► Rejection add limitation to mating success and may be performed for mate choice.