Adanson's Wall Jumper Hasarius adansoni: Courtship and mating
All spiders have a unique method of mating. Sperm is transferred from the male to the female with specialized copulatory organs, the male spider's pedipalps. The pedipalp functionally consists of three parts: a modified tarsus, called the cymbium, a reservoir for the sperm, and a narrow structure through which the sperm passes as it is transferred to the female, called the embolus.
Copulatory organs of Salticids
The genital openings in both sexes of jumping spiders are located anteriorly on the ventral surface of the abdomen, near the epigastric furrow (= a fold), and open after the final moult.
In female Salticidae the opening is surrounded by a plate called the epigynum. The epigynum contains a pair of copulatory openings connected by copulatory channels to sperm storing spermathecae, from which spermatozoa are extruded through a channel into the uterus to fertilise the eggs. Sperm may be stored alive for as long as one year. The eggs are laid through the opening ofthe epigynum.
To inseminate the female, the male must first transfer a droplet of seminal fluid from the genital opening into the copulatory organ located on the apical segments of the pedipalps. That organ develops during the last moult. It operates as a pump by changing the pressure of the haemolymph: a rise in pressure inflates the organ and squeezes its internal sperm reservoir; by a partial reduction of pressure the seminal fluid is sucked into the reservoir through the embolus. During copulation, the rising pressure of haemolymph inflates the organ and when the embolus is introduced into the copulatory opening of the female, it squeezes the reservoir and injects seminal fluid into the spermathecae of female. The male copulatory organ contains various structures which engage corresponding structures of the female’s epigynum during copulation.
Courtship and mating behaviour in Jumping Spiders
Jumping spiders conduct complex, visual courtship displays using both movements and physical bodily attributes. Unlike females, males possess plumose hairs, colored or iridescent hairs, front leg fringes, structures on other legs, and other, often bizarre, modifications. These characteristics are used in a courtship "dance" in which the colored or iridescent parts of the body are displayed. In addition to the display of colors, jumping spiders perform complex sliding, vibrational, or zigzag movements to attract females. It has also recently been discovered that many males have auditory signals as well. These amplified sounds presented to the females resemble buzzes or drum rolls. Species vary greatly in visual and vibratory components of courtship. Many species have patches of UV reflectance, which are exhibited in mature males. This visual component is used by some female jumping spiders for mate choice.
If receptive to the male, the female will assume a passive, crouching position. In some species, the female may also vibrate her palps or abdomen. The male will then extend his front legs towards the female to touch her. If the female remains receptive, the male will climb on the female's back and inseminate her with his palps.
The males die shortly after copulation; however the proverbial post-mating cannibalism by the female has been found only exceptionally in Salticidae. Females build cocoons and lay eggs a few weeks after mating, often guarding the eggs and sometimes the young spiderlings.
Mating behaviour of Hasarius adansoni
Jumping spiders perform multi-modal displays during courtship and this behaviour was studeid for the first time in 2018 for
Hasarius adansoni under lab conditions with mating trials.
Salticid spiders have excellent vision and most of their behaviors are visually guided, and courting behavior is no exception, and males from this family are known for performing extravagant visual and vibratory displays to attract females. In many species, females respond with their own display behavior. Jumping spiders also produce vibratory signals, and these are often complex and coordinated with visual displays.
H. adansoni males produce visual signals, and this is also suggested by their sexually dimorphic coloration; while females are cryptic brown, males are black with conspicuous white patches on their palps.
When the male orients and moves towards the female, he typically spreads the first pair of legs and his palps. Given the location of the white patches, this would reveal them to a female oriented towards him. The male then walks towards the female in a zig-zag fashion. Here, the female may respond in three ways:
- facilitate palp insertion by curling her legs close to her abdomen and staying motionless;
- avoid palp insertion, by running away or
- avoid palp insertion, by attacking the male.
If the first option happens, the male can approach and mount the female, and she then exposes the side of her abdomen and this facilitates palp insertion. On the other hand, females rejected a mean of 36.6% of males’ attempts. Once this happened, females frequently adopted the second possible response to courtship (i.e., attacking or running away from the male). Cannibalism of the male by the female was extremely
rare, and was observed only once in 47 trials.
Most of the pairs that failed to copulate did so because of female rejection. Females usually determine the end of remating by not accepting further attempts by a particular male. Long copulation durations have been suggested as a strategy of mate guarding in other spiders. Since monogamy is rare in spiders, and first sperm priority is common, males may try to prolong copulations.
The presence of substrateborne vibrations during courtship from both male and female was confirmed. These appeared to be primarily tremulations, a type of substrate-borne vibration signal in which a part of the spider’s body vibrates but does not touch the substrate. The energy of such vibrations, however, is transferred to the substrate by the spiders’ legs and allows communication. When the male started moving towards the female, he used tremulation of the abdomen to create vibrations that were detected by the female. Once in the receptive posture (i.e., legs curled but still touching the substrate), the female started her own abdominal tremulations as the male approached.
The features that compose the visual display in
H. adansoni (i.e., leg spreading, zig-zag walking and palp spreading) have been observed in other salticid species. Similarly, substrate-borne vibrations have also been observed during courtship in many Salticidae, although the type of vibrations and repertoire size vary substantially.
Such conspicuous traits and displays usually play a role in sexual selection and mate choice. Both visual, and vibratory displays are used by female jumping spiders to assess potential males for mating during courtship. These display characteristics typically convey male condition, which may influence brood survival and success.
29 to 36 days after mating, females build a silk cocoon and stay enclosed for 12 to 21 days while laying eggs. Usually, after the female leaves the cocoon, the young molt for the first time and only then do they disperse.
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