Alfredo V. Peretti

Copulatory dialogue: female spiders sing during copulation to influence male genitalic movements

Female behaviour during copulation that could function as communication with the male is probably more common than previously appreciated, but its functional significance remains little studied. Stridulation during copulation by the female of the spider Physocylus globosus (Taczanowski, 1873), documented here for the first time, is common and noncoercive, thus permitting simple tests regarding its possible function. Males squeezed females rhythmically with their enlarged, powerful genitalia throughout copulation, and more male genitalic squeezes were associated with increased paternity when females mated with two males. Contextual associations suggest that female stridulation represents attempts to induce the male to interrupt genitalic squeezes: female stridulation was more common when the male was squeezing her; females were more likely to stridulate when individual male squeezes were longer, and when the male had not responded to a previous stridulation by loosening a squeeze; females were more likely to refrain from stridulating when the male loosened a squeeze; males were more likely to loosen squeezes when the female stridulated; and female stridulation was associated with rejection of males in other contexts. Males that responded to female stridulation more consistently by loosening their squeezes obtained greater paternity. Possible female communicatory behaviour during copulation is known in other species. Future attention to female as well as to male behaviour, and to possible dialogues during copulation, promises to be valuable in understanding sexual interactions.

Cryptic female choice via sperm dumping favours male copulatory courtship in a spider

Males of many animals perform ‘copulatory courtship’ during copulation, but the possible reproductive significance of this behaviour has seldom been investigated. In some animals, including the spider Physocyclus globosus (Pholcidae), the female discards sperm during or immediately following some copulations. In this study, we determined which of several variables associated with copulation correlated with paternity success in P. globosus when two males mate with a single female. Then, by determining which of these variables also correlated with sperm dumping, we inferred which variables may affect paternity via the mechanism of sperm dumping. Male abdomen vibration (a copulatory courtship behaviour) and male genitalic squeezing both correlated with both paternity and sperm dumping; so, these traits may be favoured by biased sperm dumping. Biased sperm dumping may also be the mechanism by which possible cryptic female choice favours another male trait that was the subject of a previous study, responsiveness to female stridulation.

Functional morphology of spermatophores and female genitalia in bothriurid scorpions: genital courtship, coercion and other possible mechanisms

Scorpions use sclerotized spermatophores for sperm transfer. The family Bothriuridae has one of the most complex scorpion spermatophores, with a distinct capsule and lamella. This study evaluates the viability of hypotheses relating to the evolution of animal genitalia that attempt to explain the functional morphology observed in spermatophores and female genitalia of some members of this scorpion family. These hypotheses are: female choice (internal courtship), conflict of interests (morphologically forced insemination) and lock-and-key (interspecific mechanical incompatibility). Observations of the mating sequences of 13 bothriurid and one buthid scorpion were recorded. The histology of female atrium was analysed. The data suggest that: (1) a genital copulatory courtship (sexual stimulation through male genitalia) could be a widespread mechanism among the capsules of the studied spermatophores; the wall of the female genital atrium in Brachistosternus as well as of other genera is usually rubbed by spines, tubercles or capsular lobes of spermatophores; the female genital atrium is relatively soft, elastic and uniform among different species; (2) morphological coercion might be admissible only when capsular lobes are very well developed, as females will have difficulty in disengaging by themselves from the large lobes if they attempt to interrupt sperm transfer; this mainly occurs inBothriurusbonariensis ;( 3)observations of matings among closely related species indicate that the lock-and-key hypothesis is unable to explain spermatophore morphology in the studied species; however a certain degree of mechanical incompatibility occurs during interspecific mating between two sister species (B. bonariensis and B. chacoensis )o wing todifferences in capsular lobes and post-insemination behaviour; (4) these hypotheses might not be directly applied to simple spermatophores of the Buthidae Zabius fuscus .T he results indicate that even though one genital mechanism can be more frequent than others, they can also exist together, not only in different genera but also in a single species (e.g. simultaneous occurrence of genital sexual stimulation and genital coercion in B. bonariensis). Indirectly these data suggest that the hypotheses most frequently quoted to explain genital morphology are not mutually exclusive.

Sexual coercion does not exclude luring behavior in the climbing camel-spider Oltacola chacoensis (Arachnida, Solifugae, Ammotrechidae)

Sexual coercion in the form of forced copulation has been used as a typical example to illustrate the conflict of interests between females and males. Among arthropods, forced copulation has been reported for some groups of insects and crustaceans, but not for arachnids. In the present work, we analyse and describe the behavioral patterns of mating behavior of the climbing camel-spider, Oltacola chacoensis, relating it to relevant morphological features, In this species, the male forcefully clasps the female’s genital region with his chelicerae and locks her fourth pair of legs with his pedipalps. In some cases, the cuticle of the female’s abdomen was damaged by this cheliceral clasping. In contrast to other camel-spiders, the female O. chacoensis never remained motionless during mating, but continuously shook her body, opening her chelicerae notably towards the male. Despite this coercive context, males performed copulatory courtship (tapping with pedipalps) and females showed an apparent cooperative behavior (they remained still during a short period of the sperm transfer phase). These results strengthen the idea that sexual coercion (in the form of forced copulation) and luring behavior (in the form of copulatory courtship) are not two mutually-exclusive male’s strategies during a single copulation.

Ultrastructure of spermatozoa of solifuges (Arachnida, Solifugae): Possible characters for their phylogeny?

The ultrastructure of spermatozoa is a widely accepted source of characters for phylogenetic studies. In this study the fine structure of sperm cells of representatives of six different New and Old World families (Ammotrechidae, Daesiidae, Eremobatidae, Galeodidae, Karschiidae, Solpugidae) of solifuges (Arachnida, Solifugae) were investigated in order to reveal putative characters suitable for subsequent systematic and phylogenetic analyses. The spermatozoa of solifuges represent a relatively simple type of sperm cells. In general, their spermatozoa are roundish, oval shaped (Ammotrechidae, Daesiidae, Eremobatidae, Solpugidae) or plate-shaped (Karschiidae) with or without membrane protuberances and devoid of a flagellum. Only in Galeodidae, very conspicuous thin and elongated sperm cells occur. The spermatozoa either occur as single cells (Eremobatidae, Solpugidae) or in groups of loose knit cells (Ammotrechidae) or in highly ordered groups (Karschiidae). In contrast to the other families studied here, within the Galeodidae and in the genus Blossia (Daesiidae) sperm cells surrounded by a secretion sheath, clearly representing coenospermia, could be observed.

Comparative Analysis of the Male Reproductive System in Bothriuridae Scorpions: Structures Associated with the Paraxial Organs and the Presence of Sperm Packages (Chelicerata, Scorpiones)

Abstract The male reproductive system of seven species of the family Bothriuridae are compared. These scorpions are Bothriurus flavidus Kraepelin, B. cordubensis Acosta, B. bonariensis (C. L. Koch), B. chacoensis Maury & Acosta, Brachistosternus ferrugineus (Thorell), Timogenes dorbignyi (Guerin-Meneville), T. elegans (Mello-Leitao) and Urophonius brachycentrus Pocock (Bothriuridae). Additional comparisons are made with the buthid Zabius fuscus (Thorell). Observations on the structures associated with the paraxial organs (testis, seminal vesicle and accessory glands) are given. Sperm obtained from the male reproductive tract and fresh spermatophores as well as from the females genital atrium and seminal receptacles are examined. Accessory glands occur in six out of eight studied bothriurids and in the buthid Z. fuscus . In most species the distal portion of vas deferens has a developed ampulla. All structures vary in size and shape depending on species. Sperm packages were observed in all bothriurids. In contrast, there is no packaged spermatozoa in Z. fuscus . Each sperm package consists of many spermatozoa surrounded by a common membrane that breaks after the spermatophore capsule is everted into the female genital atrium, releasing the spermatozoa. One hour after insemination, the spermatozoa are found in the atrium and in the seminal receptacles of B. flavidus females, but after 24h spermatozoa are found only in the seminal receptacles. The functional significance of the accessory glands and the presence-absence of sperm packages are discussed.

Sexual dimorphism in immune response, fat reserves and muscle mass in a sex role reversed spider

In sex role reversed species, females and males adopt behaviors that are not the traditional ones for that animal group. Furthermore, this reversal can translate into physiological differences between the sexes in characteristics such as energetic demands or immune response. Allocosa brasiliensis shows a reversal in the sex roles and sexual size dimorphism that would be expected for spiders. Males are larger than females and are sedentary, while females are the mobile sex that looks for males and initiates courtship. Our objective was to explore the occurrence of sexual dimorphism in immune response, fat content and muscular mass in A. brasiliensis, and relate the results to the reproductive strategies of the species. An encapsulation response was used as an estimate of the immune response. Abdominal fat content and leg muscular mass were quantified and the results were compared between females (N = 19) and males (N = 21). Males showed higher values of the three characteristics as compared to females. Life history divergences between the sexes regarding size, mobility and foraging opportunities could be factors driving these differences in immune response and energy requirements.

Occurrence and duration of post-copulatory mate guarding in a spider with last sperm precedence

One male strategy to prevent female re-mating is post-copulatory mate guarding. In the pholcid spider Holocnemus pluchei last males fertilization success is around 74% and females remain receptive after copulation. It is, thus, reasonable to suppose that males should engage in post-copulatory mate guarding. Chronologically, the present study focused on the following aspects: (1) to determine if male permanence near females corresponds to mate guarding. For this, a second male (intruder) was introduced. Time of permanence, distance and behaviour of residents did not change whether or not an intruder was present; (2) to investigate the duration of mate guarding and male distance to the female in a time series intervals after copulation. Males remained close to females during 14 h keeping a distance of less than 15 cm; (3) to evaluate whether guarding duration is influenced by female sexual receptivity. We found that 24 h after the first copulation, when the resident was placed again next to the female, he tried to re-mate; and (4) to examine differences in paternity in relation to whether or not the resident exerted guarding. P2 was higher when second males copulated again within the first 6 h compared to 24 h after the first copulation.

Differences in sexual behavior of two distant populations of the funnel-web wolf spider Aglaoctenus lagotis

Generally, sexual repertoire within a species is conserved, but frequencies of occurrence of sexual behavioral acts often vary, and wide geographic distributions may favor these variations. Aglaoctenus lagotis is distributed along South America and belongs to Sosippinae, a subfamily of wolf spiders that builds funnel webs. Previous reports, based on different populations, suggested variations in sexual behavior and life cycle. Our objective was to describe and compare the sexual behavior of two populations of A. lagotis: ‘Southern Uruguay’ (SU) and ‘Central Argentina’ (CA). We carried out intrapopulation trials, in the laboratory, with 15 female–male pair matings. The most representative courtship acts in SU were web-stretching, striding-forward and forelegs-elevating, whereas in CA they were alternate-waving, web-stretching and leg-tapping. Juddering, forelegs-elevating and striding-forward were exclusive for SU, while alternate-waving and simultaneous-waving were exclusive for CA. We also found differences in copulatory characteristics such as frequencies of insertions and ejaculations. We documented body-shaking during copulation for the first time. Some sexual acts were exclusive of each population, while the shared ones differed in pattern and frequencies of occurrence. In addition to variations in sexual periods, these differences may favor divergence processes or an exceptional high level of flexibility in the sexual behavior of A. lagotis.

COURTSHIP AND SPERM TRANSFER IN THE WHIP SPIDER PHRYNUS GERVAISII (AMBLYPYGI, PHRYNIDAE): A COMPLEMENT TO WEYGOLDT'S 1977 PAPER

Abstract The aim of this study was to provide descriptive and quantitative data regarding behaviors involved in courtship and in sperm transfer of the whip spider Phrynus gervaisii (Pocock 1894) in order to complete the previous description for this same species given by P. Weygoldt. The specimens were captured in anthills of Paraponera clavata, on Barro Colorado Island, Panama. Ten courtship and five sperm transfer sequences were recorded. Four out of five mating sequences with sperm transfer ocurred between adults with similar body size and in the other case the female was smaller than the male. Sexual interactions did not occur between very small adults. Two male behavior patterns that have not been reported were observed during the initial stage of courtship: “pedipalp rubbing” and “female operculum rubbing”. Contrary to Weygoldts description, in this study the female never performed “shaking” movements with her antenniform legs. It was observed that the two distal horn-like extensions of the spermatophore facilitate the female´s movements during the sperm transfer. The distal part of the spermatophore stalk provides a suspension area when the female rests on those horns. It was verified that the female can move the claw-like sclerites of the gonopods in all directions. The male executed copulatory courtship and successfully transferred sperm in five analyzed sequences. The female did not pick up the sperm packages when copulatory courtship was not performed. Males that lacked one antenniform leg were able to mate, however they had to perform vibrations more intensely with their non-injured leg for a longer duration. The data are compared with those previously obtained in other whip spiders. Some functional characteristics of the spermatophore and female genitalia of P. gervaisii are also discussed. RESUMEN. El objetivo de este trabajo es aportar datos descriptivos y cuantitativos sobre patrones de comportamiento que ocurren durante el cortejo y transferencia espermática del amblipígido Phrynus gervaisii (Pocock 1894) con la finalidad de completar la descripción previa de P. Weygoldt para esta misma especie. Los especímenes fueron capturados en hormigeros de Paraponera clavata, en la Isla de Barro Colorado, Panamá. Se registraron 10 secuencias de cortejo y cinco de transferencia espermática. Cuatro de las cinco secuencias de apareamiento con transferencia espermática completa ocurrieron entre adultos de tamaño corporal similar mientras que en el otro caso la hembra fue más pequeña que el macho. No se produjeron interacciones sexuales entre adultos muy pequeños. Durante la etapa inicial del cortejo fueron observados dos patrones de comportamiento masculinos que no habían sido citados con anterioridad: “roces de pedipalpos” y “roces al opérculo genital femenino”. Al contrario de la descripción de Weygoldt, en el presente estudio la hembra nunca realizó movimientos de “latigueo” con sus patas anteniformes. Se observó que las dos expansiones distales con forma de cuerno del espermatóforo facilitan los movimientos de la hembra durante la transferencia espermática. La parte distal del tallo del espermatóforo ofrece un área de suspensión cuando la hembra se apoya sobre estos cuernos. Se verificó que la hembra puede mover los escleritos en form de uña de sus gonópodos hacia todas las direcciones. El macho efectuó cortejo copulatorio en cinco secuencias analizadas, en ellas la transferencia espermática fue existosa. Por el contrario, la hembra no recogió los paquetes espermáticos cuando no existió cortejo copulatorio. Los machos que carecían de una pata anteniforme también fueron capaces de aparear. Sin embargo, ellos tuvieron que realizar más intensamente las vibraciones con sus patas no dañadas, y sobre todo durante un tiempo más prolongado para evitar que la hembra se alejara. Se comparan los datos aquí registrados con aquellos previamente obtenidos en otros amblipígidos. Se discuten algunas características funcionales del espermatóforo y genitalia femenina de P. gervaisii.