MicroCT analysis unveils the role of inflatable female genitalia and male tibial complex in the genital coupling in the spider genus Aysha (Anyphaenidae, Araneae).

Sperm transfer in spiders is achieved by copulatory organs on the male pedipalps (i.e., copulatory bulbs), which can be simple or a complex set of sclerites and membranes. During copulation, these sclerites can be used to anchor in corresponding structures in the female genitalia by means of hydraulic pressure. In the most diverse group of Entelegynae spiders, the retrolateral tibial apophysis clade, the female role in the coupling of genitalia is considered rather passive, as conformational changes of the female genital plate (i.e., the epigyne) during copulation are scarce. Here, we reconstruct the genital mechanics of two closely related species belonging to the Aysha prospera group (Anyphaenidae) that bear a membranous, wrinkled epigyne and male pedipalps with complex tibial structures. By using microcomputed tomography data of a cryofixed mating pair, we reveal that most of the epigyne remains greatly inflated during genital coupling, and that the male tibial structures are coupled to the epigyne by the inflation of a tibial hematodocha. We propose that a turgent female vulva is a prerequisite for the genital coupling, which could implicate a female control device, and that the structures from the male copulatory bulb have been functionally replaced by tibial structures in these species. Furthermore, we show that the conspicuous median apophysis is maintained in spite of being functionally redundant, posing a puzzling situation.

The evolution and function of spider feet (Araneae: Arachnida): multiple acquisitions of distal articulations

The tip of the legs concentrates the interactions that a spider has with the substrate where it lives. We review the morphology and evolution of spider feet, discussing the functional anatomy of their articulations and proposing a coherent terminology. All spiders consistently have two tendons to operate their feet and show a stereotyped sequence of levation of the pretarsus and its claws prior to detachment from the substrate. A pair of slit sensilla, the foot slits, provide a reliable landmark across most spiders. The evolutionary reconstruction of morphological variants using a composite tree of spiders indicates that similar morphologies arose independently, with multiple acquisitions of one to four distal articulations. A distal articulation appeared repeatedly at the foot slits, the podotarsite, and at least three independent origins of highly articulated feet correspond with cuticular structures to retain the flexor tendons in the proper ventral position. Our results indicate that while in some spiders the adhesive setae were added to articulate feet, in other taxa the sequence was opposite. We conclude that a limited repertoire of feet articulations appeared and reversed many times in spider evolution, and combine in many ways to produce a highly diverse functional unit.

A revision of the wolf spider genus Diapontia Keyserling, and the relationships of the subfamily Sosippinae (Araneae: Lycosidae)

The South American genus Diapontia is revised to include nine species: Diapontia uruguayensis Keyserling, 1877 (= Diapontia senescens Mello-Leitao, 1944 syn. n.; D. infausta Mello-Leitao, 1941 syn. n.; D. pourtaleensis Mello-Leitao, 1944 syn. n.; D. albopunctata Mello-Leitao, 1941 syn. n.) from northern Paraguay, southeastern Brazil, southern Uruguay, southern to northeastern Argentina and southern Chile; D. niveovittata Mello-Leitao, 1945 from southern Paraguay, north-central Argentina and southern Brazil; D. anfibia (Zapfe-Mann, 1979) comb. n. (= Lycosa artigasi Casanueva, 1980 syn. n.) from central and southern Chile and southwestern Argentina, transferred from Pardosa C. L. Koch, 1847; D. securifera (Tullgren, 1905) comb. n. from northern Chile and northwestern Argentina, transferred from Orinocosa Chamberlin, 1916; D. arapensis (Strand, 1908) comb. n., from Peru, transferred from Hippasella Mello-Leitao, 1944; D. calama sp. n. from northern Chile; D. songotal sp. n. from southern Bolivia; D. chamberlini sp. n. from central and southern Peru; and D. oxapampa sp. n. from northern Peru. The sister-group relationship between Diapontia and Hippasella, and their placement in the subfamily Sosippinae, were supported by phylogenetic analyses based on four molecular markers (28S, 12S, NADH1 and COI), using Bayesian inference and maximum-likelihood. We tested whether DNA barcoding techniques were able to corroborate the identity of four Diapontia species. Diapontia securifera and D. anfibia were successfully identified using COI; however, D. niveovittata and D. uruguayensis were found to share identical haplotypes and thus could not be discriminated.