The female genital morphology of the orb weaving spider genus Agriognatha (Araneae, Tetragnathidae)

Abstract

The female genital morphology of the spiders in the araneoid genus Agriognatha (Tetragnathidae) is described and illustrated. The female genitalia of Agriognatha is characterized by a strong reduction of the sperm storage organs (spermathecae) and by the presence of a specialized distal compartment of the median membranous chamber that functions as a sperm storage organ (the posterior sac). The genital morphology of Agriognatha species is unique among Tetragnathidae and it provides robust synapomorphic evidence for the monophyly of genus. We discuss the phylogenetic implications of these new findings for the placement and monophyly of Agriognatha and for the monophyly of Tetragnathinae.

Revision and Cladistic Analysis of the Orbweaving Spider Genus Cyrtognatha Keyserling, 1881 (Araneae, Tetragnathidae)

“…A similar structure is found in some Tetragnatha species ( fig. 64A; see also figures in Dimitrov et al, 2007), but all of them have very well-developed spermathecae and a very small posterior sac. The posterior sac in Tetragnatha does not seem to store sperm, and its cuticle lacks the short stem gland ductules found in Cyrtognatha.…”

“…The shape of the female internal genitalia is also diagnostic for Cyrtognatha ( fig. 7) (see also Dimitrov et al, 2007). In Cyrtognatha the spermathecae are reduced and the sperm storage function is taken by an unpaired membranous structure (the posterior sac).…”

“…Webs and web posture of Cyrtognatha rucilla (A-E) (from Dominican Republic, Cachote; B and E, web diameter ca. 12.5 cm), figure 2A is from Dimitrov et al (2007: fig. 1).…”

“…The group (Pachygnatha + Glenognatha) + (Cyrtognatha + Tetragnatha) is recovered in all analyses and always receives very high support (more than 95 in all resampling approximations; its Bremer support, 12, is the second highest). In previous analyses Diphya was not recognized as a close relative of the other genera in Tetragnathinae (Schü tt, 2002), or when placed in Tetragnathinae this placement was regarded as questionable since this genus does not show some of the most characteristic features of Tetragnathinae (Á lvarezPadilla, 2007;Dimitrov et al, 2007 [1]), and epigynum with a saclike chamber connecting to the uterus externus (char. 188 [1]).…”

“…Spermathecae absent or vestigial. The uterus externus connects via an enlarged chamber with a nonpaired membranous structure that has a posterior sac (a nonpaired sperm storage organ) (see also Dimitrov et al, 2007 Bryant, 1940), C.…”