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The family Filistatidae is considered sister to Synspermiata or sister to Hypochilidae. Cytogenetic knowledge of this family could be useful for understanding the mechanism of chromosome evolution that has occurred within the group. In this work, two filistatid species belonging to distinct subfamilies, Kukulcania hibernalis (Hentz, 1842) (Filistatinae) and Misionella mendensis (Mello-Leitao, 1920) (Prithinae), were investigated using standard and differential chromosome staining. Analysis of mitotic and meiotic cells revealed the diploid 2n♂ = 25 for K. hibernalis and 2n♂ = 21 for M. mendensis. Both species exhibited a sex chromosome system of the X1X2Y type and metacentric/submetacentric chromosomes. In prophase I cells, the sex chromosomes were in a trivalent configuration with all elements associated without chiasma through their terminal regions. Both species revealed six nucleolar organizer regions on the terminal region of three autosomal pairs. In K. hibernalis, constitutive heterochromat...

Two specimens of a new spider from the Cretaceous (ca. 129 Ma) El Montsec Fossil-Lagerstatte, northeastern Spain, are described as Montsecarachne amicus gen. et sp. nov. and referred to the extant haplogyne family Plectreuridae. Plectreurids are found today in only in the southwestern USA, Mexico, Central America and Cuba, but fossils show a more widespread distribution in Eurasia. The new species adds an additional stratigraphic and biogeographical record. The paleobiogeographical history of plectreurids is discussed, and it is concluded that the most likely scenario is that the family was more widespread in the past, and has suffered extinction over much of its range, resulting in the present distribution. Possibly, extant plectreurids represent a living remnant of a more diverse group of haplogynes that were widespread in the Mesozoic.

Two new species of the spider genus Ochyrocera Simon 1891 are described from Mexico. Ochyrocera juquila new species was collected under moist rotten logs and hollow trunks on a thick bed of pine needles in oak-pine forests located in a mountain range south of the city of Oaxaca at 1400–2700 m elev. Ochyrocera juquila resembles O. quinquevittata Simon 1891 from the Island of St. Vincent, in the angular shape of the embolus, which in the new species is V-shaped and in O. quinquevittata is L-shaped. Ochyrocera chiapas new species, was collected under rotten trunks and hollow trunks in abundant leaf litter in the tropical, humid Lacandona rainforest region located in eastern Chiapas, near the border with Guatemala. The species occurs at 160–260 m elev. Ochyrocera chiapas resembles O. arietina Simon, 1891 from the island of St. Vincent, in the similar shape of the embolus and distal apophysis of the cymbium, but in O. chiapas the embolus is more strongly curved and directed toward the distal part of t...

Pholcidae (Haplogynae) encompasses 967 described species, of which only 14 have been cytogenetic analyzed. Several chromosomal features have already been described including presence of meta- and sub-metacentric chromosomes and sex determination chromosome system (SDCS) of the X, X1X2Y, and X1X2 types, which contrast with the telo- and acrocentric chromosomes and SDCS of the X1X2 type typical of entelegyne spiders. To obtain further cytogenetic information for the family, we examined two pholcid species, Crossopriza lyoni (Blackwall 1867) and Physocyclus globosus (Taczanowski 1874) using both conventional staining and silver staining techniques. Crossopriza lyoni exhibited 2n = 23 = 22 + X in males and 2n = 24 = 22 + XX in females, while P. globosus showed 2n = 15 = 14 + X and 4n = 30 = 28 + 2X, both in male adults, 2n = 16 = 14 + XX in female adults and embryos, and 2n = 15 = 14 + X in male embryos. Both species revealed predominately metacentric and submetacentric chromosomes and a SDCS of the ...

Mesabolivar luteus (Keyserling 1891) and Micropholcus fauroti (Simon 1887) specimens were collected in Ubatuba and Rio Claro, both in the state of Sao Paulo, Brazil. Mesabolivar luteus showed 2n (♂) = 15 = 14 + X and 2n (♀) = 16 = 14 + XX in mitotic metaphases and 7II + X in diplotenic cells. During late prophase I, all bivalents presented a ring shape, evidencing two chiasmata per bivalent. In this species, some diplotenic cells appear in pairs, maybe due to specific characteristics of the intercellular bridges. The metaphases II showed n = 7 or n = 8 = 7 + X chromosomes. Micropholcus fauroti evidenced 2n (♂) = 17 = 16 + X in spermatogonial metaphases and 8II+X in diplotenic cells, with only one chiasma per bivalent, contrasting with M. luteus. In both species, all chromosomes were metacentrics. The sexual chromosome X was the largest element and appeared as a univalent during meiosis I. These are the first cytogenetical data for the genera Mesabolivar and Micropholcus. Additionally, M. luteus i...

The morphology of the respiratory system of basal araneomorph spiders, the Haplogynae and of Entelegynae with female haplogyne genitalia, is reviewed. The homology of cuticular respiratory structures is discussed in light of evidence from abdominal muscles and ontogeny. Ten morphological characters (13 transformations) were coded, mainly from the posterior pulmonary (or tracheal) segment, and other 7 non-respiratory characters here added. The new data were combined with those of a previously published analysis, resulting in a data matrix of 82 characters scored for 44 terminals. The evolution of the tracheal system is traced through the phylogeny of basal spiders and the Haplogynae, and new syna- pomorphies are provided. Elongate 3rd abdominal entapophyses are a synapomorphy of Araneomorphae. True median tracheae are a synapomorphy of Entelegynae (convergently with Austrochilinae), as is the extreme posterior displacement and narrowing of the tracheal spiracle. Tetrablemmidae, Pholcidae, Di- guetidae and Plectreuridae are united by the absence of tracheae; and these taxa are united with Scytodidae, Sicariidae and Drymusidae by the fusion of 3rd entapophyses.

The spermatogenesis of four species of haplogyne spiders from Argentina is analyzed. Dysdera crocota (Dysderidae) (n = 5 + X0) has holokinetic chromosomes, achiasmatic male meiosis and a post-reductional division of the sex chromosome. Ariadna boesenbergii (Segestriidae) (n = 4 + X0) also possesses holokinetic chromosomes, but meiosis is chiasmatic and the X chromosome divides pre-reductionally. Kukulcania hibernalis (Filistatidae) (n = 11 + X1X20) and Scytodes globula (Scytodidae) (n = 6 + X0) have metacentric and submetacentric chromosomes, chiasmatic meiosis and the sex chromosomes divide pre-reductionally. Kukulcania hibernalis possesses a bimodal karyotype and a particular chromatin coiling during prophase I, while Scytodes globula has striking proximal localization of chiasmata. These results show that Haplogynae present high cytogenetic heterogeneity: species with holokinetic chromosomes as well as species with monocentric chromosomes (metacentric and submetacentric), and species with low ...