Natural history of Ctenus medius Keyserling, 1891 (Araneae, Ctenidae) I: observations on habitats and the development of chromatic patterns

Abstract

Ctenus medius Keyserling, 1891 is a common species in several spots of Mata Atlântica, however there is a great lack of studies in all aspects of its natural history. This work aims to elucidate aspects of ecotope preference compared to large spiders, and to provide data on the development of chromatic patterns during its life cycle. The observations on the behavior of C. medius were done in the campus of Centro Universitário de Barra Mansa (UBM) by means of observations and nocturnal collections using cap lamps. For observations on the development of chromatic patterns, spiderlings raised in laboratory, hatched from an oviposition of a female from campus of UBM, and others spiderlings collected in field were used. The field observations indicate that: C. medius seems to prefer ecotopes characterized by dense shrub vegetation or herbal undergrowth; Lycosa erythrognatha and L. nordeskioldii seems to prefer open sites; Phoneutria nigriventer seems to prefer shrub vegetation and anthropogenic ecotopes as rubbish hills; Ancylometes sp. seems to prefer ecotopes near streams. Concerning chromatic patterns, it was observed that males and females show well distinct patterns during the last two instars, allowing distinction by sex without the use of a microscope. Through chromatic patterns it was also possible to draw a distinction between C. medius and C. ornatus longer that 3 mm cephalothorax width. 69 specimens of C. medius (males and females) collected in the campus of UBM did not show a striking polymorphism in chromatic pattern, but one among 7 adult females collected in National Park of Itatiaia, showed a distinct chromatic pattern.

Natural history ofPhoneutria boliviensis(Araneae: Ctenidae): habitats, reproductive behavior, postembryonic development and prey-wrapping

“…Bü cherl (1969), Ramos et al (1998), and Almeida et al (2000) presented data on the development, activity, reproduction seasonality, and habitat use of Phoneutria nigriventer (Keyserling 1891). Simó & Bardier (1989) described the postembryonic development of P. keyserlingi (F.O.P.-Cambridge 1897).…”

Natural history of Ctenus medius Keyserling, 1891 (Aranae, Ctenidae) II: life cycle and aspects of reproductive behavior under laboratory conditions

“…The results of the study of the chromatic patterns by Almeida et al (2000) show that it is possible to separate C. medius from Ctenus ornatus (Keyserling, 1891) in the field though chromatic patterns. With C. ornatus, only one female carrying its egg sac was found on the UBM campus.…”

“…Ctenus medius is a spider of nocturnal habits and it is common in several spots of the Atlantic Forest. Almeida et al (2000) shows that C. medius seems to prefer ecotopes characterized by dense shrub vegetation or herbal undergrowth when compared with the remainder of ctenidofauna. The authors also provide data on the development of chromatic patterns during the spider's life cycle, noting that the biology of C. medius has been little explored.…”

Populações de aranhas errantes do gênero Ctenus em fragmentos florestais na Amazônia Central

“…Aranhas errantes da família Ctenidae, e o gênero Ctenus em particular, devido à sua abundância, têm recebido crescente interesse como bioindicadores de qualidade ambiental e como modelos para estudos de fatores que afetam a abundância de invertebrados predadores em florestas tropicais na África e na América do Sul (Gasnier, 1996;Almeida et al, 2000;Gasnier & Höfer, 2001;Salvestrini & Gasnier, 2001;FollyRamos et al, 2002;Gasnier et al, 2002;Jocqué et al, 2005;Rego et al, 2005, Gasnier et al, no prelo). Rego et al (2005) encontraram evidências que a fragmentação florestal reduz as populações de aranhas do gênero Ctenus na Amazônia Central.…”