Daily activity schedule, gregariousness, and defensive behaviour in the Neotropical harvestmanGoniosoma longipes(Opiliones: Gonyleptidae)

Chemical Defense in Harvestmen (Arachnida, Opiliones): Do Benzoquinone Secretions Deter Invertebrate and Vertebrate Predators?

“…The harvestman G. longipes is conspicuous ( Figure 1A, B) and widespread in forested areas of southeastern Brazil. This species was chosen as the source of secretion because it is abundant in our study site and because individuals produce a great amount of secretion when disturbed (see Machado et al, 2000). Moreover, the ecology and behavior of the species were previously studied (see Machado and Oliveira, 1998;Machado et al, 2000), aiding the selection of more realistic potential predators.…”

“…This species was chosen as the source of secretion because it is abundant in our study site and because individuals produce a great amount of secretion when disturbed (see Machado et al, 2000). Moreover, the ecology and behavior of the species were previously studied (see Machado and Oliveira, 1998;Machado et al, 2000), aiding the selection of more realistic potential predators. The external morphology of the ozopore of G. longipes has been described (see Figures 19 and 20 in Hara and Gnaspini, 2003), and the mode of emission occurs as follows: (a) first, a large transparent droplet of enteric fluid composed exclusively of water is regurgitated, slips along the lateral area of the dorsal scute, runs by capillarity in tegumentary grooves, and accumulates in the posterior portion of the body ( Figure 1A); (B) if the harvestman is persistently disturbed, a second fluid may be secreted by the odoriferous glands, adding to the previously colorless fluid a yellowish coloration and a characteristic sour smell ( Figure 1B).…”

“…The external morphology of the ozopore of G. longipes has been described (see Figures 19 and 20 in Hara and Gnaspini, 2003), and the mode of emission occurs as follows: (a) first, a large transparent droplet of enteric fluid composed exclusively of water is regurgitated, slips along the lateral area of the dorsal scute, runs by capillarity in tegumentary grooves, and accumulates in the posterior portion of the body ( Figure 1A); (B) if the harvestman is persistently disturbed, a second fluid may be secreted by the odoriferous glands, adding to the previously colorless fluid a yellowish coloration and a characteristic sour smell ( Figure 1B). Sometimes, the secretion may also be sprayed as a jet directly toward the aggressor without mixing with enteric fluid (Machado et al, 2000;Hara and Gnaspini, 2003).…”

“…All individuals of G. longipes used in this study were collected inside caves at the Parque Florestal do Itapetinga (23-15 ¶S, 46-45 ¶W, 900-to 1300-m altitude, 1600 mm rain/year), Atibaia, São Paulo state, southeastern Brazil (for details on the study site, see Machado andOliveira, 1998 andMachado et al, 2000). In the laboratory, adult G. longipes were maintained in a communal terrarium (60 Â 40 cm base, 35 cm high) containing cotton wetted with water to maintain the humidity and fed with dead insects twice a week.…”

“…Enoploctenus cyclothorax (Ctenidae) is a large (3-to 5-cm body length) wandering spider that is commonly found near cave entrances ( Figure 1C) and occasionally preys on adult G. longipes (Machado et al, 2000;Machado, personal observations), as well as other gonyleptid harvestmen (Willemart and Kaneto, 2004). Trechalea biocellata (Trechaleidae) is also a large (2-to 3-cm body length) wandering spider, abundant in the study site ( Figure 1D), which is generally found near river margins or in other moist habitats, such as caves.…”