Spider sedation induced by defensive chemicals of milliped prey

Feeding Frequency, Prey Acceptance, and Natural Diet of the Mygalomorph Spider Acanthogonatus centralis Goloboff 1995 (Araneae: Nemesiidae)

Gabriel Pompozzi and Sofía Copperi (2018) The family Nemesiidae is the second most diverse family of Mygalomorphae spiders. Acanthogonatus centralis (Nemesiidae) is commonly found in hilly areas of central Argentina. These spiders are considered generalists due to their basal position in the phylogeny, but little is known about the trophic ecology of the species. Therefore, the objectives of this study were to study some of the species' predatory traits, such as feeding frequency and prey acceptance, and to assess its natural diet. In addition, two parameters - attack latency and consumption time - were measured for each accepted prey. We found that A. centralis feeds every two days and accepts almost all prey offered. The most accepted prey items were beetle larvae and termites. In fact, termites were attacked faster than any other prey, suggesting they are a suitable prey for these spiders. In regard to the species' natural diet, we found remains of seven prey items, ants and beetles being the most frequent. In this study, we found that Acanthogonatus centralis is polyphagous since it accepts different kinds of prey.

Disruption of web structure and predatory behavior of a spider by plant-derived chemical defenses of an aposematic aphid

Two toxic and bitter-tasting cardenolides (cardiac-active steroids) were sequestered by the brightly colored oleander aphid,Aphis nerii B. de F., from the neotropical milkweed host plantAsclepias curassavica L. After feeding on milkweed-reared aphids, the orb-web spiderZygiella x-notata (Clerck) built severely disrupted webs and attacked fewer nontoxic, control aphids, whereas the webs of spiders fed only nontoxic aphids remained intact. The regularity and size of the prey-trapping area of webs were reduced significantly in proportion to the amount of toxic aphids eaten. The effects of toxic aphids on spider web structure were mimicked by feeding spiders the bitter-tasting cardenolide digitoxin, a cardenolide with similar steroidal structure and pharmacological activity to the two aphid cardenolides. These results show that the well-known effects of psychoactive drugs on spider web structure are more than interesting behavioral assays of drag activity. Similar effects, produced by plant-derived chemicals in the spider's aphid prey, are relevant to the ecology and evolution of interactions between prey defense and predator foraging.

Pygidial secretions ofPasimachus subsulcatus (Coleoptera: Carabidae) deter predation byEumeces inexpectatus (Squamata: Scincidae)

The carabid beetlePasimachus subsulcatus is an abundant ground-dwelling insect in west central Florida that exudes a powerful mucous membrane irritant when disturbed. This secretion can be sprayed over 10 cm from the abdominal tip. The southeastern five-lined skink,Eumeces inexpectatus, is an abundant insectivorous lizard sympatric withPasimachus. We assessed the availability ofPasimachus toEumeces and found it to be within the foraging microenvironment of the lizard. Analysis ofEumeces gut contents and field feeding trials indicate thatPasimachus are not ingested by the lizard, yet arthropods of comparable size and exoskeletal thickness are ingested. The movement response ofEumeces to isolatedPasimachus secretion constituents, conducted in a modified Y-maze laboratory experiment, was used to assess the repellent capabilities of the secretion.Eumeces are consistently repelled byPasimachus secretion constituents, indicating that the beetle is protected chemically from the lizard.

Current status of the Myriapod class diplopoda (millipedes): taxonomic diversity and phylogeny

The arthropod class Diplopoda, the millipedes, ranks among the most diverse groups of terrestrial organisms, with over 12,000 species described. Although they play an important ecological role in most terrestrial ecosystems, little is known about the group's diversity, morphology, and phylogeny compared with other arthropod groups. We review diplopod natural history and discuss the historical and current literature pertaining to millipede morphology, ecology, chemical defenses, and the paleontological record of the group's ancient history. Diplopod systematics, past and present, are reviewed with a focus on taxonomy, collections, and biogeography. The phylogenetics of the class is reviewed, with particular attention on diplopod placement within the Myriapoda and emphasis on recent advances using molecular approaches to phylogenetic reconstruction. We present (a) the first combined morphological and molecular analysis of the millipede orders, and (b) a list of critically evaluated characteristics of nominal clades identifying putative apomorphies.