Phylum Arthropoda: Introduction and Arachnida

Abstract

Spiders (Order Araneae) are among the most familiar arthropods to people, besides being very abundant in most environments. However, most spiders live on strictly defined environments, and the limitations are usually set by physical conditions, such as temperature, humidity, wind, and light intensity as well as by biological factors, such as vegetation structure, prey availability and predators (Foelix, 2011). Freshwater spiders live on specific habitats near but not in the water where they can walk on its surface and dive after tadpoles or small fishes. Neotropical spiders associated with freshwater are quite diverse, and are found in four families: Ctenidae, Lycosidae, Pisauridae and Trechaleidae, all within Lycosoidea. The families Ctenidae, Lycosidae and Pisauridae have a few freshwater representatives including Ancylometes (Ctenidae) and nursery web spiders (Pisauridae). The most diverse and widespread family associated with Neotropical freshwater environments is Trechaleidae, with 15 genera (World Spider Catalog, 2017) found almost exclusively in the Neotropics. Spiders in this family live in vegetation near the margins of rocky streams and small rivers (Carico, 1993). Aquatic spiders possess flexible tarsi that maybe helpful in locomotion on the surface of the water during foraging. They also can crawl underwater to capture prey.