User:Morristb/Agalma (siphonophore)

Agalma is a genus of siphonophores in the family Agalmatidae. Siphonophores are colonial hydrozoans that feed on zooplankton. They are considered to be one of the longest free-living animals in the world and one of the most abundant group of organisms in the open ocean.

Feeding Mechanism
Agalma are predatory animals that capture their prey by deploying a net of tentacles that their prey swim into. They create seemingly invisible three-dimensional webs using their tentacles that contain millions of toxin-filled stinging cells called cnidocytes. When prey comes into contact with the tentacle webs, the nematocysts inject the toxins into the captured prey.

The diets of Agalma correspond to their swimming behaviors and the likelihood of encountering and capturing prey. Species of Agalma that are strong swimmers and swim rapidly capture smaller zooplankton like copepods, while agalma that are weak swimmers swim slower capture both small and large zooplankton. Weak swimming agalma also exhibit mimicking mechanisms to capture larger prey like crab megalopa larvae, large copepods, and euphausiids. The stomachs of agalma are referred to as gastrozooids, that each have a tentacle with several branches known as tentilla. Variations in the morphology of tentilla reflect differences in the prey that agalma capture. Tentilla can arrange to resemble another organism to lure prey. Agalma okeni use their red tentilla to form structures that mimic copepods with long antennae.

Ecology
Siphonophores are the most complex colonial animals. They asexually reproduce multiple zooids that are homologous to a free-living siphonophore. Throughout the agalma life cycle, the zooids remain attached and physiologically integrated, making them the most functionally specialized zooids among all animals. They also exhibit the most colony-level organization.

Species

 * Agalma clausi Bedot, 1888
 * Agalma elegans (Sars, 1846)
 * Agalma okeni Eschscholtz, 1825