Ammotheidae

Ammotheidae is a family of marine arthropods belonging to the class Pycnogonida, commonly known as sea spiders. These are unique, predatory arachnids that inhabit marine environments worldwide, from shallow coastal waters to the deep sea. Ammotheidae is one of the largest and most diverse families within this order.

Sea spiders in this family, like other pycnogonids, are characterized by their extremely slender bodies and long, spindly legs. Many species have an ovigerous leg pair, used by males to carry egg masses. Their bodies are often reduced to a series of interconnected segments, with most of the internal organs extending into the legs. They feed by piercing the tissues of sessile invertebrates, such as hydroids, bryozoans, and sponges, using a proboscis to extract nutrients. Ammotheidae species exhibit a wide range of sizes, from a few millimeters to several centimeters in leg span.

Reproduction in Ammotheidae typically involves external fertilization. Males are responsible for brooding the eggs. The larval stages are also highly specialized, often undergoing significant development attached to the male's ovigerous legs before eventually metamorphosing into a juvenile form that resembles the adult. The exact number of species within Ammotheidae is subject to ongoing research and revision due to the cryptic nature and specialized morphology of these creatures.