Pelagiidae Family of Jellyfish
One Jellyfish from the Pelagiidae Family can be found in this website:
Pacific Sea Nettle, Chrysaora fuscescens. A representative of the Pelagiidae Family of Jellyfish.
Phylogeny: Jellyfish of the Pelagiidae Family, like coral polyps and sea anemones are in the phylum Cnidaria. This phylum is generally characterized by animals having radial symmetry. Their bodies consist of an inner layer (endoderm) and an outer layer (ectoderm) with the layers separated by a jelly-like mesoglea. All Cnidarians have nematocysts (stinging cells) that they use to capture food. Pelagiidae Jellyfish are in the subphylum Medusazoa and the class Scyphozoa. Scyphozoans spend most of their life cycle in the medusa (bell or umbrella shaped) form. These bells can be fairly large and are often colorful. As Scyphozoans, these jellyfish lack a vellum, a shelf-like structure around the inside margin of the bell, and, usually, lack a ring canal, a canal lined with gastrodermis that runs around margin of bell. Pelagiid Jellyfish are in the subclass Discomedusae and the order Semaeostomeae. The Pelagiidae Family is one of five families in this order. The Pelagiidae Family contains four genera and twenty-four species. The name Pelagiidae comes from the Greek word for “open ocean”, and refers to the habitat of these species.
Morphology: Pelagiid Jellyfish have the classic jellyfish appearance, with long frilly oral arms extending below the center of the bell, and shorter tentacles extending from the margins of the bell. The margins of the bell are often scalloped with lobes that are known as lappets. Tentacles or other sensory organ may be located between these lappets. The characteristics that define the Pelagiidae Family are not readily observable in the field. They refer to unbranched, radiating, pouches that surround the central stomach. Pelagiid Jellyfish are moderate to large in size. Some species have a bell that can reach 91 cm (3 feet) in diameter and some have oral arms that reach 6.0 m (20 feet) in length.
Habitat and Distribution: Pelagiid Jellyfish are generally found in open water. They propel themselves through the water by opening and closing their bell. Their swimming ability is limited and they are largely at the mercy of ocean currents. While they are generally pelagic, currents can push them into bays and estuaries. Occasionally currents will push large numbers of jellyfish ashore in mass stranding events. Most Pelagiid Jellyfish are found near the surface and seldom deeper than 100 m (328 feet). They are are found worldwide, in tropical to temperate seas. At least six species from this family are found in Mexican waters.
Reproduction: Pelagiidae Jellyfish are generally gonochoric (male or female for life), and most reproduce sexually, through broadcast spawning. The gametes are released through the mouth. The fertilized eggs develop into planula larvae, which directly metamorphose into ephyrae (free-swimming baby jellyfish with eight arms and a star-shaped outline). The ephyrae then mature into adult medusa-like jellyfish Unlike most Scyphozoans, they bypass the usual benthic polyp phase. Some species in this family do reproduce asexually through strobilation (forming polyps that release ephyrae) or by producing podocysts (resting cysts).
Ecosystem Roles: Pelagiid Jellyfish feed by trailing their tentacles and oral arms through the water and paralyze their prey with their nematocysts. They feed on small crustaceans, ctenophores, fish, fish eggs, mollusks, tunicates, and other jellyfish. In turn Pelagiid Jellyfish are preyed upon by sea birds, parasitic crustaceans, fish, sea turtles, and other jellyfish. Pelagiid Jellyfish host crustaceans and fish in commensal relationships. Some species in this family can deliver painful stings to humans.