Ctenophores Complete Guts and Tentacles

Ctenophores (phy lum Ctenophora)

were the next lineage to diverge from the lineage leading to all other animals. Cteno-phores, also known as comb jellies, have body plans that are superficially similar to those of cnidarians. Both have two cell layers separated by a thick, gelatinous mesoglea, and both have radial symmetry and feeding tentacles. Like cnidarians, ctenophores have low metabolic rates because they are

Scyphozoan medusae are the dominant life form and are familiar to us asjellyfish.

Adult medusa

Young medusa (oral surface)

Planula larvae are products of sexual reproduction.

Planula Larva Symmetry

Scyphozoan medusae are the dominant life form and are familiar to us asjellyfish.

Adult medusa

Young medusa (oral surface)

Planula larvae are products of sexual reproduction.

Jellyfish Life Cycle

32.11 Medusae Dominate Scyphozoan Life Cycles Scyphozoan medusae are the familiar jellyfish of coastal waters.The small,sessile polyps quickly produce medusae (see Figure 32.6c).

32.11 Medusae Dominate Scyphozoan Life Cycles Scyphozoan medusae are the familiar jellyfish of coastal waters.The small,sessile polyps quickly produce medusae (see Figure 32.6c).

32.12 Comb Jellies Feed with Tentacles (a) The body plan of a typical ctenophore. The long, sticky tentacles sweep through the water, efficiently harvesting small prey. (b) A combjelly photographed in Sydney Harbour, Australia, has short tentacles.

(b) Bolinopsis chuni

Anal pores

Tentacle

Ctenophore life cycles are simple. Gametes are produced in structures called gonads, located on the walls of the gastrovascular cavity. The gametes are released into the cavity and then discharged through the mouth or the anal pores. Fertilization takes place in open seawa-ter. In nearly all species, the fertilized egg develops directly into a miniature ctenophore that gradually grows into an adult.

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