Reproduction
The sexes are separate in most species, though a few are hermaphroditic or protandric. The gonads are located in the disk, and open into pouches in between the arms, called genital bursae. Fertilisation is external in most species, with the gametes being shed into the surrounding water through the bursal sacs. An exception is the Ophiocanopidae, in which the gonads do not open into bursae and are instead paired in a chain along the basal arm joints.
Many species brood developing larvae in the bursae, effectively giving birth to live young. A few, such as Amphipholus squamata are truly viviparous, with the embryo receiving nourishment from the mother through the wall of the bursa. However, there are some species that do not brood their young, and instead have a free-swimming larval stage. Referred to as an ophiopluteus, these larvae have four pairs of rigid arms lined with cilia. They develop directly into an adult, without the attachment stage found in most starfish larvae. The number of species exhibiting ophiopluteus larvae are fewer than those that directly develop.
In a few species the female carries a dwarf male, clinging to it with the mouth.
Read more about this topic: Brittle Star
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