Reproductive biology

Hermaphroditic scaphopods have been reported but are rare. Most members of the group release their eggs or sperm into the water column, either through the anterior or posterior aperture via the right kidney. Fertilization therefore occurs externally in the water; there is no courtship behavior or parental care of young. Few studies have been published on the reproductive ecology of scaphopods, although these do indicate some seasonality in gamete production. The eggs of scaphopods, particularly those of Antalis entalis and related species, have been used for over a century as models for the experimental study of early development of embryos.

Scaphopods have a free-swimming larval stage that develops in the water. The larvae have a general resemblance to the trochophore and veliger larvae of other mollusks. The orientation of the larval body eventually changes into the typical scaphopod body shape. It is noteworthy that the first shell secreted by the scaphopod, the larval praetubulus, is soon shed as growth continues at the larger anterior end of the animal— a pattern of shell secretion and dissolution that continues throughout the scaphopod's life.

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