Life Cycle
Veligers hatch from egg capsules or develop from an earlier trochophore larval stage.
Veligers mature to a point called "competence" where they settle to the substratum and metamorphose to become the juvenile stage. The process of metamorphosis involves losing their velum and undergoing both external and internal changes that produce the juvenile.
Both feeding and non-feeding veligers are possible, depending on the specific species that produced them. In the case of a feeding veliger, the larval stage is, in most cases, relatively "undeveloped" and must feed on phytoplankton for a period of time (weeks to months) in order to develop to the point where it can metamorphose. During this period the veliger grows and also develops the organ systems necessary for the benthic life of a juvenile. "Non-feeding" veligers utilize yolk stored in the egg as an energy source for development. In such cases, the organ systems necessary for juvenile life develop either during the embryonic period or also during a brief larval stage. Non-feeding veliger larvae generally are thought to metamorphose to the juvenile stage in a relatively short period of time; however, in some cases such larvae can feed secondarily and persist in the plankton for long periods.
Metamorphosis of both feeding and non-feeding competent larvae is usually induced by a chemical cue that is characteristic of the proper habitat for the juvenile. In gastropods, this chemical cue is often a substance produced by the juvenile or adult food source. In bivalves, the chemical cue may be produced by bacteria that are specific to the type of biofilm growing in the adult habitat. As a result of this inductive response, the veliger will metamorphose in a habitat where it can successfully feed and grow to adulthood.
Read more about this topic: Veliger
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