Larval development of both hybrid strains progressed in a manner typical of tridacnines, with larvae progressing through trochophore
, veliger, and pediveliger stages before metamorphosing into juvenile clams (Fig.
After 16-18 hours, embryo had differentiated into trochophore
, measuring approximately 45.
Fertilization rates were determined by percentage of mobile trochophore
larvae, 24 h after fertilization.
(free-swimming larva with cilia) and the veliger (second larval stage seen in the diagram above with beginnings of foot, shell, and mantle) bear faint resemblances to their end product, the mature bivalve mollusk that forms the basis of a tasty meal.
larvae were observed between eight and ten hours later.
Morphological and behavioral defenses of trochophore
larvae of Sabellaria cementarium (Polychaeta) against four planktonic predators.
In many spiralians, the embryo passes through a trochophore
or a trochophore
-like larval stage, characterized by a transverse belt of ciliated, trochal cells.
Presence or absence of embryos (including all stages from fertilized eggs to trochophore
larvae) and veliger larvae (including all stages from veliger larvae to juveniles; stages differentiated as described by Kraemer and Galloway, 1986) was recorded for each adult.
Samples of 1 mL at 5, 10, 15, and 30 min during the first 3 h then later each 30 min in the subsequent 6 h, and later each hour were measured to determine the embryogenic stage until the trochophore
and D-larvae appeared.
to pilidium and back again--a larva's journey.
The fertilized egg then develops into a larva called a trochophore
Many marine invertebrate groups with different adult forms have similar larvae (such as the trochophore
larva of mollusks and annelids, or the pluteus larva of sea urchins and brittle stars), and these similar larval forms are usually considered to be examples of either convergent evolution by natural selection or functional constraints on the evolution of early stages in development (Jagersten 1972; Strathmann 1988; Raff and Kaufman 1991; Wray 1992, 1995).