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(invertebrate zoology)
A generalized but distinct free-swimming larva found in several invertebrate groups, having a pear-shaped form with an external circlet of cilia, apical ciliary tufts, a complete functional digestive tract, and paired nephridia with excretory tubules. Also known as trochosphere.



the free-swimming larva of some annelid worms (polychaetes), echiuroids, sipunculids, and some mol-lusks. The microscopic body is fringed by one or more bands of cilia that facilitate locomotion in water. A preoral band or proto-troch is highly characteristic of the organism. At the upper pole of the trochophore is the sense organ, a parietal plate with a tuft of cilia and a group of nerve cells. The mouth is located on the ventral side, behind the prototroch. The intestine consists of a gullet, middle gut, and posterior gut. The anal opening is at the posterior pole. The excretory organs are a pair of protone-phridia. Alongside the intestine is a pair of primary mesodermal cells (mesoblasts), which produce a pair of mesodermal bands by repeated division. As a result of further development the trochophore acquires bristles, and its mesodermal bands become segmented, forming a series of paired coelomic sacs. The larva is then called a metatrochophore or nectochaeta.


References in periodicals archive ?
1K; 7 h 30 min) turned into an active motile early trochophore larva (52.
Giant clams are typical of bivalve molluscs, going through trochophore, veliger, and pediveliger stages before completing metamorphosis into juveniles (Lucas 1988).
5h 16-cell 19h 32-64-cell 23h Blastula 43h Gastula Day 3 (56 h) Trochophore Day 4 (104 h) Veliger Day 6 (133 h) Hatching Day 10 Competence Day 51 Metamorphosis Day 61 2.
Hatching success (Stage 14) was calculated by dividing the number of trochophores by the starting number of fertilized eggs.
At 25 hpf, individuals had developed to trochophore larvae that were actively swimming using cilial movement of their velum.
Generally, the larval development of molluscs started with a basic stage of trochophore and then progressively develop into lecithotrophic or planktotrophic veliger larvae, which are characterized by the formation of the velum.
Trochophore concepts: ciliary bands and the evolution of larvae in spiralian Metazoa.
The first larval stage differs from the classic gastropod trochophore in lacking a girdle of multiciliated trochoblast cells; instead, it is fully ciliated, with simple cilia extending through pores of an external cuticular layer (Fig.
The first polar body appears 10-15 min postfertilization of oocytes, and embryogenesis takes place to trochophore (80 [micro]m) 18 h afterward.
Representatives of some phyla also share a trochophore larval stage (e.
Trochophore and D larvae were identified in the hatchery from 18 to 24 h afterward.
Furthermore, in the Pacific oyster, spermatozoa with a high intracellular ATP content seem to be more likely to successfully fertilize oocyte as trochophore yield was positively correlated to intracellular ATP content (Boulais 2014).