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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Trochophore larvae of serpulid annelids sometimes arrest beat of the metatroch while the prototroch beats (Strathmann et al., 1972; Lacalli, 1981, 1984).
The first attempt of identifying the embryonic development of Omani abalone was conducted by Stirn and Al Hashmi (1996) which identified six stages; nonfertilized egg, cleavage (4-cell stage), advanced embryo (morula), unhatched trochophore larvae, initial veliger, and finally advanced veliger.
Understanding the hypothesized repeated losses of both spiral cleavage and trochophore larvae in the Lophotrochozoa (Dunn et al., 2008; Paps et al., 2009) requires not only a phylogenetic context but also a good grasp of the mechanisms of lophotrochozoan development.
A few annelid larvae are so highly derived--assuming that the trochophore in the sense of Rouse (1999) is indeed a plesiomorphic form--that they are not immediately recognizable as manifestations of the trochophore ground plan.
This study analyzed, for the first time in Atrina maura, the influence of the origin (depth, tidal phases) and gross condition of broodstock in reproductive performance (number and size of released and fertilized eggs; number of trochophore and veliger larvae) and larval performance (growth and survival).
The anterior part of the loop became the larger prototroch, also involved in locomotion, and the two bands together formed the downstream collecting system so characteristic of planktotrophic trochophores. The perianal part of the cirCumblas-toporal band became the telotroch.
Fewer D-stage larvae developed after exposure of trochophores to CEWAFs (12.5 mg/L) or WAFs (200 mg/L; [F.sub.15,64] = 24.91, P < 0.0001) than controls (Fig.
This stem form gave rise to trochophore and dipleurula ( = tor-naria) lineages, which each subsequently added a benthic stage to the life cycle.
Nemerteans, commonly known as ribbon worms, are a fascinating but often ignored phylum of marine invertebrates, closely related to coelomate protostome animals with spiral cleavage and trochophore larvae, such as annelids and molluscs.
Counts were used to estimate (1) the total proportion of fertilized eggs that had "survived" 24 h of incubation (trochophores + D-stage) and (2) the proportion of surviving embryos that had undergone "normal development" and were therefore D-stage larvae with a calcified shell.
An exception to this are the trochophores of polyplacophoran molluscs and the creeping-type larva of entoprocts, which both have a highly complex apical organ with 8-10 central flask cells surrounded by numerous peripheral cells, a condition that seems to occur only in these two clades (Friedrich et al., 2002; Voronezhs-kaya el al., 2002; Wanninger et al., 2007; Wanninger, 2008; Fig.
circularisquama densities and persistency in the water, and potential toxic effects for Pinctada fucata martensii trochophores and D-shaped larvae.