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
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.