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Abstract The nonfeeding planktonic larvae of marine invertebrates typically lack larval feeding structures. One puzzling exception to this generalization is the annelid clade Sabellidae, in which nonfeeding larvae possess ciliary bands (specifically, food groove and metatroch) that, to the best of our knowledge, have no function other than in feeding. Nishi and Yamasu (1992b,Bulletin of the College of Sciences, University of the Ryukyus,54, 107–121) published a scanning electron micrograph showing that nonfeeding larvae of the serpulid annelidSalmacina dysterialso possess food groove and metatrochal cilia. Here I demonstrate that nonfeeding larvae ofSalmacina tribranchiataalso bear ciliary bands identifiable as food groove and metatroch by position. High‐speed video of ciliary beat patterns shows that, together with the prototrochal cilia, these bands function in an opposed band system. The presence of feeding structures in nonfeeding annelid larvae is thus more widely distributed than previously recognized. The presence of feeding structures may make evolutionary transitions to planktotrophy more likely, and may underlie an inferred origin of larval feeding in the common ancestor of one of the two major clades of serpulid annelids, Serpulinae.
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An oral brush of cilia in the feeding larvae of Micronephtys cornuta (Annelida, Nephtyidae)
Abstract Larvae of many phyllodocidan annelids are planktotrophic, but the feeding mechanisms of larvae in this diverse clade are poorly known. Many larvae belonging to one large clade of phyllodocidans, Aphroditiformia, bear a bundle of long cilia attached to the left side of the prototroch, the oral brush, which they use in feeding. In 1936, D.P. Wilson observed that trochophore larvae ofNephtys hombergi, a member of the phyllodocidan family Nephtyidae, bore a strikingly similar bundle of long cilia on the left side of the body. Since Wilson's observation, numerous descriptions of nephtyid larvae have been published, but none remark on the presence of an oral brush. Here I show that metatrochophore I and II larvae ofMicronephtys cornutabear an oral brush, but that it is lost in the transition to the nectochaete stage, during which the larval mouth and foregut are also being remodeled to function in benthic feeding by juveniles. That an oral brush is clearly present in at least some larval stages of two genera suggests that oral brushes may be widespread in the feeding larvae of nephtyids, but have simply been overlooked for more than 80 years. Additional work is needed to make inferences on the evolutionary history of the oral brush in phyllodocidan annelids, and to distinguish among several hypotheses on the function of this peculiar group of cilia in larval feeding.
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- Award ID(s):
- 1756531
- PAR ID:
- 10456308
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Invertebrate Biology
- Volume:
- 139
- Issue:
- 2
- ISSN:
- 1077-8306
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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