The larval morphology of the marine bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea) |
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Authors: | Christopher G Reed Richard A Cloney |
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Institution: | (1) Department of Zoology, University of Washington, 98195 Seattle, WA, USA;(2) Friday Harbor Laboratories, 98250 Friday Harbor, WA, USA;(3) Present address: Museum of Comparative Zoology, Harvard University, 02138 Cambridge, MA, USA |
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Abstract: | Summary The larval morphology of the marine bryozoan Bowerbankia gracilis has been investigated by light and electron microscopy. The barrel-shaped larva (200 m long and 150 m in diameter) is light yellow without any apparent eyespots, although it is positively phototactic during its brief free-swimming existence. The primary morphological characteristics of the larva are: (1) a large corona that forms most of the larval surface, (2) a small apical disc without blastemas, (3) a deep pallial sinus lined by an extensive pallial epithelium, (4) an internal sac without regional specializations, and (5) a polypide rudiment in the oral hemisphere. This organization is characteristic of larvae of the ctenostome superfamily Vesicularioidea, and differs radically from the organization of all other bryozoan larvae examined. The major morphological differences occur in the size and organization of the apical disc, the pallial epithelium, and the internal sac. In most bryozoans, these regions of the larval epithelium represent rudiments of the polypide and the body wall epidermis of the ancestrula. The oral polypide rudiment, the extensive pallial epithelium, and the reduced internal sac in vesicularioid larvae indicate that their pattern of metamorphosis also differs radically from the metamorphoses of other bryozoans.Figure Abbreviations AB
aboral
- acr
axial ciliary rootlet
- ad
apical disc
- anc
aboral nerve cord
- ANT
anterior
- arm
apical retractor muscle
- b
basal body
- bf
basal foot process
- c
corona
- cc
ciliated cleft
- ce
centriole
- ci
cilium
- cl
cupiform layer of the polypide rudiment
- cp
ciliary pit
- cr
ciliary rootlet
- enr
equatorial neural ring
- g
glandular cells of the pyriform organ
- gl
glycocalyx
- go
Golgi complex
- gr
granule
- hcr
horizontal ciliary rootlet
- ic
intercoronal cell
- igf
inferior glandular field
- ip
infrapallial cells
- is
internal sac
- jp
juxtapapillary cells
- l
lipid droplets
- L
lateral
- m
mesenchyme
- m
Type I mesenchyme cell
- m
Type II mesenchyme cell
- m
Type III mesenchyme cell
- mb
median band of the polypide rudiment
- mc
marginal cells of the apical disc
- mi
mitochondria
- mr
microridge
- mv
microvilli
- nn
nerve nodule
- np
neural plate
- nu
nucleus
- O
oral
- oce
oral ciliated epithelium
- op
opening to the internal sac
- ovc
oral vesicular collarette
- p
papilla of the pyriform organ
- pa
pallial cell
- pe
pallial epithelium
- po
pyriform organ
- POS
posterior
- pp
parasagittal patches of undifferentiated cells
- pr
polypide rudiment
- rer
rough endoplasmic reticulum
- sc
supracoronal cells
- sg
secretory granules
- sgf
superior glandular field
- sp
suprapallial cells
- tc
terminal cone
- tf
transitional filaments
- u
undifferentiated cells
- va
vacuole
- vc
vesicular cell
- wc
wedge-shaped cells of the apical disc
- y
yolk granule
- za
zonula adhaerens
Caption Abbreviations Gp
Glutaraldehyde-phosphate
- Os
Osmium |
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Keywords: | |
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