Development of the Embryonic Shell ofNautilus

2013 ◽  
pp. 323-323
Author(s):  
John M. Arnold ◽  
Neil H. Landman ◽  
Harry Mutvei
Keyword(s):  
Embryonic Shell

Embryonic shell shape as an early indicator of pollution in marine gastropods

2021 ◽  
Vol 167 ◽  
pp. 105283
Author(s):  
M.A. Primost ◽  
A. Averbuj ◽  
G. Bigatti ◽  
F. Márquez
Keyword(s):  
Shell Shape ◽  
Marine Gastropods ◽  
Early Indicator ◽  
Embryonic Shell

scholarly journals Light and electron microscopy study of late embryonic development in the land snail Limicolaria flammea (Müller) (Pulmonata, Achatinidae)

2007 ◽  
Vol 24 (2) ◽  
pp. 436-441 ◽  
Author(s):  
Rosemary I. Egonmwan
Keyword(s):  
Electron Microscopy ◽  
Embryonic Development ◽  
Light And Electron Microscopy ◽  
Microscopy Study ◽  
Land Snail ◽  
Electron Microscopy Study ◽  
Advanced Embryo ◽  
Embryonic Shell ◽  
Advanced Stages ◽  
Late Stages

The late stages of embryogenesis in the achatinid land snail Limicolariaflammea (Müller, 1774) were described using light and electron microscopy. Embryos at various stages of development were present in the eggs during the first hour after they were laid, from 4-cell blastulae to morulae and fairly advanced stages. The advanced embryo which was fully developed on the second day bears a long cephalic sac, first to be developed, attached to the embryo and a podocyst which is attached to the foot of the embryo. Both of these structures are reduced in size as embryogenesis progresses until they finally disappear at about the 7th day after the egg was deposited. The embryonic shell was apparent on the second day and spiral coiling was apparent at about day 5. The spiral shell had one whorl when formed and more spirals were added so that at hatching the young snails had three whorls.

Development of the Embryonic Shell of Nautilus

2010 ◽  
pp. 373-400 ◽  
Author(s):  
John M. Arnold ◽  
Neil H. Landman ◽  
Harry Mutvei
Keyword(s):  
Embryonic Shell

Affinities of the alleged earliest Cambrian gastropod Aldanella

2013 ◽  
Vol 91 (12) ◽  
pp. 914-923 ◽  
Author(s):  
Jerzy Dzik ◽  
Dawid Mazurek
Keyword(s):  
Shell Morphology ◽  
Skewed Distribution ◽  
Phylogenetic Position ◽  
Soft Body ◽  
Middle Cambrian ◽  
Small Shelly Fossils ◽  
Embryonic Shell ◽  
Mode Of Life ◽  
Early Palaeozoic ◽  
Mature Size

Unlike true Palaeozoic gastropods, but similar to some coeval hyoliths, the cup-like hemispherical embryonic shell of Aldanella attleborensis (Shaler and Foerste, 1888) from the earliest Cambrian (early Tommotian) Erkeket Formation of northern Siberia bears a mucro. Also, the pattern of mortality, with right-skewed distribution and a peak at about 1.0 mm diameter, is not similar to that of early Palaeozoic gastropods; there is no evidence of metamorphosis that would end the pelagic larval stage of ontogeny. Specimens of larger size are rare in samples of phosphatized “small shelly fossils” but are known in related species of the genus, of up to 3–5 mm diameter. A phosphatized soft body is preserved in a few specimens of A. attleborensis, one bearing possible chaetae of about 5 μm diameter. Such bunches of chaetae arming locomotory organs were earlier identified in the genus Pelagiella Matthew, 1895, a more derived member of the same lineage. It shares with the genus Aldanella Vostokova, 1962 also the mucronate embryonic shell and acicular aragonitic shell wall microstructure. The presence of chaetae-bearing organs suggests pelagic mode of life of pelagiellids at maturity. Middle Cambrian Pelagiella shells reached 7 mm in diameter, suggesting evolutionary increase in mature size. Embryonic shell morphology, wall microstructure, and the presence of locomotory organs with a fan of chaetae contradicts gastropod, and even conchiferan affinity of the pelagiellids, but together with the pattern of ontogeny conforms to the enigmatic Palaeozoic hyoliths. They differ in having opercula closing the shell apertures and in lacking evidence of chaetae. The helens, paired apertural appendages of possible locomotory function occurring in apertures of some of them, do not reveal any similarity to chaetae in their development. We propose classifying the order Pelagiellida in the class Hyolitha rather than in the class Gastropoda, until its phylogenetic position is clarified. Such understood hyoliths may represent the earliest stage in evolution of molluscs, immediately following initial diversification of the spiralians (lophotrochozoans) into phyla.

scholarly journals Effects of sessile Protozoa on intracapsular oxygen tension and embryonic shell calcification in the muricid Chorus giganteus

2000 ◽  
Vol 200 ◽  
pp. 141-148 ◽  
Author(s):  
JM Cancino ◽  
JA Gallardo ◽  
F Torres ◽  
G Leiva ◽  
JM Navarro
Keyword(s):  
Oxygen Tension ◽  
Embryonic Shell
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