Morphological diversity of blastula formation and gastrulation in temnopleurid sea urchins

ABSTRACTEmbryos of temnopleurid sea urchins exhibit species-specific morphologies. While Temnopleurus toreumaticus has a wrinkled blastula, others have a smooth blastula. Embryos of T. toreumaticus invaginate continuously at gastrulation, whereas in some others invagination is stepwise. We studied blastula and gastrula formation in four temnopleurids using light and scanning electron microscopy to clarify the mechanisms producing these differences. Unlike T. toreumaticus, blastomeres of mid-blastulae in T. reevesii, T. hardwickii and Mespilia globulus formed pseudopods. Before primary mesenchyme cells ingressed, embryos developed an area of orbicular cells in the vegetal plate. The cells surrounding the orbicular cells extended pseudopods toward the orbicular cell area in T. toreumaticus, T. reevesii and T. hardwickii. In T. toreumaticus, the extracellular matrix was well-developed and developed a hole-like structure that was not formed in others. Gastrulation of T. reevesii, T. hardwickii and M. globulus was stepwise, suggesting that differences of gastrulation are caused by all or some of factors: change of cell shape, rearrangement, pushing up and towing of cells. These species-specific morphologies may be caused by the shape and surface structure of blastomeres with cell-movement.Summary statement:Temonopleurid embryology

Download Full-text

Scanning electron microscopy of gastrulation in a sea urchin (Anthocidaris crassispina)

Development ◽

10.1242/dev.67.1.27 ◽

1982 ◽

Vol 67 (1) ◽

pp. 27-35

Author(s):

Shonan Amemiya ◽

Koji Akasaka ◽

Hiroshi Terayama

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Cell Formation ◽

Cell Movement ◽

Animal Pole ◽

Vegetal Pole ◽

Mesenchyme Cell ◽

Major Motive ◽

Mesenchyme Cells ◽

Scanning Electron

Gastrulation in Anthocidaris was investigated by observing the inside and the outside of embryos by scanning electron microscopy. Furrows which possibly rėflect changes in intercellular interactions were observed on the outer surface (hyaline layer side) of embryos twice in development: firstly at the time of primary mesenchyme cell formation, and secondly at the time of vegetal plate indentation. In the latter case, the cells within and surrounding the vegetal plate appeared to change their shapes differently; the former (within the plate) having broader surfaces on the blastocoel side whereas the latter (surrounding the plate) having broader surfaces on the hyaline layer side. This suggests that the first phase of indentation may be mediated by the autonomous change of cell shape and intercellular adhesiveness, accompanied by an autonomous cell movement in the vegetal pole region. Although some pseudopodial linkages were observed between secondary mesenchyme cells on the top of the invaginating archenteron and the animal pole in the mid-gastrula and later stage embryos, they were thinner and smaller in number as compared to those in the Pseudocentrotus embryos. The rate of invagination appeared rather constant throughout gastrulation in contrast to the accelerated invagination in other embryos with larger blastocoel cavities. Moreover, the number of columnar cells on the dissected surface of embryos remained unaltered. These findings suggest that the secondary mesenchyme cells may act as a linker between the archenteron tip and the animal pole, but they may not generate major motive forces for archenteron invagination at least in the Anthocidaris embryos.

Download Full-text

Mesoblastic Cells in the Early Phase of Primitive Streak Formation in Chick Embryos. Observations by Scanning Electron Microscopy in ovo and time-Lapse Cinematography in vitro.. (chick embryo/primitive streak/mesoblastic cells/cell movement/blebs)

Development Growth & Differentiation ◽

10.1111/j.1440-169x.1984.00235.x ◽

1984 ◽

Vol 26 (3) ◽

pp. 235-247 ◽

Cited By ~ 8

Author(s):

SHIGEO TAKEUCHI

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Chick Embryo ◽

Cell Movement ◽

Primitive Streak ◽

Time Lapse ◽

Chick Embryos ◽

In Ovo ◽

Scanning Electron

Download Full-text

Chloroplast division in spinach leaves examined by scanning electron microscopy and freeze-etching

Journal of Cell Science ◽

10.1242/jcs.46.1.87 ◽

1980 ◽

Vol 46 (1) ◽

pp. 87-96

Author(s):

N. Chaly ◽

J.V. Possingham ◽

W.W. Thomson

Keyword(s):

Electron Microscopy ◽

Green Light ◽

Cell Area ◽

Low Intensity ◽

Spinach Leaf ◽

Freeze Etching ◽

Leaf Disks ◽

Scanning Electron ◽

Spinach Leaves

Spinach leaf disks were cultured for 5 days in low-intensity green light and then were transferred to high-intensity white light. Harvests over the next 16 h established that cell area increased by about 80% and chloroplast number per cell increased by about 65%, while the percentage of dumbbell-shaped chloroplasts per cell decreased by 65%. Freeze-etch replicas of fixed and unfixed leaf disks, as well as scanning electron-microscope preparations of fixed material, contained dumbbell-shaped chloroplasts constricted to various degrees. Freeze-etch replicas of unfixed cells from young leaf bases, in which the number of chloroplasts per cell is known to be rapidly increasing, also contained many constricted chloroplasts. It is concluded that dumbbell-shaped chloroplasts occur in vivo and represent a stage in the division of chloroplasts.

Download Full-text

Ultrastructure of the Tertiary Envelope of the Cyst of the Tadpole Shrimp Triops longicaudatus (Branchiopoda; Notostraca)

Microscopy and Microanalysis ◽

10.1017/s1431927600036850 ◽

2000 ◽

Vol 6 (S2) ◽

pp. 872-873

Author(s):

James R. Rosowski ◽

Terry L. Bartels ◽

James F. Colburn ◽

Jannell L. Colton ◽

Denton Belk ◽

...

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Fairy Shrimp ◽

Distilled Water ◽

Thin Sections ◽

Rainfall Events ◽

Transmission Electron ◽

Tadpole Shrimp ◽

Species Specific ◽

Scanning Electron

Tadpole shrimp inhabit temporary freshwater pools and ponds where their occurrence is largely regulated by rainfall events and water temperature. When dry basins are flooded, cysts of Triops imbibe water and hatch to produce rapidly growing, carapaced larvae. While previous studies show anostracan (fairy shrimp) cyst-surface morphology often species specific, few studies illustrate shell ultrastructure of Triops and none has considered T. longicaudatus. Here we examine the shell of T. longicaudatus (Notostraca) and compare its fine structure to other species of Triops and to that of Artemiafranciscana(Anostraca), which we previously studied.Cysts, produced in culture from Utah broodstock, were purchased from Triops, Inc., 1924 Creighton Rd., Pensacola, FL 32504. Thin sections of cysts were prepared for transmission electron microscopy (TEM) as previously described (Fig. 1). Cysts were also examined with scanning electron microscopy (SEM), dry, whole or fractured (Figs. 2,3), or after imbibition and/or hatching in oxygen saturated, double-distilled water, at 25 ° C.

Download Full-text

Eucalypt phytoglyphs: The micronanatomical features of the epidermis in relation to taxonomy

Australian Journal of Botany ◽

10.1071/bt9710173 ◽

1971 ◽

Vol 19 (2) ◽

pp. 173 ◽

Cited By ~ 17

Author(s):

SGM Carr ◽

L Milkovits ◽

DJ Carr

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Light Microscopy ◽

Thin Sections ◽

Hardening Process ◽

Leaf Surfaces ◽

The Status ◽

Species Specific ◽

High Degree ◽

Scanning Electron

The eucalypt leaf contains a store of untapped information of potentially great value taxonomic and evututionary studies. Tie cuticie of certain eucalypts is shown to possess a complex and species-specific ornamentation so distinctive that its features can be regarded as diagnostic. The term "phytoglyph" is coined for the constellation of microanatomical features of the surfaces of leaves, including the microanatomy of the cuticle. Phytoglyphic analysis relates to the combination of three methods, light microscopy of stained cuticles, scanning electron microscopy of leaf surfaces, and light microscopy of thin sections of the cuticular and associated structures. Its use is illustrated by the dissection of the "form species" E. dichromophloia into a number of separate and recognizable entities, some of which were previously accorded the status of species. The plant geographical and other implications of this dissection are dealt with. In particular, E. dichromophloia F. Muell. is to be regarded as a species of very restricted distribution. The microanatomical characters of the cuticle are closely controlled products of the epidermal layers. The fact that specimens which (on other grounds) can be grouped together as a species have identical cuticular microanatomy suggests that the phytoglyph is genetically strongly determined and does not consist of inadvertent, trivial surface features with a high degree of plasticity. This in turn raises the problem of the development of the cuticular microanatomy which cannot be explained on current views of the formation of the cuticle by passive diffusion of precursor substances through the epidermal walls, followed by a hardening process.

Download Full-text

Increase in Epidermal Planar Cell Density Accompanies Decreased Russeting of ‘Golden Delicious’ Apples Treated with Gibberellin A4+7

HortScience ◽

10.21273/hortsci.47.2.232 ◽

2012 ◽

Vol 47 (2) ◽

pp. 232-237 ◽

Cited By ~ 24

Author(s):

Eric Curry

Keyword(s):

Electron Microscopy ◽

Cell Density ◽

Cell Area ◽

Tissue Samples ◽

Air Blast ◽

Epidermal Tissue ◽

Cellular Debris ◽

High Incidence ◽

Golden Delicious ◽

Scanning Electron

A 2-year study was conducted in a ‘Golden Delicious’ (Malus ×domestica Borkh.) orchard with a high incidence of physiological fruit russeting to examine the effect of gibberellin A4+7 (GA4+7) on apple epidermal cell size. Beginning at petal fall, four sequential applications of GA4+7 (0, 15, or 30 mg·L−1) were applied to whole trees every 7–10 days with an orchard air-blast sprayer at a volume of ≈1000 L·ha−1. Fruit epidermal tissue samples were taken approximately monthly beginning 1 week after the fourth application. Tissue was treated in the laboratory with an enzyme mixture to remove cellular debris in preparation for examination using either light or scanning electron microscopy (SEM). In 2007, because russeting was insignificant, treatment differences could not be established. Moreover, transillumination microscopy did not permit accurate measurement of ‘Golden Delicious’ fruit epidermal planar cell area beyond midseason because the isolated cuticle became thick and multilayered. In 2008, however, respective treatments of 15 and 30 mg·L−1 reduced calyx end russeting by 40% and 83% and increased epidermal planar cell density by 14% and 27% as measured using SEM.

Download Full-text

The mechanism of somite segmentation in the chick embryo

Development ◽

10.1242/dev.51.1.227 ◽

1979 ◽

Vol 51 (1) ◽

pp. 227-243

Author(s):

Ruth Bellairs

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Tissue Culture ◽

Chick Embryo ◽

Neural Tube ◽

Cell Shape ◽

Fibroblast Cell ◽

General Shape ◽

Major Factors ◽

Scanning Electron

The segmentation of somites in the chick embryo has been studied by transmission and scanning electron microscopy (stages 8–14). The segmental plate mesoderm consists of loosely arranged mesenchymal cells, whereas the newly formed somites are composed of elongated, spindle-shaped cells arranged radially around a lumen, the myocoele. The diameter of each somite is thus two cells plus the myocoele. Two major factors appear to be responsible for the change in cell shape at segmentation: (1) Each prospective somite cell becomes anchored at one end to the adjacent epithelia (i.e. the neural tube, the notochord, the ectoderm, the endoderm or the aorta) by means of collagen fibrils. These fibrils are already present in the segmental plate before the somites begin to form. (2) A change in cell-to-cell adhesiveness causes the free ends of these cells to adhere to one another. (Bellairs, Curtis & Sanders, 1978). This adhesion is then supplemented by the development of tight junctions proximally in the somite. Because it is anchored at both ends, each somite cell is under tension in much the same way as a fibroblast cell in tissue culture is under tension. Each somite cell therefore becomes elongated and the somite as a whole accommodates its general shape to that of the space available between the adjacent tissues. The arrangement of the cells in the more differentiated somites (stages 17–18) has also been examined and it has been found that the chick resembles Xenopus in that the myotome cells undergo rotation and become orientated in an anteroposterior direction.

Download Full-text

A study of the arrangement of osteoblasts of rat calvarium cultured in medium with, or without, added parathyroid extract

Journal of Cell Science ◽

10.1242/jcs.25.1.247 ◽

1977 ◽

Vol 25 (1) ◽

pp. 247-263

Author(s):

S.J. Jones ◽

A.R. Ness

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Cell Area ◽

Neonatal Rats ◽

Initial State ◽

Significant Alignment ◽

Parathyroid Extract ◽

Scanning Electron

The osteoblast layers on the inner surfaces of the half-calvaria of neonatal rats of 2 litters were studied by scanning electron microscopy. Some halves were fixed immediately on dissection. Others were carried through incubation in an Eagle's medium, with or without the addition of parathyroid extract (PTE): for 2, 4, 8 or, most importantly, 24 h. In their initial state, presumed as like the o-h material, the osteoblasts presented as a dense tesselation. After 24 h of culture in the medium, osteoblasts were more sparse in the fields examined and although, in a set of 4 preparations, they retained significant alignment, their orientation had become more random. In addition, they were broader and larger in area. By contrast, with PTE added to the medium, osteoblasts almost maintained their number per field, did maintain their cell area, but became longer and narrower and strikingly parallel in their array. The aligning effect of the PTE preceded, and thus was independent of, its elongating effect.

Download Full-text

Comparative anatomy and phylogeny of the Forcipulatacea (Echinodermata: Asteroidea): insights from ossicle morphology

Zoological Journal of the Linnean Society ◽

10.1093/zoolinnean/zlz127 ◽

2019 ◽

Vol 189 (3) ◽

pp. 921-952 ◽

Cited By ~ 1

Author(s):

Marine Fau ◽

Loïc Villier

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Phylogenetic Analysis ◽

Comparative Anatomy ◽

Morphological Diversity ◽

Consensus Tree ◽

Sea Stars ◽

Extant Species ◽

Tree Resolution ◽

Scanning Electron

Abstract A new phylogenetic analysis of the superorder Forcipulatacea is presented. Forcipulatacea is one of the three major groups of sea stars (Asteroidea: Echinodermata), composed of 400 extant species. The sampled taxa are thought to represent the morphological diversity of the group. Twenty-nine forcipulate taxa were sampled belonging to Asteriidae, Stichasteridae, Heliasteridae, Pedicellasteridae, Zoroasteridae and Brisingida. Specimens were dissected with bleach. Detailed description of the skeleton and the anatomy of the ossicles were investigated using scanning electron microscopy. Comparative anatomy allowed the scoring of 115 phylogenetically informative characters. The consensus tree resulting from the analysis recovers Asteriidae, Stichasteridae, Zoroasteridae and Brisingida as monophyletic. All types of morphological features contribute to tree resolution and may be appropriate for taxon diagnosis. The synapomorphies supporting different clades are described and discussed. Brisingida and Zoroasteridae are the best-supported clades. The potentially challenging position of Brisingida in the tree may be explained by homoplastic changes, but also by the presence of numerous non-applicable characters.

Download Full-text