scholarly journals MORPHOLOGY OF GAMETE MEMBRANE FUSION AND OF SPERM ENTRY INTO OOCYTES OF THE SEA URCHIN

1965 ◽  
Vol 25 (2) ◽  
pp. 81-100 ◽  
Author(s):  
Luther E. Franklin
Keyword(s):  
Electron Microscope ◽  
Sea Urchin ◽  
Acrosome Reaction ◽  
Sea Water ◽  
Sea Urchins ◽  
Detailed Examination ◽  
Lytechinus Variegatus ◽  
Arbacia Punctulata ◽  
Sperm Entry ◽  
Ultrathin Sections

Sea urchin gametes predominate in molecular studies of fertilization, yet relatively little is known of the subcellular aspects of sperm entry in this group. Accordingly, it seemed desirable to make a detailed examination of sperm entry phenomena in sea urchins with the electron microscope. Gametes of the sea urchins Arbacia punctulata and Lytechinus variegatus were used in this study. Samples of eggs containing 2 to 8 per cent oocytes were selected and fixed with osmium tetroxide in sea water at various intervals after insemination. Fixed specimens were embedded in Epon 812, sectioned, and examined with an electron microscope. An apical vesicle was observed at the anterior end of the acrosome. The presence of this structure, together with other observations, suggested that initiation of the acrosome reaction in sea urchin sperm involves dehiscence of the acrosomal region with the subsequent release of the acrosomal granule. Contact and initial fusion of gamete membranes was observed in mature eggs and oocytes and invariably involved the extended acrosomal tubule of the spermatozoon. Only one spermatozoon normally enters the mature egg. The probability of locating such a sperm in ultrathin sections is exceedingly low. Several sperm do normally enter oocytes. Consequently, observations of sperm entry were primarily restricted to the latter. The manner of sperm entry into oocytes did not resemble phagocytosis. Organelles of the spermatozoon were progressively divested of their plasma membrane as they entered the ground cytoplasm of the oocyte fertilization cone. Initiation of the acrosome reaction, contact and initial fusion of gamete membranes, and sperm entry into oocytes of sea urchins conform to the Hydroides-Saccoglossus pattern of early fertilization events as described by Colwin and Colwin (13).

Fine Structure of Sea Urchin Sperm Membranes

1970 ◽  
Vol 28 ◽  
pp. 312-313
Author(s):  
S. Inoue ◽  
A. Buday ◽  
G.H. Cousineau
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Sea Urchin ◽  
Sea Water ◽  
Sea Urchins ◽  
Water Mixture ◽  
Thin Sections ◽  
Surface Replica ◽  
Sperm Membrane ◽  
Surface Replica Method

From electron microscope studies of thin sections it is known that the entire surface of a spermatozoon of sea urchin is covered by a plasma membrane, or sperm membrane, of an approximate thickness of 100Å (1). In these experiments the surface replica method was applied for the study of the fine structure of the sperm membrane.Spermatozoa from Strongylocentrotus purpuratus (sea urchins supplied by the Pacific Biomarine Supply Company, Venice, Calif.) were washed several times by centrifugation in Millipore-filtered sea water. After fixation in a 2.5% glutaraldehyde-paraformaldehyde (sea water mixture at 4°C) for an hour, spermatozoa were washed with sea water and then with distilled water for several times. A few drops of specimen were dried on a glass slide and the surface replica was prepared according to the method previously described (2) with the exception that the spermatozoa were decomposed in 18 N H2SO4 for about 20 hours at room temperature. The replica films were examined with a JEM-7A electron microscope.

scholarly journals THE EXTRACELLULAR RELEASE OF ECHINOCHROME

1946 ◽  
Vol 29 (5) ◽  
pp. 267-275 ◽  
Author(s):  
Herbert Shapiro
Keyword(s):  
Sea Urchin ◽  
Sea Water ◽  
Potassium Content ◽  
Red Pigment ◽  
Anaerobic Conditions ◽  
Outward Diffusion ◽  
Arbacia Punctulata ◽  
Extracellular Release

A study was made of the diffusion of the red pigment echinochrome from the eggs of the sea urchin, Arbacia punctulata, into sea water. Unfertilized eggs retained their pigment, over periods of hours. Outward diffusion of pigment from unfertilized eggs normally is entirely negligible, or does not occur at all. Enchancing the calcium or potassium content of the artificial sea water (while retaining isosmotic conditions) did not induce pigment release. Under anaerobic conditions, unfertilized eggs release pigment in small quantities. Fertilization alone brings about echinochrome release. Fertilized eggs invariably released pigment, whether in normal sea water, or sea water with increased calcium or potassium. This diffusion of the pigment began during the first cleavage, possibly soon after fertilization. The pigment release is not a consequence solely of the cell's permeability to echinochrome (or chromoprotein, or other pigment combination) but is preceded by events leading to a release of echinochrome from the granules in which it is concentrated within the cell. These events may be initiated by activation or by anaerobiosis. The phenomenon was not due to cytolysis.

scholarly journals Chronic toxicity test with sea urchin Echinometra lucunter and Lytechinus variegatus (Echinodermata: Echinoidea), exposed to light-stick - flag paternoster used for longline surface fishing

2010 ◽  
Vol 58 (spe3) ◽  
pp. 71-75 ◽  
Author(s):  
Caio Cesar-Ribeiro ◽  
Maria Fernanda Palanch-Hans
Keyword(s):  
Toxicity Test ◽  
Chronic Toxicity ◽  
Sea Water ◽  
Sea Urchins ◽  
Preliminary Test ◽  
Lytechinus Variegatus ◽  
Confidence Limits ◽  
Potential Danger ◽  
Final Test ◽  
Chronic Toxicity Test

In this work, the chronic toxicity of a mixture of light-stick chemicals and water was tested. The light-stick is used in fishery activities to catch swordfish. The tubes were collected on the beaches of the Costa dos Coqueiros - BA, Brazil, in the period from 14th to 31st July 2007. The method used was a short chronic toxicity test where embryos of the sea urchins Echinometra lucunter and Lytechinus variegatus were exposed to a stock solution consisting of the supernatant formed from a mixture of sea water and the orange-colored light-stick chemical. After a preliminary test, concentrations defined were 0.002, 0.003, 0.01, 0.02, 0.1, 1.0% of stock solution. The final test ran for 36 hours for E. Lucunter and 24 hours for L. variegatus with 4 replicates for each concentration. The value of EC50 - 36h was 0.062% with confidence limits ranging from 0.042 to 0.079% and the EC50 - 24h was 0.011% with confidence limits ranging from 0.009 to 0.014%, i.e., the chemical mix present in the light-stick is potentially toxic. So, as these flags are commonly used for fishing there is potential danger in their disposal in the open ocean.

scholarly journals Activation of sea urchin eggs by inositol phosphates is independent of external calcium

1988 ◽  
Vol 252 (1) ◽  
pp. 257-262 ◽  
Author(s):  
I Crossley ◽  
K Swann ◽  
E Chambers ◽  
M Whitaker
Keyword(s):  
Sea Urchin ◽  
Calcium Ions ◽  
Sea Water ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Egg Activation ◽  
Lytechinus Variegatus ◽  
Lytechinus Pictus ◽  
Sea Urchin Eggs ◽  
External Calcium

We investigated the contribution of external calcium ions to inositol phosphate-induced exocytosis in sea urchin eggs. We show that: (a) inositol phosphates activate eggs of the sea urchin species Lytechinus pictus and Lytechinus variegatus independently of external calcium ions; (b) the magnitude and duration of the inositol phosphate induced calcium changes are independent of external calcium; (c) in calcium-free seawater, increasing the volume of inositol trisphosphate solution injected decreased the extent of egg activation; (d) eggs in calcium-free sea water are more easily damaged by microinjection; microinjection of larger volumes increased leakage from eggs pre-loaded with fluorescent dye. We conclude that inositol phosphates do not require external calcium ions to activate sea urchin eggs. This is entirely consistent with their role as internal messengers at fertilization. The increased damage caused to eggs in calcium-free seawater injected with large volumes may allow the EGTA present in the seawater to enter the egg and chelate any calcium released by the inositol phosphates. This may explain the discrepancy between this and earlier reports.

scholarly journals V. Skeletal development in Arbacia , Echinarachnius and Leptasterias

1929 ◽  
Vol 217 (440-449) ◽  
pp. 289-334 ◽  
Keyword(s):  
Sea Urchin ◽  
Sea Water ◽  
Skeletal Development ◽  
Mediterranean Species ◽  
Marine Biological Laboratory ◽  
Glass Vessel ◽  
Arbacia Punctulata ◽  
Marine Biological ◽  
Points Of Interest ◽  
Arbacia Lixula

The echinopluteus of the genus Arbacia has been known since 1853. Echinoplutei of the species at present under investigation were first reared in 1880 by Fewkes, and two years later Garman and Colton (1882) succeeded in rearing them through the metamorphosis. The Mediterranean species Arbacia lixula , L. (syn. A . pustulosa , Gray) has also been reared through metamorphosis, and Übisch (1913) was the first to attempt an analysis of the test of the imago. The composition of the corona in the imago of A . pustulosa , as described in the paper just referred to (Übisch, 1913), is very different from that in the imago of e. g . Echinus or Strongylocentrotus . The opportunity of working at the Marine Biological Laboratory, Woods Hole, presenting itself, it was thought that a study of the development of the test in Arbacia punctulata , Gray, might reveal some points of interest. Accordingly, cultures of this common sea-urchin were started on July 28, 1926, and the echinoplutei were fed on the diatom Nitzschia closterium W. Sm. forma minutissima . Forty days later (September 6th) the first imago was obtained and the echinoplutei continued to metamorphose throughout the rest of September. Early in August a shallow glass vessel containing filtered sea-water was infected with plankton obtained by towing, and, by the first week of September, the bottom and sides of the vessel were well coated with diatoms. Many of the imagines, which measure 0·5 mm. in diameter including the spines, were transferred to this vessel and a number increased considerably in size. The largest specimen obtained in this way was 1·63 mm. in diameter inclusive of the spines; the diameter of the test alone was 0·9 mm.

scholarly journals Ligands and receptors mediating signal transduction in sea urchin spermatozoa

Reproduction ◽  
2004 ◽  
Vol 127 (2) ◽  
pp. 141-149 ◽  
Author(s):  
Anna T Neill ◽  
Victor D Vacquier
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Signaling Pathways ◽  
Sea Urchin ◽  
Acrosome Reaction ◽  
Sea Urchins ◽  
Model System ◽  
Surrounding Seawater ◽  
Sea Urchin Sperm

Sea urchins have long been a model system for the study of fertilization. Much has been learned about how sea urchin sperm locate and fertilize the egg. Sperm and eggs are spawned simultaneously into the surrounding seawater. Sperm signaling pathways lead to downstream events that ensure fertilization. Upon spawning, sperm must acquire motility and then they must swim towards or respond to the egg in some way. Finally, they must undergo a terminal exocytotic event known as the acrosome reaction that allows the sperm to bind to the vitelline layer of the egg and then to fuse with the egg plasma membrane. Motility is stimulated by exposure to seawater, while later events are orchestrated by factors from the egg. The sperm signaling pathways are exquisitely tuned to bring the sperm to the egg, bind, and fuse the two cells as quickly as possible.

Differences in ion regulation in the sea urchins Lytechinus variegatus and Arbacia lixula (Echinodermata: Echinoidea)

2007 ◽  
Vol 87 (3) ◽  
pp. 769-775 ◽  
Author(s):  
Denilton Vidolin ◽  
Ivonete A. Santos-Gouvea ◽  
Carolina A. Freire
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Tap Water ◽  
Distinct Species ◽  
Coelomic Fluid ◽  
Lytechinus Variegatus ◽  
Ion Regulation ◽  
Magnesium Supplementation ◽  
Ionic Concentrations ◽  
Arbacia Lixula

The regular sea urchin Lytechinus variegatus, a species previously reported from areas of reduced salinities, and Arbacia lixula, a species unreported from diluted waters, were submitted to seawater dilution or seawater dilution in magnesium-supplemented waters. Seawater (35 psu) was either proportionally diluted with filtered dechlorinated tap water (30 psu, 25 psu), or diluted and supplemented with magnesium as MgCl2 (30+Mg, 25+Mg), up to full-strength seawater Mg2+ levels (35 psu, ~54 mM Mg2+). Magnesium supplementation was intended to verify the interfering effect of magnesium on osmo-ionic concentrations of the coelomic fluid (CF) of two ecologically distinct species of sea urchins. After 6 h in control (35 psu) or experimental seawater, CF samples were withdrawn by puncturing through the peristomial membrane. Coelomic fluid osmolality ([Osm]), and concentrations of ([Na+]), ([Cl-]), ([Mg2+]) and ([K+]) were measured for both species. Under all conditions, L. variegatus displayed higher CF osmolality, [Na+], and [K+] values than the water (and A. lixula). Comparatively, L. variegatus is designated as a‘hyper-conformer’, while A. lixula is an ‘iso-conformer’. The CF [Mg2+] showed no evidence of being controlled by either species. Mg2+ supplementation in diluted seawater affected Mg2+ and Cl- levels only. Na+ appears to be taken up actively by L. variegatus, rendering its CF mostly hyper-ionic for Na+ (and hyperosmotic) relative to external seawater. The different gradients observed with the different ions suggest selective permeabilities or ion regulation by L. variegatus.

scholarly journals THE EFFECT OF CERTAIN ELECTROLYTES AND NON-ELECTROLYTES ON PERMEABILITY OF LIVING CELLS TO WATER

1928 ◽  
Vol 12 (1) ◽  
pp. 129-138 ◽  
Author(s):  
Morton McCutcheon ◽  
Balduin Lucke
Keyword(s):  
Osmotic Pressure ◽  
Sea Urchin ◽  
Quantitative Study ◽  
Sea Water ◽  
Living Cells ◽  
Arbacia Punctulata ◽  
Dextrose Solution

1. Permeability to water in unfertilized eggs of the sea urchin, Arbacia punctulata, is found to be greater in hypotonic solutions of dextrose, saccharose and glycocoll than in sea water of the same osmotic pressure. 2. The addition to dextrose solution of small amounts of CaCl2 or MgCl2 restores the permeability approximately to the value obtained in sea water. 3. This effect of CaCl2 and MgCl2 is antagonized by the further addition of NaCl or KCl. 4. It is concluded that the NaCl and KCl tend to increase the permeability of the cell to water, CaCl2 and MgCl2 to decrease it. 5. The method here employed can be used for quantitative study of salt antagonism.

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