The Fertilization Reaction in the Sea-Urchin

1951 ◽  
Vol 28 (3) ◽  
pp. 403-416 ◽  
Author(s):  
LORD ROTHSCHILD ◽  
M. M. SWANN
Keyword(s):  
Sea Urchin ◽  
Inverse Relationship ◽  
Physical Nature ◽  
Conduction Time ◽  
The Past ◽  
Sperm Density ◽  
Psammechinus Miliaris ◽  
Sperm Suspension ◽  
Source Of Error ◽  
Kinetic Treatment

1. Unfertilized eggs of the sea-urchin (Psammechinus miliaris) were left for known but varying times in contact with homologous sperm suspensions containing known numbers of spermatozoa. Counts were made of the numbers of fertilized and unfertilized eggs at times ranging from 0 to 300 sec. after mixing. 2. If spermatozoa are considered as particles moving in random directions, the frequency of sperm-egg collisions can be calculated if the density and mean speed of the sperm suspension are known. 3. The information in (1) and (2) enables an estimate to be made of the probability of a successful sperm-egg collision. 4. The estimated probability of a successful collision, p, varies with sperm density, d. At the lowest density used, 7.44x104/ml., p was found to be 0.226. At the highest density, 9.62/106/ml., p was about 0.011. The inverse relationship between p and d may be due to sperm-sperm interactions of a physical nature. 5. The presence of jelly round the eggs increases p. This disposes of the possibility, raised in the past, that egg jelly may have an adverse effect on the fertilizing capacity of homologous spermatozoa under normal conditions of fertilization. 6. The technique of subjecting eggs to a pre-determined number of collisions facilitates investigation of the conduction time of the block to polyspermy. Preliminary experiments suggest that the conduction time may be of the order of seconds rather than fractions of a second. 7. Sources of error arising from the ‘kinetic’ treatment of sperm suspensions are discussed in detail. One source of error concerns the alleged chemotaxis of spermatozoa towards eggs and egg secretions. No chemotaxis was observed.

The Fertilization Reaction in the Sea-Urchin

1952 ◽  
Vol 29 (3) ◽  
pp. 469-483
Author(s):  
LORD ROTHSCHILD ◽  
M. M. SWANN
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Standard Errors ◽  
Conduction Time ◽  
Normal Sperm ◽  
Psammechinus Miliaris ◽  
Sperm Suspension ◽  
Small Incidence ◽  
High Concentrations ◽  
First Time

1. The reactions of sea-urchin eggs (Psammechinus miliaris) to high concentrations of homologous spermatozoa have been investigated by a new method. 2. The method was to inseminate eggs with high concentrations of spermatozoa (108/ml.), which ensured that all eggs were fertilized for the first time at the beginning of the experiment; and then functionally to separate the eggs and spermatozoa at known times after the original insemination. 3. The proportion of polyspermic eggs in the suspension rises from zero at t=0 to a constant value at a time T, which is the conduction time of the block to polyspermy. In fourteen experiments on eggs from different sea-urchins, the estimated values of T were 17, 69, 72, 74, 94, 85, 26, 60, 31, 91, 85, 34, 75 and 67 sec. (arithmetic mean 63 sec.). The standard errors of the estimates of T, which are tabulated in the text, ranged from 5 to 15 sec. 4. These results confirm previous experiments which strongly suggested that the conduction time of the block to polyspermy was of the order of seconds; these earlier experiments were incompatible with a block to polyspermy lasting a fraction of a second. 5. At the same time experiments in this paper made it possible to estimate the fertilization parameter or sperm-egg interaction rate α, during the conduction of the block to polyspermy, and to compare it with the pre-fertilization α. In a given sperm suspension, α is a measure of the receptivity of the egg surface to spermatozoa. During the conduction of the block to polyspermy α was found to be markedly lower (1/20) than in unfertilized eggs. 6. This suggests that at fertilization there is a fast but incomplete block to polyspermy, whose conduction time may be 1 sec. or less. This is followed by the slower block which finally makes the egg impermeable to spermatozoa. This also confirms previous observations on the small incidence of polyspermy at normal sperm densities, which is not consistent with the concept of a slow block to polyspermy.

The Physiology of Sea-Urchin Spermatozoa

1950 ◽  
Vol 27 (1) ◽  
pp. 59-72
Author(s):  
LORD ROTHSCHILD ◽  
P. H. TUFT
Keyword(s):  
Sea Urchin ◽  
Sea Water ◽  
Dilution Effect ◽  
O2 Uptake ◽  
Time Curve ◽  
Sperm Density ◽  
Negative Results ◽  
Catalytic Function ◽  
Sperm Suspension ◽  
Dense Suspensions

1. When a suspension of sea-urchin semen in sea water is diluted, the total O2 consumed and the rate of O2 uptake per spermatozoon are greater than before dilution. This is the Dilution Effect, first described by Gray (1928 a). A further investigation of this phenomenon has been made, using the semen of Echinus esculentus. 2. The form of the O2 uptake-time curve of such suspensions varies according to the ratio semen: sea water. 3. In very dense suspensions (d ≥ 5 x 109 sperm/ml.), the apparent low O2 uptake per unit quantity of spermatozoa is mainly due to inadequate O2 saturation of the lower layers of the suspension, in which the spermatozoa are virtually unable to respire. Such suspensions are not suitable for experiments in Warburg or Barcroft manometers. 4. In dense suspensions (4 x 108 < d ≤ 109 sperm/ml.) the Dilution Effect was observed when sea water was added to the suspension, in such proportions that the sperm density was only reduced by a factor of 1.14. No Dilution Effect occurred when isotonic ‘Analar’ NaCl was added in the same proportions. On the basis of the small dilution involved, and the negative results with ‘Analar’ NaCl, it is concluded that the Dilution Effect is not exclusively due to the sperm having more space to move after dilution and therefore being able to expend more energy. 5. The Dilution Effect occurs when isotonic ‘Analar’ NaCl containing 1 p.p.m. CuCl2 is added to a dense sperm suspension, in the above proportions. Stimulation of O2 uptake is proportional, over certain limits, to the amount of CuCl2 added. Both CuCl, ZnCl2, and to a lesser extent CuSO2, have similar effects. 6. In a particular experiment, egg-water and Cu salts were about equally efficacious in increasing the O2 uptake of a sperm suspension. 7. The characteristic decline in the O2 uptake of dense suspensions can be partly reversed by the addition of Cu salts. 8. In dilute suspensions (d < 4 x 108 sperm/ml.), there is no Dilution Effect when sea water or CuCl2 are added in the above proportions. On the other hand, the decline in O2 uptake can be partly arrested by the addition of Cu salts. 9. Diethyldithiocarbamate markedly inhibits the O2 uptake of unwashed sea-urchin spermatozoa diluted with sea water. The inhibition does not take place in the presence of added CuCl2. Cu may therefore have a catalytic function in the metabolism of sea-urchin semen. 10. The possibility that Cu lack is responsible for the reduced O2 uptake of spermatozoa in dense suspensions is considered.

The Effect of Three Antimetabolites on Sea-Urchin Development

Development ◽  
1954 ◽  
Vol 2 (3) ◽  
pp. 216-226
Author(s):  
Sven Hörstadius ◽  
Tryggve Gustafson
Keyword(s):  
Growth Factor ◽  
Sea Urchin ◽  
Lithium Ion ◽  
Metabolic Effects ◽  
Phenyllactic Acid ◽  
Thiocyanate Ion ◽  
The Past ◽  
Psammechinus Miliaris ◽  
Embryonic Metabolism ◽  
Insight Into

The metabolic background for morphogenesis has been the object of intense investigations during the past decades. As an approach to this problem the metabolic effects of the vegetalizing lithium ion and the animalizing thiocyanate ion have been investigated (cf. Lindahl, 1936, and Gustafson, 1952). The studies of antimetabolites (growth-factor analogues) during the last decade have opened pathways for interfering with the embryonic metabolism in a predictable way. Using the antimetabolites it is now possible to get a deeper insight into the relation between metabolic processes and different developmental trends. The effect of some antimetabolites on the early development of the eggs of Psammechinus miliaris were studied during the summer of 1953 at Kristinebergs Zoologiska Station, Sweden. The results obtained with 8-chloroxanthine, β-phenyllactic acid, and 3-acetylpyridine will be reported here. The substances were obtained from the Nutritional Biochemicals Corporation, Cleveland, Ohio. The statements regarding the antimetabolic character of the substances are takenfrom the catalogue of that firm.

C-Microtubules in Isolated Mitotic Spindles

1971 ◽  
Vol 9 (3) ◽  
pp. 603-619
Author(s):  
W. D. COHEN ◽  
T. GOTTLIEB
Keyword(s):  
Cross Section ◽  
Sea Urchin ◽  
Cross Sections ◽  
Metaphase Chromosome ◽  
Inverse Relationship ◽  
Mitotic Spindles ◽  
Cylindrical Structure ◽  
Arbacia Punctulata ◽  
Alternate Possibility

Microtubules with incomplete cylindrical structure are present in isolated mitotic spindles of the sea urchin, Arbacia punctulata. In cross-section they appear C-shaped, and are thus similar to the ‘C-microtubules’ or ‘C-filaments’ observed previously in other systems. The C-microtubules are not uniformly distributed within isolated spindles, but are typically numerous in the interzonal region of anaphase spindles and in the metaphase chromosome ‘plate’. In chromosome-to-pole regions they are seen much less frequently, and microtubules with the usual O-configuration predominate. Counts of C- and O-microtubules in anaphase spindle cross-sections of known location show an inverse relationship between the number of C-microtubules present and the total number of microtubules present. The observations suggest that the C-microtubules are not simple artifacts of fixation or isolation, but rather may represent a stage of microtubule disassembly which occurs in the interzone during isolation or during anaphase in vivo. The alternate possibility of assembly is not excluded, however. The significance of C-microtubules is further discussed with respect to their occurrence in other systems, and to potential differences between mitotic microtubules.

The Mechanism of Cell-division

1953 ◽  
Vol s3-94 (28) ◽  
pp. 369-379
Author(s):  
M. M. SWANN
Keyword(s):  
Carbon Monoxide ◽  
Cell Division ◽  
Sea Urchin ◽  
White Light ◽  
Time Lapse ◽  
Psammechinus Miliaris ◽  
Energy Store ◽  
Time Lapse Photography

1. Developing eggs of the sea-urchin Psammechinus miliaris were subjected to carbon monoxide inhibition, which was controlled by changing from green to white light. The behaviour of the eggs was recorded by time-lapse photography. 2. If inhibition is applied before the eggs enter mitosis, their first cleavage is delayed by a time which is roughly equal to the period of the inhibition. 3. If the inhibition is applied when the cells have already entered mitosis, they complete mitosis and cleave with little or no delay, but their second cleavage is delayed by a time which is roughly equal to the period of the inhibition. 4. It is suggested that the necessary energy for the second mitosis and cleavage is being stored up during the first mitosis and cleavage, and that this energy store operates like a reservoir which is continually being filled but siphons out when it is full. Once the energy has siphoned out, it carries mitosis and cleavage through, even though the reservoir is not filling up because of carbon monoxide inhibition.

scholarly journals Kelp forest ecosystems: biodiversity, stability, resilience and future

2002 ◽  
Vol 29 (4) ◽  
pp. 436-459 ◽  
Author(s):  
Robert S. Steneck ◽  
Michael H. Graham ◽  
Bruce J. Bourque ◽  
Debbie Corbett ◽  
Jon M. Erlandson ◽  
...  
Keyword(s):  
Case Studies ◽  
Sea Urchin ◽  
North Atlantic ◽  
Forest Ecosystems ◽  
Kelp Forest ◽  
Kelp Forests ◽  
Apex Predators ◽  
The Past ◽  
The North ◽  
Fishing Impacts

Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

scholarly journals PROPERTIES OF FLAGELLAR "RIGOR WAVES" FORMED BY ABRUPT REMOVAL OF ADENOSINE TRIPHOSPHATE FROM ACTIVELY SWIMMING SEA URCHIN SPERM

1974 ◽  
Vol 63 (3) ◽  
pp. 970-985 ◽  
Author(s):  
Barbara H. Gibbons ◽  
I. R. Gibbons
Keyword(s):  
Sea Urchin ◽  
Sperm Suspension ◽  
Complete Relaxation ◽  
Viscous Shear ◽  
Radial Spokes ◽  
Wave Forms ◽  
Cross Bridges ◽  
Triton X ◽  
The Waves ◽  
Sea Urchin Sperm

Sea urchin sperm were demembranated and reactivated with a solution containing 0.04% Triton X-100 and 0.03 mM ATP. The ATP concentration was then lowered abruptly by diluting the sperm suspension 50-fold into reactivating solution containing no ATP. The flagella of the sperm in the diluted suspension were not motile, but they were bent into a variety of stationary rigor wave forms closely resembling the wave forms occurring at different stages of the flagellar bending cycle during normal movement. The form of these rigor waves was unchanged upon storage for several hours in the presence of dithiothreitol and EDTA. Addition of 1 µM ATP induced slow relaxation of the waves, with most of the sperm becoming partially straightened over a period of about 30 min; somewhat higher concentrations gave a more rapid and complete relaxation. Concentrations of ATP above 10 µM induced resumption of normal beating movements. Addition of ITP, GTP, or GDP (up to 1 mM) produced no relaxation of the rigor waves. Digestion with trypsin to an extent sufficient to disrupt the radial spokes and the nexin links caused no change in the rigor wave forms, suggesting that these wave forms could be maintained by the dynein cross-bridges between the outer doublet tubules of the flagellar axoneme. Study of the effects of viscous shear on the rigor wave axonemes has shown that they are resistant to distortion by bending, although they can be twisted relatively easily.

Sign in / Sign up

Export Citation Format

Share Document