Studies on Factors Affecting the Local Distribution of Two Sea Urchins, Arbacia Punctulata and Lytechinus Variegatus

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).

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Taxol inhibits the nuclear movements during fertilization and induces asters in unfertilized sea urchin eggs.

The Journal of Cell Biology ◽

10.1083/jcb.94.2.455 ◽

1982 ◽

Vol 94 (2) ◽

pp. 455-465 ◽

Cited By ~ 66

Author(s):

G Schatten ◽

H Schatten ◽

T H Bestor ◽

R Balczon

Keyword(s):

Immunofluorescence Microscopy ◽

De Novo ◽

Sea Urchins ◽

Microtubule Assembly ◽

Lytechinus Variegatus ◽

Sperm Tail ◽

Arbacia Punctulata ◽

Video Recordings ◽

Transmission Electron ◽

Sperm Aster

Taxol blocks the migrations of the sperm and egg nuclei in fertilized eggs and induces asters in unfertilized eggs of the sea urchins Lytechinus variegatus and Arbacia punctulata. Video recordings of eggs inseminated in 10 microM taxol demonstrate that sperm incorporation and sperm tail motility are unaffected, that the sperm aster formed is unusually pronounced, and that the migration of the egg nucleus and pronuclear centration are inhibited. The huge monopolar aster persists for at least 6 h; cleavage attempts and nuclear cycles are observed. Colcemid (10 microM) disassembles both the large taxol-stabilized sperm aster in fertilized eggs and the numerous asters induced in unfertilized eggs. Antitubulin immunofluorescence microscopy demonstrates that in fertilized eggs all microtubules are within the prominent sperm aster. Within 15 min of treatment with 10 microM taxol, unfertilized eggs develop numerous (greater than 25) asters de novo. Transmission electron microscopy of unfertilized eggs reveals the presence of microtubule bundles that do not emanate from centrioles but rather from osmiophilic foci or, at times, the nuclear envelope. Taxol-treated eggs are not activated as judged by the lack of DNA synthesis, nuclear or chromosome cycles, and the cortical reaction. These results indicate that: (a) taxol prevents the normal cycles of microtubule assembly and disassembly observed during development; (b) microtubule disassembly is required for the nuclear movements during fertilization; (c) taxol induces microtubules in unfertilized eggs; and (d) nucleation centers other than centrioles and kinetochores exist within unfertilized eggs; these presumptive microtubule organizing centers appear idle in the presence of the sperm centrioles.

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Geographic and environmental factors affecting the distribution of kelp beds and barren grounds and changes in biota associated with kelp reduction at sites along the Norwegian coast

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f97-186 ◽

1997 ◽

Vol 54 (12) ◽

pp. 2872-2887 ◽

Cited By ~ 48

Author(s):

Knut Sivertsen

Keyword(s):

Environmental Factors ◽

Sea Urchins ◽

Strongylocentrotus Droebachiensis ◽

The Arctic ◽

Laminaria Hyperborea ◽

Factors Affecting ◽

Kelp Beds ◽

The Mean ◽

Transition Areas ◽

Barren Grounds

Sites at 244 locations along the west and north Norwegian coasts were investigated to evaluate whether kelp (Laminaria hyperborea) beds had been overgrazed by the sea urchins Strongylocentrotus droebachiensis and Echinus esculentus in the years 1981-1992. Barren ground communities were found in sheltered and moderately wave-exposed areas mainly in the inner and middle archipelago from Nordmøre (63°N) northwards. Densities of large-sized (adult and intermediate) L. hyperborea were 20.7 individuals ·m-2 in kelp beds and 9.7 individuals ·m-2 in transition areas. Juvenile Laminaria spp. were present at densities of 23.9 individuals ·m-2 in kelp beds, 3.6 individuals ·m-2 in transition areas, 0.0 individuals ·m-2 in barren grounds, and 59.1 individuals ·m-2 in kelp-harvested locations. Both the densities and the mean size of S. droebachiensis in barren grounds decreased northwards. The mean densities were 52.2 and 26.1 individuals ·m-2 for the areas south and north of the Arctic Circle, respectively. Multivariate analysis (CANOCO) showed that seven ``environmental'' factors (i.e., kelp depth gradient, distance (latitude), time of sampling, nematode infection in S. droebachiensis, wave exposure, coastal gradient, and substratum) contributed significantly to variability in the distribution of kelp beds and barren grounds. Species in hard-bottom communities in shallow waters could be divided into three distinct BIOTA.

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

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592010000700009 ◽

2010 ◽

Vol 58 (spe3) ◽

pp. 71-75 ◽

Cited By ~ 3

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.

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UV radiation influences covering behaviour in the urchin Lytechinus variegatus

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315407055865 ◽

2007 ◽

Vol 87 (5) ◽

pp. 1257-1261 ◽

Cited By ~ 16

Author(s):

Jessica E. Sigg ◽

Karena M. Lloyd-Knight ◽

Jean Geary Boal

Keyword(s):

Uv Radiation ◽

Functional Significance ◽

Sea Urchins ◽

Uv Exposure ◽

Lytechinus Variegatus ◽

Energetic Costs ◽

Trade Off ◽

Familiar Objects

Many species of sea urchins cover their bodies with a variety of materials. One hypothesis for this behaviour is that the urchins are reducing their exposure to UV radiation. The effect of UV radiation on the covering behaviour of twelve sea urchins, Lytechinus variegatus, was recorded and the shells used as covering materials were quantified. During UV exposure, urchins used significantly greater numbers, areas and masses of shells than did urchins during non-UV exposure. Results suggest that not only were L. variegatus covering in response to UV exposure, but they were also making distinct choices regarding preferred covering items. Unlike in previous studies, the urchins did not simply choose familiar objects or even the lightest objects; rather, when exposed to UV radiation they selected intermediate-sized objects, perhaps demonstrating a trade-off between the energetic costs of carrying objects and the physiological costs of exposure to UV radiation. While there appear to be many reasons for why urchins cover, these results indicate that urchin covering is non-random and has important functional significance.

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Allometry Analysis and Physiological Index of Sea Urchin Heliocidaris crassispina (A. Agassiz, 1864) (Camarodonta, Echinometridae) on the Reef Flat in Tongkeina and Malalayang Dua, Manado, Sulawesi

JURNAL ILMIAH PLATAX ◽

10.35800/jip.4.2.2016.13774 ◽

2016 ◽

Vol 4 (2) ◽

pp. 45

Author(s):

Muhammad S. Hasi ◽

Lawrence J. L. Lumingas ◽

Anneke V. Lohoo

Keyword(s):

Reef Flat ◽

Sea Urchins ◽

Gonad Index ◽

Test Diameter ◽

Physiological Index ◽

Factors Affecting ◽

Weight Growth ◽

The Difference ◽

Relationship Of ◽

The Relationship

The purpose of this study was to analysis the structure of the size, morphometry (test diameter-high relationship, test diameter-weight relationship) as well as gonad indices, intestine indices, and Aristotle lantern indices of Heliocidaris crassispina in two different habitats, Malalayang Dua and Tongkeina. At each habitat, free sampling on the reef flat have be done one time for approximately two hours at the lowest tide. The abundance of individuals H. crassispina in Malalayang Dua was much lower than in Tongkeina. The means diameter of sea urchins test were not significantly different between habitats. The comparison of regression lines of both diameter-high and diameter-weight relationships were not differ significantly between habitats. Its morphometry reveal an isometric relationship of high-diameter (slope = 1) in both habitats, while the relationship of weight-diameter reveals a negative allometric growth (slope < 3) in Tongkeina but isometric growth in Malalayang Dua. The gonad index in Malalayang Dua was higher than in Tongkeina. The intestine index in Tongkeina was higher than in Malalayang Dua. The lantera index in Tongkeina was higher than in Malalayang Dua. The difference in abundance of sea urchins and the acquisition of the energetic value of food presumably serve as the factors affecting the differences of these indices and its weight growth pattern. ________________________________________________________________ Keywords: Heliocidaris crassispina, allometry analysis, physiological index ABSTRAK Tujuan dari penelitian ini adalah untuk menganalisis struktur ukuran, morfometri (hubungan diameter-tinggi cangkang, hubungan diameter-berat) serta indeks gonad, indeks usus, dan indeks lentera Aristoteles dari Heliocidaris crassispina di dua habitat yang berbeda, Malalayang Dua dan Tongkeina. Pada setiap habitat, sampling bebas di rataan terumbu telah dilakukan satu kali selama kurang lebih dua jam pada saat pasang terrendah. Kelimpahan individu H. crassispina di Malalayang Dua jauh lebih rendah daripada di Tongkeina. Diameter rata-rata cangkang bulu babi tidak berbeda nyata antara habitat. Perbandingan garis regresi hubungan diameter-tinggi dan diameter-berat tidak berbeda secara signifikan antara habitat. Analisis morfometri menunjukkan hubungan isometrik tinggi-diameter (slope = 1) di kedua habitat, sedangkan hubungan berat-diameter menunjukkan pertumbuhan alometrik negatif (kemiringan <3) di Tongkeina tetapi di Malalayang Dua menunjukkan pertumbuhan isometrik. Indeks gonad di Malalayang Dua lebih tinggi daripada di Tongkeina. Indeks usus di Tongkeina lebih tinggi daripada di Malalayang Dua. Indeks lantera di Tongkeina lebih tinggi daripada di Malalayang Dua. Perbedaan kelimpahan bulu babi dan perolehan nilai energik makanan diduga berperan sebagai faktor yang mempengaruhi perbedaan indeks ini dan pola pertumbuhan beratnya. ________________________________________________________________ Kata kunci: Heliocidaris crassispina, analisis allometri, indeks fisiologis ____________________ 1Bagian dari Skripsi 2Mahasiswa Program Studi Manajemen Sumberdaya Perairan FPIK-UNSRAT 3Staf Pengajar Fakultas Perikanan dan Ilmu Kelautan UNSRAT

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