scholarly journals Aggregative feeding behavior in sea urchins leads to destructive grazing in a Nova Scotian kelp bed

2012 ◽  
Vol 444 ◽  
pp. 69-83 ◽  
Author(s):  
C Feehan ◽  
RE Scheibling ◽  
JS Lauzon-Guay
Keyword(s):  
Feeding Behavior ◽  
Sea Urchins ◽  
Kelp Bed ◽  
Nova Scotian

Aquacultural Techniques for Creating and Restoring Beds of Giant Kelp, Macrocystis spp.

1976 ◽  
Vol 33 (4) ◽  
pp. 1015-1023 ◽  
Author(s):  
Wheeler J. North
Keyword(s):  
Baja California ◽  
Sea Urchins ◽  
Food Additives ◽  
Stable Population ◽  
Giant Kelp ◽  
Herbivorous Fishes ◽  
Kelp Beds ◽  
Mass Cultures ◽  
Kelp Bed ◽  
Reproductive Processes

Giant kelp (Macrocystis spp.) occurs as extensive beds along the coasts of Baja California and California. The kelp beds form desirable habitat for fishes and invertebrates. The kelp plants are harvested and processed to produce food additives and chemicals. Many Califorman kelp beds have dwindled or disappeared since 1940. We have developed a number of aquacultural techniques to reverse trends of deterioration. One important cause of kelp bed damage can arise from grazing by sea urchins or herbivorous fishes. Urchins can be controlled by quicklime or by crushing the animals with hammers. Fishes can be controlled by netting. In areas where kelp is sparse or has disappeared, stands can be recreated by transplantation techniques. Where reproductive processes are not adequate to maintain a stable population, mass cultures of microscopic gametophytes and sporophytes can be introduced.

Relationship Between Destructive Grazing by the Sea Urchin, Strongylocentrotus droebachiensis, and the Abundance of American Lobster, Homarus americanus, on the Atlantic Coast of Nova Scotia

1981 ◽  
Vol 38 (11) ◽  
pp. 1339-1349 ◽  
Author(s):  
W. G. Wharton ◽  
K. H. Mann
Keyword(s):  
Population Structure ◽  
Nova Scotia ◽  
Sea Urchins ◽  
Atlantic Coast ◽  
Homarus Americanus ◽  
Strongylocentrotus Droebachiensis ◽  
American Lobster ◽  
History Of ◽  
Kelp Bed ◽  
The Relationship

Relationships between percentage cover of macroalgae, population structure of sea urchins (Strongylocentrotus droebachiensis), and the history of the lobster fishery were examined at nine sites distributed along the Atlantic coast of Nova Scotia from Guysborough County in the northeast to Pubnico in the southwest. At Pubnico there was dense algal cover and a small number of urchins living in crevices, and at Cape Sable there was an area of transition, but at all other sites there were urchin-dominated barren grounds. When the population structure of the urchins was compared with that previously observed in St. Margaret's Bay before, during, and after destruction of beds of kelp (Laminaria spp. and Agarum) by overgrazing, it was concluded that kelp bed destruction occurred on the coast north of Halifax prior to 1970, and on the coast south of Halifax after 1970. From the records of American lobster (Homarus americanus) catches it was concluded that a critical decline in catches at each site occurred a few years after kelp bed destruction. Information from various sources is synthesized into a coherent theory of the relationship between lobsters, other predators, sea urchins, and kelp.Key words: lobsters, Homarus americanus; sea urchins, Strongylocentrotus droebachiensis; destructive grazing, kelp, Laminaria, Agarum

Some Estimates of Population Density and Feeding Habits of the Rock Crab, Cancer irroratus, in a Kelp Bed in Nova Scotia

1982 ◽  
Vol 39 (4) ◽  
pp. 636-639 ◽  
Author(s):  
N. C. Drummond-Davis ◽  
K. H. Mann ◽  
R. A. Pottle
Keyword(s):  
Nova Scotia ◽  
Population Density ◽  
Sea Urchins ◽  
Feeding Habits ◽  
Atlantic Coast ◽  
Carapace Width ◽  
Hermit Crabs ◽  
Cancer Irroratus ◽  
Kelp Bed ◽  
Rock Crab

The population density of rock crabs (Cancer irroratus) in a kelp bed on the Atlantic coast of Nova Scotia was examined by mark–recapture techniques and found to be about one crab (> 45-mm carapace width) per 2 square metres. Prey taken by the crabs included hermit crabs (Pagurus), mussels (Mytilus), sea urchins (Strongylocentrotus), and various small crustaceans and polychaetes. It was concluded that the crab population would exert a strong predation pressure on these invertebrates.Key words: Cancer irroratus, rock crabs, predation, population density, kelp

Repopulation of the shallow subtidal zone by green sea urchins (Strongylocentrotus droebachiensis) following mass mortality in Nova Scotia, Canada

2005 ◽  
Vol 85 (6) ◽  
pp. 1511-1517 ◽  
Author(s):  
Sheanna M. Brady ◽  
Robert E. Scheibling
Keyword(s):  
Sea Urchins ◽  
Disease Outbreak ◽  
Mass Mortality ◽  
Strongylocentrotus Droebachiensis ◽  
Subtidal Zone ◽  
Test Diameter ◽  
Lower Margin ◽  
Primary Means ◽  
Kelp Bed ◽  
Shallow Subtidal

Repopulation by green sea urchins Strongylocentrotus droebachiensis of a steeply sloping rock bottom was monitored at a wave-exposed headland (Chebucto Head) following a disease outbreak that caused mass mortality in September 1999. Density and size of urchins were sampled in four depth strata: at 8–10 m in an urchin grazing aggregation (front) along the lower margin of a kelp bed, at 12 m and 16 m on a bedrock ramp, and at 24 m on a cobble and boulder field where urchins were unaffected by the disease. Shoreward migration of adults along the ramp from the surviving population at 24 m was the primary means of repopulation, which was augmented by recruitment via planktonic larvae. At 16 m, urchin density stabilized (at ∼50 urchins m−2) within six months of the die-off while repopulation at 12 m took more than eight months. A grazing front of large urchins (40–60 mm, test diameter) had formed along the lower edge of a kelp bed by January 2002, which reached densities of up to 284 urchins m−2. Video surveys at Chebucto Head and two adjacent locations of similar bathymetry revealed an extensive urchin population between 25 and 55 m depth, with a mean density on rocky substrata of 73 urchins m−2.

Growth and gonad development of the sea urchin Hemicentrotus pulcherrimus in an Eisenia kelp bed in the Oshika Peninsula, northern Japan*

Zoosymposia ◽  
2012 ◽  
Vol 7 (1) ◽  
pp. 225-230 ◽  
Author(s):  
YUKIO AGATSUMA ◽  
NANAKO TODA ◽  
MAKOTO OGASAWARA ◽  
JUNJI KINOSHITA ◽  
MASAYUKI WATANABE ◽  
...  
Keyword(s):  
Sea Urchins ◽  
Gonad Development ◽  
Total Body Weight ◽  
High Availability ◽  
Gut Content ◽  
Eisenia Bicyclis ◽  
Kelp Bed ◽  
Total Body ◽  
Hemicentrotus Pulcherrimus ◽  
Northern Japan

To elucidate growth and gonad development of Hemicentrotus pulcherrimus in the bed of Eisenia bicyclis, we examined gonad indices, gonad histology, gut content indices and ages of the sea urchins collected approximately monthly from March 2008 to September 2009 in Kitsunezaki in the Oshika Peninsula, northern Japan. We also monitored the densities of the kelp in six 1 m2 quadrates. The kelp at 1- to 3-years of age decreased in density from January to July due to strong wave action. The urchin test diameters at 1-, 2- and 3-years of age were 12.7 mm, 23.7 mm and 30.5 mm, respectively and these growth rates were equal to that measured in Sargassum beds in previous studies. The gonad recovering stage was classified into the two sub-class stages; the recovering I stage with relict spermatozoa or ova surrounded by renewed nutritive phagocytes, and the recovering II stage with nutritive phagocytes filling the lumen. The recovering I stages was prolonged from February to April when the gonad indices were around 10 % of total body weight, then rose sharply through the recovering II stage during May to August and the growing stage until October. The gonad indices rose sharply from November and reached a maximum of 18.8 in December when the gonad shifted from the premature to mature stages, then fell in January at the partly spawned and spent stages. Gut content indices were high at the recovering I stage, suggesting high availability of the drift thalli and lateral blades dislodged from the kelps and accumulation of nutrients in nutritive phagocytes.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Fate of sperm membrane in fertilized ova

1993 ◽  
Vol 51 ◽  
pp. 40-41
Author(s):  
Frank J. Longo
Keyword(s):  
Electron Microscopy ◽  
Electrical Activity ◽  
Sea Urchins ◽  
Morphological Changes ◽  
Integrated System ◽  
Electrophysiological Recording ◽  
Experimental Conditions ◽  
The Status ◽  
Sperm Membrane ◽  
Temporal And Spatial

Measurement of the egg's electrical activity, the fertilization potential or the activation current (in voltage clamped eggs), provides a means of detecting the earliest perceivable response of the egg to the fertilizing sperm. By using the electrical physiological record as a “real time” indicator of the instant of electrical continuity between the gametes, eggs can be inseminated with sperm at lower, more physiological densities, thereby assuring that only one sperm interacts with the egg. Integrating techniques of intracellular electrophysiological recording, video-imaging, and electron microscopy, we are able to identify the fertilizing sperm precisely and correlate the status of gamete organelles with the first indication (fertilization potential/activation current) of the egg's response to the attached sperm. Hence, this integrated system provides improved temporal and spatial resolution of morphological changes at the site of gamete interaction, under a variety of experimental conditions. Using these integrated techniques, we have investigated when sperm-egg plasma membrane fusion occurs in sea urchins with respect to the onset of the egg's change in electrical activity.

Comparative quantification of phosphatidylcholine in sea urchins eggs by instrumental TLC with various detection techniques

Planta Medica ◽  
2010 ◽  
Vol 76 (12) ◽  
Author(s):  
S Ivanova ◽  
I Urakova ◽  
O Pozharitskaya ◽  
A Shikov ◽  
V Makarov
Keyword(s):  
Sea Urchins ◽  
Detection Techniques
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