Amoebae in tissues of diseased echinoids (Strongylocentrotus droebachiensis) in Nova Scotia

Echinodermata ◽  
2020 ◽  
pp. 289-293
Author(s):  
G.M. Jones ◽  
R.E. Scheibling ◽  
A.J. Hebda ◽  
R.J. Miller
Keyword(s):  
Nova Scotia ◽  
Strongylocentrotus Droebachiensis

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

Erratum: Response of the sea urchin, Strongylocentrotus droebachiensis, to reduced salinities: importance of size, acclimation, and interpopulation differences

1984 ◽  
Vol 62 (11) ◽  
pp. 2352-2352 ◽  
Author(s):  
John H. Himmelman ◽  
Helga Guderley ◽  
Gilles Vignault ◽  
Guy Drouin ◽  
Peter G. Wells
Keyword(s):  
Nova Scotia ◽  
Strongylocentrotus Droebachiensis ◽  
Test Diameter ◽  
Lawrence Estuary ◽  
Stress Acclimation ◽  
Hypoosmotic Stress ◽  
Size Groups ◽  
Percentage Weight ◽  
St Lawrence Estuary ◽  
Neuromuscular Coordination

Weight change, mortality, and neuromuscular coordination, as measured by righting time, were used to evaluate the resistance of Strongylocentrotus droebachiensis to hypoosmotic stress. Acclimation to a salinity of 24 or 25‰ decreased the righting time of urchins after 96 h of hypoosmotic stress. The effect of acclimation was the same for four size groups of urchins (10–15, 20–25, 34–37, and 50–60 mm in test diameter). A comparison of urchins from the St. Lawrence Estuary and from Nova Scotia, both acclimated to 24‰, showed that for the three larger size classes, the salinity at which there was a significant increase in righting time was lower for urchins from an estuarine environment than for urchins from the oceanic environment. The percentage weight gain following hypoosmotic stress increased with decreasing urchin size. For small urchins the increase was less marked after acclimation to 24‰. The mortality rates following these experiments showed that acclimation to a reduced salinity increased the tolerance to hypoosmotic stress, that urchins from the St. Lawrence Estuary were better able to withstand low salinities than urchins from Nova Scotia, and that small urchins were more sensitive to osmotic stress than large urchins. The latter was confirmed in a field experiment in which four size groups of urchins were kept in cages at a location exposed to periodic decreases in surface salinities.

Response of the sea urchin, Strongylocentrotus droebachiensis, to reduced salinities: importance of size, acclimation, and interpopulation differences

1984 ◽  
Vol 62 (6) ◽  
pp. 1015-1021 ◽  
Author(s):  
John H. Himmelman ◽  
Helga Guderley ◽  
Gilles Vignault ◽  
Guy Drouin ◽  
Peter G. Wells
Keyword(s):  
Nova Scotia ◽  
Strongylocentrotus Droebachiensis ◽  
Test Diameter ◽  
Lawrence Estuary ◽  
Stress Acclimation ◽  
Hypoosmotic Stress ◽  
Size Groups ◽  
Percentage Weight ◽  
St Lawrence Estuary ◽  
Neuromuscular Coordination

Weight change, mortality, and neuromuscular coordination, as measured by righting time, were used to evaluate the resistance of Strongylocentrotus droebachiensis to hypoosmotic stress. Acclimation to a salinity of 24 or 25‰ decreased the righting time of urchins after 96 h of hypoosmotic stress. The effect of acclimation was the same for four size groups of urchins (10–15, 20–25, 34–37, and 50–60 mm in test diameter). A comparison of urchins from the St. Lawrence Estuary and from Nova Scotia, both acclimated to 24‰, showed that for the three larger size classes, the salinity at which there was a significant increase in righting time was lower for urchins from an estuarine environment than for urchins from the oceanic environment. The percentage weight gain following hypoosmotic stress increased with decreasing urchin size. For small urchins the increase was less marked after acclimation to 24‰. The mortality rates following these experiments showed that acclimation to a reduced salinity increased the tolerance to hypoosmotic stress, that urchins from the St. Lawrence Estuary were better able to withstand low salinities than urchins from Nova Scotia, and that small urchins were more sensitive to osmotic stress than large urchins. The latter was confirmed in a field experiment in which four size groups of urchins were kept in cages at a location exposed to periodic decreases in surface salinities.

Destructive grazing, epiphytism, and disease: the dynamics of sea urchin - kelp interactions in Nova Scotia

1999 ◽  
Vol 56 (12) ◽  
pp. 2300-2314 ◽  
Author(s):  
Robert E Scheibling ◽  
Allan W Hennigar ◽  
Toby Balch
Keyword(s):  
Nova Scotia ◽  
Sea Urchin ◽  
Canopy Cover ◽  
Strongylocentrotus Droebachiensis ◽  
Exposed Site ◽  
Membranipora Membranacea ◽  
Kelp Beds ◽  
Sheltered Site ◽  
Kelp Canopy ◽  
Over Time

We measured the rate of advance of urchin (Strongylocentrotus droebachiensis) feeding aggregations (fronts) as they destructively grazed kelp beds (Laminaria longicruris) at both a wave-exposed site and a sheltered site in Nova Scotia over 3.5 years. The grazing fronts were composed of high densities of large adults (up to 98 and 70 per 0.25 m2 at the exposed and sheltered sites, respectively). Urchins in the recently formed barrens, or in adjacent kelp beds, occurred at much lower densities and consisted mainly of juveniles. The fronts moved onshore into shallower water at each site, but their rate of advance varied markedly between sites and over time at each site, ranging from 0 to 4 m·month-1. The rate of advance of a front was related to the biomass of urchins; fronts did not advance below a threshold biomass of ~2 kg·m-2. Infestations of kelp by an epiphytic bryozoan (Membranipora membranacea) caused marked reductions in kelp canopy cover and biomass during winter, but the canopy regenerated through recruitment of juvenile sporophytes in spring. A localized outbreak of disease decimated S. droebachiensis at the exposed site in 1993, which enabled kelp to recolonize the barrens. Surviving urchins gradually reaggregated and resumed destructive grazing after ~1.5 years. A recurrence of disease in 1995 eliminated urchins at both sites and terminated the transition from kelp beds to barrens on a coastal scale. Our findings have important implications for the management of the urchin fishery, which targets grazing fronts for harvesting.

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