Thomas A. Ebert

Longevity and lack of senescence in the red sea urchin Strongylocentrotus franciscanus.

The red sea urchin Strongylocentrotus franciscanus is a long-lived species and may live in excess of 100 years based on tagging studies in the field and corroboration from radiocarbon analyses as reported in the literature. Size-specific survival estimates reported here show no change in annual survival probability across the 6 largest 0.5 cm size classes from 14.6 to 18.1cm. In addition to no change in survival probability there is no reduction in reproductive capacity with size. Red sea urchins show no evidence of senescence and so do not fit well within the context of the disposable soma theory of the evolution of longevity.

FIELD ESTIMATES OF GROWTH AND MORTALITY OF THE GREEN SEA URCHIN, STRONGYLOCENTROTUS DROEBACHIENSIS

Abstract Growth and annual mortality rates of the green sea urchin, Stronglocentrotus droebachiensis, were estimated by marking individuals with fluorescent tags, releasing them in the field, and collecting them 1 year later. In 1994, 533 animals were tagged in 7 tidepools and in 1995, 458 were collected of which 262 were tagged. Tanaka function growth parameters were estimated for the demi-pyramids, or “jaws,” one of the ossicles of Aristotles lantern. Estimates of annual test diameter growth were attained by calculating the allometric relationship between jaw and test diameter. By assuming size at settlement (0.5 mm test diameter) is age zero, and using the size specific growth rates, the relationship between test diameter and age was established. Our results indicate that these animals are long lived and slow growing. The largest sea urchins in our samples may be more than 50 years. The difference in size between tagged and untagged sea urchins in the 1995 collections strongly suggests that smaller in...

Lack of age-associated telomere shortening in long- and short-lived species of sea urchins

The red sea urchin, Strongylocentrotus franciscanus, can live in excess of 100 years while the sea urchin Lytechinus variegatus has an estimated lifespan of only 3–4 years. In an effort to understand the molecular mechanism underlying the difference in their longevity we characterized telomere biology in these species of sea urchins. Telomerase activity was found throughout early stages of development in L. variegatus and is maintained in adult tissues of L. variegatus and S. franciscanus. Terminal restriction fragment analysis indicated a lack of age‐associated telomere shortening. These data suggest that long‐ and short‐lived sea urchins do not utilize telomerase repression as a mechanism to suppress neoplastic transformation.

Growth and Survival of Postsettlement Sea Urchins

Abstract Sea urchins have skeletons made of calcareous plates, and growth occurs by enlarging plates and adding new ones. Spines grow as do ossicles of Aristotles lantern. Differences in chemical composition of ossicles correlate with growth. Ossicles have growth lines that have been used to estimate age, and various tagging methods have been developed to model growth. The methods used include physical tags, as well as chemicals that are incorporated into the skeleton and later detected to measure growth increments. A large number of growth models have been employed, including the Bertalanffy, logistic, Gompertz, Tanaka, Gaussian, logistic dose response, and inverse logistic models, and these are compared using the Akaike Information Criterion. A frequent problem with data is a lack of small and large individuals. Survival is modeled using a negative exponential and annual rates are determined using a combination of growth models and population size structure.

Chapter 6 Growth and survival of postsettlement sea urchins

Publisher Summary This chapter discusses the growth and survival of postsettlement sea urchins. Growth in echinoids means change in mass, diameter, and shape of the testes, which requires the expansion, calcification, and production of soft tissues. Skeletal growth is based on cellular processes that result in both shape changes during growth and rates of diameter change. Various forces that determine shape during growth have been explored in earlier studies, but shape seems best described as a response to forces generated by skeletal weight. Different skeletal elements of echinoids from a wide range of habitats are analyzed by using X-ray diffraction. Echinoid skeletons consist of ossicles that include spines, elements of Aristotles lantern, and plates of the test that are attached to each other by small projections and collagen threads. Growth is by calcification around individual plates and the addition of new plates at the aboral ends of the ambulacral and interambulacral rows. Ossicles are calcite that contains various amounts of magnesium and are constructed as a fenestrated stereom that varies in porosity and construction. The resorption of calcite appears to be a general phenomenon in echinoids.

Half a century (1954–2009) of dissection data of sea urchins from the North American Pacific coast (Mexico–Canada)

Total body size, mass or linear measurements, and gonad mass or volumes have been recorded for the North American Pacific coast sea urchins Strongylocentrotus purpuratus, Mesocentrotus (Strongylocentrotus) franciscanus, and Lytechinus pictus by various workers at diverse sites and for varying lengths of time from 1954 to 2009. Some dissections included other body components such as the gut, body wall, and Aristotles lantern, and some dissections included both wet and dry mass. There are numerous peer-reviewed publications that have used some of these data, but some data have appeared only in graduate theses or in the gray literature. There also are data that have never appeared outside the original data sheets. Historically, data were used to describe reproductive cycles and then to compare responses to stressors such as food limitation or pollution. Differences in temperature among sites also have been explored. More recently, dissection data have linked gonad development to ocean conditions, so called bottom-up forcing. The data set presented here is a historical record of gonad development for a common group of marine invertebrates in intertidal and nearshore environments, which can be used to test hypotheses concerning future changes associated with climate change and ocean acidification along the Pacific Coast of North America.