Effects of temperature, season and locality on wasting disease in the keystone predatory sea star Pisaster ochraceus
ABSTRACT This study investigates wasting disease in the northeast Pacific keystone predatory sea star Pisaster ochraceus on the outer west coast of Vancouver Island (British Columbia, Canada). To quantify the effects of temperature, season and locality on the vulnerability of P. ochraceus to wasting disease, we conducted surveys and experiments in early and late summer. To test the prediction that a small increase in temperature would result in heightened infection intensities, we housed sea stars at different temperatures in the laboratory and caged sea stars subtidally at 2 depths. Prevalence and infection intensity were always higher in warm temperature treatments and did not differ between the sexes or with increasing size. Disease effects also varied with season and locality. Specimens held in aquaria displayed significantly higher disease prevalence and infection intensity in June versus August. Furthermore, sea stars from a sheltered inlet showed markedly higher prevalence of the disease in late summer, while wave-exposed sites had consistently low disease prevalence. Seasonal changes in reproductive potential, host condition and/or physiological acclimation, as well as differences in environmental regime among localities, may impact the dynamics of wasting disease. These results demonstrate that small increases in temperature could drive mass mortalities of Pisaster due to wasting disease, with vulnerability possibly reaching a peak in spring and in populations from sheltered localities. This is the most northern report of wasting disease in the class Asteroidea on the west coast of North America.
Full-textDOI: · Available from: Amanda E Bates, Aug 12, 2015
- SourceAvailable from: William Stickle
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- "We did not conduct long-term experiments with P. ochraceus because some of the animals held in the lab for longer than 4 days showed signs of flesh wasting disease (Eckert et al., 1999; Bates et al., 2009). However, A. miniata was healthy in laboratory conditions after 21 (May 5–26) days (hereafter, A21: Bamfield Inlet, n = 48). "
ABSTRACT: Global warming has important implications for the dynamics and ecological impacts of emerging diseases. We investigated temperature effects on scuticociliate, Orchitophrya cf. stellarum, infections in ripe testes of two Pacific northeast sea stars (Asterina miniata Brandt and Pisaster ochraceus Brandt) using laboratory and field approaches. We predicted that a small increase in temperature would result in higher ciliate growth rates and heightened infection intensities. To test this we (1) cultured free-living O. stellarum at 10 and 15 °C and quantified ciliate abundance after 3 days, and (2) housed sea stars of both species at 10 and 15 °C for durations varying from 4 to 21 days and then measured the infection intensity. Ciliate densities in cultures were two orders of magnitude higher in the warmer treatment. Infection intensity was also temperature sensitive: greater proportions of testes were infected and infection stage was more advanced at 15 versus 10 °C, leading to a reduction in spermatozoa and regression of the germinal layer within three weeks. In seven field populations surveyed, we found a tight linear correlation between infection prevalence (percent infected sea stars) and infection intensity (proportion of infected testes per individual and mean infection score). However, 45% of P. ochraceus testes exhibited heavy infections versus 8% of A. miniata testes, which may relate to the different thermal habitat of each species: P. ochraceus occurs higher on the shore and likely reaches higher body temperatures at low tide. While the sex ratio of A. miniata is unbiased, P. ochraceus populations are consistently female-biased and show no relationship to infection prevalence (ranged from 30 to 90%). O. cf. stellarum infections of testes of both sea stars are prevalent in field populations, are highly temperature sensitive, and lead to rapid loss of reproductive potential.Journal of Experimental Marine Biology and Ecology 03/2010; 384(1). DOI:10.1016/j.jembe.2009.12.001 · 2.48 Impact Factor
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ABSTRACT: This study investigated patterns in the relative abundance of two photosynthetic algal symbionts, zoochlorellae (ZC) and zooxanthellae (ZX), hosted by two temperate anemones, Anthopleura elegantissima and A. xanthogrammica. Previous studies have documented varying proportions of each symbiont along environmental gradients, presumably determined by their respective physiological capabilities. To test for differences in the algal type between the two host species, we sampled anemone tissues (tentacle or tentacle and body column) of similarly sized polyps that were located close together in multiple habitats: tidepools, crevices, underneath rock ledges, and along natural light gradients in caves. The ZC-A. elegantissima symbiosis was rare on the west coast of Vancouver Island, British Columbia, Canada. Even in low-irradiance habitats, ZC were the dominant algae hosted by A. xanthogrammica, while nearby A. elegantissima hosted ZX or was algae-free. As a first step in determining whether symbiont growth rates differed between the two host species, we quantified mitotic index (MI), the percentage of cells with division furrows, under artificial light and in the field by simultaneously sampling tentacles from both species. MI was more stable in A. elegantissima: the MI of ZX isolated from the tentacles of A. xanthogrammica was slightly higher at a light level of 80 micromol quanta m(-2) s(-1) than it was for ZX from A. elegantissima (respectively, 7.3 vs. 6.2) and relatively lower at 40 micromol quanta m(-2) s(-1) (3.9 vs. 5.6). Our data indicate host-specific differences in symbiont distributions and MI when extrinsic physical parameters were similar.Biological Bulletin 06/2010; 218(3):237-47. DOI:10.2307/27822916 · 1.57 Impact Factor
- Pediatric News 08/2010; 44(8):13-13. DOI:10.1016/S0031-398X(10)70355-6