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Charleston, OR, United States

The gumboot chiton Cryptochiton stelleri Middendorff, 1847, is the largest intertidal invertebrate herbivore in the northeast Pacific, but little is known about the fine-scale distribution of this species within its range. In this study, extensive intertidal surveys were used to determine the distribution of C. stelleri within six rocky intertidal sites on the southern coast of Oregon, USA, and found that gumboot chitons show a patchy and clumped distribution. At all six sites, individuals were found at highest densities within small coves, and small specimens (< 15 cm long) were found almost exclusively in sea urchin pits. Age-frequency histograms were created for populations of C. stelleri at all six sites and showed sporadic cohort success, likely as a result of sporadic recruitment. Successful cohorts were indicated by peaks in the age-frequency histograms and were compared between sites in order to determine whether or not successful cohorts occurred at the same time at all sites. There was low similarity between sites, and a negative correlation was found between distance between sites and percent similarity in age-frequency peaks. Combined with other factors, this suggests that larval settlement and cohort success of C. stelleri is driven by local factors, not such large-scale factors as upwelling or El Nio. Source


Vendetti J.E.,California State University, Los Angeles | Trowbridge C.D.,Oregon Institute of Marine Biology | Krug P.J.,California State University, Los Angeles
Integrative and Comparative Biology | Year: 2012

Credible cases of poecilogony, the production of two distinct larval morphs within a species, are extremely rare in marine invertebrates, yet peculiarly common in a clade of herbivorous sea slugs, the Sacoglossa. Only five animal species have been reported to express dimorphic egg sizes that result in planktotrophic and lecithotrophic larvae: the spionid polychaete Streblospio benedicti and four sacoglossans distributed in temperate estuaries or the Caribbean. Here, we present developmental and genetic evidence for a fifth case of poecilogony via egg-size dimorphism in the Sacoglossa and the first example from the tropical Indo-Pacific. The sea slug Elysia pusilla produced both planktotrophic and lecithotrophic larvae in Guam and Japan. Levels of genetic divergence within populations were markedly low and rule out cryptic species. However, divergence among populations was exceptionally high (10-12 at the mitochondrial cytochrome c oxidase I locus), illustrating that extensive phylogeographic structure can persist in spite of the dispersal potential of planktotrophic larvae. We review reproductive, developmental, and ecological data for the five known cases of poecilogony in the Sacoglossa, including new data for Costasiella ocellifera from the Caribbean. We hypothesize that sacoglossans achieve lecithotrophy at smaller egg sizes than do related clades of marine heterobranchs, which may facilitate developmental plasticity that is otherwise vanishingly rare among animals. Insight into the environmental drivers and evolutionary results of shifts in larval type will continue to be gleaned from population-level studies of poecilogonous taxa like E. pusilla, and should inform life-history theory about the causes and consequences of alternative development modes in marine animals. © The Author 2012. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. Source


Cryptochiton stelleri is the largest herbivore in the intertidal and subtidal zone throughout its North Pacific range, but its larval development and metamorphosis have not been well documented. A description of larval development for specimens in Hokkaido, Japan, has been used in multiple textbooks yet shows many features atypical of chiton development. In the present study in Oregon, C. stelleri larvae were raised in culture and displayed developmental stages similar to other chitons, very different from the previous description. Plate development began 3 days after hatching. Larvae were competent beginning 3 days posthatching and metamorphosed in response to extract from encrusting coralline algae. Larvae survived for over a month without metamorphosing and did not metamorphose in response to increased temperature, presence of adults or the addition of algal foods of adults or juveniles. Juvenile C. stelleri were discovered in the field and grew c. 4 mm per month in captivity. Juveniles had exposed shell plates and fed on the red alga Cryptopleura. © The Author 2011. Source


Meyer K.S.,Oregon Institute of Marine Biology | Bergmann M.,Alfred Wegener Institute for Polar and Marine Research | Soltwedel T.,Alfred Wegener Institute for Polar and Marine Research
Biogeosciences | Year: 2013

Epibenthic megafauna play an important role in the deep-sea environment and contribute significantly to benthic biomass, but their population dynamics are still understudied. We used a towed deep-sea camera system to assess the population densities of epibenthic megafauna in 2002, 2007, and 2012 at the shallowest station (HG I, ∼1300 m) of the deep-sea observatory HAUSGARTEN, in the eastern Fram Strait. Our results indicate that the overall density of megafauna was significantly lower in 2007 than in 2002, but was significantly higher in 2012, resulting in overall greater megafaunal density in 2012. Different species showed different patterns in population density, but the relative proportions of predator/scavengers and suspension-feeding individuals were both higher in 2012. Variations in megafaunal densities and proportions are likely due to variation in food input to the sea floor, which decreased slightly in the years preceding 2007 and was greatly elevated in the years preceding 2012. Both average evenness and diversity increased over the time period studied, which indicates that HG I may be food-limited and subject to bottom-up control. The community of HG I may be unique in its response to elevated food input, which resulted in higher evenness and diversity in 2012. © 2013 Author(s). Source


Burkepile D.E.,Florida International University | Allgeier J.E.,University of Georgia | Shantz A.A.,Florida International University | Pritchard C.E.,Florida International University | And 4 more authors.
Scientific Reports | Year: 2013

On coral reefs, fishes can facilitate coral growth via nutrient excretion; however, as coral abundance declines, these nutrients may help facilitate increases in macroalgae. By combining surveys of reef communities with bioenergetics modeling, we showed that fish excretion supplied 25 times more nitrogen to forereefs in the Florida Keys, USA, than all other biotic and abiotic sources combined. One apparent result was a positive relationship between fish excretion and macroalgal cover on these reefs. Herbivore biomass also showed a negative relationship with macroalgal cover, suggesting strong interactions of top-down and bottom-up forcing. Nutrient supply by fishes also showed a negative correlation with juvenile coral density, likely mediated by competition between macroalgae and corals, suggesting that fish excretion may hinder coral recovery following large-scale coral loss. Thus, the impact of nutrient supply by fishes may be context-dependent and reinforce either coral-dominant or coral-depauperate reef communities depending on initial community states. Source

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