Multiple resiliency metrics reveal complementary drivers of ecosystem persistence: An application to kelp forest systems.

Human-caused global change produces biotic and abiotic conditions that increase the uncertainty and risk of failure of restoration efforts. A focus of managing for resiliency, that is, the ability of the system to respond to disturbance, has the potential to reduce this uncertainty and risk. However, identifying what drives resiliency might depend on how one measures it.

Bimodal spore release heights in the water column enhance local retention and population connectivity of bull kelp, .

Dispersal of reproductive propagules determines recruitment patterns and connectivity among populations and can influence how populations respond to major disturbance events. Dispersal distributions can depend on propagule release strategies. For instance, the bull kelp, , can release propagules (spores) from two heights in the water column ("bimodal release"): at the water surface, directly from the reproductive tissues (sori) on the kelp's blades, and near the seafloor after the sori abscise and sink through the water column.

Sunflower sea star predation on urchins can facilitate kelp forest recovery.

The recent collapse of predatory sunflower sea stars () owing to sea star wasting disease (SSWD) is hypothesized to have contributed to proliferation of sea urchin barrens and losses of kelp forests on the North American west coast. We used experiments and a model to test whether restored populations may help recover kelp forests through their consumption of nutritionally poor purple sea urchins () typical of barrens. consumed 0.

Proton exchange by the vacuolar nitrate transporter CLCa is required for plant growth and nitrogen use efficiency.

Nitrate is a major nutrient and osmoticum for plants. To deal with fluctuating nitrate availability in soils, plants store this nutrient in their vacuoles. Chloride channel a (CLCa), a 2NO3-/1H+ exchanger localized to the vacuole in Arabidopsis (Arabidopsis thaliana), ensures this storage process.

Progress Toward Complete Life-Cycle Culturing of the Endangered Sunflower Star, .

AbstractUntil recently, the sunflower star, , was a dominant and common predator in a wide variety of benthic habitats in the northeast Pacific. Then, in 2013, its populations began to plummet across its entire range as a result of the spread of a phenomenon known as sea star wasting disease, or sea star wasting. Although dozens of sea star species were impacted by this wasting event, seems to have suffered the greatest losses and is now listed by the International Union for the Conservation of Nature as the first critically endangered sea star.

Culturing echinoderm larvae through metamorphosis.

Echinoderms are favored study organisms not only in cell and developmental biology, but also physiology, larval biology, benthic ecology, population biology and paleontology, among other fields. However, many echinoderm embryology labs are not well-equipped to continue to rear the post-embryonic stages that result. This is unfortunate, as such labs are thus unable to address many intriguing biological phenomena, related to their own cell and developmental biology studies, that emerge during larval and juvenile stages.

Sand Dollar Larvae Show Within-Population Variation in Their Settlement Induction by Turbulence.

Settlement-the generally irreversible transition from a planktonic phase to a benthic phase-is a critical stage in the life history of many shoreline organisms. It is reasonable to expect that larvae are under intense selection pressure to identify appropriate settlement habitat. Several decades of studies have focused mainly on local indicators that larvae use to identify suitable habitat, such as olfactory cues that indicate the presence of conspecifics or a favored food source.

Probing glycosaminoglycan spectral signatures in live cells and their conditioned media by Raman microspectroscopy.

Spectroscopic markers characteristic of reference glycosaminoglycan molecules were identified previously based on their vibrational signatures. Infrared spectral signatures of glycosaminoglycans in fixed cells were also recently demonstrated but probing live cells still remains challenging. Raman microspectroscopy is potentially interesting to perform studies under physiological conditions.

A newly identified left-right asymmetry in larval sea urchins.

Directional asymmetry (DA) in body form is a widespread phenomenon in animals and plants alike, and a functional understanding of such asymmetries can offer insights into the ways in which ecology and development interface to drive evolution. Echinoids (sea urchins, sand dollars and their kin) with planktotrophic development have a bilaterally symmetrical feeding pluteus larva that undergoes a dramatic metamorphosis into a pentameral juvenile that enters the benthos at settlement. The earliest stage of this transformation involves a DA: a left-side invagination in mid-stage larvae leads to the formation of the oral field of the juvenile via a directionally asymmetric structure called the echinus rudiment.

Rethinking competence in marine life cycles: ontogenetic changes in the settlement response of sand dollar larvae exposed to turbulence.

Complex life cycles have evolved independently numerous times in marine animals as well as in disparate algae. Such life histories typically involve a dispersive immature stage followed by settlement and metamorphosis to an adult stage on the sea floor. One commonality among animals exhibiting transitions of this type is that their larvae pass through a 'precompetent' period in which they do not respond to localized settlement cues, before entering a 'competent' period, during which cues can induce settlement.

Manipulation of developing juvenile structures in purple sea urchins (Strongylocentrotus purpuratus) by morpholino injection into late stage larvae.

Sea urchins have been used as experimental organisms for developmental biology for over a century. Yet, as is the case for many other marine invertebrates, understanding the development of the juveniles and adults has lagged far behind that of their embryos and larvae. The reasons for this are, in large part, due to the difficulty of experimentally manipulating juvenile development.

A detailed staging scheme for late larval development in Strongylocentrotus purpuratus focused on readily-visible juvenile structures within the rudiment.

Background: The purple sea urchin, Strongylocentrotus purpuratus, has long been the focus of developmental and ecological studies, and its recently-sequenced genome has spawned a diversity of functional genomics approaches. S. purpuratus has an indirect developmental mode with a pluteus larva that transforms after 1-3 months in the plankton into a juvenile urchin.

Turbulent shear spurs settlement in larval sea urchins.

Marine invertebrates commonly produce larvae that disperse in ocean waters before settling into adult shoreline habitat. Chemical and other seafloor-associated cues often facilitate this latter transition. However, the range of effectiveness of such cues is limited to small spatial scales, creating challenges for larvae in finding suitable sites at which to settle, especially given that they may be carried many kilometers by currents during their planktonic phase.

Expanding networks: Signaling components in and a hypothesis for the evolution of metamorphosis.

Metamorphosis is a substantial morphological transition between 2 multicellular phases in an organism's life cycle, often marking the passage from a prereproductive to a reproductive life stage. It generally involves major physiological changes and a shift in habitat and feeding mode, and can be subdivided into an extended phase of substantial morphological change and/or remodeling, and a shorter-term phase (for example, marine invertebrate "settlement," insect "adult eclosion," mushroom fruiting body emergence) where the actual habitat shift occurs. Disparate metamorphic taxa differ substantially with respect to when the habitat shift occurs relative to the timing of the major events of morphogenetic change.

Interspecific variation in metamorphic competence in marine invertebrates: the significance for comparative investigations into the timing of metamorphosis.

Metamorphosis in marine invertebrate larvae is a dynamic, environmentally dependent process that integrates ontogeny with habitat selection. The capacity of many marine invertebrate larvae to survive and maintain metamorphic competence in the absence of environmental cues has been hypothesized to be an adaptive convergence (Hadfield and others 2001). A survey of the literature reveals that a single generalized hypothesis about metamorphic competence as an adaptive convergence is not sufficient to account for interspecific variation in this character.

What is metamorphosis?

Metamorphosis (Gr. meta- "change" + morphe "form") as a biological process is generally attributed to a subset of animals: most famously insects and amphibians, but some fish and many marine invertebrates as well. We held a symposium at the 2006 Society for Integrative and Comparative Biology (SICB) annual meeting in Orlando, FL (USA) to discuss metamorphosis in a comparative context.

Hormone signaling in evolution and development: a non-model system approach.

Cooption and modularity are informative concepts in evolutionary developmental biology. Genes function within complex networks that act as modules in development. These modules can then be coopted in various functional and evolutionary contexts.

Heterochronic developmental shift caused by thyroid hormone in larval sand dollars and its implications for phenotypic plasticity and the evolution of nonfeeding development.

Recent work on a diverse array of echinoderm species has demonstrated, as is true in amphibians, that thyroid hormone (TH) accelerates development to metamorphosis. Interestingly, the feeding larvae of several species of sea urchins seem to obtain TH through their diet of planktonic algae (exogenous source), whereas nonfeeding larvae of the sand dollar Peronella japonica produce TH themselves (endogenous source). Here we examine the effects of TH (thyroxine) and a TH synthesis inhibitor (thiourea) on the development of Dendraster excentricus, a sand dollar with a feeding larva.

Parallel alterations in the timing of ovarian ecdysone receptor and ultraspiracle expression characterize the independent evolution of larval reproduction in two species of gall midges (Diptera: Cecidomyiidae).

Although most insects reproduce in the adult stage, facultative larval or pupal reproduction (paedogenesis) has evolved at least six times independently in insects, twice in gall midges of the family Cecidomyiidae (Diptera). Paedogenesis in gall midges involves the precocious growth and differentiation of the ovary in an otherwise larval form. We have previously shown that the timing of expression of the Ecdysone Receptor (EcR) and Ultraspiracle (USP), the two proteins that constitute the functional receptor for the steroid hormone 20-hydroxyecdysone, regulates the timing and progression of ovarian differentiation in Drosophila melanogaster (Diptera: Drosophilidae).

Different mechanisms underlie phenotypic plasticity and interspecific variation for a reproductive character in drosophilids (Insecta: Diptera).

The insect ovary is a modular structure, the functional unit of which is the ovariole. Ovariole number is positively correlated with potential reproductive output. Among drosophilids (Insecta: Diptera), ovariole number shows both phenotypic plasticity and substantial interspecific and interpopulational variation.

Plasticity and constraints in development and evolution.

Morphological similarities between organisms may be due to either homology or homoplasy. Homologous structures arise by common descent from an ancestral form, whereas homoplasious structures are independently derived in the respective lineages. The finding that similar ontogenetic mechanisms underlie the production of the similar structures in both lineages is not sufficient evidence of homology, as such similarities may also be due to parallel evolution.

The ecdysone receptor and ultraspiracle regulate the timing and progression of ovarian morphogenesis during Drosophila metamorphosis.

Ecdysteroids regulate insect metamorphosis through the edysone receptor complex, a heterodimeric nuclear receptor consisting of the ecdysone receptor (EcR) and its partner ultraspiracle (USP). Differentiation in the Drosophila ovary at metamorphosis correlates with colocalization of USP and the EcR-A isoform in all but one of eight mesoderm-derived somatic cell types. The one exception is the larval terminal filament (TF) cells, in which only USP is detectable during cell differentiation.