Effect of parabranchial position on ventilatory pressures in the Pacific spiny dogfish (Squalus suckleyi).

The mechanics of ventilation in elasmobranchs have been described as a two-pump system which is dependent on the generation of differential pressures between the orobranchial and parabranchial cavities. However, this general model does not take into account sources of variation in parabranchial form and function. For example, the relative pressures that drive flow in each parabranchial chamber during ventilation remain largely unexplored.

Factors influencing recruitment and appearance of bull kelp, Nereocystis luetkeana (phylum Ochrophyta).

The dynamics of annual species are strongly tied to their capacity for recruitment each year. We examined how competition and propagule availability influence recruitment and appearance and tracked survivorship of an annual species of marine macroalgae, the bull kelp (Nereocystis luetkeana), which serves as major biogenic habitat in the Salish Sea of Washington State. We hypothesized that (i) juvenile N.

The evolution of underwater flight: The redistribution of pectoral fin rays, in manta rays and their relatives (Myliobatidae).

Batoids are a diverse clade of flat cartilaginous fishes that occur primarily in benthic marine habitats. The skates and rays typically use their flexible pectoral fins for feeding and propulsion via undulatory swimming. However, two groups of rays have adopted a pelagic or bentho-pelagic lifestyle and utilize oscillatory swimming-the Myliobatidae and Gymnuridae.

The comparative hydrodynamics of rapid rotation by predatory appendages.

Countless aquatic animals rotate appendages through the water, yet fluid forces are typically modeled with translational motion. To elucidate the hydrodynamics of rotation, we analyzed the raptorial appendages of mantis shrimp (Stomatopoda) using a combination of flume experiments, mathematical modeling and phylogenetic comparative analyses. We found that computationally efficient blade-element models offered an accurate first-order approximation of drag, when compared with a more elaborate computational fluid-dynamic model.

Finite element modeling of occlusal variation in durophagous tooth systems.

In addition to breaking hard prey items, the teeth of durophagous predators must also resist failure under high loads. To understand the effects of morphology on tooth resistance to failure, finite element models were used to examine differences in total strain energy (J), first principal strain and the distribution of strains in a diversity of canonical durophagous tooth morphologies. By changing the way loads were applied to the models, I was also able to model the effects of large and small prey items.

When is dispersal for dispersal? Unifying marine and terrestrial perspectives.

Recent syntheses on the evolutionary causes of dispersal have focused on dispersal as a direct adaptation, but many traits that influence dispersal have other functions, raising the question: when is dispersal 'for' dispersal? We review and critically evaluate the ecological causes of selection on traits that give rise to dispersal in marine and terrestrial organisms. In the sea, passive dispersal is relatively easy and specific morphological, behavioural, and physiological adaptations for dispersal are rare. Instead, there may often be selection to limit dispersal.

Clustering of low-valence particles: structure and kinetics.

We compute the structure and kinetics of two systems of low-valence particles with three or six freely oriented bonds in two dimensions. The structure of clusters formed by trivalent particles is complex with loops and holes, while hexavalent particles self-organize into regular and compact structures. We identify the elementary structures which compose the clusters of trivalent particles.

FATTY ACID SIGNATURES DIFFERENTIATE MARINE MACROPHYTES AT ORDINAL AND FAMILY RANKS(1).

Primary productivity by plants and algae is the fundamental source of energy in virtually all food webs. Furthermore, photosynthetic organisms are the sole source for ω-3 and ω-6 essential fatty acids (EFA) to upper trophic levels. Because animals cannot synthesize EFA, these molecules may be useful as trophic markers for tracking sources of primary production through food webs if different primary producer groups have different EFA signatures.

Cellular symmetry breaking during Caenorhabditis elegans development.

The nematode worm Caenorhabditis elegans has produced a wellspring of insights into mechanisms that govern cellular symmetry breaking during animal development. Here we focus on two highly conserved systems that underlie many of the key symmetry-breaking events that occur during embryonic and larval development in the worm. One involves the interplay between Par proteins, Rho GTPases, and the actomyosin cytoskeleton and mediates asymmetric cell divisions that establish the germline.

The distribution of polarization sensitivity in the crayfish retinula.

In many arthropod eyes the ommatidia contain two classes of retinular cells with orthogonally oriented microvilli. These receptors provide the basis for two-channel polarization vision. In several contexts such as navigation or the detection of polarization contrast, two channels may be insufficient.

Immunochemical and electrophysiological analyses of magnetically responsive neurons in the mollusc Tritonia diomedea.

Tritonia diomedea uses the Earth's magnetic field as an orientation cue, but little is known about the neural mechanisms that underlie magnetic orientation behavior in this or other animals. Six large, individually identifiable neurons in the brain of Tritonia (left and right Pd5, Pd6, Pd7) are known to respond with altered electrical activity to changes in earth-strength magnetic fields. In this study we used immunochemical, electrophysiological, and neuroanatomical techniques to investigate the function of the Pd5 neurons, the largest magnetically responsive cells.