The dynamics of epidermal stratification during post-larval development in zebrafish.

BACKGROUND: The epidermis, as a defensive barrier, is a consistent trait throughout animal evolution. During post-larval development, the zebrafish epidermis thickens by stratification or addition of new cell layers. Epidermal basal stem cells, expressing the transcription factor p63, are known to be involved in this process. Zebrafish post-larval epidermal stratification is a tractable system to study how stem cells participate in organ growth. METHODS: We used immunohistochemistry, in combination with EdU cell proliferation detection, to study zebrafish epidermal stratification. For this procedure, we selected a window of post-larval stages (5-8 mm of standard length or SL, which normalizes age by size). Simultaneously, we used markers for asymmetric cell division and the Notch signaling pathway. RESULTS: We found that epidermal stratification is the consequence of several events, including changes in cell shape, active cell proliferation and asymmetrical cell divisions. We identified a subset of highly proliferative epidermal cells with reduced levels of p63, which differed from the basal stem cells with high levels of p63. Additionally, we described different mechanisms that participate in the stratification process, including the phosphorylation of p63, asymmetric cell division regulated by the Par3 and LGN proteins, and expression of Notch genes.

Subterranean life: Behavior, metabolic, and some other adaptations of Astyanax cavefish.

The ability of fishes to adapt to any aquatic environment seems limitless. It is enthralling how new species keep appearing at the deep sea or in subterranean environments. There are close to 230 known species of cavefishes, still today the best-known cavefish is Astyanax mexicanus, a Characid that has become a model organism, and has been studied and scrutinized since 1936. There are two morphotypes for A. mexicanus, a surface fish and a cavefish. The surface fish lives in central and northeastern Mexico and south of the United States, while the cavefish is endemic to the "Sierra del Abra-Tanchipa region" in northeast Mexico. The extensive genetic and genomic analysis depicts a complex origin for Astyanax cavefish, with multiple cave invasions and persistent gene flow among cave populations. The surface founder population prevails in the same region where the caves are. In this review, we focus on both morphotype's main morphological and physiological differences, but mainly in recent discoveries about behavioral and metabolic adaptations for subterranean life. These traits may not be as obvious as the troglomorphic characteristics, but are key to understand how Astyanax cavefish thrives in this environment of perpetual darkness.

Octopus insularis as a new marine model for evolutionary developmental biology.

Octopuses are intriguing organisms that, together with squids and cuttlefishes, form the extant coleoid cephalopods. This group includes many species that can potentially be used as models in the fields of biomedicine, developmental biology, evolution, neuroscience and even for robotics research. The purpose of this work is to first present a simple method for maintaining Octopus insularis embryos under a laboratory setup. Second, we show that these embryos are suitable for detailed analyses of specific traits that appear during developmental stages, including the eyes, hearts, arms, suckers, chromatophores and Kölliker's organs. Similar complex traits between cephalopods and vertebrates such as the visual, cardiovascular, neural and pigmentation systems are generally considered to be a result of parallel evolution. We propose that O. insularis embryos could be used as a model for evolutionary developmental biology (or EvoDevo) research, where comparisons of the morphogenetic steps in the building of equivalent organs between cephalopods and known vertebrate model systems could shed light on evolutionary convergences and deep homologies.

Linking host morphology and symbiont performance in octocorals.

Octocorals represent an important group in reef communities throughout the tropical seas and, like scleractinian corals, they can be found in symbiosis with the dinoflagellate Symbiodinium. However, while there is extensive research on this symbiosis and its benefits in scleractinians, research on octocorals has focused so far mainly on the host without addressing their symbiosis. Here, we characterized and compared the photophysiological features of nine Caribbean octocoral species with different colony morphologies (sea fan, plumes, whips and rods) and related key morphological features with their respective symbiont photobiology. Colony features (branch shape and thickness), as well as micromorphological features (polyp size, density), were found to be significantly correlated with symbiont performance. Sea fans and plumes, with thinner branches and smaller polyps, favor higher metabolic rates, compared to sea rods with thicker branches and larger polyps. Daily integrated photosynthesis to respiration ratios > 1 indicated that the autotrophic contribution to organisms' energy demands was important in all species, but especially in sea whips. This information represents an important step towards a better understanding of octocoral physiology and its relationship to host morphology, and might also explain to some extent species distribution and susceptibility to environmental stress.

Transit-Amplifying Cells in the Fast Lane from Stem Cells towards Differentiation.

Stem cells have a high potential to impact regenerative medicine. However, stem cells in adult tissues often proliferate at very slow rates. During development, stem cells may change first to a pluripotent and highly proliferative state, known as transit-amplifying cells. Recent advances in the identification and isolation of these undifferentiated and fast-dividing cells could bring new alternatives for cell-based transplants. The skin epidermis has been the target of necessary research about transit-amplifying cells; this work has mainly been performed in mammalian cells, but further work is being pursued in other vertebrate models, such as zebrafish. In this review, we present some insights about the molecular repertoire regulating the transition from stem cells to transit-amplifying cells or playing a role in the transitioning to fully differentiated cells, including gene expression profiles, cell cycle regulation, and cellular asymmetrical events. We also discuss the potential use of this knowledge in effective progenitor cell-based transplants in the treatment of skin injuries and chronic disease.

Rotavirus infections in Galapagos sea lions.

Group A rotaviruses infect and cause diarrhea in the young of a broad range of terrestrial mammals, but it is unknown, to our knowledge, whether they infect marine mammals. During February and March of 2002 and 2003, we collected 125 serum samples and 18 rectal swab samples from Galapagos sea lion pups (GSL, Zalophus wollebaeki), and 22 serum samples from Galapagos fur seal pups (GFS, Arctocephalus galapagoensis) from nine islands of the Galapagos archipelago, Ecuador. Sera were tested for antibodies (immunoglobulin G [IgG]) to rotavirus by an enzyme immunoassay using rhesus rotavirus as the capture antigen. In addition, rectal swabs were analyzed for the presence of rotavirus genomic double-stranded RNA by silver-stained polyacrylamide gel electrophoresis. Antibodies to rotavirus were detected in 27 GSL pups (22%) and five GFS pups (23%), and rotavirus RNA was detected in the fecal sample from one GSL pup (6%). These results provide the first evidence that rotavirus infections are prevalent at an early age in Galapagos sea lions and Galapagos fur seals.