‘SeaStats’: hard figures on sea and coast

Looking for reliable figures on our seas and coasts? In need of that particular number to finish your introduction or presentation? ‘SeaStats’ offers interesting facts, each with a direct link to the source document and author(s). The primary criteria for selection are 1) reliability and quality of the source and 2) relevance of the figures. ‘SeaStats’ is a bilingual product that allows for a thematic search through 9 topics and 40 subtopics that are relevant marine, coastal and estuarine themes. ‘SeaStats’ wishes to a) facilitate the search for reliable anecdotic information on seas and coasts, with a focus on figures and numbers and 2) provide an additional exposure of marine and coastal research results to a wider public. Figures can be looked up through the 9 different symbols in the start-screen www.vliz.be/cijfers_beleid/zeecijfers (Dutch and English) or by filling in specific search terms. Take this example; you want to know the exact length of the Belgian coastline? Follow the symbol ‘Sea of space’ on the start-screen, click on ‘geography’, or use the search term ‘coastline’. The result of your search will inform you that there are 3 different and www.vliz.be/docs/Zeecijfers/seabordernl.pdf, where each alternative is explained. Source documents are by preference full texts of publications documented in IMIS, on relevant Belgian research or relating to the Belgian part of the North Sea, the Scheldt Estuary and the Belgian coastal zone

Development of the retinal tapetum lucidum of the walleye (Stizostedion vitreum vitreum)

The development of the retinal tapetum lucidum within the cells of the retinal pigment epithelium (RPE) has been investigated by both light and electron microscopy in the walleye (Stizostedion vitreum vitreum) in specimens ranging in total length from 25-140 mm. In addition changes in the arrangement of the photoreceptors (both rods and cones) in both light and darkadaptation have also been studied. At 25 mm no evidence of a tapetum is present. At about 30 mm it makes its initial appearance as granular bodies formed within the apical smooth endoplasmic reticulum (SER) cisternae of the RPE cells in the superior temporal fundus. The developing tapetum then spreads peripherally and continues to thicken in existing areas. By 90 mm it is well established throughout the fundus but always appears better developed in the superior fundus. By 125-140 mm it is essentially adult in appearance. At 60-70 mm the rods and cones begin to form bundles producing macroreceptors of 20-30 photoreceptors. In dark-adaptation the rod bundles are retracted and have one or more cone cells centrally located in each bundle, with the bundles separated from one another by melanosomes. Initially when no tapetal material is present, post-larva1 walleye are positively phototactic and feed on zooplankton. In the adult condition when a tapetum lucidum and large macroreceptors are present, the walleye is negatively phototactic and feeds almost exclusively on larger organisms such as other fish

Fine structure of the pecten oculi of the barred owl (Strix varia)

The pecten oculi of the barred owl (Strix varia) has been examined by light and transmission electron microscopy. The pecten in this species is of the pleated type and is small in comparison to the size of the ocular globe. The pecten consists of 8-10 accordion-like folds that are linked apically by a pigmented tissue bridge. Each fold contains numerous capillaries, larger supply and drainage vessels, and abundant pleomorphic melanocytes. Most of these capillaries are extremely specialized vessels that possess plentiful microfolds on both the luminal and abluminal surfaces. Some capillaries however display only a few microfolds. The endothelial cell bodies are extremely attenuated, with most organelles located near the nucleus. All capillaries are surrounded by a very thick fibrillar basal lamina, which is thought to provide structural support to these small vessels. Pericytes are commonly found within these thickened basal laminae. Numerous melanocytes are also present, with processes that form an incomplete sheath around the capillaries. These processes are also presumed to provide structural support for the capillaries. As in other avian species, the morphology of the barred owl pecten is indicative of extensive involvement in substance transport. When compared to the pecten of more visually-oriented species, this pecten is smaller, has fewer folds, and displays a reduced number of microfolds within the capillaries. In these and other features, the barred owl pecten is similar to the pecten of the great horned owl (Bubo virginianus)