101. Sea Urchins Revisited Photographic study by Jean-Marie Cavanihac of the sea urchin with some microscopic features of interest to the amateur naturalist. http://www.microscopy-uk.org.uk/mag/artmay02/urchin2.html

Sea urchins - Revisited - by Jean-Marie Cavanihac, France Some months ago I wrote an article about sea urchins. So why am I writing again on this topic? Perhaps it's because I always have an urchin spine in my left forefinger! But the real reason is different: at that time I didn't use a color still camera and the images were 'hand colored'. Some features of urchins are so beautiful in their true colors, that I have prepared a second article to show some of these features to Micscape readers; particularly the pedicellariae and their tiny internal 'bones', such as these below: But to recap a little: some parts of an urchin are made of calcium carbonate, (calcite, with magnesium carbonate an important additional component), and these materials are able to rotate plane polarized light. Some additional equipment is needed to add polarized lighting to your microscope. Some methods, including using clip-on Polaroid sunglasses, have been described in past articles in Micscape, but I have used a different approach. Liquid crystal displays (LCD's) like those used in handheld calculators, car temperature indicators, low priced watches etc. include a polarizing filter to increase the display contrast. Some filters for computer screens are also polarizers. On an LCD this filter is a film glued onto the glass display, in other cases it's just a removable plastic grey plate. It's this last type I have used:

102. Calcareous Flowers: Tests And Cross-sections Of Sea Urchin Spines. Photographic study by Richard Howey with some fine photographs of the intricate beauty of these structures. http://www.microscopy-uk.org.uk/mag/artaug05/rh-seaurchin.html

Calcareous Flowers: Tests and Cross-Sections of Sea Urchin Spines by Richard L. Howey, Wyoming, USA For over 50 years, I have been fascinated with echinoderms and from time to time I would come across drawings or photographs in a zoology book of a cross-section of a sea urchin spine and marvel at the complexity and symmetry. However, only in the last few years, by means of the Internet, have I been able to locate a few slides of such sections at prices that I could afford. All of the examples I have acquired are 19 th Century and I don’t know of any supply house that provides such slides made now. To me this is rather surprising. These sections are lovely objects, have an instructional value, and would certainly appeal to collectors. It is certainly true that these sections are not easily produced as I know from personal experience having had less than satisfactory results from several attempts. However, with modern equipment and techniques, I would think that it should be reasonably straightforward for a professional laboratory in a biological supply house to produce such sections but, as I said, I have never come across any and, who knows, they might end up selling for more than the 19 th Century slides.

103. Strongylocentrotus Exercise from Invertebrate Anatomy OnLine covering the systematics, external and internal anatomy of the green sea urchin. http://webs.lander.edu/rsfox/invertebrates/strongylocentrotus.html

TEXT ONLY PRINT Home Invertebrate Anatomy OnLine ... Invertebrate Anatomy OnLine Invertebrate Anatomy OnLine Strongylocentrotus drobachiensis Green Sea Urchin Richard Fox Lander University Preface This is one of many exercises available from Invertebrate Anatomy OnLine an Internet laboratory manual for courses in Invertebrate Zoology. Additional exercises, a glossary, and chapters on supplies and laboratory techniques are also available at this site. Terminology and phylogeny used in these exercises correspond to usage in the Invertebrate Zoology textbook by Ruppert, Fox, and Barnes (2004). Hyphenated figure callouts refer to figures in the textbook. Callouts that are not hyphenated refer to figures embedded in the exercise. The glossary includes terms from this textbook as well as the laboratory exercises. Systematics Echinodermata P , Eleutherozoa, Cryptosyringida, Echinozoa, Echinoidea C , Euechinoidea sC , Echinoida O , Strongylocentrotidae F (Fig 9-26, 27-12, 28-62) Echinodermata P Echinoderms are secondarily radially symmetric deuterostomes whose ancestors were bilaterally symmetric. The adult radial symmetry is pentamerous with body parts occurring in fives or multiples thereof.

104. The Echinoid Directory - Natural History Museum Biology, phylogeny, and classification of sea urchins. http://www.nhm.ac.uk/research-curation/projects/echinoid-directory/intro/introdu

@import url("/includes/css/research-curation/research-projects/projects/echinoid-directory/echinoid-directory.css"); Skip to page content Research and curation Business centre About us Search Home Visit us Nature online Kids only ... Tring You are here: Home Research Research projects Echinoid directory The Echinoid Directory Home Introduction Morphology Keys ... Log in Introduction Mode of life Composition of the skeleton Soft-tissue anatomy Life history and reproduction ... Evolutionary history Sea urchins are a group of marine invertebrates that today can be found in almost every major marine habitat from the poles to the equator and from the intertidal zone to depths of more than 5,000 metres. There are around 800 extant species and the group has a long and detailed fossil record stretching back about 450 million years ago to the Late Ordovician Period. They belong to the Echinoidea, one of the five classes of the phylum Echinodermata, the others being holothurians, crinoids, starfish and brittlestars. Like all echinoderms, echinoids have a skeleton composed of calcitic plates embedded in their skin (their skeleton is internal, like ours). This skeleton has a very particular structure, termed stereom. In almost all groups of echinoid the plates are firmly bound together to form a solid skeleton, called the test. Plates in the test are arranged into columns radiating from an aboral apical zone to the mouth. In regular echinoids the test is globular and perfectly pentaradiate, but in irregular echinoids there is a secondary bilateral symmetry superimposed upon the primary pentaradiate pattern.

105. FAO Fisheries & Aquaculture - Species Fact Sheets Factsheet from the FAO on the Chilean Sea Urchin which is eaten in Chile and Peru, its distinguishing features, distribution, habitat and biology. http://www.fao.org/fishery/species/3621

106. Urchin Sex! - Divernet Short article from Diver Magazine on how research into these marine creatures is playing an important role in human reproductive biology. http://www.divernet.com/Marine-Life/159801/urchin_sex.html

@import url(/styles/default.css); @import url(/style/starbox.css); @import url(/styles/home_custom.css); Home Diving News Travel News Travel Features ... World Liveaboards Guide SEARCH Advanced Diving News Travel News Travel Features ... Directories Gear Retailer QuickLinks SimplyScuba Travel Operator QuickLinks Home Marine Life Archive Appeared in DIVER October 2008 Urchin sex! Seen close up by the camera, urchins can be surprisingly colourful. Urchins boring? Their sex lives revolutionised our understanding of reproduction, says Louisa Butler. Pictures by Adam Butler WHAT DO YOU THINK WHEN YOU SEE ONE? BORING? SPIKY? OUCH? They make me imagine underwater hedgehogs already curled up in preparation for their predators, which is ironic, because the word 'urchin' is the Old English word for hedgehog! Few divers seem to be interested in these creatures. They don't move much, do anything particularly outwardly interesting and they don't even have brains! However, as you can see from these pictures they can be engaging subjects, as well as having some interesting biology. As humans, we should be saying a big thankyou to sea urchins, rather than bemoaning their existence as we attempt to tweeze out the spines in our hand or foot (delete as appropriate), because they play an important scientific role in human reproductive biology. If not for the sea urchin, we might still think that a sperm is actually a tiny human being, and the egg merely there to give it a comfy home!

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