EOSC 326 Case Study 1, Community Members 3 to 7 - Sponge Groups

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University of British Columbia *

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326

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Biology

Date

Apr 3, 2024

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pdf

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3/1/24, 10:25 AM Case Study 1, Community Members 3 to 7 - Sponge Groups: EOSC 326 99C 2023W2 Earth and Life Through Time https://canvas.ubc.ca/courses/130823/pages/case-study-1-community-members-3-to-7-sponge-groups?module_item_id=6194743 1/21 Case Study 1, Community Members 3 to 7 - Sponge Groups Porifera or sponges are organized at the cellular level and are relatively primitive biologically. Most sponges are asymmetric. They lack true differentiated tissues and organs, having no nervous system, circulatory system, mouth, or anus. Although sponges are multicellular, the cells have relative independence from one another. If cells are separated and then put back together, they will recombine, clump and redistribute to re-form the organism. Figure - A modern Cayman Island sponge. Color-adjusted (but not color accurate) underwater photograph taken by Dlloyd, courtesy of Wikipedia (http://en.wikipedia.org/) . Sponges are sessile benthic animals that are all aquatic and mostly marine. There are over 10,000 species of sponges which vary considerably in shape and morphology based on their habitat. Stalk-shaped sponges tend to live in deeper water environments whereas sponges that are more broad and flat tend to live in shallower, higher energy environments. Sponges first appeared in the Cambrian and they are still extant.

3/1/24, 10:25 AM Case Study 1, Community Members 3 to 7 - Sponge Groups: EOSC 326 99C 2023W2 Earth and Life Through Time https://canvas.ubc.ca/courses/130823/pages/case-study-1-community-members-3-to-7-sponge-groups?module_item_id=6194743 2/21 Basic Sponge Morphology Sponges are sac-shaped and are composed of two layers of cells separated by mesoglea or jelly. Within the mesoglea is the sponge's skeleton that is often made up of spongin, a network of flexible protein fibers. In addition, sponges often have hard spicules that reinforce the mesoglea. Sponges have a central cavity, the paragaster, which opens at the top through the operculum. The outside of the sponge contains many small openings called ostia, which mark the entrance to tiny canals. The largest ostia is approximately 0.1 mm. A sponge includes 3 types of cells: epithelial cells, choanocytes, and amoebocytes. The epithelial cells line the outside of the sponge and the canals. The choanocytes occupy the internal chamber and assist with moving water through the sponge. The amoebocytes function in digestive, reproductive, and skeletal roles. Figure - Basic sponge morphology. a: choanocyte cells; b: epithelial cells; c: amoebocytes cells; d: ostia; e: mesoglea; f: spicule; g: paragaster; h: operculum. Illustration modified from The Biology Corner (http://www.biologycorner.com/) .

3/1/24, 10:25 AM Case Study 1, Community Members 3 to 7 - Sponge Groups: EOSC 326 99C 2023W2 Earth and Life Through Time https://canvas.ubc.ca/courses/130823/pages/case-study-1-community-members-3-to-7-sponge-groups?module_item_id=6194743 3/21 Basic Feeding Sponges are filter feeders. They pump water through their bodies from which they extract oxygen and nutrients. Water is drawn in through the ostia and along the tiny canals by the choanocytes, which have flagella that beat and create a positive pressure in the interior of the sponge. Once inside the paragaster, the oxygen and organic matter adhere to the choanocytes where the nutrients are then ingested. Food is then digested and distributed by amoebocytes. Wastewater and carbon dioxide exit out the operculum. Figure - A choanocyte cell. Image courtesy of Department of Biology, University of Miami (http://www.bio.miami.edu) . Optional Material To read more on how sponges feed, click here (https://canvas.ubc.ca/courses/130823/pages/how-does-sponge-feeding-work) . How can we tell how much water a sponge filters? Click here (https://canvas.ubc.ca/courses/130823/pages/how-much-water-does-a-sponge-filter-in-24-hours) to find out! Classification In addition to distributing food, amoebocyte cells are also responsible for secreting spicules. Spicules are fundamental to sponge taxonomy in the fossil record as the soft-tissue of most sponges decay completely, so the spicules are all that is preserved. Sponge spicules come in many shapes and are important in classifying the sponges into different groups. For this Case Study, we will be focusing on five different groups of sponges, as each one has played a very different role in reef ecosystems in the past. These are the archeocyathids, the

3/1/24, 10:25 AM Case Study 1, Community Members 3 to 7 - Sponge Groups: EOSC 326 99C 2023W2 Earth and Life Through Time https://canvas.ubc.ca/courses/130823/pages/case-study-1-community-members-3-to-7-sponge-groups?module_item_id=6194743 5/21 Figure - (left) Archaeocyathid structure as viewed from the side and (right) as viewed from the top . Illustrations (left) with permission from Benton, M.J., and Harper, D.A.T., 2009, "Introduction to paleobiology and the fossil record", Wiley- Blackwell, 595 pp. and (right) by L. Longridge. Both the cones and the septae had pores, with the pores on the inner cone being larger than those of the outer cone. These pores probably allowed the animal to filter feed by drawing water through the outer wall, filtering the nutrients in the intervallum and then expelling the wastewater out through the pores in the inner wall and out the top. The animal attached to the substrate by the tip. It sometimes had roots or holdfasts that improved the strength of its anchorage and its stability in the water column. Some groups of archaeocyathids were solitary whereas other groups formed branching colonies. It is not certain at this point but it is possible that archeocyathids had photosymbionts in their tissues which would have increased their speed of growth. 2. Simple Chambered Sponges The second group is composed of the simple chambered sponges. This group has spicules made of silica that can be monaxon although in this group, tetraxon spicules, which are four- rayed, are also common. In the cases with tetraxon spicules, the rays diverge at angles of 60° or 120°. Many sponges from this group have spicules called desmas, which have a lumpy, irregular shape.