Rhabdocalyptus dawsoni are deep sea sponges we know as Glass sponges. They rarely come into human contact because of how deep in the ocean they live, where normally no human activity takes place. They can vary from 0.2 to 5 feet tall, and can be just as wide as they are tall. They possess an internal skeleton made up of tiny silica pieces through which soft body cells are strung through. An area of tightly woven spicules coats the osculum through which water is released. Glass sponges have body plans that are in between the syconoid and the leuconoid stages.
They have a very pale color, such as a creamy yellow or white, and appear as a cup or basket-shaped with a large spongocoel. They are also upright and possess strong, specialized structures that are used to help them attach to the ocean floor. These sponges are cylindrical, and can also be branching. They lack epidermal covering and possess no nerve structure, but are able to send electrical signals through their skeletons, and can instantly shut down their feeding current.
Glass sponges are found worldwide, at depths reaching between 200 and 1000 meters below sea level. They are mostly abundant in the Arctic. They adapt well in environments in which water temperatures are between 35 – 52F or 2 – 11C. These sponges are often found in areas with a low light intensity, attached to muddy or hard, rocky surfaces at great depths, and can also be found growing on other dead fused sponge skeletons. It is said that the stability of deep water environments allows them to survive. Like any other sponge, Glass sponges are clearly “Filter feeders,” which means they filter their food from the water. They contain a cavernous central cavity called the atrium, through which water passes. Using collar cells covered in food – trapping micro villus, they feed on small detritus, cellular and bacterial particles in the ocean water. Sponges use central flagella that beat and suck in water, and will digest any material small enough to go through the sponge. Sometimes organisms that are so small are unable to be seen without a microscope, or they will be digested and eaten by the sponge! Sponges compete with other animals over food that also feed off of materials in the ocean, such as shrimp. There are approximately 500 different species of hexactinellids.
Most sponges inhabit far away from human activity, so they are rarely ever in contact with people. But when accidents do strike and sponges are harmed, little effort is made by humans to preserve them. In areas such as Northeastern Pacific in British Columbia, new legislation for the establishment of marine protected areas is still under development.
Glass sponges are known for “Prolific budding.”When reproducing sexually, Sperm move through the water, making their way to the eggs. After fertilization takes place, Larva mature and are released through the osculum. At the larvae stage, they can swim for several days before they settle on the ocean floor. They then metamorphose, and begin to grow into adult sponges. Glass sponges are also able to reproduce asexually by fragmentation. Glass sponges lack a protective shell, but they do have another way of protecting themselves from predators. Spongivores (organisms that feed only off of sponges) such as certain fish, turtles and invertebrates such as sea stars are examples of predators to these sponges; but sponges can fight back. They use their silica protection as a way to evade being eaten. The spicula on them posses sort of a very sharp, glass – like texture, which stabs other organisms and wards them off. Another way to prevent attack is a toxic chemical glass sponges produce. This substance keeps other organisms out of the way, and surprisingly, it is used today for medical purposes by humans. This chemical glass sponges have acts in preventing a host of human diseases such as AIDS, Cancer, bacterial diseases and other common sicknesses.
As I studied my glass sponge, I learned how unique it is. I think it’s amazing how this animal survives and how different it is from other common organisms. One thing that stood out as I read about my animal, was that the Euplectella aspergillum is known to commonly harbor a pair of crustaceans ( one male, one female). The two shrimp then feed off of the particles inside the sponge and grow, large enough to enclose in a permanent cavity for life, and is given to Newlyweds in Japan as a symbol of bonding.
Author: Marci M
Published: 02/20/2008
Sources:
Infoplease.com Porifera: Class hexactinellida (Glass sponges) Copyright 2000 – 2007 Pearson Education, publishing as infoplease. Atwater, D. and D. Fautin. “Hexactinellida” 2001. (On – line) Animal Diversity Web Copyright 1995 – 2008, The regents of the University of Michigan and its Licensors. Encyclopedia Britannica Online “Glass sponge” Encyclopedia Britannica Copyright 2008 Encyclopedia Britannica Online
Photo Credit: http://www.mareco.org/KML/sponges/pages/pages% 202007/rhabdocalyptus%20dawsoni%201_jpg.htm