The largest biosilica structures on earth, which is 3m, is the Monorhaphis Chuni (hexactinellida). Many of the largest hexactinellids are as wide as they are tall. The length of hexactinellids varies from 0.2 to 5 feet (0.5cm to 1.5m). The oldest fossil record of multi-cellular animals on Earth were left by Hexactinallids. Their fossilized skeletons now make up the outcrops upon which many castles are built from; France through southern Spain, Poland, Romania, and Germany. Hexactinellids tissue is generally creamy yellow to white.
Complex behavior of sponges aren’t noted but hexactinellids can respond to mechanical or electrical stimuli by instantly shutting down the feeding current. The trabecular reticulum acts like a nervous system for them. Depths greater than 1,000 ft. (304.8m) are where the majority of hexactinellids live. These species are found at depths accessible by scuba divers like Antarctica, the northeastern Pacific, New Zealand, and some caves in the Mediterranean. Cold water (30-52 F. or 2-11), relatively high levels of dissolved silica, and low light intensity are what these habitats have in common.
Although some hexactinellids grow on fused skeletons of dead sponges, and others still live over soft sediments, many require a firm substratum, such as rocks, for attachment. Though not numerous, the latter group support themselves on struts made of bundles of long spicules that protect down into the sediment. Most hexactinellid sponges generally inhabit areas well out of reach of human activity. Several city blocks in area of trawlers have damaged reefs of hexactinellid sponges in the continental shelf of the northeastern Pacific in British Columbia. Marine protected areas around these reefs is under development of new legislation for the establishment. Species of hexactinellid isn’t listed by the IUCN.
Majority of sponges pump water through the choansome which glass sponges are thought to filter food from. Sponges produce sufficient organic carbon for themselves and their host which it is thought that the organisms coating. Structures equivalent to coenocytes, the collar body, lacks a nucleus, in hexactinellid sponges and in most species examined so far the collar body is enveloped by extensions of the orbicular synctium 9the primary and secondary reticula), which do most of the particulate capture and uptake.Hexactinellids get protected from many predators by their siliceous skeleton, but at lest one asteroid species is not deterred.
Facts that really stood out and caught my attention were… A seasonal reproductive period is lacked by most hexactellids because of their deep water habitat. When studied in a laboratory settings, larva swim slowly to the surface of dishes in left-handed rotations which is clockwise. They begin and transform into juvenile sponges, within 12 hours of release from the parent sponge, although they can swim for several days.
Author: Mona V.
Published: 02/20/2008
Sources:
http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Monorhaphis_chuni.html http://www.answers.com/topic/monorhaphis-chuni http://www.springerlink.com/content/b726134583617rqk/ Photo Credit: Michel Roux http://scienceblogs.com/deepseanews/2007/07/post_5.php