the age of fossils with considerable accuracy The Paleozoic era stretched from 650 million years ago to 225 million years ago and it is divided into seven periods The earliest the Ediacarian 650 to 570 million years ago saw the appearance of the first animal fossils They are not easily assigned to any phyla we know today but resembled present day sea anemones worms and jointed limbed creatures By the end of the next period the Cambrian 570 to 500 million years ago invertebrates with hard skeletons had begun to appear They fossilized quite well and most of the phyla we recognize today were represented including trilobites a kind of crustacean brachiopods a type of mollusk and primitive echinoderms sea urchins By the end of the Ordovocian period 500 to 430 million years ago most of the classes of invertebrates we recognize today had established themselves and some such as the echinoderms and nautiloid mollusks had reached their peak of development The shorter Silurian period 430 to 395 million years ago saw the decline of some of the great marine groups but terrestrial invertebrates such as millipedes began to appear on land Arachnids and wingless insects next appeared on land in Anchor damage by small boats visiting coral reefs is just one example of thoughtless harm to the environment the Devonian period and winged insects developed in the Carboniferous period that ended 280 million years ago At this time there was a slow decline in the diversification of life forms and by the end of the Permian period 225 million years ago most groups had 7 1 5 2 3 dramatically declined in fact many had become extinct probably as a result of the cooling of the earth A slow recovery in invertebrate diversity began During the Jurassic period 192 to 135 million years ago most of the modern orders of animals became established and invertebrate classification would have started to 4 An Arctic seabed community during the Cretaceous period 135 to 64 million years ago Organisms included the belemnite 1 ammonite 2 sea anemone 3 gastropod 4 sea urchin 5 bivalve mollusk 6 and crab 7 6 6
look much the same as it does today Development declined in the Cretaceous period Coming to the Tertiary period beginning 64 million years ago most genera and families of invertebrates were established Why are Invertebrates at Risk Many invertebrates are small and some lack sophisticated means of controlling what is inside them Some the marine forms therefore take on an internal environment and salt and water balance that resembles seawater itself Others that live in fresh water may have only the crudest mechanisms to control their osmotic balance how much water and salt they have in their bodies and quite a few simple terrestrial forms cannot survive out of contact with moist soils Thus in many cases such species are unable to prevent their bodies taking in chemical pollutants or are unable to control the loss of moisture if the environment becomes starved of water For those invertebrates that are attached to the sea floor such as corals and sponges changes in seawater levels can be disastrous and changes in temperature cannot be overcome by migratory movements In contrast a number of other endangered invertebrate species such as butterflies and dragonflies are highly mobile but their life cycles may demand a particular type of vegetation or aquatic environment for their larvae to develop in Such environments are frequently damaged or destroyed by human activity especially the development of industries or urban areas The Situation Today Because invertebrates are relatively unknown and often lack the charisma of the large vertebrates such as mammals they do not gain the same amount of public support People are much more likely to contribute to conservation of the panda than an endangered beetle or spider species Furthermore it is difficult to give precise figures on the endangered status of the invertebrates There are probably over 40,000 species of vertebrate but no one knows how many species of invertebrate exist on earth Nearly 1,400,000 have been named but probably many more exist Even so the number of described species is vast and WHAT IS AN INVERTEBRATE it is difficult to get data on how many of these invertebrates are under threat Recent estimates suggest that more than 2,600 are affected but since this is less than twice the number of recognized threatened mammals it is almost certainly an underestimation of the real situation Statistics can be misleading From the figures in the table below in the IUCN Red List 2008 you might think that very few invertebrate species are threatened just 0 5 percent of the total assessed in comparison with 27 percent of mammal species But the number of invertebrate species is huge And of the species studied the percentage assessed as threatened is higher than for mammals Are 35 percent of invertebrates under threat No Scientists could not evaluate all insects as they do mammals so they look at those species that are rarer and more likely to be under threat This display of butterflies and tarantulas is a sad reminder of the continuing trade in animal specimens Numbers of species and percentages of mammals and invertebrates threatened in 2008 Threatened Mammals and Invertebrates No of species in group 5,488 1,400,000 of total in group threatened 27 0 5 Mammals Invertebrates Mammals Invertebrates No of threatened species 1,466 2,639 of total assessed threatened 27 35 7
EW Broad Sea Fan EX CR EN VU NT LC O Eunicella verrucosa The sea fan is a type of coral made up of many simple polyps joined together to form a colony in a fanlike pattern In common with a number of other marine invertebrates sea fans are beautiful and often form major attractions in submarine gardens A slow growing animal it is now under threat from overcollection Sea Sea fans are found in most of the world’s seas and oceans They may grow from shallow water down to the edge of the continental shelves and beyond they are even found at depths of about 13,000 feet 4,000 m in some parts of the world The broad sea fan occurs in the northeastern Atlantic and in the Mediterranean Sea Sea fans are attractive to souvenir hunters and thoughtless collecting by divers has recently reduced their populations around European coasts Sea fans are colonial that is they are made up of many individual polyps or zooids cylindrical forms joined together to form a colony Such a lifestyle is not DATA PANEL only Individual polyps arranged in double rows Diet Minute drifting plankton Breeding Details not well known planula free swimming larva results from fertilization of eggs attaches itself to a new substrate develops into a new colony which produces new zooids Related endangered species Probably many including red coral Corallium rubrum Status IUCN VU Broad sea fan Eunicella verrucosa Family Anthozoa World population Unknown Distribution Mediterranean Sea northeastern Atlantic off coasts of France Ireland U K Mauritania Morocco Portugal and Spain Habitat Rocks and hard surfaces from 49 ft 15 m downward to about 984 ft 300 m Size Colony grows to 11 8 in 30 cm in height Form Plantlike pink or white colony made up of polyps cylindrical sessile attached forms branches in 1 plane 8 unusual in the phylum Cnidaria to which they belong In the broad sea fan the polyps are arranged in two rows along the top and bottom of the branches Each polyp is a miniature animal in its own right and has its own mouth that also serves as its anus The mouth is surrounded by eight minute branching tentacles that are armed with stinging cells The tentacle form is a feature of the order Gorgonacea horny corals and is ideal for sieving the passing water currents to trap microscopic plankton Once collected the prey is manipulated into the gastric cavity via the mouth The gastric cavity extends into a number of tubes that increase the surface area for absorption and digestion of food products Many species of sea fan are virtually two dimensional and they grow so that the colony faces the prevailing currents at right angles thus maximizing their ability to catch prey Growth is slow so some sea fans are very old The colony is supported by an internal horny skeleton made up of a substance called gorgonin The tissue from which the polyps are made is further supported and protected by crystals of calcium carbonate that are embedded within it
BROAD SEA FAN Sperms and eggs develop inside the polyps and fertilization results in the development of a planula free swimming larva which escapes from the parent via its mouth and swims into the sea The planula has a simple structure and is covered with microscopic beating filaments cilia that drive it through the water However the planula can detect a suitable substratum usually rock on which to settle and develop into a new colony producing at first a founder polyp The polyp grows and produces more individual polyps and the necessary skeleton so that a colony structure is developed once again Vulnerability The emerging interest in marine conservation has led to an increased awareness of the effects of overcollection and human disturbance on some marine animals and plants Although it has not been significantly at risk in the past threats to the broad Sea fans come in a variety of colors from deep red yellow and orange to pink and white The polyps spread out their tentacles forming a net with which they catch plankton sea fan have risen recently with the increase in popularity of scuba diving The broad sea fan and its Mediterranean relative red coral Corallium rubrum are both slow growing so they are potentially more vulnerable Unlike the broad sea fan Corallium has been collected for centuries certainly since classical times A rich red color it was considered semiprecious and made into jewelry by the Greeks and Romans it was also thought to be able to ward off illnesses Corallium is now scarce in the Mediterranean and is found only at great depths Collection of the animal seems as yet to be poorly regulated 9
