How many invertebrate phyla

Scientists have formally described approximately 1. New species continue to be discovered, especially among groups that have small body sizes or live in remote areas such as the deep sea, polar ice, or cloud forests. Estimates of the total number of species range from two million to 20 million.

Among these 1. The remaining 1. In terms of species diversity, the invertebrates far outpace the vertebrates. Only five percent of all known living animal species are vertebrates or animals with backbones Fig. The vast majority of animal species 95 percent are invertebrates. Among all animal species, one particular group easily claims the highest number of species: the insects.

Insects—a group within the phylum Arthropoda—have evolved into several millions of species, particularly beetle insects order Coleoptera. Approximately three out of every four animal species is an insect, and one in three animal species is a beetle! Scientists think that 1. What might happen to our pie graph Fig. In general, it is reasonable to think that most of the large mammals and other vertebrates have been found and described, with only a very small proportion such as deep sea fishes remaining as yet unknown.

Many invertebrates are small and dwell in hard-to-reach places. For example, the group of worms called nematodes currently consists of about , described species. However, scientists believe that there may be as many as 1,, species in existence. There are probably thousands upon thousands of invertebrates as yet undescribed. The percentage of animals without backbones is likely only to increase as new species are discovered. Orthonectids and rhombozoans , enigmatic parasites of marine invertebrates may also be lophotrochozoans, but this hypothesis is not yet well supported.

Protostomia and Deuterostomia are the major subgroups of Bilateria bilaterally symmetrical animals. Most multicellular animals Metazoa are bilaterians, but there are four predominantly marine groups that diverged at the base of the metazoan tree: cnidarians jellyfish, corals, sea anemones and their kin , ctenophores comb jellies , placozoans very simple, marine animals , and poriferans sponges.

The relationships among these lineages and Bilateria have proven to be difficult to resolve. Brusca, R. Second Edition. Sunderland, Massachusetts: Sinauer. Chapman, A. Numbers of Living Species in Australia and the World. Canberra, Australia. Edgecombe, G. Higher-level metazoan relationships: Recent progress and remaining questions. Tudge, C. The Variety of Life. Oxford: Oxford University Press. What is EOL? This tiny meiofaunal kinorynch was collected from m deep in the top 1 cm layer of mud from a core taken in the Kermadec Trench by the lost-at-sea Remotely Operated Vehicle Nereus.

This animal was found on Healey Seamount on the Kermadec Ridge at m deep. This worm is in the genus Sabatieria and is in the phylum Nematoda, which are the most common meiofaunal organisms. They can be found living in the sediment between sand grains and some species are parasitic living inside other organisms such as fish and amphipods.

This specimen measures about 1. This is a stunning photo of Pelagonemertes rollestoni Moseley, , an unusual midwater example of the phylum Nemertea — the ribbon or proboscis worms.

This specimen was collected on the Chatham Rise and was the first record of this species to be found in New Zealand waters. Onycophorans are an invertebrate that looks a bit like a caterpillar.

All living velvet worms are terrestrial land-living and prefer to live in dark environments such as caves, under leaf litter, moss and fallen tree trunks in forests. At least 30 species can be found in New Zealand, but only 9 of them have been formally described. We happen to have one sample jar of the species Peripatoides novaezelandiae in our collection from the s, as terrestrial invertebrates are not something we usually collect.

This photo is of a cluster of horseshoe worms, Phoronopsis albomaculata Gilchrist, in Paterson Inlet, Stewart Island. They are a member of the phylum Phoronida, which have a U-shaped gut that loops back so that the anus opens close to the mouth. The feeding tentacles entirely surround the mouth in a horse-shoe shape arrangement called a lophophore. This very tiny 0. It has not yet been identified for us but we think it is a beautiful example of the phylum Platyhelminthes. Lefroyella ceramensis Ijima, is a glass sponge known from northern New Zealand in the phylum Porifera.

Glass sponges have a skeleton made of silicon structures called spicules, which in this species have formed a rigid funnel shaped basket. This animal was found in the Bay of Plenty at m. This worms belongs to another unique phylum, Priapulida. The name of the phylum relates to the Greek god of fertility, because their general shape and their extendable spiny proboscis which you can see here may recall the shape of a penis.