Critter of the Week: Barentsia - Entoprocta – Goblet worms, or nodding animals

What’s in a name? That’s the challenge facing marine biologists when studying ecology or invasive species – they need to know the names of the species or their work is unrepeatable and unverifiable.

This week’s Critters include a large branching hydroid (phylum Cnidaria), to which is attached two curious, and little-known, invertebrates. The bright white one on the left is the moss animal Bicrisia edwardsiana (phylum Bryozoa) and the yellow one on the right is the nodding animal Barentsia discreta (phylum Entoprocta). Both species are widespread in the South Pacific. 

A large branching hydroid (phylum Cnidaria), plays host to two curious, and little-known, invertebrates. The fluffy, bright white one on the left is the moss animal Bicrisia edwardsiana (phylum Bryozoa) and the yellowish one in the middle right is the nodding animal Barentsia discreta (phylum Entoprocta). [Crispin Middleton]

Hydroids are delicate ‘stingers’, related to the larger corals and jellyfish. Bryozoans and entoprocts used to be included in the same phylum but are now known, from their structure, life history and genes, to be distinct but on the same general branch of the animal family tree. This branch (Lophotrochozoa) also includes shellfish and various wormy groups. But the animal family tree is only part of the larger picture.

A close up on the rarely seen entoprocts, Barentsia discreta, the whole colony would be just 1.5 cm across. [Crispin Middleton]

A Higher Level Classification of All Living Organisms

To celebrate last week’s International Day for Biological Diversity we posted an important new paper – “A Higher Level Classification of All Living Organisms” by a host of esteemed authors and based on a community of over 3000 taxonomists work worldwide. This has just been released and can be accessed for free online here

A Higher Level Classification of All Living Organisms

The consensus classification is the product of a collaboration among taxonomic experts and bioinformatics managers, linking the Catalogue of Life, Integrated Taxonomic Information System, World register of Marine Species, SeaLifeBase, Worldfish, Algaebase and Dictionary of Fungi. Collectively, all of these providers list all species of life and, thanks to the classification just published, will be unified in their use of species names and the management classification that accommodates them.

Why is biological classification so important? Basically, it’s a tool to deal with the vast diversity of life – the approximately 1.9 million described species of organisms, and those yet to be discovered. Importantly, the point of classifying organisms in a ‘system’ (which is why biological classification and naming are called ‘systematics’) is to show their genetic relatedness in a great big family tree of life.

And what shape does the tree of life take these days? Gone is the idea of classifying all of life into two kingdoms – animals and plants. The new consensus classification organises life into seven kingdoms! Two of them are ‘bacterial’, or rather prokaryotic, and the remainder are eukaryotic, comprising protozoans, Chromista, true plants, fungi and animals.  To revise your basic biology knowledge ‘Prokaryote’ (Greek pro-, before, and karyon, nucleus), refers to cells in which a nucleus is lacking (Bacteria and Archaebacteria). The other five kingdoms are ‘eukaryotic’ because cells have a nucleus (eu-, true).  

NIWA’s Dennis Gordon examining specimens in the NIWA Invertebrate Collection. [Dave Allen]

NIWA’s Dennis Gordon is one of the authors of the paper and he tells us more about the new classification below. We have included hyperlinks to explain more about some of these weird but fascinating groups: “Protozoa is basal among the eukaryote kingdoms in that it includes the ancestors of the other four kingdoms and comprises such forms as euglenas, trypanosomes, amoebas, collar flagellates, Giardia, some other zooflagellates, and microscopic forms like Microsporidia that straddle the boundary between protozoans and fungi. Shelly foraminifera and radiolaria, and the ciliates, dinoflagellates, and parasitic sporozoa, now all belong, along with water moulds and the golden and brown seaweeds and diatoms, to kingdom Chromista, united by molecular and ultrastructural criteria.

The plant kingdom in the 21st century is restricted to glaucophyte algae, green and red algae, and land plants. True fungi include chytrids and the familiar pin moulds, yeasts, sac fungi, toadstools, rusts and their relatives. Excluded from kingdom Fungi are the water moulds and downy mildews as well as the plasmodiophoras, labyrinthulid slime nets, and thraustochytrids (all Chromista). The animal kingdom includes everything from sponges to vertebrates.”