Critters of the Week: invertebrate phyla

Every animal on Earth belongs to one of about 35 groups called phyla. In biology, a phylum (plural: phyla) is a taxonomic rank below kingdom and above class.

Taxonomic rank. Photo credit: Peter Halasz

The NIWA Invertebrate Collection holds specimens from 23 invertebrate phyla and has examples of at least 6369 species, and that is just a glimpse of life in our world oceans.  The number of species per phylum is always changing, as more animals are discovered. In just the past three years NIWA biologists have discovered 141 new marine creatures.

NIWA discovers 141 new creatures

Invertebrate phyla

Below we feature a selection of species from each of the invertebrate phyla in our collection.

Acanthocephala – the spiny headed worms.

These are parasites usually found in the guts of fish. We have one example in our collection, but it is pretty tiny and we sadly don’t have a good photo of it! An example can be seen on this Danish researcher’s website:

The fascinating inner life of the cod

Annelida – the segmented worms

The fireworm, Chloeia inermis Quatrefages, 1865, is a member of the phylum Annelida – the segmented worms. This specimen was collected on the Challenger Plateau at 498 m. [Peter Marriott, Oceans Survey 20/20 Chatham-Challenger Expedition]

Arthropoda – insects, spiders and crustaceans

Pycnoplax victoriensis (Rathbun, 1923), collected from Challenger Plateau at 657 m, is a crab species that belongs to the phylum Arthropoda. [Peter Marriott, Oceans Survey 20/20 Chatham-Challenger Expedition]

Brachiopoda – the lamp shells

A lamp shell, Dallina triangularis Yabe & Hatai, 1934 from phylum Brachiopoda. This specimen was found on Rumble II Seamount on the Kermadec Ridge at 1108 m deep. [Rob Stewart, Ocean Survey 20/20 - NZASMS]

Bryozoa – lace corals, moss animals

This pink lacey specimen is Hippellozoon novaezelandiae (Waters, 1895) and was collected in the Bay of Islands at 117 m deep. It is in the phylum Bryozoa, aptly sometimes known as lace coral for obvious reasons. [Peter Marriott, Ocean Survey 20/20 – Bay of Islands]

Chaetognatha – Arrow worms

This is a drawing of an arrow worm species Pterosagitta draco (Krohn, 1853), which is cosmopolitan, occurring in warm-temperate seas round the globe. It is from phylum Chaetognatha, which are exclusively marine planktonic predators. They all have long curved chitinous hooks projecting from each side of the head, and these are seizing prey along with multiple rows of teeth! [Image credit: Figure 2 from Lutchinger, S. (1993). The marine fauna of New Zealand: Chaetognatha (Arrow worms). New Zealand Oceanographic Institute memoir 101. P14]

In 1993 Austrian researcher Dr. Sigrid Lutchinger wrote a memoir about the New Zealand species published in the New Zealand Oceanographic Institute (now NIWA) Biodiversity Memoir series.

Chordata – contains the vertebrates and some other strange groups that creep into our collection, such as the Tunicates and the Lancelets

This strange creature is a Lancelet or Amphioxus. They are in subphylum Cephalochordata and split off from the vertebrates 520 million years ago. This specimen of Branchiostoma lanceolatum (Pallas, 1774) was collected from 65 m deep in the Bay of Islands and is just a couple of centimetres long. [Peter Marriott, Ocean Survey 20/20 – Bay of Islands]

Cnidaria – the stinging animals (jellyfish, anemones, corals)

This specimen of Flabellum aotearoa Squires, 1964 was found in the Bay of Islands at 204 m. It is a stony coral in the phylum Cnidaria. You can see tentacles extending out of its stony skeleton in this image, which contain stinging cells (cnidocytes), a character of the phylum. [Peter Marriott, Ocean Survey 20/20 – Bay of Islands]

Ctenophora – comb jellies

We don’t have any fabulous photos of our ctenophores, the comb jellies, so we’ve included a link to a video of comb jellies from the Plankton Chronicles – a very nice explanation of these beautiful planktonic predators.

Iridescent Ctenophores video

Echinodermata – spiny skinned animals (sea urchins, seastars, sea cucumbers, sea lillies and brittle stars)

This spiny sea star is called Coronaster reticulatus, and was found on Rumble V Seamount in the Kermadec Ridge at 463 m. It belongs to the class Asteroidea, one of the five classes of animals in the phylum Echinodermata. [Rob Stewart, TAN1213 NIRVANA survey]

Echiura – spoon worms

An unidentified bonellid echiuran (spoon worm) collected from the Tangaroa Seamount in the Kermadec Ridge at 866 m (left image), and the forked proboscis of an echiuran trailing across the rocks on the seabed to feed on Clark Seamount, Kermadec Ridge, 1200 m (right image). [Owen Anderson, Vulnerable Deep-Sea Communities (left image)] [DTIS Camera, Vulnerable Deep-Sea Communities (right image)]

Entoprocta – Goblet worms, or nodding animals

Entoprocts, sometimes called Kamptozoa, are very small (0.5-5 mm) goblet shaped animals with a crown of tentacles, which are rarely seen and only 150 species have been described worldwide. This line drawing is of some New Zealand species of Pedicellina, the most common genus. [Image credit: taken from Gordon, 2009 p. 299 originally by Ryland, 1965]

Hemichordata – Acorn worms

This is just a couple of centimetres fragment (the head end) of an acorn worm from the family Ptychoderidae (left image). It was collected from 644 m deep in the Tauranga Canyon, Bay of Plenty, and is a member of the phylum Hemichordata. These animals make characteristic spiral tracks in the mud on the seafloor as can be seen on this seafloor image from the Challenger Plateau (right image).

[Rob Stewart, NIWA, Vulnerable Deep-Sea Communities (left image), DTIS Camera, NIWA, Oceans Survey 20/20 Chatham-Challenger Expeditions]

Kinorhyncha – mud dragons

This tiny meiofaunal kinorynch was collected from 9000 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. [Daniel Leduc, NIWA, HADES Kermadec Trench]

Mollusca – squid, octopus, snails and clams

This beautiful jewel squid Pyroteuthis margaritifera (Rüppell, 1844) is a cephalopod in the phylum Mollusca. Molluscs all have shells, but the remnant shell of a squid (its pen) is internal in most cases so you can’t see it here. This animal was found on Healey Seamount on the Kermadec Ridge at 1150 m deep. [Rob Stewart, NIWA, Ocean Survey 20/20 - NZASMS]


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 1.5 mm. [Daniel Leduc]

Nemertea – ribbon worms

This is a stunning photo of Pelagonemertes rollestoni Moseley, 1875, 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.  [Owen Anderson, Fisheries Oceanography II]

Onychophora – velvet worms and peripatus

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 1960s, as terrestrial invertebrates are not something we usually collect. This brochure from the Department of Conservation has some important information about how we can help to protect our native onycophorans and their forest habitats from disturbance: Peripatus: A guide to New Zealand's velvet worms/ ngaokeke

Phoronida – horseshoe worms

This photo is of a cluster of horseshoe worms, Phoronopsis albomaculata Gilchrist, 1907 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. [Image credit: Karen Gowlett-Holmes, Figure in Gordon, 2009, p 268]

Platyhelminthes – flatworms

This very tiny (0. 5 cm) flatworm was collected from 125 m deep in the Bay of Islands. It has not yet been identified for us but we think it is a beautiful example of the phylum Platyhelminthes. [Peter Marriott, Oceans Survey 20/20 - Bay of Islands]

Porifera – sponges

Lefroyella ceramensis Ijima, 1927 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 1363 m. [Owen Anderson, Vulnerable Deep-Sea Communities]

Priapulida – Penis worms

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. This specimen was collected from the Chatham Rise at 472 m. [Peter Marriott, NIWA]

Sipuncula – Peanut worms

This selection of sipunculid worms were found in muddy sediment in the Kaikoura canyon at 1079 m deep. They are recognisable from their little tube or siphon that use to collect their food (organic detritus from the surrounding mud and water), and their lack of segmentation or bristles. [NIWA]

All animals in 35 photos

This link from the BBC nicely explains the types of animals that we can find in each phyla in the ocean:

BBC Earth - All animal life in 35 photos

You will recognise some, but there are a lot of very strange animals out there. Many of these phyla also occur on land and in freshwater.