Just the Facts

First, we got an octopus, then a couple more arrive.

We are being observed by three octopuses or three octopede. Either is correct, but octopi is wrong.
Reference source - Chambers Twentieth Century Dictionary, 1964 (The oldest dictionary I could find).

  1. Octopi
  2. Octopuses
  3. Octopede


Now we got things with hard shells.

A crustacean, an echinoderm and a bivalve.

Crustaceans have an external, jointed skeleton which covers the body and limbs like a suit of armour (crabs, crayfish).

Echinoderms are spiny-skinned animals (sea urchins, sea cucumbers, sea stars). In sea cucumbers the skin spines/plates are small and deeply embedded in the skin.

A bivalve has two shell sections (such as a scallop), not one as do the univalves (nudibranchs, pauas and shield shells).

  1. A reef star, a nudibranch and a paua.
  2. A paddle crab, a sea cucumber and a scallop.
  3. A crayfish, a kina and a shield shell.

Put them all in the pot? No way, that nudibranch is my friend.


Jumping shellfish!

Scallops can flap their shells to propel themselves through the water. Their eyes are lined all around the edge of their shells. 

  1. scallop
  2. horse mussel
  3. bluff oyster


Yike, that's big!

Bryozoa are tiny animals living in colonies of calcium houses - they may appear like a rough coat of paint on rock, or like a frilly lace coral.

Chiton or coat-of mail shells are molluscs which cling to rocks.

A transparent tube about a metre across and three metres long would be a salp.

  1. bryozoa
  2. snakeskin chiton
  3. salp


In the weed line.

Cute wee fish which can be variously emerald green, weedy yellow or silver, but all having a single spot on their side, would be female spottys, notolabrus celidotus. Spottys are all born female and tend to take on the colour of the weed they live in until they grow up. At that time the dominant female changes sex and her single dot breaks up and moves onto the top of his back as a blotch.

  1. female
  2. spottys
  3. notolabrus celidotus sp.


Still in the weed line.

The sex roles in hippocampus abdominalis (sea horse) are curiously reversed from normal. The female deposits eggs in the brood pouch of the male with a sort of ovipositor - a small penis-like thing sticking out of the bottom of her abdomen. This sea horse was a female.

  1. female
  2. male
  3. juvenile


Canyon country.

A dark grey ray with white spots along its sides is a short-tailed stingray.

A ray having a prominent ridge around its head is an eagle ray.

A ray with a tail twice as long as its body is a long-tailed stingray.

  1. a short-tailed stingray, a long-tailed stingray, an eagle ray
  2. a short-tailed stingray, an eagle ray, a long tailed stingray
  3. an eagle ray, a short-tailed ray, a manta ray


Fat black lumps.

A black lump about 150 mm (6 inches) long, having a velvety feel, with a back that splits open when stroked, is a shield shell. It was snoozing because it is a nocturnal animal - at night it has feelers sticking out and looks like a wide-awake black lump.

  1. a snoozing shield shell
  2. a paua that has lost its shell
  3. a paua growing a new shell
  4. a large sea slug


How did you rate then? Got them all correct and feeling smug? Quite right, you should do.

How about those folk who didn't do so well or want to dispute the issue? Apart from me being in a position of power here (Dive Guide site manager, can do no wrong, etc.) send me your thoughts. And hey, if you want to recommend other tricky little quiz questions, I would be happy to consider suggestions. I hope that your next dive will be more interesting for you as you go around waking up shield shells, saying 'hi' to octet's of octopede, and chatting up the little girl spottys.

Have fun diving,


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