We have multiple research teams working together on our Southwest Pacific expedition to document the incredible biodiversity of this relatively unexplored marine environment. Our invertebrates experts - Steve Keable and Anna Murray from the Australian Museum and Severine Hannam from Auckland Museum - have made some exciting observations but they’ve had to look extra carefully to find what they’re searching for.

Many of the invertebrate species the team are looking for are small and difficult to see, so they find them by collecting the surfaces these species live on. A good example of this is the presence of commensal animals living on other invertebrates such as crinoids (feather stars), echinoids (sea urchins), holothurians (sea cucumbers) and gorgonians (sea fans). (Commensal animals basically benefit by living on another species, without causing any harm to that species.)

In this case the smaller invertebrates are using the protection of their host for safety from predators, as well as benefiting from a ready-made food supply.

Many of these commensals are shrimps, crabs, polychaetes (marine worms), or small ophiuroids (brittle stars), but we have also found tiny clingfish sheltering inside the arms of crinoids.

Crinoids are these rather beautiful fan-like organisms  (hence their other name ‘feather stars’) and it can be extra hard to see what is living on them, because the commensals often take on the colouration of their hosts to help them blend in.

A dark green-black feather star yielded two black alpheid shrimps (male and female), while on a yellow, brown and white coloured crinoid (Oxycomanthus bennetti) we found yellow-brown-and-white striped galatheoid squat lobster (Allogalathea babai), a small brown-and-yellow striped clingfish (Discotrema crinophila) as well as several dark-brown-and-transparently striped shrimp (Laomenes sp.). Some hosts have more than their fair share of hangers-on!