Ryan Photographic - Crinoidea - Feather Stars


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Class Crinoidea

The Class Crinoidea consists of the sea lilies which are typically stalked and attached to the bottom and the feather stars which are free-swimming. I have yet to photograph a sea lily and in view of the depths they typically inhabit I am unlikely to do so. Crinoids have an ancient lineage, the fossil record going back as far as the Ordovician 450 million years ago.

Like the other Echinoderm classes they are pentamerously symmetrical but only in the very young individuals is this immediately obvious. As they grow they add new arms until they reach their adult form. Many species possess jointed cirri which enables them to hold onto the substrate and most of them can swim in a wondrously elegant and stately manner. One set of arms beats down while the other moves back upwards for the next down stroke. The name feather star comes from the shape of their arms which possess a central stalk with pinnules coming off it. Thse pinnules sub-divide. They feed using their arms - organic particles stick to secreted mucus and the tube feet scrape it off the pinnules and into the ambulacral groove. Interestingly the groove is open - and this allows a multitude of thieves to steal from them. Perhaps because they have had so long to co-evolve with feather stars they are infested with a multitude of parasites - these include snails, polychaete worms, shrimp and even the crinoid clingfish which apparently forgoes the groove and feeds on small invertebrates. On occasion it is possible to see myzostomes, tiny circular aberrant polychaetes moving over the surface of the central disk. These guys are extraordinarily cool and I wish I had photos of them to show you.

Few things seem to feed on the feather stars themselves but as they are basically all bone this isn't that surprising. I have seen a large puffer looking guilty with a small piece of crinoid stuck around its mouth so predation does occur. If you promise to come back I'm going to send you to a wonderful write up about feather stars.

I once tried to study feather star taxonomy because I wanted to identify the feather star symbionts. I wasn't very good at it - but it was replete with cool words like syzygy - I have been trying to get it down in Scrabble but thus far without success.

Successful identification of feather stars often requires the skeleton. The identifications here are all tentative. Expert advice would be appreciated.

 

Colobometra perspinosa Very spiny feather star

Colobometra perspinosa Very spiny feather star, Beqa, Fiji

ECHIN 539 Colobometra perspinosa (ID tentative) Very spiny feather star, Beqa, Fiji.

Comanthus parvicirrus Common crevice featherstar

Comanthus parvicirrus Common crevice featherstar (ID tentative) Kri Eco, Raja Ampat

ECHIN 8671 Comanthus parvicirrus Common crevice featherstar (ID tentative) Kri Eco, Raja Ampat.

Comaster schlegelii Schlegel's feather star

Comaster schlegelii (ID tentative) Kri Eco, Raja Ampat

ECHIN 8546 Comaster schlegelii Schlegel's feather star (ID tentative) Kri Eco, Raja Ampat.

Comaster schlegeli

ECHIN 8547 Comaster schlegelii Schlegel's feather star (ID tentative) Kri Eco, Raja Ampat.

Comaster schlegeli Schlegels Feather star (ID tentative), Kadavu, Fij

ECHIN 7079 Comaster schlegelii Schlegel's Feather star (ID tentative), Kadavu, Fiji.

Comaster schlegelii Schlegel's Feather star Matamanoa, Fiji

ECHIN 3500 Comaster schlegelii? Schlegel's Feather star Matamanoa, Fiji.

Himerometra robustipinna Robust feather star

Himerometra robustipinna, Robust feather star, Kri Eco, Raja Ampat

ECHIN 8188 Himerometra robustipinna (ID tentative) Robust feather star, Kri Eco, Raja Ampat.

Robust feather star arm

ECHIN 8566 Himerometra robustipinna (ID tentative) Robust feather star arm detail, Kri Eco, Raja Ampat.

Himerometra robustipinna (ID tentative) Robust feather star arm detail, Kri Eco, Raja Ampat

ECHIN 2385 Himerometra robustipinna (ID tentative) Robust feather star arm detail, Kri Eco, Raja Ampat.

Oxycomanthus bennetti Bennett's feather star

Oxycomanthus bennetti (ID tentative) Bennett's feather star Kri Eco, Raja Ampat

ECHIN 1235 Oxycomanthus bennetti (ID tentative) Bennett's feather star, Fiji.

Oxycomanthus bennetti (ID tentative) Bennett's feather star Kri Eco, Raja Ampat

ECHIN 8550 Oxycomanthus bennetti (ID tentative) Bennett's feather star Kri Eco, Raja Ampat.

Oxycomanthus bennetti Bennett's feather stars (ID tentative)  Raja Ampat, West Papua

ECHIN 0966 Oxycomanthus bennetti Bennett's feather stars (ID tentative) Raja Ampat, West Papua.

Oxycomanthus plectrophorum Red featherstar

Oxycomanthus plectrophorum featherstar

ECHIN 1240 Oxycomanthus plectrophorum Red featherstar, Fiordland, New Zealand.

Stephanometra species Feather star

Stephanometra species Feather star, Raja Ampat, West Papua

ECHIN Stephanometra species Feather star, Raja Ampat, West Papua.

Stephanometra species Feather star, , Raja Ampat, West Papua

ECHIN 2410 Stephanometra species Feather star, Raja Ampat, West Papua.

Stephanometra species, Feather star, Kadavu, Fiji

ECHIN 7071 Stephanometra species, Feather star "walking" over bottom, Kadavu, Fiji

Stephanometra species Feather star on seafan, Raja Ampat, West Papua

ECHIN 0646 Stephanometra species Feather star on seafan, Raja Ampat, West Papua.

Feather star close up

ECHIN 956 Stephanometra species, central disk detail, Fiji.

Featherstar arm pattern, Raja Ampat, West Papua

ECHIN 1944 Stephanometra? Feather star arm pattern, Raja Ampat, West Papua.

Unidentified feather stars

Featherstar on seafan, Kri, Raja Ampat, West Papua

ECHIN 0167 Featherstar on seafan, Kri, Raja Ampat, West Papua.

Featherstar on sponge, Raja Ampat, West Papua

ECHIN 0406 Featherstar on sponge, Raja Ampat, West Papua.

Unidentified featherstar Kri Eco, Raja Ampat

ECHIN 8668 Unidentified featherstar Kri Eco, Raja Ampat. I think the bumps on the pinnules are where eggs or sperm are stored.

Unidentified feather star Kri Eco, Raja Ampat

ECHIN 8559 Unidentified feather star Kri Eco, Raja Ampat - its is possible the bumps on the pinnules contain gametes.

Young featherstars

soft coral featherstar

ECHIN 1244 Tiny Soft coral featherstar, Fiji.

Young featherstar Taveuni,  Fiji

ECHIN 4522 Young featherstar Taveuni, Fiji.

 

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