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Page 1 of 3 Feather Star.
 Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form".
They live both in shallow water and in depths as great as 6,000 meters.
Crinoids are characterized by a mouth on the top surface that is surrounded by feeding arms. They have a U-shaped gut, and their anus is located next to the mouth.
Although the basic echinoderm pattern of fivefold symmetry can be recognized, most crinoids have many more than five arms. Crinoids usually have a stem used to attach themselves to a substrate, but many live attached only as juveniles and become free-swimming as adults.
There are only a few hundred known modern forms, but crinoids were much more numerous both in species and numbers in the past. Some thick limestone beds dating to the mid- to late-Paleozoic are almost entirely made up of disarticulated crinoid fragments.
Morphology
 Crinoids comprise three basic sections; the stem, the calyx, and the arms. The stem is composed of highly porous ossicles which are filled with muscular tissue. The Calyx contains the crinoid's digestive and reproductive organs, and the mouth is located at the top of the dorsal cup, while the anus is located peripheral to it. The arms display pentameral symmetry and comprise smaller ossicles than the stem and are equipped with cirri which facilitate feeding by moving the organic media down the arm and into the mouth.
NutritionCrinoids feed by filtering small particles of food from the sea water with their feather like arms.
ReproductionCrinoids reproduce sexually by the males releasing their sperm and the females releasing their eggs into the current where they will develop into a bottom-dwelling non-feeding larval stage and then eventually grow a stalk (in the stalked crinoids), and within 10 to 16 months will be able to reproduce. In some cases the female of the species has been known to temporarly brood the larva.
MobilityMost modern crinoids are free-swimming and lack a stem. Examples of fossil crinoids that have been interpreted as free-swimming include Marsupitsa, Saccocoma and Uintacrinus.
In 2005, a stalked crinoid was recorded pulling itself along the sea floor off the Grand Bahama Island. While it has been known that stalked crinoids move, prior to this recording the fastest motion of a crinoid was 0.6 meters/hour (2 ft/h). The 2005 recording showed a crinoid moving at much faster speeds.
EvolutionThe earliest known crinoids come from the Ordovician. They are thought to have evolved from primitive echinoderms known as Eocystoids. Confusingly, another early group of echinoderms were also the Eocrinoids, but that group is currently thought to be an ancestor of blastoids rather than of crinoids.
The crinoids underwent two periods of abrupt adaptive radiation; the first during the Ordovician, the other after they underwent a selective mass extinction at the end of the Permian period. This Triassic radiation resulted in forms possessing flexible arms becoming widespread; motility, predominantly a response to predation pressure, also became far more prevalent. After the end-Permian extinction, crinoids never regained the morphological disparity they enjoyed in the Paleozoic; they occupied a different region of morphospace, employing different ecological strategies from those that had proven so successful in the Paleozoic.
The long and varied geological history of the crinoids demonstrates how well the echinoderms have adapted to filter-feeding. The fossils of other stalked filter-feeding echinoderms, such as blastoids, are also found in the rocks of the Palaeozoic era. These extinct groups can exceed the crinoids in both numbers and variety in certain horizons. However, none of these others survived the crisis at the end of the Permian period.
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Koh Racha Yai:
Dive sites at Koh Racha Yai:
Bungalow Bay, Home Run, Lucy's reef, Eastern coast, Siam Bay etc.
Bungalow Bay:
Bungalow bay is situated on the west coast of Koh Racha Yai. Average depth is around 17 meters / maximum depth 30 meters. This site can be split; you can opt to follow either of the bay's shorelines.
The rocky formations visible above the surface continue underwater, with a good presence of reef fish. Around the rocks swim surgeonfish and fusiliers, while below you can see inquisitive paired goatfish, nudibranchs, urchins and plenty of blue spotted ribbontail rays.
Eastern Coast:
The first site begins at the northeast tip of Koh Racha Yai and heads south, the second follows the southeastern apex. Average depth is around 12 meters / maximum depth 22 meters. This is a very popular diving destination and is suitable for all levels of diver. There's also enjoyable snorkeling around the rocks in the shallow waters off the islands coastline.
The shallower sections of the reef feature table corals and smaller examples of leaf corals; the deeper waters have similar species, but larger. There are many featherstars, lionfish, puffers and a few parrotfish and wrasse.
The site's southern end has the bonus of encountering mating cuttlefish along with a greater display of reef creatures, including good sized titan triggerfish, moray eels and octopus; plus on a smaller scale, a better selection of colorful fish and invertebrates. Leopard sharks and hawksbill turtles are occasionally seen around the coastline.
Koh Racha Noi:
Dive sites at Koh Racha Noi:
The rock, North Pinnacle, Kanpela point. The beach, South pinnacle.
Northern Tip:
Average diving depth is around 17 meters / maximum diving depth 30 meters at Koh Racha Noi. A very reasonable multilevel dive site, which takes divers around pinnacles and large rocks. There is a fair display of hard corals and soft corals, and the usual reef fish are present in reasonable quantities.
If you are lucky you should be able to sight small reef sharks, but the main attraction is probably the presence of large bullet-head parrotfish, and the magical manta rays. However, diving here can be demanding because of the currents.
Southern Tip:
Average diving depth around 23 meters / maximum diving depth 40 meters +. This is a really great dive for the experienced diver. The underwater terrain is similar to that around the island's northern tip, but much deeper, the shallowest part of any consequence is at 18 meters.
Fine soft corals highlight the smooth sided boulders. Crinoids and featherstars are well represented. There are fairly plentiful, reasonably sized fish, including lionfish, parrotfish, wrasse and triggerfish, as well as large visiting pelagic's such as barracuda, rainbow runners and trevally.
Manta rays and marbled rays frequently seen here as are whale sharks, although with slightly less regularity. All in all, this site can be compared with some sites found around Ko Similan Marine National Park, Thailand.
Phi Phi Islands:
Dive sites at phi Phi Islands:
Koh Bida Nok, Koh Bida Nai, Maya Bay.
The spectacular Phi Phi islands lie in the mouth of the Phang Nga Bay and form the Haad Nopparattara Mo Koh Phi Phi National Park. White limestone crags splashed with greenery jut vertically up wards out of the clear turquoise waters to tower over magnificent sandy beaches.
You will see an amazing variety of fish life, beautiful soft corals, staghorn coral gardens and huge sea fans. On the sandy bottom, leopard sharks can be found resting. Diving in the Phi Phi islands is an experience not to be missed. From shallow sheltered bays to wall and drift dives, there's something for every level of diver.
Visibility ranges on average from 10-25 meters with weak to moderate currents. Water temperature remains a fairly constant 27 - 30C throughout the year, depths from 10 - 30 meters, and, there's plenty of marine life! For non divers the Phi Phi area offers superb snorkeling, with the opportunity to see not only beautiful coral gardens but also some of the larger fish at shallow depths.
Koh Doc Mai:
Koh Doc Mai is a small island off Phuket, In Thai language Doc Mai means "Tiny Flower".
When you scuba dive here you will see why this island has this name. Koh Doc Mai's underwater area is famous for its hard and soft corals covering the vertical outcrop. Also famous for its circumnavigational wall dropping down to 30 meters.
Koh Doc Mai also has a few caves were you will find some weird and wonderful reef species. Perfect for macro photographers who want to spot that little yellow seahorse. Lots of soft and hard corals, white eyed moray eels, schools of trevally, trigger fish and lots lots more.
For more detailed dive site information: Koh Doc Mai, Kata Beach, King Cruiser, Koh Poo, Koh Racha Yai, Koh Racha Yai Bays, Koh Racha Noi, Anemone Reef, Similan Islands,Anita's Reef, Beacon Reef, Boonsung Wreck, Boulder City, Breakfast Bend, Christmas Point, Deep Six, Donald Duck Bay, East Of Eden, Elephant Head Rock, Honeymoon Bay, Koh Bon, Richelieu Rock, Rocky Point, Shark Fin Reef, Tachai Pinnacle, Tachai Reef, Turtle Rock, Waterfall Bay, West Of Eden.
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Day Trip Diving