THE OCEAN DEEP

Holothuroidea are a class of marine animals (phylum Echinodermata) with an elongated body and leathery skin, which is found on the sea floor worldwide. Many holothurian species and genera, informally known as sea cucumbers, are targeted for human consumption. The harvested product is also known as trepang, bêche-de-mer, balate, or sea slug. The body contains a single, branched gonad. Like all echinoderms, sea cucumbers have an endoskeleton just below the skin, calcified structures that are usually reduced to isolated microscopic ossicles (or sclerietes) joined by connective tissue. These can sometimes be enlarged to flattened plates, forming an armour. In pelagic species such as Pelagothuria natatrix (Order Elasipodida, family Pelagothuriidae), the skeleton and a calcareous ring are absent. Holothuroidea are generally scavengers, feeding on debris in the benthic zone of the ocean. Exceptions include pelagic cucumbers and the species Rynkatropa pawsoni, which has a commensal relationship with deep-sea anglerfish. The diet of most cucumbers consists of plankton and decaying organic matter found in the sea. Some sea cucumbers position themselves in currents and catch food that flows by with their open tentacles. They also sift through the bottom sediments using their tentacles. These incredible creatures communicate with each other through sending hormone signals through the water which others pick up.
A remarkable feature of these animals is the catch collagen that forms their body wall. This can be loosened and tightened at will and if the animal wants to squeeze through a small gap it can essentially liquefy its body and pour into the space. To keep itself safe in these crevices and cracks the sea cucumber hooks up all its collagen fibres to make its body firm again. Some species of coral-reef sea cucumbers within the order Aspidochirotida can defend themselves by expelling their sticky cuvierian tubules (enlargements of the respiratory tree that float freely in the coelom) to entangle potential predators. When startled, these cucumbers may expel some of them through a tear in the wall of the cloaca in an autotomic process known as evisceration. Replacement tubules grow back in one-and-a-half to five weeks, depending on the species.The release of these tubules can also be accompanied by the discharge of a toxic chemical known as holothurin, which has similar properties to soap. This chemical can kill any animal in the vicinity and is one more way in which these sedentary animals can defend themselves. They can be found in great numbers on the deep sea floor, where they often make up the majority of the animal biomass. At depths deeper than 5.5 mi (8.8 km), sea cucumbers comprise 90% of the total mass of the macrofauna.Sea Cucumbers form large herds that move across the bathygraphic features of the ocean, hunting food. The body of some deep water holothurians is made of a tough gelatinous tissue with unique properties that makes the animals able to control their own buoyancy, making it possible for them to either live on the ocean floor or to float over it to move to new locations with a minimum of energy, for instance Enypniastes eximia, Peniagone leander and Paelopatides confundens.
In more shallow waters, sea cucumbers can form dense populations. The strawberry sea cucumber (Squamocnus brevidentis) of New Zealand lives on rocky walls around the southern coast of the South Island where populations sometimes reach densities of 1,000 animals per square metre. For this reason, one such area in Fiordland is simply called the strawberry fields. Sea cucumbers extract oxygen from water in a pair of 'respiratory trees' that branch off the cloaca just inside the anus, so that they 'breathe' by drawing water in through the anus and then expelling it. A variety of fish, most commonly pearl fish, have evolved a commensalistic symbiotic relationship with sea cucumbers in which the pearl fish will live in sea cucumber's cloaca using it for protection from predation, a source of food (the nutrients passing in and out of the anus from the water), and to develop into their adult stage of life. The largest American species is Holothuria floridana, which abounds just below low-water mark on the Florida reefs.
Visitors to Guam often encounter the local variation, called balate, which litters the sea floor all around the island, including in water as shallow as 3 feet. These jet black sea cucumbers are normally 10-12 inches long, 1.5-2.0 inches in diameter and are often curled up, partially covered with sand from the sea floor.
The most common way to separate the subclasses is by looking at their oral tentacles. Subclass Dendrochirotacea has 8-30 oral tentacles, subclass Aspidochirotacea has 10-30 leaflike or shieldlike oral tentacles, while subclass Apodacea may have up to 25 simple or pinnate oral tentacles and is also characterized by reduced or absent tube feet, as in the order Apodida.

Beaked seasnake (Enhydrina schistosa, also known as the hook-nosed sea snake, the common sea snake, and the Valakadyn sea snake ) is a species of sea snake.
It is found in the Arabian Sea and Persian Gulf (off Oman), south of the Seychelles and Madagascar, the seas off South Asia (Pakistan, India and Bangladesh), Southeast Asia (Myanmar (formerly Burma), Thailand, Vietnam), and Australia (Northern Territory and Queensland) and New Guinea.
Rostral more deep than broad, in contact with four shields; frontal more long than broad, shorter than the parietals; nasals in contact with the two anterior labials; sometimes partially divided; one pre- and one or two postoculars; temporals l—3; seven or eight upper labials, fourth or third and fourth entering the eye, the last sometimes divided; anterior chin-shields rather indistinct, separated. Scales with a tubercle or keel, in 50—70 rows; ventrals 230—314, slightly enlarged. Uniformly dark grey above; sides and lower parts whitish. Young specimens olive or grey with black transverse bands, broadest in the middle. Length of head and body 1110 mm.; tail 190 mm.
The name valakadyn is from the Malayalam and Tamil word Vala kadiyan meaning net biter.
Habitat and behaviour
These snakes are generally found in the coast and coastal islands of India. They are amongst the most common of the 20 kinds of sea snakes found in that region.
They are active both during the day and at night. They are able to dive up to 100 m and stay underwater for a maximum of five hours before resurfacing. Seasnakes are equipped with glands to eliminate excess salt. They are venomous, but not aggressive and are thus handled by the fishermen without fear, though they are thrown back into the sea upon sight. The venom of this snake is rated four to eight times as toxic as cobra venom. About 1.5 milligrams of its venom is estimated to be lethal.
The principal food is fish. The snake is also eaten as meat by Hong Kong and Singapore fishermen and locals alike.

Phyllopteryx taeniolatus, the weedy sea dragon or common sea dragon, is a marine fish related to the seahorse. It is the only member of the genus Phyllopteryx. It is found in water 3 to 50 m deep around the southern coastline of Australia, approximately between Port Stephens, New South Wales and Geraldton, Western Australia, as well as around Tasmania. Weedy sea dragons are named for the weed-like projections on their bodies that camouflage them as they move among the seaweed beds where they are usually foundWeedy sea dragons can reach 45 cm in length. They feed on tiny crustaceans and other zooplankton, from places such as crevices in reef, which are sucked into the end of their long tube-like snout. They lack a prehensile tail that enables similar species to clasp and anchor themselves. Phyllopteryx taeniolatus swim in shallow reefs and weed beds, and resemble drifting weed when moving over bare sand.
Sea dragons, sea horses and pipe fish are the only species where the male carries the eggs.
The male of the species carries the fertilized eggs, attached under his tail, where they are incubated for about eight weeks. The young are independent at birth, beginning to eat shortly after. Mating in captivity is rare since researchers have yet to understand what biological or environmental factors trigger them to reproduce. In captivity the survival rate for weedy sea dragons is about 60%.
A more cryptic relative of the weedy sea dragon is the leafy sea dragon Phycodurus eques. In the November 2006 issue of National Geographic magazine, marine biologist Greg Rouse is reported as investigating the DNA variation of the two sea dragon species across their ranges.
The Aquarium of the Pacific in Long Beach, California, Melbourne Aquarium in Australia, and the Tennessee Aquarium in Chattanooga, Tennessee, are the only facilities in the world to have successfully bred weedy sea dragons in captivity, though others occasionally report egg laying.As of June 2008, the Georgia Aquarium in Atlanta has a pregnant sea dragon, which is expected to give birth in early-mid July.
The weedy sea dragon is the marine emblem of the State of Victoria.