Reef & Marine Biology

12/02/2017

Sad day

In one of the saddest news stories to come out this week, hundreds of pilot whales have died overnight after stranding themselves on a New Zealand beach. C

29/10/2016

Strapw**d filefish (Pseudomonacanthus macrucus, monacanthidae), The Jetty, Padang Bai, Indonesia.

The strapw**d filefish (also known as Strapw**d Leatherjacket, Small-spotted Filefish, Small-spotted Leatherjacket) are tropical to subtropical tetraodontiform marine fish of the diverse family Monacanthidae, closely related to the triggerfish, pufferfish and trunkfish. Although closely related to the triggerfish, their "trigger spine" cannot be locked into place.

Strapw**d filefish are found in the Indo-west Pacific oceans, and can reach a length of about 18-24 cm. Their body has lots of small circular dots and often a broad white stripe or blotch along the centre of the body from the gill opening. They may have dark blotches and a colourful band on their underside (here blue). They are found singly in w**d or seagrass beds on reef flats and in lagoons and feed on invertebrates and algae.

Their laterally compressed bodies and rough, sandpapery skin inspired the filefish's common name; it is said that dried filefish skin was once used to finish wooden boats. Filefish can alter their colour and pattern to match their surrounds and so deter predators.

15/10/2016

Leaf slug at night (Melibe sp., nudibranch, mollusc), Bannerfish Bay, Dahab.

Melibe is a genus of sea slugs, nudibranchs, marine gastropod mollusks. Most nudibranchs are carnivores, but their prey are usually sessile or slow-moving animals such as sponges or bryozoans. In contrast, Melibe is an active predator which traps fast-moving free-swimming animals. Species of Melibe feed on shrimps, crabs and other small crustacea which they catch by waving their inflated oral hood over the substrate like a metal detector. When the sensory papillae touch a crustacean the hood rapidly closes, trapping the prey inside the 'mouth'. Species of Melibe lack a radula, prey remaining alive in the gut until killed by digestive juices.

This species has a transparent body lightly frosted with brown flecks. It appears to feed primarily at night when it moves to the tips of the algae and sweeps the water rhythmically with its hood. During the day, it conceals itself in the algae rather than under rubble. It can swim readily by lateral flexing.

This species is widespread in the Indo-Pacific area, and can occur in blooms in the spring.

27/09/2016

Short-beaked common Dolphin (Delphinus delphis, marine mammal), Algarve, Portugal, Atlantic Ocean.

The short-beaked common dolphin is a species of common dolphin, a marine mammal, that occur in warm-temperate to tropical oceans, incl. the Mediterranean, Carribean, Red Sea, Atlantic, Pacific and Indian ocean. There are more short-beaked common dolphins than any other dolphin species in the warm-temperate portions of the Atlantic and Pacific Oceans. They are found off coastal-waters and well at sea. The common dolphin is not the dolphin of popular imagination despite its name; that distinction belongs to the bottlenose dolphin due to its widespread use in marine parks and its appearance in the television series Flipper.

Common dolphins are small (1.9-2.5 m, 100 kg) and have two distinct colours. The back is either black or dark brown, and they have a white or cream-colored underside. The flippers and flukes are the same colour as the back, black or dark brown, and the eyes are encircled with black markings that extend to the beak. They are distinguished from other species by a unique crisscross/hourglass colour pattern on the flanks.

Short-beaked common dolphins are highly social animals. They are often found in large, active schools: jumping and splashing can be seen and even heard from a considerable distance. Several members of a group often surface together. School size often varies seasonally and according to time of day, from hundreds to thousands. They sometimes associate with other dolphin species, such as pilot whales. They have also been observed bow riding on baleen whales, and they also bow ride on boats. The prey of common dolphins consists largely of small schooling fish (such as herring, pilchard, anchovies, hake, sardines) and squid/octopus. Co-operative feeding techniques are sometimes used to herd fish schools.

Common dolphins reach sexual maturity around 12-15 years of age, having an estimated life-span of 35-40 years. Females normally give birth to one baby at a time and gestation usually lasts 10 to 12 months, when the calf is born tail first. They are considered as a species of least concern by the IUCN, stating: “Despite ongoing threats to local populations, the species is widespread and very abundant (with a total population in excess of four million), and none of these threats is believed to be resulting in a major global population decline.”

04/09/2016

Southern oceanic Sunfish (Mola ramsayi, bony fish), Padang Bai, Bali, Indonesia.

The oceanic sunfish family (Molidae), also known by its scientific name Mola mola (for its better known representative, the common sunfish), comprises some of the biggest and heaviest of all bony fish in the ocean. Large specimens of Mola mola can reach a size of 4.2 meters vertically and 3.1 meters horizontally and weigh upwards of 2 tons! Sharks and rays can be heavier, but they're cartilaginous fish. They are members of the order Tetraodontiformes, which also includes pufferfish, porcupinefish, and filefish.

They resemble a fish head with a tail, and their main body is flattened laterally. Sunfish develop their truncated, bullet-like shape because the back fin which they are born with simply never grows. Mola mola have a rounded tail, gritty sandpapery skin covered with copious amounts of mucus. Typically silvery in colour with a slight opalescent sheen, they can exhibit strikingly changeable spotty patterns.

Sunfish are found in temperate and tropical oceans around the world. They are frequently seen basking in the sun near the surface and are often mistaken for sharks when their huge dorsal fins emerge above the water. However, sunfish are pelagic and spend most of their time swimming at depths of 200 to 600 m.

Sunfish live on a diet consisting mainly of jellyfish (and zooplankton, algae, small fish), but because this diet is nutritionally poor, they consume large amounts to develop and maintain their great bulk. Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths. Females of the species can produce more eggs than any other known vertebrate, up to 300,000,000 at a time.

Despite their size, ocean sunfish are docile, and pose no threat to human divers. Adults are consumed by sea lions, orca, and sharks. Their population is considered stable, though they frequently get snagged in drift gill nets and can suffocate on sea trash, like plastic bags, which resemble jellyfish.

31/08/2016

Colonial coral tube worms (Filogranella elatensis, serpulidae), Tulamben, Bali, Indonesia.

Unlike their terrestrial counterparts, marine worms can be considered quite beautiful…

This species of colonial worms lives in thin rigid calcareous white tubes, pencil-like, and have red plumes which gradually become white towards the end. The plumes are 2.5 cm in diameter, the tubes can grow much longer. They form colonies, which normally consist of dozens of similar rigid tubes sheltering serpulid worms. They are usually found in shaded areas underneath coral heads, out of direct sunlight. This species and many other tube worms are very sensitive to light changes. If you approach it too quickly or abruptly, it will retract into its tube.

They can be found in the Red Sea, the Gulf of Aqaba, the Indian Ocean and the Indo-Pacific. They attach to hard substrates such as rocks and boulders, but are also seen in harbours and pier pilings, in overhangs and under coral heads, starting at 5 metres and down to considerable depths, well beyond the dive limit.

Like most sessile (immobile) species of plumes worms, they are filter feeders, sifting out food particles from the water current. This species is supposed to be extremely fragile and sensitive to pollution. The health of this species of worm can thus be a strong indicator of the overall health of its hosting reef. They are not very common, but spread widely due to ballast water discharge from ships.

22/08/2016

Whitetip reef shark (Triaenodon obesus, Elasmobranch), Padang Bai, Bali, Indonesia.

Whitetip reef sharks, Trianodon obesus, are a slender species of requiem sharks with a short, blunt snout. They are brown-grey on their dorsal sides, white on their ventral sides. They have scattered dark grey spots along the sides of their bodies. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. This species has an average length of 1.6 m long, a max weight of 18 kilos and max lifespan of 25 years.

One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far east as South Africa and as far west as Central America. It is typically found on or near the bottom in clear water, at a depth of 8–40 m. They are most abundant on the fore-reef, and during daylight hours are often associated with coral reefs or lying on the bottom in caves and under ledges, often the same resting site for several years in a row, often in groups (highly social species).

Whitetip reef sharks feed nocturnally on benthic animals such as fish, octopuses, spiny lobsters, and crabs. Foraging individuals often wriggle their elongate bodies into crevices and under coral heads, twisting and turning violently and often breaking off coral and tearing their fins and skin, more like a moray eel than a typical shark.

Whitetip reef sharks are viviparous and have an internal fertilisation producing 1 to 5 60 cm young per litter, after a gestation period of 12 months.

The whitetip reef shark is a curious species that often approaches divers. It is not considered dangerous to humans. It is considered as near threatened by the IUCN, but its restricted habitat, depth range, small litter size and moderately late age at maturity suggest that, with increasing overfishing, this species may become threatened.

12/08/2016

Ladybug amphipods on sponge (Cyproideidae, crustacean), Tulamben, Bali, Indonesia.

Cyproideidae is a family of amphipod crustaceans, cousin to the caprellidae (skeleton shrimps). Ladybug amphipods are benthic and form associations with corals, sponges, crinoids, tunicates and hydroids, but other amphipods can live a pelagic life as part of the zooplankton. Interestingly, ladybug amphipods seem to be found only in the Komodo National Park and have not apparently been documented elsewhere so far.

Amphipods are small and very diverse crustaceans which lack a carapace and occur all over the world in marine, freshwater and even terrestrial habitats (sandhoppers such as Talitrus saltator). They are distinctive in that their bodies are laterally compressed, in other words, their bodies are "taller" than they are wide. Most amphipods are pretty tiny (about 1.0 to 20 millimetres) but some giants approach 34 centimetres such as supergiant amphipods which live in the abyss of the deep-sea at 7,012 metres! More than 9,500 species of amphipods have been described.

The size of these ladybug amphipods is 1/4 of a rice grain. To the naked eye, they resemble fleas – and like fleas, they jump around so they are very difficult to shoot.

There's an enormous amount of diversity within the group. Some are transparent, while others are colourful. Sometimes they occur in huge densities and are often thought of as the "bugs" of the sea. They often act as detritivores/scavengers as well as predators…

02/08/2016

Mud sagartia anemone (Sagartia troglodytes, cnidarian), Oosterschelde, Zeeland, the Netherlands.

The mud sagartia or cave-dwelling sagartia is a species of sea anemone distributed throughout western Europe from Iceland and Scandinavia to the Mediterranean, up to 50 metres deep.

A common and widespread species likely to be encountered in any habitat where anemones occur. They are typically found buried in mud, sand or gravel, usually attached to a stone or shell fragment. They may be very abundant on mud or sand flats exposed at low water in sheltered localities, rocky shores, in pools, in holes or crevices, under stones, or in kelp holdfasts.

The column is a bland colour and is almost completely buried in the sediment. The tentacles are moderate in length, neatly arranged in a regularly hexamerous manner, up to 200. Disc and tentacles are infinitely variable in colours: almost any colour except blue may occur, plain or variegated, with or without a pattern. Tentacles have a darker spot at their base. The diameter of the anemone usually reaches 4-6 cm.

This species of anemone is solitary and carnivorous, feeding on approx. 80% zooplankton and 20% small prey captured by tentacles, paralysed and led to the central mouth, which is raised on a small mound in the middle of the disk. After digestion, the waste is expelled through the same or***ce.

This species is habitually hermaphrodite and viviparous, although the production of young is not often observed, probably because they are very small - usually less than 1 mm diameter - at birth. In case of adverse conditions, the animal can fissure itself in half vertically to create two new individuals by regeneration (natural cloning).

20/07/2016

European flounder (Platichtys flesus, flatfish), Oosterschelde, Zeeland, the Netherlands.

The European flounder is a flatfish found in the Eastern Atlantic: coastal and brackish waters of western Europe and from the White Sea to the Mediterranean and the Black Sea. It is a migratory fish, which is for the majority of the year found in estuaries. It has a broad geographic range and is common within its range. It is found from 1 to 100 m depth.

Flounders are part of the family of the pleuronectiformes - flat fish, which are flattened laterally and swim and rest on one side. It has an oval shape (around 30-50 cm) and during development, its eyes usually migrate to the right side of the fish and what appears to be its upper surface is in reality its right side. In about thirty percent of individuals, its eyes move to the left and the left side becomes uppermost. The European flounder is green-olive coloured, the bottom side is white, and with irregular reddish spots on the eye side.

Adults usually burrow in mud and sand bottom in shallow water, but can occur at sea and in brackish, estuarine waters. Adults are carnivores: they feed on benthic fauna, mostly small fish and invertebrates. They are nocturnal and are well known for their unique camouflage abilities. Flounders are able to change the colour of their brown dull-coloured and spotted backside to match the colour and texture of their surroundings.

The European flounder is fished (commercial/aquaculture) and marketed fresh and frozen for human consumption. The most important fisheries are in the Baltic Sea and the waters around the Netherlands and Denmark. In 2010, the total world catch was about nineteen thousand tonnes, mostly caught by destructive methods like bottom trawling.

15/07/2016

Common brittle stars (Ophiotrix fragilis, ophiuroidea, echinoderm), Oosterschelde, Zeeland, Netherlands.

Ophiothrix fragilis is a species of brittle star in the order Ophiurida. This species is common around the coasts of Britain and Ireland and in the North Sea down to the Mediterranean. The common brittle stars sometimes congregate offshore in vast numbers and as many as two thousand individuals have been recorded in a single square metre!

Brittle stars are cousins of the sea stars and basket stars and are part of the phylum Echinodermata, which comprises other underwater critters like sea cucumbers, sea urchins, sand dollars, feather stars, and sea lilies. Echinoderms are linked together by such characters as radial symmetry, usually 5-point. Most echinoderms are capable of locomotion and live anywhere in the ocean, from tide pools near the surface to abyssal depths (more than 6,000 metres).

Brittle stars crawl on the seafloor by wriggling their flexible arms to make snake-like movements. The common brittle star is extremely variable in colouration. Brittle stars usually have 5 of these long, slender and whip-like arms that surround a disk-like central body, about one centimetre in diameter. The disk contains all the organs and the mouth/anus is ventral. Most brittle stars have no eyes and no specialised sense organs. However, they have several types of sensitive nerve endings in their tissues, and are able to sense chemicals in the water, touch, and even the presence or absence of light.

There are more than 2,000 species of brittle stars in the world, and more than 1,200 of them live at depths greater than 200 metres. Brittle stars are also common, if cryptic, members of reef communities, where they hide under rocks and even within other living organisms. They are generally scavengers or detritivores. Small organic particles are moved into the mouth by the arms, which can also be used for suspension feeding by raising an arm to catch particles floating by. Like some other brittle stars, Ophiothrix fragilis has symbiotic bacteria under its cuticle.

Brittle stars can readily regenerate lost arms or arm segments unless all arms are lost. They use this ability to escape predators, in a way similar to lizards which deliberately shed (autotomy) the distal part of their tails to confuse pursuers.