Species: Medusagyne oppositifolia
Size: Leaf length up to 8 cm
Height up to 10 m
Description: The Jellyfish Tree is the sole representative of the genus Medusagyne and was thought to be extinct until the 1970’s were rediscovered. Despite this discovery the species remains on the brink of extinction. A relatively small tree the species can attain heights of 10 metres and have a dense, rounded crown of foliage. The bark is dark and has many distinctive, deep fissures which readily distinguish the plant when not in bloom. The leaves are shiny and leathery in appearance with a slightly scalloped edge which will turn bright red with age. The small, white flowers of the Jellyfish Tree are difficult to distinguish amongst the dense foliage; both male and bisexual flowers are carried on the drooping inflorescence. The flowers have numerous stamens and it is thought that these may have given rise to the name of Medusagyne after the ‘Medusa’ of Greek mythology who had a head of snakes. The fruits are green and rounded; the outer coat becomes reddish-brown with maturity and then dries, exposing the seeds within, which are dispersed via wind. Given the species is considered to be relatively “desert adapted” despite inhabiting a moist archipelago it has been hypothesised that the species may represent a Gondwanan lineage.
Habitat and Distribution: The Jellyfish Tree is only known from the island of Mahé within the Seychelles archipelago. The species was thought to be extinct since 1930 until 6 trees were ‘rediscovered’ in 1970. Today, 4 native populations consisting of approximately 50 trees in total are known. The species inhabits exposed granite slopes, at present all locations are within 2 km of the sea.
Biology and Ecology: Very little at present is known about the biology and ecology of the species and ongoing work is being conducted into nutrient requirements and favorable germinating conditions.
Status and Threats: The Jellyfish Tree is classified as Critically Endangered under the IUCN Redlist. The Jellyfish Tree presents an interesting botanical conundrum in that perhaps its greatest threat is that the seeds are unable to germinate in natural population; no seedlings have been observed in the natural stands to date. Successful cultivation in botanic gardens has occurred in very humid conditions, but high humidity is unlikely in the exposed habitat where these trees are found in the wild. It has been suggested that Jellyfish Trees have been lost from the more appropriate habitat of moist forests through competition with other species and climate change. Thus research is currently aimed at selecting appropriate sites for translocation that will allowing for self-sustaining populations with viable reproduction in natural habitat.
Time for a little photo spam from my nature walk the other day :)
Then a couple of species posts.
Species: Hemiscyllium hallstromi
Description: The Papuan Epaulette Shark (Hemiscyllium hallstromi) is named after the conspicuous epaulette spots, or shoulder patches, on the side of its body, above the pectoral fins. Closer examination of the spots reveals that they are actually white rings surrounded by two or three large, black spots. The Papuan epaulette shark has a scattering of wide-spaced, small and large dark spots across the majority of its body, except for the snout. The mouth is positioned well in front of the eyes, and the spineless dorsal fins are located far back on the extremely elongated, thick tail. The Papuan epaulette shark can be easily distinguished from the rather similar Hooded Carpet Shark (Hemiscyllium strahani) by the lack of a dark hood covering its head.
Habitat and Distribution: The Papuan Epaulette Shark is known to occur only around the southern coast of Papua New Guinea, in the Gulf of Papua. Little is known about the exact habitat requirements of the Papuan Epaulette Shark. The species is known to inhabit coastal tropical waters, where it is likely to be found primarily on coral reefs.
Biology and Ecology: The Papuan Epaulette Shark spends most of its time on the bottom of the sea bed, where it is thought to feed on a variety of invertebrates, as do other sharks in the genus Hemiscyllium. Although nothing is known about reproduction in this species, other Hemiscyllium sharks, such as the Indonesian Speckled Carpet Shark (Hemiscyllium freycineti), are oviparous, meaning that they lay eggs rather than give birth to live young. It is therefore likely that the Papuan Epaulette Shark is also oviparous.
Status and Threats: The Papuan Epaulette Shark is classified as Vulnerable under the IUCN Redlist. Habitat destruction is the main threat to the Papuan Epaulette Shark. Gold mining near the Fly River in Papua New Guinea causes large quantities of pollutants to drain directly into the Gulf of Papua, resulting in heavy pollution of the Papuan Epaulette Shark’s habitat. It is also thought that the Papuan Epaulette Shark is being heavily impacted upon by destructive fishing practises, such as dynamite fishing. The Papuan Epaulette Shark may also be at risk due to exploitation by the aquarium industry. It is a very attractive and hardy species, which may be appealing to both public and private aquariums, though the extent of this trade is unknown.
Species: Haploblepharus fuscus
Description: A small species the Brown Shyshark has a stocky body and a short, broad head. The snout is blunt and dorsally flattened. The eyes are large and oval-shaped, with a rudimentary nictitating membrane (protective third eyelid) and a strong ridge underneath. The nostrils are very large, and are flanked by greatly expanded, triangular flaps of skin that reach the mouth. These nasal flaps cover a pair of deep grooves that connect the nasal excurrent (outflow) openings and the mouth. There are furrows at the corners of the mouth on both jaws. The teeth have a central cusp and a pair of smaller cusplets on the sides. The five pairs of gill slits are positioned on the upper sides of the body.
The first dorsal fin originates well behind the pelvic fin origins, and the second originates behind the anal fin origin. The pectoral fins are moderately large, and the dorsal, pelvic, and anal fins are of similar sizes. The caudal fin is short and broad, with a notch near the tip of the upper lobe and an indistinct lower lobe. The skin is thick and covered by well-calcified leaf-like dermal denticles. The coloration is a plain brown above and while below, though some individuals have a series of faint darker saddle-like markings or black or white spots.
Habitat and Distribution: The Brown Shyshark has a rather restricted distribution in the western Indian Ocean, where it is endemic to the waters around South Africa. The Brown Shyshark typically found close to the bottom over sandy flats or rocky reefs, from the intertidal zone to a depth of 35 m (115 ft) though has been reported from as deep as 133 m (436 ft).
Biology and Ecology: The diet of the Brown Shyshark primarily consists of lobsters and small fish and may also include crabs, cuttlefish and worms. As with other catsharks, the species is oviparious and the eggs typically take the form of rectangular egg cases, often with long tendrils at the corners. Females typically lay two eggs at a time. The male Brown Shyshark reaches sexual maturity at around 63 to 69 centimetres in length, and the female at 60 to 73 centimetres.
The common name of this and other ‘shysharks’, also known as ‘shy-eyes’, comes from the peculiar habit of coiling the body up with the tail held over the eyes when the shark is caught. This defensive behaviour may help deter predators from swallowing the shark.
Status and Threats:The Brown Shyshark is classified as Vulnerable under the IUCN Redlist. Although a locally common species, which is not targeted by commercial fisheries or caught for its meat, the Brown Shyshark inhabits heavily fished and potentially degraded inshore waters. Its status is not well known, but the species is likely to occur as bycatch, both in coastal fisheries and by sports anglers, and may also be threatened by habitat degradation and pollution. The Nrown Shyshark’s limited range makes it particularly vulnerable, with any threats likely to affect the whole population.
Species: Nebrius ferrugineus
Description: The Tawny Nurse Shark has a robust, cylindrical body with a broadly rounded and flattened head. The eyes are small and face laterally, with prominent ridges over them and smaller spiracles behind. There are a pair of long, slender barbels in front of the nostrils. The mouth is small, with the lower lip divided into three lobes. There are 29–33 tooth rows in the upper jaw and 26–28 tooth rows in the lower jaw, arranged in an imbricate (overlapping) pattern with the outermost 2–4 functional rows separated from the rest by a narrow space. Each tooth resembles a fan, with a broad base rising to a small, sharp central point flanked by 3 or more smaller cusps on both sides. As the shark ages, the teeth become relatively taller and thicker. The fourth and fifth pairs of gill slits are placed close together than the preceding gill slits.
The dorsal and pelvic fins are angular, with the first dorsal fin larger than the second. The pectoral fins are narrow, pointed, and falcate (sickle-shaped); their shape separates this species from the Grey Nurse Shark which is similar in appearance. The origin of the first dorsal fin is about even with the origin of the pelvic fins, while the origin of the anal fin is even with or somewhat behind the origin of the second dorsal fin. The caudal fin has a shallow upper lobe and barely present lower lobe, comprising about a quarter of the total length in adults. The dermal denticles are diamond-shaped, bearing 4–5 faint ridges radiating from a blunt point. Tawny Nurse Sharks are yellowish, reddish, or grayish brown on the dorsal surface and off-white on the ventral surface, and are capable of slowly changing their color dependent on the colour of the surrounding environment. Young sharks have starkly white lower eyelids.
Many Tawny Nurse Sharks found off the coasts of Japan, Taiwan, and the Ryukyu Islands lack a second dorsal fin. This physical abnormality has been speculated to result from pregnant females being exposed to water of unusually high salinity and/or temperature, possibly from human activity. In 1986, a 2.9 m (9 ft 6 in) long adult male with both a missing dorsal fin and partial albinism (in the form of white body color with gray-brown eyes) was captured off Wakayama Prefecture, Japan. This anomalous individual is the largest albino shark recorded to date.
Habitat and Distribution: The Tawny Nurse Shark is widely distributed across the Indian and west and central Pacific Oceans, ranging from the Red Sea, East Africa and the Arabian Gulf to southern Japan, south through Indonesia to Australia. This is a continental and insular shelf species restricted to a narrow band of shallow water from intertidal waters to depths of up to 70 m. The Tawny Nurse Shark lives on or near the bottom in lagoons, or close to coral and rocky reefs. Like other nurse sharks, this species uses crevices and caves for shelter.
Biology and Ecology: With a more streamlined form than other nurse sharks, the Tawny Nurse Shark is believed to be a less benthic, more active swimmer. This species primarily nocturnal, though is said to be active at all hours off Madagascar, and in captivity they will become diurnally active if presented with food. During the day, groups of two dozen or more sharks can be found resting inside caves and under ledges, often stacked atop one another. Individual sharks have small home ranges that they consistently return to each day.
The Tawny Nurse Shark may be one of the few fishes specializing in preying on octopus. Other known food items include corals, sea urchins, crustaceans (e.g. crabs and lobsters), squid, small fishes (e.g. surgeonfish, queenfish, and rabbitfish), and the occasional sea snake. Hunting Tawny Nurse Sharks swim slowly just above the sea floor, poking their heads into depressions and holes. When a prey item is found, the shark forcefully expands its large, muscular pharynx, creating a powerful negative pressure that sucks the prey into its mouth.
Reproduction in the Tawny Nurse Shark is known to occur from July to August off Madagascar. Adult females have one functional ovary and two functional uteri. The mode of reproduction is aplacental viviparity, meaning that the embryos hatch inside the uterus. Females in captivity have been documented depositing up to 52 non-viable egg capsules, which has led to erroneous reports of this shark being oviparous. The egg capsules of this species are onion-shaped, with thin, brown, translucent shells. The Tawny Nurse Shark is the only carpet shark in which there is oophagy: once the developing embryos exhaust their supply of yolk, they gorge on eggs produced by the mother and acquire the distended abdomen characteristic of such oophagous embryos.
Various authors have reported the length at birth anywhere from 40 to 80 cm (16 to 31 in), with the discrepancy possibly reflecting geographic variation. Although females release up to four fertilized eggs into each uterus, the very large size of the newborns suggest that the litter size may be as few as one or two. In one examined female that had two embryos sharing a single uterus, one embryo was much smaller and thinner than the other, implying that competition may eliminate the additional siblings. Males attain sexual maturity at a length of 2.5 m (8 ft 2 in), and females at a length of 2.3–2.9 m (7 ft 7 in–9 ft 6 in).
Status and Threats: The Tawny Nurse Shark is classified as Vulnerable under the IUCN Redlist. The shallow water that the Tawny Nurse Shark is restricted to is heavily fished, with the species being captured in demersal trawls, floating and fixed bottom gill nets and baited hooks across most of its range outside Australia. The flesh is sold for human consumption, with the fins making their way into the oriental sharkfin market. The species liver may also be processed for vitamins and oil, the offal processed for fishmeal, and the hide potentially for leather. The exact impact fishing is having on population numbers is unknown, but there are reports of local extinctions in waters around India and Thailand. Certainly, the sharks narrow habitat range, apparently limited dispersion and low reproductive turnover make it highly vulnerable to the effects of over-fishing. Fortunately, this shark is still abundant in Australian waters, where it is captured only in very small numbers in gillnets and meshing.
Species: Rhincodon typus
Weight: 12.5 tonne
Description: The Whale Shark (Rhincodon typus) is the largest fish in the world; with its vast size it resembles the whales from which its common name is derived. The head is dorso-ventrally flattened and the wide mouth, positioned at the tip of the snout, is almost equivalent in width to the body. The dorsal fin is particularly large and the tail has a half-moon shape. The patterning of the body is very distinctive with the dorsal surface dark greyish-blue in colouration with an array of pale yellow blotches; the ventral surface is pale in contrast. Stout ridges travel the length of the body, ending at the tail shaft. Five massive gill slits occur on each side of the head and within these there are a number of gill rakers (sieve like structures comprised of cartilage). Curiously, the mouth contains around 300 tiny teeth although the function of these largely remains unknown.
Habitat and Distribution: Found throughout the world’s oceans in temperate and tropical waters, the Whale Shark most commonly occurs in a global band around the equator between 30° to 40° latitude. The Whale Shark inhabits shallow coastal areas as well as the open ocean. This species prefers warm water, with surface temperature between 21° to 30° Celcius, but can tolerate water temperatures experienced on deep dives (over 1,000 metres) as low as 3° centigrade.
Biology and Ecology: The Whale Shark is primarily solitary, but loose groups of up to 100 individuals have been sighted, often when they are feeding. The species appears to be highly migratory, and have been tracked for thousands of kilometres. Individuals who regularly visit the Ningaloo Reef in Australia, between March and May every year, appear to be mainly immature males. It is not clear whether movements across deep ocean basins follow prey routes or are undertaken for other reasons. Very little is known about the reproductive biology of the world’s largest fish, but in 1995, one pregnant female was captured and examined with close to 300 embryos evident in the reproductive tract. The Whale Shark is ovoviviparous; the young hatch from eggs retained within the female and are born live. Whale Sharks are fairly docile creatures and feed on planktonic organisms and small fish by suction filter-feeding. This species is thought to be a more dynamic filter-feeder than, for example, the Basking Shark, actively sucking food in through their vast mouths and passing the water over the gill arches, where prey are retained and then swallowed.
Status and Threats: The Whale Shark is classified as Vulnerable under the IUCN Redlist and is listed under Appendix II of CITES and the Bonn Convention. Whale Sharks have been fished throughout their range, and their flesh is highly valued in some Asian markets. The recent increase in the demand for shark-fin soup threatens this species; in 1999, a large whale shark fin sold for around £11,000. Although little is known about the reproductive ecology of this species, it is likely to be long-lived with a slow reproduction rate, making populations particularly vulnerable to exploitation. Where these shy creatures regularly come close to shore, they have become important tourist attractions, but the impact of shark-watching tours is at present poorly understood.
Websites for Whale Shark conservation:
I know I said seven species yesterday but we had a late afternoon call out for an emu so my best laid plans failed.
I shall finish them now :D