Coconut Crabs of Fiji
Coconut Crab – (Birgus Latro) – is the largest invertebrate land crab in the world. They can grow up to 40 inches in total length and weigh up to 4kg (4 bags of sugar). It is a type of hermit crab with an Indo-Pacific distribution but confined to the islands only.
The adult coconut crab is a terrestrial animal in nature that is very comfortable living on land and developing skills, with its elongated pointed legs it can climb palm trees to get its favorite delicacy, from which its name has derived. They have a palate for fruit and occasionally acquire the taste of small birds or reptiles. Adults are secretive, hiding by day in a burrow and feeding by night, especially near human habitations. (Worth a glance – Colossal crabs may hold clues to Amelia Earhart’s fate – Does the secret of the famed aviator’s disappearance lie in the underground haunts of the world’s largest land invertebrate? – National Geographic)
Developmental Stage of the Coconut Crab
The coconut crab’s initial developmental stage takes place in the sea and comes ashore as a juvenile crab. The gills adapt to allow respiration on the land provided they are kept moist, to accomplish this they will normally dip their leg into the water and wipe them over the gills (surrounded by spongy tissue), with the occasional drink of seawater to maintain the salt levels in its body.
The reproductive stage of the coconut crabs’ life cycle requires the parlous journey back into the sea where the female can carry and sheds up to 100 000 eggs, the eggs hatch as they make contact with the seawater, releasing small microscopic larvae into the surrounding waters. This will be their home for the duration as they grow and develop into juvenile coconut crabs, where they will ultimately venture ashore hiding in shallow burrows on the coastline, as they are very vulnerable to land-based predators. In the initial stages, they will live in a shell very similar to a hermit crab, slowly shedding their shells by molting them as they grow, mature adults are free.
The locals capture the Coconut crabs in two ways – Firstly they can be lured to a staked piece of coconut bait and caught by hand – Secondly, ‘they can be captured by human trickery! A piece of turf is placed on the coconut tree trunk about 3m from the ground. A descending crab reverses down the trunk and when its abdomen touched the turf, it lets go thinking it has reached the ground thus falling to the ground, knocking itself out, and is easily captured.
Corals of Fiji
Coral reefs with their immense diversity and myriad of colours are among the most productive and important ecosystems in the world today. Coral reefs are home to a huge array of fish, crustaceans, molluscs, and worms. They provide refuge from predators and protection from the power of the waves. Coral reefs are important for mankind as they provide coastal protection from destructive waves, food for villagers, and the marketplace. Coral reefs also create a major attraction for tourists which brings in substantial revenue.
There are over 148 species of hard coral (Sceractinians) and soft coral (Alcyonarians) within the waters of the Fiji Islands. All species consist of polyps that secrete calcium carbonate (limestone). In hard corals, this provides a solid, stoney skeleton, while in soft corals the tissues are reinforced by a matrix of microscopic calcareous particles (spicules).
Fiji Spiny Lobster
Lobsters (sometimes called ‘crayfish’ or ‘crawfish’) are crustaceans with ten legs and large, fleshy tails. The name of the scientific order they belong to, Decapoda, means literally ‘ten feet’. The spiny lobsters of Fiji, unlike most lobsters of more temperate climes, have long spiny antennae, no claws, and are very colorful. They are usually found in crevices in coral reefs, giving away their presence by waving their two long antennae. Lobsters are nocturnal and only venture out onto the reef to forage during the night.
Bivalve – Giant Clams
As T.S Eliot wrote ‘Home is where one starts from” and William J. Bennett ‘Home is a shelter from storms all sorts of storms’ The gentle giant Clam has only one opportunity to find a home, as when it fixes to the reef floor, it will reside there creating a micro-ecosystem for its whole life.
These behemoths have the capability to reach anywhere from one to four feet in length and weigh up to 450 pounds. The Fiji islands currently have three species of Giant Clam Tjnaxima, r.squamosa, and T.derasa.
Giant clams are remarkable creatures. All members of this group have undergone adaptation to act as symbiotic hosts to single-celled zooxanthellae (Algae). These algae have removed the giant clam’s necessity to filter food from the water and instead, the clam can obtain almost all its nutritional requirements (sugars and proteins), via the billions of algae that live in their tissues and from sunlight. Light levels will play a large part in defining their habitat. This symbiotic relationship has a number of interesting consequences for the ecology of the animal, for example, the giant clams do not need to compete and expend large amounts of energy collecting food, enabling them to grow in size.
These clams have become a protected creature within Fiji, as they command a high price on the Asian market as a fine delicacy, resulting in their rapid decline over the last few decades. Concerted efforts from the Fijian Government, the Fijian tourism industry, and International marine bodies have started to work together to restore the Giant Clam levels of the past and protect their marine environment from human interference.