4 Fijian Invertebrate Behemoths

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What is an Invertebrate? –  An invertebrate is any animal that lacks a vertebral column, or backbone  In this article, we have started our discovery of these amazing animals with 4 behemoths of the invertebrate family, the Coconut Crabs (the largest land crab in the world), corals that make up the diverse and natural marine coastline of the Fijian Archipelago, the spiny lobster crustacean, and the Giant Clams that grace our coastline.

Table of Contents

Coconut Crabs of Fiji


Coconut Crab Climbing up a Palm Tree in Fiji - Fijian Invertebrate Behemoth
Coconut Crab | Image: Supplied

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 fateDoes the secret of the famed aviator’s disappearance lie in the underground haunts of the world’s largest land invertebrate? – National Geographic)

YouTube Video:  Coconut Crabs – Searching for Amelia


Coconut Crabs Devour Pig Carcass / Searching for Amelia

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.

Fun Facts 1: It is also called the robber crab because of an interesting habit it possesses – the crab has been known to be attracted to shiny items and has the habit of stealing them!

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.

Table: Additional Crabs of Fiji


Crabs of FijiDescriptions
Parasesarma Erythrodactylum Red fingered Marsh Crab FijiKukadamu Red handed Shore Crab – (Parasesarma erythrodactyla)
Lairo Brown Land Crab Cardisoma CarnifexLairo Brown Land Crab – (Cardisoma Carnifex)
Mud Crab Scylla SerrataMud Crab – (Scylla Serrata)
Fiji Coconut CrabCoconut Crab – (Birgus Latro) is the largest 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.
No ImageKukaloa Shore Crab – (Metopograpsus Messor)

Corals of Fiji


A vibrantly coloured Coral Reef - Invertebrate Behemoths of FIji
Coral Reef around Beqa Island Fiji | Image: Supplied

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).

Table: Corals of Fiji


Corals of FijiDescription
Pocillopora verrucosa transformedPocillopora verrucosa – This hard coral is also present in a wide range of habitats. It is common in the shallow waters of the lagoon and reflect, but occurs as thickly branched colonies in the wave affected areas of the reef slope. Colonies are characterised by branches with small protuberances (verrucae) on them. The branches are thicker and more compact where there is wave action, with a more open appearance in protected areas such as lagooons.
Favia rotumanaFavia rotumana – This species was first described from an early expedition to Fiji. It was hard coral found on the upper reef slopes and in the pools on the flat reef. Its growth form is messy and usually hemispherical or rounded. The corallites are irregular in shape, with the polyps often containing more than one centre or mouth. Its robust growth form makes it resistant to wave action. Tolerance of the environmental variation (turbidity, temperature and salinity fluctuations) in the shallow reef flat zone allows the colonisation of a variety of reef habitats.
Sinularia spSinularia sp. – This is soft coral. They can be distinguished from hard corals by their large fleshy colonies, which are soft or leathery in nature without a rock-like skeleton. The living polyp has eight tentacles (Octocorals), for feeding, whereas the hard corals have six or multiples of six (Hexacorals). They are common on the back reef margin of the barrier and inshore on fringing reefs where there is a silt or turbid environment. They are the dominant organism on some reefs, completely covering large areas to the exclusion of all else.
Dendronephthya sp.Dendronephthya sp. – This is the most colourful of soft corals appearing as iridescent reds, pinks and yellows. Their bright colour is due, in part, to the lack of the small, unicellular algae which live in the tissues of most hard and soft corals. As a consequence, the preferred habitat is deeper water, in shaded areas under overhangs and the entrance to caves. They occur on offshore reefs where there is clear water and good circulation. The colonies from branching tree-life colonies where the polyps are borne on the end of the branches. They have prominent skeletal spicules or sclerites which provide defence and give the colony a spiky appearance.

YouTube Video:  Coral Spawning in Fiji


Coral Spawning in Fiji with Victor Bonito

Fiji Spiny Lobster


Fiji Spiny Lobster
Fiji Spiny Lobster | Image: Supplied

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.

Table: Lobster Species in Fiji


Fijian LobsterDescriptions
Double Spined Lobster (Panulirus penicillatus)Golden Rock Lobster – (Panulirus penicillatus) – Small, black and red found mostly on the ocean side of coral reefs, and known for its tough carapace.
Painted Rock Lobster P versicolorPainted Rock Lobster – (P. versicolor) – The most colourful, found mostly in coral patches and is essentially dark green, with narrow black and white stripes, and long antennae which are red at the base.
Whiskered Lobster P. longipipes femoristrigain FijiWhiskered Lobster – (P. longipipes femoristriga)
Ornate Rock Lobster P. ornatusOrnate Rock Lobster – (P. ornatus) – Large light blue, which has black and white striped legs and antennae, prefers a quieter lagoon habitat.
Mana Mangrove Mud Lobster Thalassina anomala in FIjiMana Mangrove Mud-Lobster – (Thalassina anomala)
spiny blue lobster panulirus versicolor in FijiBlue Spiny Lobster – (Panulirus versicolor)
No ImageSlipper Lobster – (Parribacus caledonicus)

Bivalve – Giant Clams


Giant Clam | Image: Supplied
Giant Clam | Image: Supplied

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.

YouTube Video:  Arrival of Giant Clam


Video Title: John John Florence & Kelly Slater Celebrate the Arrival of Giant Clams in Fiji

Additional Fijian Invertebrates – Shallow Water Marine Prawns – Shrimps – Fiji Freshwater Snails and Shells of Fiji – Sea cucumber – Nudibranchs

References

  • Actinopyga echinites. (2022, October 18). In Wikipedia. Link
  • Actinopyga mauritiana. (2022, December 15). In Wikipedia.
  • Avery, D. (2023). Brown Land Crab (Cardisoma carnifex) [Photograph]. INaturalist. Link
  • Bohadschia vitiensis [Photograph]. EOL. Link
  • Green, A. (2019). Panulirus longipes Palinuridae Coral Spiny Lobster [Photograph].
  • Reef Life Survey. Link
  • Holothuria fuscopunctata. (2021, November 12). In Wikipedia. Link
  • INaturalist. (2022). Lollyfish Sea Cucumber Holothuria atra [Photograph]. INaturalist Australia. Link
  • Parasesarma erythrodactyla. (2022, June 12). In Wikipedia. Link
  • Thelenota ananas. (2022, August 31). In Wikipedia. Link
  • Unknown (2018). Clithon diadème [Photograph]. Fishipedia. Link
  • Unknown (2012). Flax snail/pupurangi [Photograph]. Department of Conservation New Zealand. Link
  • Unknown (2023). Stichopus Cucumber [Photograph]. Tankstop. Link
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