Life On Galapagos: The Invertebrates

The unique flora and fauna of the Galapagos Archipelago attract nature lovers from all over the world to explore the region. The best way to do it is on a Galapagos wildlife cruise, which affords participants the opportunity to experience the astounding diversity of the island's habitats and encounter a wide range of animals.  

The mammals, reptiles, birds and marine animals of the archipelago are fairly well known by visitors, and many of the high-profile species can be seen on a Galapagos wildlife cruise. Surprisingly, though, the largest group of organisms is often overlooked. 

The Invertebrates

Invertebrates have no backbone and are officially classified as animals that "neither possess nor develop a vertebral column". They include insects, spiders, snails, worms, centipedes and many others. Like all the wildlife, this group had to arrive at the islands either on the ocean currents, with birds, or attached to vegetation or driftwood washed up on the shoreline. 

The terrestrial invertebrates exist in every habitat and account for around 51% of the archipelago’s total biodiversity. While they may be small in size, they are absolutely crucial to the delicate balance of the ecosystem. Not only do they act as pollinators, they contribute to the formation of soils by recycling organic matter, and they also feature as an important link in the food chain as part of the diet for birds and small mammals. 

The marine invertebrates include the molluscs, sponges, annelids (segmented marine worms), cnidarians (including corals), echinoderms (sea cucumbers and urchins) and many others.

Unique and Imbalanced

While many are still identical to their ancestors on the South American mainland, due to the remoteness of the region and the diversity of habitat just as many have adapted in order to survive. It's estimated that around 52% of them are endemic. This means that some groups are represented in greater proportion than others, so they are considered to be "imbalanced". 

It is not known exactly how many invertebrate species are found throughout the archipelago, although in 2001 the number was estimated to be well over 2,000 (just for terrestrial ones), with the insects the most diverse and numerous. Some of the insects that may be seen on a Galapagos wildlife cruise include butterflies, dragonflies, moths, wasps, grasshoppers, spiders and flies.

Giant Snails and Colourful Crabs

The giant land snails are a distinctive group comprising around 60 species. They are similar to Darwin's Finches in that they appear to have made specific adaptations to survive in particular habitats.

While most invertebrates don't enjoy the glamorous status of some of the mammals and reptiles seen on a Galapagos wildlife cruise, one certainly attracts attention. The delightfully skittish Sally Lightfoot Crab can be seen scurrying between rocks on the shoreline, and its vibrant red and blue shell makes it a favourite with nature lovers.

While at first glance this group may not be as impressive as the Giant Tortoise or have the character of the quirky Blue-footed Booby, they are no less interesting and just as important to maintaining the status quo of archipelago's ecosystem.

Author Plate 

Marissa Ellis-Snow is a freelance nature writer with a special interest in the Galapagos Islands. For those interested in a Galapagos wildlife cruise, Marissa recommends the itineraries organised by Naturetrek, which have brought her unforgettable sightings of a wide range of species in one of the most spectacular regions on Earth.