Did you guess correctly?
This is a lobster, not a crayfish. We often use both names for the same animal, but crayfish are found in fresh water and lobsters live in the marine environment. Lobsters and crayfish are crustaceans, relatives of crabs, and like crabs they move about by walking. Unlike crabs, lobsters can use their tail to rapidly swim backwards and lack claws.
Along Victoria’s coastline live the southern rock lobster and the eastern rock lobster. These animals live on rocky reefs, using the many cracks and crevices as their homes. They are omnivores, feeding at night on seaweeds and bottom-dwelling invertebrates like worms, crabs, urchins and molluscs. They, in turn, are food for octopus, sharks, reef fish and of course humans.
The lobster has many remarkable features. The lobster eyes have a wide field of view and are exceptionally good at detecting motion in dim light. They have extremely long antennae to gather information about their environment. They have teeth, which are located inside their stomach, not in their mouth. These teeth grind the food like our molars and have growth rings like a tree which can be used to determine the age of a lobster.
In the dark rocky landscape of the reef with the constant noise of the waves, communication is challenging. Lobsters use chemical messengers called pheromones to communicate with each other. While pheromones are common in the animal kingdom, lobsters have a unique way of distributing them. They mix the pheromones with their urine which they release from under the antennae on their head. The urine/pheromone mixture is washed forwards by water that exits their body after passing over the gills. Lobsters of different ages and sexes produce different pheromones that tell other lobsters about themselves, especially when it comes time to reproduce.
Lobsters reproduce sexually, with the females in charge of the process. She chooses the biggest male who provides a sperm packet which she uses to fertilise her eggs. She may have up to 1,000,000 eggs, so a bigger male provides a bigger sperm packet capable of fertilizing all her eggs. She carries the fertilised eggs on her tail for between 4-6 months before releasing the newly hatched larvae into the currents which carry them out past the continental shelf, a journey of thousands of kilometres. Over the next 9-24 months the larvae grow and eventually become a transparent miniature lobster that returns to the reef. Only a few of the larvae survive to return to the reef and even less reach sexual maturity in another 5-6 years.
Watch the tiny transparent lobster, called a phyllosoma swim. It spends between 9-24 months swimming before returning to the reef.
If you would like to learn more about lobsters and the huge diversity of life that can be found in the shallows along our shorelines please contact Education Director Mandy Robertson on education@dolphinresearch.org.au
