ECOLOGY
MICRO-HABITAT
Gonodactylaceus falcatus, one species of 'smashing' Mantis shrimp, was collected at the reef flat on Heron Island swimming between coral rubble at sunset and lowtide. Although they are highly predatory animals, many Mantis shrimpare surprisingly reclusive, spending the majority of their time guarding a particular cavity within the coral rubble (Atkinson et al.,1998; Caldwell & Dingle, 1975). When not in their cavities, mantis shrimp become apparent from their extremely fast swimming action while on the lookout for resources.
The area of the reef flat where G. falcatus was found, is the location of a very strong intertidal current. Mantis shrimps are known for their preference of turbulant intertidal regions particularly areas away from biofouling elements. Thereason for this may well have a chemo-sensory basis(Mead et al., 2003). The anntenules of various crustaceans possess sensory hair-like structures or aesthetascs which contain olfactory neurons. These contribute to sensory behaviours such as the tracking of odour plumes, and mantis shrimp are known to sample odours by flicking their antennules (Mead et al., 1999). The antennules and, in particular, their plume tracking behaviour in micro-habitats with strong waves have been shown to be more active (Mead etal., 2003). See video below.
ASSOCIATIONS
As predators, stomatopods are key ecological contributors to various trophic levels within an ecosystem (Caldwell et al., 1989). While there is a great deal of research has been conducted regarding their biology, phylogeny and distribution, less is known about their specific role and interactions within the ecosystem (Antony etal., 2010). It is known that smashing stomatopods, such as G. falcatus and including other members of the Superfamily Gondactyloidea, predate on hard-shelled molluscs and many types of crustaceans. Size relative to itself may limit the predation of the stomatopod. Predators of mantis shrimp include some species of octopus, however in many cases, stomatopods are fully capable of succeeding in defensive battles.
The diversity of the invertebrate phyla associated with this animal (within its ecological niche) was awe-inspiring on the afternoon of its collection. Hidden beneath the rubble, approximately 500m from the site of the Mantis Shrimp, was a species of octopus (Phylum Mollusca)- entirely hidden within the boulder plates. Only its eye was visible to us. When we attempted to take an empty shell outside the entrance to its lare, it extended one long tentacular arm, thus confirming its identity. Within its cavity, a pile of such shells had been accumulated and it may have been that the octopus was using the remnants of its prey for protection and camoflage as well.
After collecting the mantis shrimp, we noticed a tiger-printed object flash past us on the surface of the outgoing tide. An epaulette shark (Phylum Chordata) had caught our attention and its swimming style was remarkable. It appeared to almost.....walk across the shallow low tide reef flat. Apparently very shy, it hid itself within the coral with only its long tail visible. These noctural sharks are remarkable for their ability to conserve oxygen during the anoxic conditions ofthe night time intertidal reef pools. Reefs are typically less oxygenated at night time as photosynethetic processes shut down. Additionally, numerous hermit crabs (Phylum Arthropoda, Order Decapoda) and stomes (Phylum Mollusca), a species of marine snails were spotted within the stomatopod's micro-habitat. These are a common prey for various species of mantis shrimp.
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