DrMurray Thomson

Project Opportunities

Title: The anatomy and physiology of the intertidal marine isopod Cirolana harfordi

Summary of opportunity:

The intertidal isopod is a remarkably successful scavenger and predator and yet almost nothing is known about its development, anatomy and physiology, so this animal presents a unique challenge to a motivated and inquiring biological scientist.

Opportunity synopsis:

Cirolanid isopods are important to marine food webs around the world but can also be damaging pests to the fishery industry, especially to fish cultured in nets. These isopods are also known to attack dead, dying or living animals including humans.  It is thought that cirolanids are especially attracted to fish that have been injured by events such as ostracod attack and will affix to fish using the sharp dactyls of the pereopods so as to eat various tissues including the gills. In addition, polychaetes, crustaceans and carrion are common elements of the cirolanid diet and some species are known to also eat ostracods, foraminiferas, sponges, bryozoans, tunicates, nematodes, cephalopods, plant material and mammalian tissue. The smallest organism a cirolanid isopod will eat, however, has not been determined and the smallest size of particle of food ingested by these animals is also not known. Crustaceans that have a suitable compliment of setae on the mouthparts can retain small animals and particles of food such as those in the 2 – 200 micrometre diameter range using their setae as a mesh or net to prevent loss of food from the pre-oral space  Additionally, crustacean mouthpart setae have the roles of housing olfactory receptors and mechanoreceptors as well as acting to clean and groom mouthparts and surrounding structures.

Cirolana harfordi (Lockington, 1877) is a common and widely distributed intertidal cirolanid isopod, that has been found in Australia, Japan and along the West Coast of North America. C. harfordi has been described as a scavenger as well as a predator, it eats small crustaceans and polychaetes that are up to 0.5 mm in diameter without macerating these with its mouthparts and appears to eat larger animals, living or dead by biting off sections of tissue. The food from one meal can fill the animal’s elastic digestive system which expands to fill the posterior body cavity maintaining nutritional sustenance for two to three weeks.

Recent studies on the mouthparts of C. harfordi suggest that the animal may also be a filter feeder, and studies using restrained animals and video cameras then introducing different sized particles of food and of different types into the water will yield valuable data on its strategies. The movement of the animals can be tracked with video and analysed using computer software.

C. harfordi like many crustaceans has two sets of antennae that it uses to sense food in the environment, studies that ablate one or more of these then introduce food into a maze will elucidate the roles of these different antennae in food detection and tell if different antennae play different roles such as long range detection versus long range detection.

Just like a shark is followed or carries remora fish, the isopod C. harfordi carries with it an amazing menagerie of organism ‘hangers on’ that are either attached to its body (epibonts) or that cling on and are mobile in its body. Characterizing the microscopic ecosystem that C. harfordi provides is an exciting opportunity for a scientist to plunge into uncharted territory. How this ecosystem would react to a changing world e.g. increased temperature, acidification and pollution such as copper from anti fouling paints provides a wealth of research opportunity for someone who is interested in discovering what some of the effects of global warming and marine acidification will have on this important marine food web component.

How the animal reacts to stress at a cellular and tissue level, provides a fascinating field for students interested in molecular biology and cell biology techniques to study the stress mechanisms triggered by environmental change. Heat shock proteins, reactive oxygen species and apoptosis provide systems to study the effects of stress in this marine animal under different scenarios.

----------Current Research Projects----------

Honours Projects

The Anatomy and Physiology of the Marine Isopod Cirolana harfordi

C. harfordi is a small crustacean that lives in the intertidal regions of the coast and estuaries. Prior to 2014 this animal was thought to lay eggs into a marsupial pouch, I discovered that was not true for Australian specimens and that this animal gives live birth. The mother carries 20-40 young called manca inside her body until term when they are born strong swimmers. The mother develops tissue that surrounds the young that may function as a primitive placenta. The mancas can obtain food directly from the mother either by biting holes in her digestive system to access pre-digested food or eating parts of her digestive system and its contents. Amazingly, the mother survives this incredibly stressful experience and can subsequently become pregnant again after her previous young are delivered. Both males and females in the species are social animals and their gregarious behaviour can be studied using arenas and video tracking. This social behaviour may have evolved to counteract predation. Other stressful issues for C. harfordi include dealing with desiccation, changing salinity and temperature as well as pollutants. Another fascinating feature of this animal is that it is at a stage of evolutionary transition showing the start of amphibious adaptation from sea to land. Various honours projects are available to study the biology of this fascinating species.

Heat Shock Proteins as Indicators of Stress in Echinoderms

Supervisors: Maria Byrne (Anatomy and Histology), Murray Thomson.

Many newly expressed cellular proteins need a little help to fold into their correct 3 dimensional structure and they are given this help by specialized proteins that are referred to as molecular chaperones. Heat shock proteins are a major family of molecular chaperones and these proteins were discovered for their ability to help reform the high levels of incorrectly folded proteins that are produced by elevated temperatures.

This kind of stress is pertinent to organisms that live in marine environments with widely fluctuating temperatures and of increasing interest in the face of climate change. This presents an exciting opportunity to work in the field and the lab in studying the cellular effects of environmental stress on marine creatures such as sea urchins and sea stars (an adult and juvenile of each shown below) and you can work in both Maria's, and my lab.

For more honours project opportunities in Behaviour, Physiology and Ecology click here.

Behaviour, Physiology and Ecology Lab

This is a large and modern shared lab space utilized by academics, postdocs, PhD and honours students and other researchers. Equipment includes a cryostat to cut thin sections of tissue, electrophoresis gear for nucleic acid and protein studies and digital microscopes that can record with stills and video.