Experimental biology topics

Country codes: HO (Honduras), IN (Indonesia), MA (Madagascar), ME (Mexico), PE (Peru), SA (South Africa)

HO20 Physiology and behaviour of the long-spined sea urchin, a keystone Caribbean coral reef herbivore

The long-spined sea urchin (Diadema antillarum), is responsible for the maintenance of coral reef health throughout the Caribbean. However, in the early 1980s a region wide epidemic reduced their populations by an average of 98%, which stimulated the widespread macroalgal phase-shifts that currently plague the Caribbean. Despite the fact that restoration of D. antillarum is widely believed to be a conservation priority we know surprisingly little about their physiology and behaviour. The aim of this project is therefore to explore the innate responses of this keystone species to numerous external environmental and physical factors, such as food and habitat availability, rising sea surface temperatures and ocean acidification, which may affect the success of targeted conservation efforts. These questions will be answered through a series of laboratory manipulations on urchin specimens collected from nearby reefs.

Extended Project Summary

HO21 The behaviour of invasive lionfish on Caribbean reefs

The invasion of lionfish in the Caribbean has developed into one of the greatest threats to the survival of the region’s coral reefs thanks to the devastating effect they have on native fish populations. Research has naturally focused on mapping the spread of lionfish, quantifying their ecological impacts, and exploring management interventions to reduce their numbers. However, improving our understanding of the behaviour of this species on non-native reefs is of particular interest to better grasp the underlying success of their invasion. This project will assess lionfish behaviour both on the reefs and in a small laboratory, where individuals will be captured and processed. Particular focuses of this work could include prey selectivity, and habitat preferences to investigate the cryptic nature of this species, and data can be linked to ecological characteristics of the reef itself.

Extended Project Summary

IN27 Behaviour adaptations of dwarf cuttlefish, Septa bandensis

(start dates 20 June, 27 June or 04 July)

As a group, cephalopods display a high level of nervous integration resulting in complex behavioural responses and social interactions that rival those seen in higher vertebrates. The Wakatobi National Park is home to at least 30 cephalopod species, many of which can be found inhabiting reef and reef-associated habitats. The dwarf cuttlefish (Sepia bandensis) is the most abundant cephalopod species found in the park, occurring in large numbers near rocky shorelines, on coral rubble, in seagrass meadows and at mangrove margins. While the species has some minor commercial value in local artisanal markets, its major importance lies in their ability to shape habitat ecology by indiscriminately preying on large numbers of small to medium sized crustaceans. In spite of their ecological importance, little is known about the feeding behaviour or social interactions in this species. The primary objective of dissertation projects could include aspects of feeding behaviour, effects of competition, and social interactions between individuals of different gender and/or size. Other studies may be considered but require approval of the field supervisor. All studies would be conducted using captive animals housed in the Hoga Island Research Laboratory and proposed studies must be non-lethal. Students must also check with their university advisor regarding their universities policies and procedures for working with cephalopod animals. Students are strongly encouraged to contact their project field supervisor early in the proposal development process.

Extended Project Summary

IN31 Evaluating potential effects of rising environmental temperatures in thermal ecology of fiddler crabs, Uca spp.

Often exhibiting high levels of biodiversity and endemism, mangroe forests demonstrate a remarkable interdependence between local flora and fauna such that a loss of diversity or density in one group has marked adverse effects on the other. Declines in burrowing crustacean populations, for example, have been shown to result in reduced organic turnover, decreased nutrient and energy cycling, and diminished primary productivity in mangrove species. Fiddler crabs (Uca species) are one of several semi-terrestrial, burrowing, mangrove decapods making up a keystone group commonly referred to as engineers. Indonesia boasts the highest diversity of fiddler crab species of any country in the world with 14 total species, seven of which can be found within an area of 4-square meters within the Ambeua Mangrove near Hoga Island. Previous research at the Hoga Marine Laboratory has shown that local fiddler crab populations are relatively tolerant of high temperatures; however, with environmental temperatures across the Malay Archipelago expected to increase by up to 4°C in coming decades, it is unclear how fiddler crab populations and ultimately mangrove ecosystems, may be affected. Potential dissertation projects could evaluate differences in thermal adaptations of Uca spp. occupying different intertidal regions, or may look at acclimation responses of a single Uca species. All studies would include a field observation component, though most of the empirical work would take place in the Hoga Island Research Laboratory. Students are strongly encouraged to contact their project field supervisor early in the proposal development process.

Extended Project Summary

IN32 Using the past to predict the future: long-term changes in the community ecology of coral reefs

The global demise of coral reefs has been well documented in the scientific literature. The reefs of the Wakatobi have been assessed by Operation Wallacea for the past 15 years. The abundance of reef building corals has declined but other functional benthic taxa, such as soft corals, have increased. As well as an overall decrease in reef building corals, the types of corals present, both in terms of species and colony structure have also changed. Where once reefs in the region harboured a mix of different colony growth forms (including branching, table and foliose corals) the system today is dominated by massive (boulder-like) and encrusting corals. The physical form of the reef is therefore changing which has implications for resident and transient fish communities. During 2018 the research teams would like to continue to monitor the reefs around Hoga Island data from which can be compared to previous data to determine rates of change in key coral reef community characteristics. In 2017 the monitoring team trialled a recently developed technique to 3D model patches of reefs to gain a better understanding of the interactions between the physical structure of the habitat and fish biodiversity. The relationship between benthic structure and fish community is a complex one but if habitats are to be actively restored we need to know how the fish community is likely to respond. Within this research area dissertations could focus on the system as a whole (e.g. long-term changes in reef biodiversity and community structure), or could focus on particular fish whose abundance has changed and combine with studies that compares the behavioural traits of species whose abundance has decreased, remained constant or increased to identify successful ecological strategies. Other projects could expand on the 3D reef modelling techniques to gain better understanding of benthic-fish interactions. It may be expected for example that smaller fish species respond to different physical characteristics than larger fish which may respond to structures over greater spatial scales. Data collected will be used to define future protective and active management intervention.

MA37 Colour variability and the ecological use of colour in the chameleons and geckos of Mahamavo

There are a wide range of endemic lizards in the dry deciduous forests of northwestern Madagascar. Colour is used in fundamentally distinct ways by the different taxonomic groups of lizards found in Mahamavo. Chameleons are depicted in the media as solely using colour change for crypticity, but in reality the main role of colour change here is in communication with other chameleons. There is some interesting colour variability within Angel’s chameleon and Oustalet’s chameleon as well. There are three species of Uroplatus geckos that really do use colour and colour-change to maintain crypticity. One species is a dead-leaf mimic, a second is a twig mimic and the third is a bark mimic. Colour is variable within species and some change colour quite effectively. Phelsuma are a third group of lizards in which there is substantial colour variability within individuals. They respond to changes in lighting and temperature as well as potential threats from predators. Questions regarding variation in colour and how colour-change is being used can be addressed in all three groups of lizards. Colour can be quantified through using standardized photographs or by using a specialised reflectance spectrometer depending on the specific research question being addressed. Analyses of colour can use general linear models to examine variation in hue, saturation and value and look for statistically significant differences or by using principal components analysis to examine and compare entire reflectance spectrums.

Extended Project Summary