Marine sponges are known to produce secondary metabolites that have roles including chemical defence against cellular challenge. An investigation into Cliona celata around the Bay of Plenty (New Zealand) was conducted in response to discovery of unusual metabolites that had the potential to be biologically active. The study was designed to determine chemical variation in the sponge over small spatial and temporal scales and to determine the possible ecological triggers for the presence of these metabolites. The hypothesis was that a chemical defensive response would be elicited 24-48 hours post a cellular challenge event such as physical damage. The hypothesis was based on the fact that the sponge heals quickly when damaged with little evidence of necrosis.
Cliona celata was chosen as there is little knowledge of the species within New Zealand, and previous work showed a single specimen to produce brominated compounds, never before reported for this genus. This project examines whether the production of brominated compounds is common throughout all C. celata within the Bay of Plenty region or is a localised response.
A preliminary study was conducted to investigate spatial chemical variability of sponges from three locations, Leisure Island (intertidal), Rabbit Island (subtidal) (both on the coast adjacent to Mount Maunganui, Tauranga) and White Island (geothermal subtidal). A damage response experiment for Leisure Island and Rabbit Island specimens was conducted to determine chemical differences in healthy versus damaged sponges, and whether a chemical defence mechanism was utilised by the sponge species. Lastly, a stratification experiment was performed to establish whether chemical changes occur throughout the sponge or are localised to the immediate damage site.
Cliona celata identification was confirmed using spicule mounts. However, some variation between intertidal and subtidal specimens was noted with differences in spicular morphology, likely due to variations in chemistry and micro-environments.
On a small scale, extracts of each sample were prepared and analysed using Liquid Chromatography Mass Spectrometry (LCMS). Damaged and non damaged sponge specimens were subjected to an MTT assay using the human cervical cancer cell line (HeLa). But the crude extracts showed no bioactivity in this assay.
Chromatograms obtained from LCMS, for all samples contained a common set of peaks, however, variations in intensities and some minor peak variations within the sites (intertidal, subtidal and geothermal subtidal) and individual specimens were noted, and could represent interactions with different micro-environments. A lack of chemical response to damage was not expected. It is therefore hypothesised that the lack of secondary metabolite production observed, is due to cells reverting to archaeocytes to repair and re-grow the removed sponge section, a histological response rather than a chemical one.
It was hypothesised that specimens with increased levels of epibiont coverage had increased production of certain metabolites, as represented by increased intensities of some peaks in chromatograms, however, to a threshold. Once epibiont coverage of approximately 50% was met, novel chemicals were thought to be produced by the sponge. Two sponge samples did produce monobrominated and dibrominated compounds, however, these were localised events and could potentially be the response to an unidentified external stressor or epibiont coverage. The stratification experiment indicated that the isolation and production of these brominated compounds may be restricted to the pinacoderm of the sponge, possibly suggesting a transient chemical response as cells re-organise themselves in a healing process. However, further investigation is required with all experiments and a more comprehensive time series of samples needs to be taken post damage treatment.
This project provides a preliminary study into the chemical variation and chemical response to damage for intertidal and subtidal Bay of Plenty Cliona celata. Any hypotheses made during this thesis need to be further examined to be accepted.
