Graduate School of NOC PhD Project Description

Dr Jon Copley (SOES), Dr Adrian Glover (NHM): Ecology and reproductive biology of whale-fall annelids and wood-fall molluscs

Suitable for graduates with degrees in: Biology

This project has possible CASE support

Keywords: deep sea, osedax, xylophaga

Rationale

The normally food-poor deep sea is punctuated in space and time by organic-rich remains such as the carcasses of dead whales, or sunken wood. Studies have shown that although whales are rapidly consumed by scavenging organisms, their large oily bones may remain on the seabed for several years, perhaps hundreds of years in some instances (Smith & Baco, 2003). One of the more astonishing discoveries in recent years is an entire clade of novel polychaete worms, Osedax, that are able to bore into whale bones and consume the lipids and collagen within using a novel bacterial symbiosis (Rouse et al., 2004; Glover et al., 2005). Remarkably similar functional adaptations exist for the clade of deep-water molluscs, Xylophaga, that are able to bore into wood that has fallen to the seabed (Turner, 1973). Reproduction in both these groups is a unique challenge as the organisms are sessile, yet must be able to colonise highly dispersed, ephemeral habitats. Reproductive studies on Osedax have shown that they have evolved dwarf males which fertilise eggs as they are released into the water column. Few studies have yet been made of Xylophaga, and no comparisons made between the two groups.

Methodology

The overall aim of the project is to determine how organisms such as Osedax and Xylophaga are able to disperse across the deep seafloor, and rapidly colonise available habitats. The project will be divided into the following objectives:
(1) To determine the presence of potentially novel species of Osedax and Xylophaga at new experimental sites in the Cayman Trough and the Antarctic;
(2) To calculate the growth rates and onset of gametogenesis in these species;
(3)To describe the degree of sexual dimorphism and determine the method of egg fertilization in Osedax and Xylophaga;
(4) To determine larval longevity in shallow water Osedax and teredinid species at an experimental location in a Swedish fjord (this will involve collaboration with thesis advisory panel member Dr Thomas Dahlgren at the University of Goteborg);
(5) To model suitable habitat and dispersal requirements for both species using inferences from reproductive biology, population genetics, hydrography and the availability of substrate.

Training

The student will receive training in oceanographic sampling at sea, participating in a research cruise to recover a whalebone and wood-fall experiment from 5500 metres deep in the Cayman Trough. They will also undertake experimental studies in aquaria, micron-CT scanning, scanning electron microscopy, microscopy, histology and sectioning, image analysis, larval biology, hydrography, data analysis and computer modelling. The student will be expected to spend approximately 50% of their time at the NHM in London and NOCS respectively. At NOCS, they will take part in the Graduate School training programme that includes communication skills (writing research papers, presenting seminars, communicating with wider audiences) and career development.

Wider implications

The project has relevance to a fundamental question in deep-sea biology – how organisms can disperse between apparently isolated habitats, and to societal issues such as the impacts of whaling on marine ecosystems, and the human impact on Antarctica of wood, wood-borers and invasive species. Commercial interest is in the field of understanding how wood is destroyed in the marine environment.

Background reading

Glover AG, Kallstrom B, Smith CR and Dahlgren TG (2005). World-wide whale worms? A new species of Osedax from the shallow north Atlantic. Proceedings of the Royal Society B, 272: 2587-2592.
Rouse GW, Goffredi SK and Vrijenhoek RC (2004). Osedax: Bone-eating marine worms with dwarf males. Science, 305: 668-671.
Smith CR and Baco AR (2003). Ecology of whale falls at the deep-sea floor. Oceanography and Marine Biology: an annual review, 41: 311-354.
Turner RD (1973). Wood-boring bivalves, opportunistic species in the deep sea. Science, 180: 1377-1379.

This project is associated with NOCS research in Ocean Biogeochemistry & Ecosystems

jtc@noc.soton.ac.uk Pages served at NOCS