Dr Mary Sewell

Marine Invertebrate Ecology Laboratory

Female Odantaster validus	Leptosynapta clarki with young
A Hawaiian fashion shop	A Great Barrier Reef sea cucumber

Research in this lab focuses on aspects of the reproduction and development of marine invertebrates. We are located in the Basement of the Thomas Building (Level 1), though considerable research takes place at the Leigh Marine Laboratory, and at other aquaculture facilities in Auckland and Northland.

For further information contact Dr. Mary Sewell.

Maternal Investment

Maternal reserves in echinoderm eggs typically involve two main components: protein and lipid (Jaeckle 1995). Planktotrophic, feeding, larvae tend to have a higher protein: lipid ratio in spawned eggs; related in part to the need for structural proteins to build the larval feeding structures (Jaeckle 1995). Lecithotrophic, non-feeding, larvae tend to have a lower protein: lipid ratio, with higher amounts of lipids to sustain development in the absence of feeding (Jaeckle 1995). Recent research on the types of lipid found in echinoderm eggs have shown that small eggs contain low levels of triglycerides, while larger eggs have larger concentrations of wax esters (Villinski et al. 2002). In collaborative research with Assoc-Prof. Maria Byrne (University of Sydney) we are using the School of Biological Sciences Iatroscan TLC/FID system to examine the evolution of maternal provisioning in congeneric asteroids and ophiuroids from New Zealand and Australia with feeding and non-feeding modes of development.

	Step 1: After the lipids are extracted from the sample material a 1 ul volume is spotted on the Chromarods.
	Step 2: The Chromarods are developed in an appropriate solvent system to separate the lipid classes based on polarity. We are using the Parrish (1997, 1999) triple development that separates up to 11 different lipid classes.
	Step 3: After solvent removal the Chromarods are read in the Iatroscan and a chromatogram produced with the associated computer software.

The chromatogram below was produced from the eggs of the New Zealand echinoid.

Evechinus chloroticus using the Parrish (1997, 1999) triple development. The major lipid classes are phospholipids (PL, AMPL), triglycerides (TG), cholesterol (ST) and aliphatic hydrocarbon (HC). Ketone (KET) is the internal standard and non-lipid material (NLM) remains at the origin.

Antarctic Biodiversity

The pelagic community of the Ross Sea consists of a permanent component (= holoplankton) and a temporary component which is primarily made up from the larval stages of benthic marine invertebrates and fish (= the meroplankton). To date little attention has been paid to the distribution and abundance patterns of the meroplankton in the Ross Sea - research we have been doing since 2001.

To understand the biodiversity of the Ross Sea plankton it is important to be able to identify the larvae of marine invertebrates and fish to the species-level. Traditionally identification of larvae to the species-level has relied on the time consuming and labour-intensive process of fertilizing eggs and culturing the larvae through to metamorphosis. In Antarctica, the low seawater temperatures and long developmental times make this procedure even more problematic than in temperate environments. We are instead using a molecular-based approach to match DNA sequences of the meroplankton with adult benthic marine invertebrates. With funding from New Zealand’s Ministry of Fisheries (ZBD 2002-02 Whose larvae is that?: Sewell, Lavery & Baker) we conducted field work in McMurdo Sound in November and December 2002 and have developed a method for obtaining DNA sequence from Antarctic larval forms.

In our research programme we are using a collapsible plankton net that allows us to take samples through the 2-3 metres of sea-ice that is found in McMurdo Sound and the coastal Ross Sea. The pictures above show the net in the open position. This net can be used through a 10cm drilled ice hole, or through a tidal crack as shown.

Plankton samples have been collected from McMurdo Sound (Sewell, 2005, Polar Biology) and as part of the Latitudinal Gradient Project of Antarctica New Zealand at Cape Hallett in the northern Ross Sea.

Laboratory Members

Researchers in the Marine Invertebrate Ecology Group include:

	Dr. Mary A. Sewell. Mary is working on a variety of topics in the general area of marine invertebrate reproduction and development. m.sewell@auckland.ac.nz
	Berit Finkennest. PhD student. Berit is investigating the metabolic rates of the sea urchin Evechinus chloroticus during early development. b.finkennest@auckland.ac.nz
	Jennifer Jury. BSc(Hons) student. Jennifer is investigating the seasonality and abundance of benthic marine invertebrate larvae in the Ross Sea, Antarctica. Jjur005@ec.auckland.ac.nz
Lincoln Tubbs. PhD student. Lincoln is investigating the use of oral anthelmintics for monogenean parasites of the kingfish. l.tubbs@auckland.ac.nz
Marcus Cameron. MSc student. Marcus is investigating the use of the sediment dwelling heart urchin, Echinocardium cordatum, as a potential bioindicator and bioaccumulator of marine pollutants. m.cameron@auckland.ac.nz