Abstract
M.Sc.
Abalone are among the world’s leading shellfish consumed by human populations.
Harvesting in California began in the late 1800s from intertidal zones and in the early
1900s wild abalone were collected by diving. Popular demand for abalone products in
the Far East then led to extensive harvesting of wild abalone and a drastic decline in
population numbers. This problem was overcome to a degree by the development of
land-based abalone farms. At these farms it was possible to breed abalone on a large
scale. Currently twelve abalone farms operate in South Africa and the estimated
production for 2006 was 537 tons of meat, worth R 80 mil. Parasites and diseases
pose threats to the production of abalone, especially under farmed conditions, and can
cause considerable financial loss. Labyrinthuloides haliotidis, Haplosporidium nelsoni
and Terebrasabelle heterouncinata are a few parasites that contribute to the above
mentioned problems. Lately, a new protozoan parasite was discovered in the digestive
glands of Haliotis midae farmed in the Western Cape Province, during routine health
assessments. For the purposes of this dissertation it is designated an unidentified
digestive gland parasite (UDP). The aims of this study are thus to undertake a
comprehensive literature review of parasites infecting wild and farmed abalone, as
well other shellfish species, describe and characterise the UDP infecting the digestive
gland of Haliotis midae based on its structure and ultrastructure, evaluate the role of
this parasite in disease by analysing data from histological studies, provide a
preliminary indication of the life cycle of this parasite, attempt analysis of DNA from
the UDP, and identify potential areas for further research into control of the parasite.
A total of 180 abalone, (Haliotis midae) were collected from three abalone farms in
the Western Cape during May 2005, October 2005, January 2006 and January 2007.
To establish whether this parasite also occurs in wild abalone, a single sampling (six
H. midae and 28 H. spadicea) took place during 2006 in Tsitsikamma National Park.
Collected farmed and wild abalone were weighed and measured, removed from their
shells and then killed according to accepted methods before their digestive glands
were removed.