Digestive enzymology in two
species of clam
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, Aquaflow ref. :
TL2003-172
The objective of this project is to study the
digestive process in 2 species of clam of commercial interest: Ruditapes
decussatus and Venerupis pollastra,
focusing on their enzyme biochemistry. The project aims to develop in vitro formulation systems to assess the nutritional quality of
feedstuffs for clam-seed culture. The project began in December 2002 and
will last 3 years.
At present Galicia produces 4.000 tonnes of clams,
but market demand requires 20,000 tonnes. There is an obvious need for a
production increase, which implies the transformation from the actual
extraction method (hand gathered shellfish) into a real culture. However,
the most limiting factor is the supply of seed from hatcheries.
If clam hatchery seed productivity is to be
increased, improvements in any other aspect involved in its production
(nutrition, pathology, culture conditions, etc) will eventually benefit clam
availability. In that respect, it is of high interest to reduce dependence
on live food used in the production of clam seed. A viable alternative to
the provision of live food is the use of dry formulated diets, which would
reduce costs and increase total production. An in
vitro test can be used as a tool to assess dry diets used for feeding
bivalve seed (these tests are already available for other groups of cultured
species). This test would allow both feed companies and others producing
seed to assess nutrient quality of various alternative feedstuffs, more
rapidly and less costly than the in
vivo tests.
The objectives are:
To improve the basic knowledge on digestive
enzymology of two cultured bivalve species of high commercial interest.
To characterise digestive enzymes of the two species
of clam, through larval and post-larval development.
To assess potential enzymatic induction mechanisms
determined by changes in feed quality in each species.
To use acquired knowledge in order to improve
formulation of alternative feeds; thus reducing dependence on seed
production and a general decrease in cost production, and
To assess raw materials which have not been
previously used in bivalve feeding.
Results obtained so far include an aproximation of
the digestive enzymology in these species, which have enabled the
determination of enzymatic activities. Amylase activity has also been
characterised. Although the presence of digestive enzymes is similar in both
species, amylase activity in V.pollastra is significantly higher than
in R. decussatus. The
optimal operating temperature and pH were also similar in both species.
These preliminary results determining digestive
enzymology will be very useful in the development of specific diets in
future experiments.
This collaborative project is funded by the Spanish
“Plan Nacional de I+D+I (2000-2003)” and involves: “Instituto Español
de Oceanografía” and “Departamento de Biología Aplicada de la
Universidad de Almería”.
For more information, contact:
Marina Albentosa
Centro Oceanográfico de Murcia - IEO
Varadero, 1, Apdo. 22
30740 San Pedro del Pinatar
Murcia - Spain
Tel: 968 18 05 00 - Fax: 968 18 44 14
E-mail:
malbentosa@mu.ieo.es