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Life cycle studies on Renicola spp. (Digenea: Renicolidae) infecting
sea birds: DNA tools provide an update
N. Campbell1, C. Collins2, M. A. Cross3, J. C. Chubb3, C. O. Cunningham2, K. MacKenzie1, E. Hatfield2
1.School of Biological Sciences (Zoology) University of Aberdeen, Aberdeen AB24 2TZ. 2. FRS Marine Laboratory, 375 Victoria Road,
Aberdeen, AB11 9DB. 3. School of Biological Sciences, University of Liverpool, Liverpool, L69 7ZB.
Introduction
As part of a multidisciplinary EU funded research project (WESTHER),
which aims to identify stocks of Herring (Clupea harengus L.) to the west
of the British Isles, the parasite fauna of herring is being studied with the
aim of identifying potentially useful biological tags. Results of earlier
studies have shown metacercariae of Renicola spp (Fig. 1) may be
informative tags.
The complete life cycles of many renicolid digeneans are still unknown
due to the difficulty of identifying morphologically similar adult stages in
kidneys of seabird hosts to species level.
Fig 1. Renicolid Cercariae doricha left and
Cercariae pythionike metacercarial cysts.
Sea Birds
One way of solving this problem is to compare DNA from adult and larval
parasite stages. DNA sequences obtained from different life stages will be
the same irrespective of morphology, and can be used to associate the
relatively easily identifiable metacercarial stage with its adult form.
Turitella communis
Herring
Fig. 2. Life Cycle of Renicola spp. which
infect herring.
Methods
Renicola metacercariae were extracted from the abdominal cavity of
herring collected in sea-lochs on the west coast of Scotland. Adult
Renicola specimens were isolated from kidneys of puffin (Fratercula
arctica), fulmar (Fulmarus glacialis) and common guillemot (Uria
aalge) (Fig. 3a, 3b & 3c) collected from an RSPB site on Skye, on the
west coast of Scotland. Crude DNA lysates were obtained from
Renicola metacercariae and adults. These lysates were used in PCR
reactions to amplify the Internal Transcribed Spacer (ITS) region of
the
parasites’
ribosomal
DNA
using
primers
and
conditions
as
a
b
Fig. 3 .(left) Puffin, Fratercula arctica. Fig. 3 (centre) Fulmar,
described in Cunningham (1997).
Fulmarus glacialis. Fig. 3c (right) Guillemot, Uria aalge.
The ITS region of the ribosomal DNA is widely used for species identification, as it is robust and displays little geographical
variation. The ITS PCR products from larval and adult Renicola were purified and sequenced, and the sequences compared
with each other, and to sequence databases. Sequences were obtained from three individuals of C. pythionike and C. doricha
from herring, and from three adult Renicola from each seabird species.
Results and Discussion
• ITS PCR products of 950 bases were obtained from metacercarial and adult Renicola.
• 85% similarity was found between the ITS sequences of C. doricha and C. pythionike.
• Identical ITS sequences were obtained from C. pythionike and adult forms of Renicola from all of the
seabird species examined, indicating that C. pythionike is the larval form of Renicola which infect
fulmars, puffins and guillemots.
Three renicolid species, R. glacialis, R. wrighti and R.
pseudosloanei have been described from the fulmar, puffin and
common guillemot respectively. The identical DNA sequences
obtained for adult worms from these seabirds questions the
validity of these as different species. R. glacialis and R. wrighti
may now have to be considered as junior synonyms of R.
pseudosloanei (Wright, 1954), first described from the common
guillemot. The identity of the final host for C. doricha remains
unknown.
Puffin
Fulmar
Guillemot
R. pseudosloanei Renicola spp.
R. glacialis R. wrighti R. pseudosloanei
Combining DNA and morphological analysis is a useful approach
to
investigating
parasite
life-cycles
especially
where
morphologically indistinguishable stages occur. Further analysis
C. pythionike
C. doricha
of Renicola specimens from fish and bird hosts will help clarify Fig. 4 Analysis of ITS sequences reveals puffins, guillemots and
are infected by the same species of Renicola, while the final
the taxonomy of the genus and improve the efficiency of their fulmars host
of Renicola cercaria doricha remains unknown.
References
use as biological tags for herring.
Cunningham CO. (1997) Species variation within the internal transcribed spacer (ITS) region of
Gyrodactylus (Monogenea:Gyrodactylidae) ribosomal RNA genes. J Parasitol. 83(2):215-9.
This project is funded by the European Union under the
5th Framework, Contract no. QLRT-2001-01056