Parasitology



Infection of Gammarus duebeni populations by two vertically transmitted microsporidia; parasite detection and discrimination by PCR–RFLP


J. C.  HOGG  a1 , J. E.  IRONSIDE  a1 , R. G.  SHARPE  a1 , M. J.  HATCHER  a2 , J. E.  SMITH  a1 and A. M.  DUNN  a1 c1
a1 School of Biology, University of Leeds, Leeds LS2 9JT, UK
a2 School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK

Article author query
hogg j   [PubMed][Google Scholar] 
ironside j   [PubMed][Google Scholar] 
sharpe r   [PubMed][Google Scholar] 
hatcher m   [PubMed][Google Scholar] 
smith j   [PubMed][Google Scholar] 
dunn a   [PubMed][Google Scholar] 

Abstract

We screened a population of the brackish water crustacean Gammarus duebeni from the Isle of Cumbrae for the presence of vertically transmitted microsporidia. We compared 2 screening techniques; light microscopy and PCR-based detection using generic 16S rDNA microsporidian primers. Fifty percent of females from this population tested positive for vertically transmitted microsporidia. The PCR screen was 100% efficient in comparison with existing LM based screening. In addition, the PCR screen produced bands of 2 sizes suggesting that more than 1 species of microsporidian was present. Sequencing revealed 2 distinct species of vertically transmitted microsporidia; 33% of females were infected with the feminizer Nosema granulosis and 17% were infected with a new species which we provisionally designate Microsporidium sp. On the basis of sequence information, we developed a discriminatory PCR–RFLP test based on MspI and HaeIII digests. This screen allows rapid detection and discrimination of vertically transmitted microsporidia in natural field populations. We applied the PCR–RFLP screen to a second G. duebeni population from the Isle of Man. This population also hosted these 2 parasite species. In total 45% of females harboured N. granulosis and 10% harboured Microsporidium sp. No dual-infected individuals were found in either population. The occurrence of 2 vertically transmitted parasites within a population has implications for our understanding of parasite–host relationships in the field and we discuss factors affecting the dynamics of parasite–parasite competition and coexistence.

(Received December 14 2001)
(Revised February 12 2002)
(Accepted February 12 2002)


Key Words: Nosema granulosis; Microsporidium sp.; microsporidia; PCR–RFLP; Gammarus duebeni; vertical transmission.

Correspondence:
c1 Corresponding author: School of Biology, University of Leeds, Leeds LS2 9JT, UK. Tel: +44 (0) 113 3432856. Fax: +44 (0)113 3432835. E-mail: a.dunn@leeds.ac.uk


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