With respect to the phylogenetic tree, it may be argued that
comparison using 848 bp of a single gene does not cover a sufficient
proportion of the target genomes to prepare a robust tree. Despite
this caveat, the relationships among the database
microsporidians in our phylogenetic tree (Fig. 6) are similar to
those reported for them in more comprehensive comparisons (Vossbrinck
and Debrunner-Vossbrinck, 2005). In any case, our preliminary
analysis based solely on this region indicates that E.
hepatopenaei tends to group with other microsporidians associated
with aquatic host species. This intriguing relationship may be followed
up using longer sequences and more genes whenever this
information becomes available.
For other members of the family Enterocytozoonidae previously
described from crab hosts (i.e., genus Enterospora, Stentiford, 2007)
there is no available genetic information. However, they differ
from E. hepatopenaei greatly in that they develop within the host
nucleus rather than the cytoplasm. In addition, E. hepatopenaei infected
all cell types of the hepatopancreatic tubule epithelium except
F-cells while Enterospora canceri infected all cell types except
B-cells (Stentiford et al., 2007; Stentiford and Bateman, 2007).