Morphology and small-subunit ribosomal DNA sequence of Henneguya adiposa (Myxosporea) from Ictalurus punctatus (Siluriformes).

The original description of Henneguya adiposa, a myxozoan parasitizing channel catfish Ictalurus punctatus, is supplemented with new data on spore morphology, including photomicrographs and line drawings, as well as 18S small-subunit (SSU) ribosomal DNA (rDNA) sequence. Elongate, translucent, linear plasmodia were situated between the connective tissue bands of the adipose fin. The myxospore possessed an elongate, lanceolate spore body, flattened parallel to the suture line: 17.1 +/- 1.6 microm (range 14.7-20.5) in length, 4.1 +/- 0.3 microm (range 3.4-4.6) wide in valvular view, and 3.7 +/- 0.3 microm (range 3.2-4.0) thick in sutural view. Polar capsules were pyriform and unequal in length, measuring 7.2 +/- 0.6 microm (range 5.8-8.3) long and 1.3 +/- 0.2 microm (range 0.9-1.9) wide, with at least 8 turns in the polar filament coil. The caudal appendages were 38.0 +/- 6.2 microm (range 23.2-48.8) and split posteriorly. The total length of the spore was 55.6 +/- 6.5 microm (range 40.7-65.8). Phylogenetic analysis of 18S SSU rDNA sequence data placed this isolate within the Myxobolidae, indicating a close relationship to a group of Henneguya species parasitizing channel catfish in the southeast United States.