Myxobolus lepomis n. sp. (Cnidaria: Myxobolidae), a gill myxozoan infecting Lepomis marginatus Holbrook and Lepomis miniatus Jordan (Perciformes: Centrarchidae), in the Big Thicket National Preserve, Texas, USA.

A parasitological survey of freshwater fishes in the Big Thicket National Preserve in southeast Texas revealed myxozoan infections in two species of sunfish, Lepomis marginatus Holbrook and Lepomis miniatus Jordan (Perciformes: Centrarchidae). Pseudocysts were elongate-oval, 988 × 485 µm (ex L. marginatus) and 800 × 606 µm (ex L. miniatus) and demonstrated a predilection to the edge of the primary gill lamellae. Myxospores consistent with the genus Myxobolus were oblong, 16.8-21.3 (19.0 ± 0.9) µm long, 7.0-8.8 (7.9 ± 0.5) µm wide and 5.3-6.1 (5.8 ± 0.3) µm thick (ex L. marginatus) and 17.2-20.3 (18.8 ± 0.7) µm long, 7.5-9.9 (8.7 ± 0.6) µm wide, and 6.8-7.2 (7.0 ± 0.2) µm thick (ex L. miniatus); with 2 pyriform polar capsules 8.3-9.8 (9.0 ± 0.5) µm long, 2.2-2.7 (2.5 ± 0.2) µm wide (ex L. marginatus) and 9.2-10.5 (10.0 ± 0.4) µm long, 2.2-3.0 (2.8 ± 0.2) µm wide (ex L. miniatus). Statistically, the measurements of spore body width, polar capsule length, and polar capsule width were significantly different between myxospores from L. marginatus and L. miniatus. However, intraspecific genetic variability between isolates at the 18S rRNA gene was negligible, with < 0.8% variability across > 2,000 bp of sequence. The isolates shared no significant sequence similarity with any myxozoan deposited in the GenBank nucleotide database. Phylogenetic analysis inferred from the 18S rRNA gene from both L. marginatus and L. miniatus placed the isolates within a clade of myxozoan parasites of perciform fishes. Based on shared tissue and host family tropism, overlapping morphological characters and high degrees of sequence conservation at the 18S rRNA gene, we propose these isolates as morphologically distinct, genetically conspecific representatives of M. lepomis n. sp. from the gills of L. marginatus and L. miniatus in the Big Thicket National Preserve in Texas, USA.