On February 21, 2004, staff from the Clearwater Marine Aquarium responded to a stranding call for an ocean sunfish in the shallow waters of north Clearwater Beach, Florida. The animal was in lateral recumbency and was not making attempts to swim. Opercular movements were still evident. Since the animal was alive and no medical assistance could be provided, the United States Coast Guard helped relocate the animal a mile and half offshore in the Gulf of Mexico.3 On February 25, the animal's body was recovered for a second time from the beach; the animal was dead.
The fish was taken to the Marine Mammal Pathology Laboratory of the Fish and Wildlife Research Institute (Florida Fish and Wildlife Conservation Commission) in St. Petersburg for necropsy. The animal was correctly identified as a sharp-tail mola, Masturus lanceolatus, based on tail morphology. The animal weighed 298 kg. Total length was 230.5 cm; standard length (from mouth to end of peduncle) was 208.5 cm. Maximum body height was 111.5 cm. The dorsal fin was 85 cm long and its maximum width was 40 cm. Dimensions of the anal fin were 75 cm and 38 cm, respectively. The fin span was measured at 242 cm. The length of the pectoral fin was 21 cm and its width was 15.2 cm. The diameter of the eye was 8.2 cm.
The body cavity was filled with abundant serosanguinous fluid. Aerobic culture of this fluid resulted in no bacterial growth. There was a severe, diffuse cysticercoid-like cestode infestation of the liver. Additionally, there was a large number of cestodes and digenean trematodes present in the upper intestinal tract. Other organs had varying degrees of autolysis, but no gross lesions were observed. No specific cause of death could be identified on gross necropsy or histology although extreme parasitism may have been a contributing factor.
Detailed scientific reports on the Masturus lanceolatus are rare. This is a descriptive poster aimed at disseminating information on the dimensions, anatomy, necropsy findings, histology and parasites of this individual.
Four species of ocean sunfish are commonly recognized in the family Molidae: Mola mola, Mola ramsayi, Masturus lanceolatus, and Ranzania laevis.2 They belong to the order Tetraodontiformes. Heavy parasitic loads are notorious on the Mola mola; over forty genera of parasites have been found on this species. The parasitic burden on Masturus lanceolatus is said to be generally lighter than that of the Mola mola. The diet of both species is believed to consist mainly of jellyfish, salps and ctenophores with occasional eel grass, crustaceans and fish, raising the question of how molas become infested with such large numbers of parasites.1
1. http://www.oceansunfish.org/lifehistory.html, retrieved February 7, 2004.
2. Parenti, P. 2003. Family Molidae Bonaparte 1832: molas or ocean sunfish. California Academy of Sciences Annotated Checklists of Fishes 18:1-9.
3. Scott M. 500-pound sunfish was no tall tale at Clearwater Beach. 2004. St. Petersburg Times, retrieved August 1, 2004, http://www.sptimes.com/2004/02/24/Northpinellas/500_pound_sunfish_was.shtml