Deep Sea News tells the story of that time when shark parasite expert Janine Caira found out about a mako shark that had been hauled up dead, a victim of longline fishing. Caira and her co-author Nancy Kohler went to investigate.
To make the most of the unfortunate death of this mako, they raced across the sound from Connecticut to collect parasites from the beast. It was a huge animal, nearly 900lbs, and during necropsy, as they say in the paper, they “were astonished to find two anguilliform fish in the lumen of the heart”. Thats right, eels; this shark had two eels living in the chambers of the heart! These particular eels, called pugnose eels, Simonchelys parasitica, have been recorded before burrowing into the flesh of halibut and other large North Atlantic fishes (hence their species name), but never completely internal and certainly not in the lumen of the heart, so this was a truly remarkable find.
Janine and her colleagues were unable to determine the path of entry, but they showed good evidence that the eels were alive in the heart prior to the shark being killed and put in the fridge, because their guts were full of blood and there were pathologic changes to the heart.