The black swallower (Chiasmodon niger), capable of eating 10 times its weight, is only one of the curious animals introduced to visitors at the American Museum of Natural History's new Life At The Limits exhibition.
Tardigrades (aka waterbears or moss piglets) are another.
From the Life At The Limits AMNH page:
The exhibition, curated by Mark Siddall, a parasitologist, and John Sparks, an ichthyologist, introduces visitors to bizarre mating calls, extreme examples of parasitism, and other extraordinary means of survival using specimens, videos, interactive exhibits, and models, including a climbable Hercules beetle.
Live animals on display include the surprisingly powerful mantis shrimp; the highly mobile nautilus; and the axolotl, an entirely aquatic salamander that breathes through external gills.
More images at: The 8 Oddest Freaks of Nature Showcased in "Life at the Limits" (Scientific American)