whiptail gulper; gulper eel (family Saccopharyngidae)
Deep-sea fish known for its huge mouth and expandable stomach. Typically written in katakana.
In the deep sea, there is a strange fish called the whiptail gulper.
Katakana spelling is standard for this deep-sea fish; the kanji form 風船鰻 is rare and mainly used in taxonomic contexts.
Kanji spelling; rarely used outside scientific literature.
From 風船 (balloon) + 鰻 (eel), referring to its balloon-like expandable stomach.