黒海馬

黒(くろ) (kuro, “black”) + 海馬(うみうま) (umiuma, “sea horse”)

黒(くろ)海(うみ)馬(うま) or 黒海馬(クロウミウマ) • (kuroumiuma) 

1. a estuary seahorse, Hippocampus kuda

As with many terms that name organisms, this term is often spelled in katakana, especially in biological contexts (where katakana is customary).