Recent research has revealed that the deep-sea jellyfish species *Botrynema brucei ellinorae* exhibits two distinct forms: one with a knob on its bell and another without. This morphological variation is linked to the jellyfish's distribution patterns in the North Atlantic Ocean.
Specimens with a knob are found across various oceanic regions, while those without are primarily confined to Arctic and sub-Arctic areas. Genetic analyses indicate that, despite these differences, all specimens belong to the same genetic lineage. This suggests the presence of an unknown biogeographic barrier in the North Atlantic, potentially associated with the North Atlantic Drift, which may restrict the movement of knobless jellyfish southward.
Understanding these distribution patterns is crucial for marine biodiversity studies, as it highlights the impact of ocean currents on species dispersal and the complex interactions between marine organisms and their environments.