Tube-building
Guides
Jassa marmorata
Marbled Scud
A tube-building amphipod native to the northeast Atlantic Ocean, now introduced to northeast Asia. Distinguished by greyish coloration with reddish-brown markings and a maximum length of 10 mm. Notable for exhibiting two distinct male morphs with alternative mating strategies: larger 'major' males that fight for access to females, and smaller 'minor' males that sneak copulations. Constructs protective tubes from detritus and algae fragments bound with mucus secretions.