Relationship between dimorphism and drift in the Portuguese man-of-war

Abstract

One interesting feature of the Portuguese man-of-war (Physalia physalis) is its dimorphism, with the existence of two distinct forms (left- and right-handed individuals). The worldwide distribution of this dimorphic wind-propelled siphonophore is a much discussed but poorly understood phenomenon. Here we investigate the most likely region of origin and routes of more than 3,500 individuals of this species that were collected along the Basque coast (southeastern Bay of Biscay) in August 2010. We also test the hypothesis that most of these individuals were right-handed. To do this, we used the Sediment, Oil spill and Fish Tracking model (SOFT). From our model results, we can conclude that the region of origin of these individuals was probably located in the northern part of the North Atlantic Subtropical Gyre. The findings also suggest that our hypothesis is very likely to be correct.