Why Sailing Sea Animals Have Mirror Images

Abstract

The worldwide distribution of Physalia physalis (L.) (the Portuguese man-of-war), a wind-propelled jellyfish-like animal on sea-surface waters, is a much discussed but poorly understood phenomenon. The radically different courses sailed by the two mirror-image forms of this organism appear to result from simply their need for maximum dispersion by the winds on the earth's warmer seas. Study reveals, however, that the two forms of P. physalis sail different mirror-image courses and gain separate access to upwelling, diverging sea-surface waters that probably contain their major food. These courses are sailed without obvious steering efforts by the animals. Thus the wind-induced pattern of motion of the waters appears to have markedly influenced the animal's form and sailing courses. Their behavior apparently results from their natural involuntary use of steering effects of two wind induced surface-water motions.