Presenter: Shirah Strock (Roger Williams University)

Description:
Physonect siphonophores are hydrozoan colonies of the phylum Cnidaria that are ubiquitous members of epipelagic and midwater communities (Fig. 1). The physonect swimming of these organisms relies upon multiple individuals or colony members, termed nectophores, which are specialized solely for jet propulsion. Groups of multiple nectophores and their central stem are collectively termed the nectosome (Fig. 1) and it is the total necotosomal jet production that propels the colony during swimming. However, it is unknown whether individual nectophores are coordinated or acting independently. Using high-resolution video cameras attached to remotely operated vehicles (ROVs), the swimming behavior and kinematics of multiple nectophores of several physonect species in the Monterey Bay National Marine Sanctuary, Panama, and Friday Harbor, WA were quantified. Analysis of the kinematics of individuals nectophores for five different species was completed, resulting in data for jetting frequency, the duration between pulses, and the pulse duration. Metachronal nectophore pulsation was also analyzed and seen frequently among several species. In these cases, a leading nectophore contracted first and adjacent, trailing nectophores subsequently contracted with an almost-constant phase shift between individual nectophores. However, this was not true for all nectophores within a nectosome. We discuss the implications of these patterns for siphonophore swimming.