Maggie MacMahon1, Dr. Kirt Onthank2, Katherine Pekar2, Dr. Alan Verde1
1Maine Maritime Academy, Castine, USA, 2Walla Walla University, College Place, USA
Muusoctopus leioderma, normally found at deep depths (90-1400 m) of the Pacific, have recently been observed in the shallow waters (10-15 m) of Burrows Bay. It is unknown what has caused this “migration” from deep waters into a shallow ecosystem and what makes up the octopuses’ diet in this habitat. Consequently, this study investigated the potential prey items of M. leioderma in a shallow water environment to maintain them in a laboratory setting for further studies. To reveal potential prey species, numerous epibenthic and infaunal marine invertebrates were collected from Burrows Bay along with 35 M. leioderma. Natural abundance 13C and 15N analysis revealed that infaunal invertebrates composed the majority of the diet of M. leioderma; for corroboration, a lab-based prey preference trial was also performed. Octopuses were collected at night using SCUBA and maintained at the Rosario Beach Marine Laboratory for the duration of the study. Three different live prey taxa: polychaetes, bivalves, and crustaceans, found within Burrows Bay were separately enriched with the stable isotopes 13C, 15N, and 2H, respectively, and offered to octopuses for consumption. Stable isotope analysis of arm tissue indicates that both polychaetes and bivalves, but not crustaceans, were consumed by M. leioderma; these results were corroborated by additional observational feeding experiments that provided strong evidence that polychaetes are highly preferred over bivalves and crustaceans. Although the density of polychaetes in Burrows Bay are two times higher and more evenly distributed than bivalves and crustaceans, these polychaetes have a much lower energy content and implies that these octopuses may utilize a nutrition-energy tradeoff scheme that directly aligns with the Optimal Foraging Theory. These predator-prey-energetics feeding experiments suggest that the more abundant prey resources (albeit lower energy content) in Burrows Bay may be a primary driver in the “migration” of this octopus species to shallower waters.
Presentation Slides – Maggie MacMahon
