My group was the first (and only) to deploy pop-up satellite tags and video packages (National Geographic Crittercam) on large Humboldt squid to record their second-to-second movements and color-changing behaviors. This work showed that this active predator spends a great deal of its time at depths of 300 m or more where the oxygen concentration is extremely low – less than 10% of that at the surface. This ‘oxygen minim zone’ (OMZ) is found throughout the southern half of the Gulf of California and much of the eastern Pacific Ocean, including Monterey Bay. The OMZ has been moving closer to the sea surface over the last few decades, and this aspect of marine climate change is expected to have major ecological consequences as ocean’s oxygenated surface zone becomes increasingly vertically compressed.
Our work in the Gulf of California has recently focused on the relationship between the size of Humboldt squid and environmental variation, particularly temperature at depth. Since an unusual El Niño event in 2009-10, the temperature at depths of up to 100 m has been increasing, and squid have responded by attaining maturity at a vastly smaller size and younger age than they had before 2009. Small size at maturity is normally a characteristic phenotype of this species in the tropical eastern Pacific, and the change in the squid’s life history in the Sea of Cortez is consistent with the decreasing productivity and increasing temperatures observed over the last 6 years. Humboldt squid are telling us that the Gulf of California may be changing from a seasonally highly productive, upwelling-driven system to a low productivity tropical system.
Current laboratory work on squid chromatophores uses methods of electrophysiology, cell and molecular biology and electron microscopy, through collaborations with Univ. Puerto Rico, Univ. North Carolina Chapel Hill and Univ. Kansas. A major hypothesis guiding the work is that a “horizontal” pathway for communication between chromatophores exists in the plane of the skin, and that this network can mediate chromogenic behaviors in the absence of descending motor control by the central nervous system. We use a comparative approach to take advantage of natural differences in behavioral capabilities of Humboldt squid (Dosidicus gigas) and CA market squid (Doryteuthis opalescens) that inhabit environments with extremely different visual features. Market squid are a coastal species that use spatial patterning of chromatophore displays to provide camouflage in order to match benthic features like seaweed and rocks. Humboldt squid are an open ocean species that primarily generate temporal patterning and use spatially global flashing in intra-specific signaling. We hypothesize that these striking behavioral differences will be reflected in structural and functional elements of the peripheral control pathway.
Another project examines the role of the giant axon system in controlling escape responses in both Dosidicus and Doryteuthis, with a focus on sensitivity of the system to temperature and hypoxia. Both of these environmental variables are relevant to these species in the ocean. Methods used include electrophysiology, anatomy and particle image velocimetry.
Laboratory work is carried out both at Hopkins Marine Station and at our lab facility in Santa Rosalia, BCS, Mexico.