Scanning electron micrographs of radulae from over 15 species of cephalopods are compared in this study. Vampire squid have a unique homodont radula with a single cusp on all seven teeth. In comparison to the robust cutting heterdont radula and rhachidian teeth of shallow predators, the radula of V. infernalis has long gracile teeth that appear to be well suited to tearing apart very soft tissue and perhaps picking apart marine detritus. Despite living in extremely low oxygen concentrations with very low metabolic rates, adult vampire squid can be fairly active swimmers and likely feed on a variety of soft-bodied organisms.
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0rder Vampyromorpha
V. infernalis (homodont)
So far there is evidence to show that species within the same order have similar characteristics of their radula, specifically in regards to homodont or heterodont. More research needs to be done to add more orders and more species to orders, as well as measurements, stable isotope analysis comparisons, and comparisons to other deep-sea cephalopods.
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Vampire squid have a unique homodont radula with a single cusp on all seven teeth. In comparison to the robust cutting heterdont radula and rhachidian teeth of shallow predators, the radula of V. infernalis has long gracile teeth that appear to be well suited to tearing apart very soft tissue and perhaps picking apart marine detritus. Despite living in extremely low oxygen concentrations with very low metabolic rates, adult vampire squid can be fairly active swimmers and likely feed on a variety of soft-bodied organisms.
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I started taking preliminary measurements of teeth and marginal plates. More work needs to be done.
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Deep-living squids possess a variety of feeding strategies that increase with lower depth as oxygen, temperature, and decreasing light change the metabolic and morphological requirements needed for catching prey and avoiding predators (Childress 1995).
Childress J. J., (1995). Are there physiological and biochemical adaptations of metabolism in deep-sea animals? Trends Ecol. Evol. 10, 30–36.
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The Humboldt squid and the vampire squid are able to lower their metabolic needs when oxygen is hard to come by (Seibel et al. 1999).
Stable isotope analysis is a powerful tool to infer movement patterns and nutritional sources of aquatic life. Cephalopods have some of the highest metabolisms of marine predators. Cephalopod heocyanins (respiratory proteins that use copper binding sites to bind and transport oxygen) are sensitive to drops in environmental pH which would reduce oxygen loading in their gills, shown to reduce oxygen consumption in D. gigas (Fabry et al. 2008). Stomach content analysis has been the method of choice historically for observing cephalopod diets (Field et al, 2013)
Seibel et al. (1997) measured metabolic rates of 33 cephalopod species and found that metabolic rates decrease with depth and that cephalopods have more extreme metabolic trends than fish or crustaceans due to their highly efficient & active lifestyles.
Fabry, V.J., Seibel, B.A., Feely, R.A., and Orr, J.C. (2008). “Impacts of ocean acidification on marine fauna and ecosystem processes”. ICES Journal of Marine Science: Journal du Counseil 65(3): 414-432
Field, J.C., Elliger, C., Baltz, K., Gillespie, G.E., Gilly, W.F., Ruiz-Cooley, R.I., Pearse, D., Stewart, J.S., Matsubu, W. and Walker, W.A. 2013. Foraging ecology and movement patterns of jumbo squid (Dosidicus gigas) in the California Current System. Deep. Sea. Res. Part. II Top. Stud. Oceanogr. doi:10.1016/j.dsr2.2012.09.006
Onthank, Kirt Lee. (2013). “Exploring the Life Histories of Cephalopods using stable isotope analysis of an archival tissue”. Dissertation WSU: School of Biological Sciences.
Seibel, B.A.; Thuesen, E.V.; Childress, J. J.; Gorodezky, L.A. (1997) “Decline in pelagic cephalopod metabolism with habitat depth reflects differences in locomotory efficiency.” Biological Bulletin 192: 262-278.