Figure 1.
The subject female brooding her eggs on a nearly vertical rock face at a depth of 1397Neptunea amianta. Near the octopus are two Lithodid crabs and a non-brooding Graneledone can be seen above and to the right of the brooder. The mantle length of the specimen, when first encountered, was 21.2 cm.
Figure 2.
Graneledone boreopacifica, identification marks.
Images of a brooding female over the course of 53 months, each showing the identifying scar on the web between arms R1 & R2. In each frame the characteristic scar is outlined by an oval. a, April, 2007, crawling across the sediment toward the brooding site. b, May, 2007, on the rock face, covering the recently deposited clutch of eggs. The arrow points to a circular scar on arm L1, which provides additional confirmation. c, May, 2009. d, October, 2009. The second arrow points to a scar on arm L2. e, December, 2010. f, September, 2011.
Figure 3.
The continued growth of the eggs throughout the measurement period indicates that we were observing a single clutch. Because we did not wish to disturb the brooding female, only eggs at the periphery of the clutch were measured.
Figure 4.
Close-up of the egg capsules in December, 2010.
In month 43, the mantles of the embryos can be seen in the apex of each capsule and their dark eyes are apparent.
Figure 5.
Empty egg cases, October 2011.
This is a composite figure, showing empty egg cases, and attachment sites (indicated by green cement residue), used to enumerate the number of egg cases in the clutch, after hatching.
Figure 6.
The duration of embryonic development in octopodid cephalopods is related to temperature.
Each point represents a different species, measured at the coldest temperature for which data are available (Table S2 in Information S1). The solid line is the best-fit power function for the data from the literature (black symbols). The dashed line extends the model to 3°C, but falls 307 days short of our measured development time for Graneledone boreopacifica (open symbol). See also Table S2 in Information S1.
Figure 7.
Species living in cold environments have larger eggs.
This relationship is, in part, responsible for the longer development times at cold temperatures. It suggests that cold water environments select for better-developed hatchlings and that one mechanism by which octopods achieve this is by increasing egg size. Data from Table S2 in Information S1.