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First published online December 14, 2006
Journal of Experimental Biology 210, 1-11 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02588

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On the depth and scale of metabolic rate variation: scaling of oxygen consumption rates and enzymatic activity in the Class Cephalopoda (Mollusca)

Brad A. Seibel

Biological Sciences Department, University of Rhode Island, 100 Flagg Road, Kingston, RI 02881, USA

View larger version (20K): [in this window] [in a new window]   Fig. 1. Effect of body mass on (A) oxygen consumption rates (µmol O2 g-1 h-1; 5°C) and (B) citrate synthase activity (units g-1; 20°C) of cephalopod molluscs. The relationships drawn are for families Loliginidae (filled blue triangles), Ommastrephidae (open blue triangles), Gonatidae (blue crosses), Octopodidae (open brown inverted triangles), Histioteuthidae (brown circles), Cranchidae (open brown circles), Bolitaenidae (black squares), Vampyroteuthidae (white squares). The scaling coefficients for oxygen consumption rates of Loliginid squids are significantly different from benthic Octodidae (ANCOVA, P<0.05), and others, and the s.e.m. does not include quarter power (-0.25). Regression equations are presented in Table 1 while sources of data can be found in supplementary material Tables S1-S4.

View larger version (18K): [in this window] [in a new window]   Fig. 2. Intraspecific scaling patterns of cephalopod molluscs. (A) Three published intraspecific scaling curves for benthic octopods are drawn with the interspecific pattern from Fig. 1. (B) Intraspecific scaling relationships are similar to intrafamilial relationships in Fig. 1. Colors and lines represent different families. Loliginidae, solid blue; Ommastrephidae, broken blue; Octopodidae, broken red; Histioteuthidae, solid red; Cranchidae, long broken red; Bolitaenidae, solid black; Vampyroteuthidae, broken black. (C) Intraspecific scaling coefficients (b from Eqn 1 in text) are significantly higher (less negative) for epipelagic squids (grey bar; Loliginidae and Ommastrephidae) than for mesopelagic cephalopods (black bar) (N in parentheses; values are means ± s.d.). Gonatids are not shown because the relationship between oxygen consumption and body mass was not significant (b0.0). See Table 2 for equations and sources.

View larger version (6K): [in this window] [in a new window]   Fig. 3. Minimum depth of occurrence (MDO), defined as the depth below which 90% of the individuals of a given species are captured (Childress, 1995), explains more than 90% of the variation in the normalization constants (b0) derived from oxygen consumption (solid circles, b0=79.1MDO-0.9; r2=0.92) and citrate synthase activity (open circles, b0=141.2MDO-0.80; r2=0.94) scaling relationships in cephalopod families (Table 1). The family Octopodidae is benthic, allowing similar lifestyles, and hence similar metabolic rates, across a depth gradient as described in the text and elsewhere (Seibel and Childress, 2000). Octopodids are exluded from the analysis presented in this figure. Individuals of some cranchid species can be found occasionally in near-surface waters despite their low metabolic rates, an ability facilitated by their extreme transparency and associated relief from visual predation (Seibel et al., 1997). However, the majority of specimens in this family are collected below 300 m (MDO>300 m).

View larger version (20K): [in this window] [in a new window]   Fig. 4. Comparisons of cephalopod oxygen consumption rates with those from other distantly related taxa (adjusted, as necessary, to 5°C). (A) Epipelagic loliginid and ommastrephid squids are compared with deep-sea vampyroteuthid squids, mammals (White et al., 2006), medusae (pelagic cnidarians) (Thuesen and Childress, 1994), and benthic crustaceans and echinoderms (Seibel and Drazen, in press). (B) Cephalopods are compared with pelagic fishes (broken lines) including gadids (cod), benthic anguilliform eels (Clarke and Johnston, 1999), and a deep-sea pelagic anglerfish, Melanocetes johnsoni (Cowles and Childress, 1995). Statistics and data sources are given in Table 1 and supplementary material Tables S1, S2 and S4.

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