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. 2015 Jan 13:3:e715.
doi: 10.7717/peerj.715. eCollection 2015.

Sizing ocean giants: patterns of intraspecific size variation in marine megafauna

Craig R McClain  1 , Meghan A Balk  2 , Mark C Benfield  3 , Trevor A Branch  4 , Catherine Chen  5 , James Cosgrove  6 , Alistair D M Dove  7 , Leo Gaskins  5 , Rebecca R Helm  8 , Frederick G Hochberg  9 , Frank B Lee  5 , Andrea Marshall  10 , Steven E McMurray  11 , Caroline Schanche  5 , Shane N Stone  5 , Andrew D Thaler  12
Affiliations

Sizing ocean giants: patterns of intraspecific size variation in marine megafauna

Craig R McClain et al. PeerJ. .

Abstract

What are the greatest sizes that the largest marine megafauna obtain? This is a simple question with a difficult and complex answer. Many of the largest-sized species occur in the world's oceans. For many of these, rarity, remoteness, and quite simply the logistics of measuring these giants has made obtaining accurate size measurements difficult. Inaccurate reports of maximum sizes run rampant through the scientific literature and popular media. Moreover, how intraspecific variation in the body sizes of these animals relates to sex, population structure, the environment, and interactions with humans remains underappreciated. Here, we review and analyze body size for 25 ocean giants ranging across the animal kingdom. For each taxon we document body size for the largest known marine species of several clades. We also analyze intraspecific variation and identify the largest known individuals for each species. Where data allows, we analyze spatial and temporal intraspecific size variation. We also provide allometric scaling equations between different size measurements as resources to other researchers. In some cases, the lack of data prevents us from fully examining these topics and instead we specifically highlight these deficiencies and the barriers that exist for data collection. Overall, we found considerable variability in intraspecific size distributions from strongly left- to strongly right-skewed. We provide several allometric equations that allow for estimation of total lengths and weights from more easily obtained measurements. In several cases, we also quantify considerable geographic variation and decreases in size likely attributed to humans.

Keywords: Allometry; Body size; Cline; Intraspecific variation; Megafauna.

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Conflict of interest statement

Craig R. McClain and Shane Stone are employees of the National Evolutionary Synthesis Center, James A. Cosgrove is an employee of the Royal British Columbia Museum, Alistair Dove is an employee of the Georgia Aquarium, Eric Hochberg is an employee of Santa Barbara Museum of Natural History, Andrea Marshall is an employee of the Marine Megafauna Foundation, Andrew Thaler is CEO of Blackbeard Biologic: Science and Environmental Advisors.

Figures

Figure 1
Figure 1. Linear regression between Log10 Base Diameter (m) and Log10 Volume (m3) for Xestospongia muta.
See Table 2 for regression equations.
Figure 2
Figure 2. Distribution of (A) Base diameter (m), (B) Height (m), and (C) Volume (m3) for Xestospongia muta.
Figure 3
Figure 3. Allometric equations for Xestospongia muta.
(A) Log10 Base Diameter (m) and Log10 Height (m). (B) Log10 Osculum Diameter (m) and Log10 Base Diameter (m). (C) Log10 Osculum Diameter (m) and Log10 Height (m). See Table 2 for regression equations.
Figure 4
Figure 4. Distribution of Carapace Length (cm) for all individuals separated by sex for Bathynomus giganteus.
Figure 5
Figure 5. Distribution of Shell Length (cm) from (A) a literature survey, (B) a census by Pearson & Munro (1991), and (C) online sales for Tridacna gigas.
Figure 6
Figure 6. Linear regression between Log10 Shell Length (cm) and Log10 Price (US) for Tridacna gigas.
See Table 2 for regression equations.
Figure 7
Figure 7. Linear regression between Shell Width (cm) and Shell Length (cm) from online sales and from natural populations for Tridacna gigas.
See Table 2 for regression equations.
Figure 8
Figure 8. Distributions of Shell Length (cm) from (A) the literature and museum collections and from (B) online sales for Syrinx aruanus.
Figure 9
Figure 9. Linear regression between Log10 Shell Length (cm) and Log10 Price (US) for Syrinx aruanus.
See Table 2 for regression equations.
Figure 10
Figure 10. (A) Distribution Mass (kg), (B) distributions of Mass between 0 and 40 kg, and (C) Interocular Distance (m) for male and female Enteroctopus dofleini.
Figure 11
Figure 11. Linear regression between Log10 Interocular Distance (m) and Log10 Mass (kg) for Enteroctopus dofleini.
See Table 2 for regression equations.
Figure 12
Figure 12. Distribution of (A) Total Length (m), (B) Mantle Length (m), and (A) Mass (kg) for Architeuthis dux.
Figure 13
Figure 13. Linear regressions for Architeuthis dux.
(A) Log10 Total Length (m) and Log10 Mass (kg). (B) Log10 Mantle Length (m) and Log10 Total Length (m). (C) Log10 Mantle Length (m) and Log10 Mass (kg). See Table 2 for regression equations.
Figure 14
Figure 14. Distribution of Total Length (m) of mature Cetorhinus maximus by hemisphere.
Figure 15
Figure 15. Distribution of Total Length (m) for Carcharadon carcharias reported in the (A) literature by sex and (B) media.
Figure 16
Figure 16. Boxplots of Total Length (m) as reported in the media for Carcharadon carcharias by encounter type.
Figure 17
Figure 17. Boxplots of Total Length (m) of mature Carcharadon carcharias by (A) Hemisphere, and (B) Ocean.
Figure 18
Figure 18. Linear regression between Log10 Total Length (m) and Log10 Mass (kg) for Carcharadon carcharias.
See Table 2 for regression equations.
Figure 19
Figure 19. Distribution of Total Length (m) of mature Somniosus microcephalus by sex.
Figure 20
Figure 20. Distribution of (A) Total Length (m) and (B) Mass (kg) of mature Hexanchus griseus.
Figure 21
Figure 21. Linear regression between Log10 Total Length (m) and Log10 Mass (kg) for Hexanchus griseus.
See Table 2 for regression equations.
Figure 22
Figure 22. Distribution of Disc Width (m) for Manta birostris by measurement method, sex, and region.
Figure 23
Figure 23. Distribution of Total Length (m) for Regalecus glesne.
Figure 24
Figure 24. Boxplots of Disc Width (m) for Regalecus glesne by region.
Figure 25
Figure 25. Distribution of (A) Total Length (m) and (B) Mass (kg) for Mola mola.
Figure 26
Figure 26. Boxplots of (A) Total Length (m) and (B) Mass (kg) for Mola mola by Ocean.
Figure 27
Figure 27. Linear regressions for Mola mola.
(A) Log10 Total Length (m) and Log10 Mass (kg). (B) Log10 Doral to Anal Fin Height (m) and Log10 Mass (kg). (C) Log10 Doral to Anal Fin Height (m) and Log10 Total Length (m). See Table 2 for regression equations.
Figure 28
Figure 28. Relationship between Log10 Total Length (m) and Log10 Mass (kg) for Dermochelys coriacea.
See Table 2 for regression equations.
Figure 29
Figure 29. Distribution of Curved Carapace Length (m) for Dermochelys coriacea.
Figure 30
Figure 30. Distribution of Total Length (m) for Mirounga leonine.
Figure 31
Figure 31. Boxplots of Total Length (m) and for Mirounga leonine divided by sex and location.
Figure 32
Figure 32. Distribution of (A) Total Length (m) and (B) Mass (kg) for Odobenus rosmarus.
Figure 33
Figure 33. Boxplots of (A) Total Length (m) and (B) Mass (kg) for Odobenus rosmarus divided by subspecies and sex.
Figure 34
Figure 34. Distribution of Total Length (m) for Physeter macrocephalus.
Figure 35
Figure 35. Boxplots of Total Length (m) by region and sex for Physeter macrocephalus.
Figure 36
Figure 36. Total Length (m) versus year by region for Physeter macrocephalus.
Figure 37
Figure 37. Distribution of Total Length (m) for Balaenoptera musculus.
Figure 38
Figure 38. Boxplots of Total Length (m) by region and sex for Balaenoptera musculus.
Figure 39
Figure 39. Total Length (m) verses year by region for Balaenoptera musculus.
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