Taxonomy and biology of the argonauts (Cephalopoda: Argonautidae) with particular reference to Australian material

Abstract

Argonauts (Argonautidae: Cephalopoda) are a family of pelagic octopuses that inhabit tropical and temperate oceans of the world. Argonauts are most commonly recognised by the beautiful white shells of females (known as “paper nautiluses”) that wash up on beaches throughout the world. Historically, taxonomic delineation of the group has relied on features of these shells—structures not homologous to true molluscan shells and prone to extreme variability. As a consequence, more than 50 species names have been coined worldwide to date. This study constitutes the first thorough examination of argonauts from Australian waters. All argonaut material housed in Australian museums was examined using modern octopus taxonomic methodology and compared to material from key museums throughout the world. Three argonaut species are identified from Australian waters: Argonauta nodosus, Argonauta hians and Argonauta argo. All species can be separated based on morphological characters of males and females, and features of the shells of females. Detailed diagnoses, synonymies, maximum size records, distributional records, nomenclature corrections and biological information are included for each species. Details of the east Pacific Argonauta nouryi, the only other species recognised worldwide, are included for comparative purposes.

Keywords:

• paper nautilus
• Argonauta nodosus
• Argonauta hians
• Argonauta argo
• Argonauta nouryi
• Australia
• taxonomy
• Coleoidea
• Octopoda

Acknowledgements

This study would not have been possible without the generous financial support of Australian Biological Resources Study, the Hermon Slade Foundation, the Malacological Society of London, the Linnean Society of New South Wales, La Trobe University and Museum Victoria. This study relied heavily on previously collected argonaut material and historic references housed in museum collections throughout the world. Special thanks go to the museum staff who facilitated access to this material, including (but not limited to): Paul Callomon (ANSP), Bob Hamilton-Bruce (SAMA), Eric Hochberg (SBMNH), Thierry Laperousaz (SAMA), Ian Loch (AM), Melanie Mackenzie (NMV), Alison Miller (AM), Darryl Potter (QM), Martina Roeleveld (SAM), Clyde Roper (USNM), Chris Rowley (NMV), Shirley Slack-Smith (WAM), David Staples (NMV), Liz Turner (TMAG), Corey Whisson (WAM), Genefor Walker-Smith (TMAG), Michael Vecchione (USNM), Kathie Way (BMNH) and Richard Willan (NTM). Key references were also provided by Bob Burn, LouElla Saul, Mike Sweeney and the South Australian Naturalist Club. Special thanks go to the individuals who provided feedback on various versions of this manuscript, including: Eric Hochberg, Chung-Cheng Lu, Bruce Marshall, Mark Norman, Winston Ponder, Mandy Reid and Richard Young. Rhyll Plant deserves special thanks for producing all new illustrations, as do Rudie Kuiter (for providing live photographs), Pam Beesley of ABRS (for allowing use of line drawings previously illustrated by Kathie Hollis), Vyacheslav Bizikov (for allowing reproduction of previously published line drawings) and the Food and Agriculture Organization of the United Nations (for allowing reproduction of distribution maps). Additional thanks go to Daniel Geiger and Mark Norman for assistance with scanning electron microscopy.

Notes

1. Males of the related families in the superfamily Argonautoidea (i.e., Alloposidae, Ocythoidae and Tremoctopodidae) possess modified third right arms.

2. Document full title: A Catalogue of the Portland Museum, lately the property of The Duche(s)s Dowager of Portland, deceased: which will be sold by auction, by Mr. Skinner and Co. on Monday the 24th of April, 1786, and the thirty-seven following days, at twelve o'clock, Sundays and the 5th of June, (the Day his Majesty's Birth-Day is kept) excepted; at her late dwelling-house, in Privy-Garden, Whitehall; by order of the Acting Executrix.

3. Indices using standards other than dorsal mantle length do not tend to follow this trend—FOI and FOLI tend to increase while HMI and FFI tend to remain constant.

4. Arm Length Indices calculated from tabulated raw data (Table 41, p. 101) using Mantle Length as the standard.

5. Free Funnel Indices calculated from tabulated raw data (Table 41, p. 101) using Funnel Length as the standard.

6. Web Depth Indices calculated from tabulated raw data (Table 41, p. 101) using longest Arm Length, excluding first arms, as the standard.

7. Specimens of A. nodosus that had been collected in south eastern Australia in 1875, 1877, 1891, 1901, 1902, 1914, 1923, 1925, 1935, 1939, 1948, 1949, 1959, 1960, 1961, 1964, 1965, 1966, 1968, 1970, 1971, 1972, 1974, 1976, 1978, 1981, 1985, 1986, 1988, 1990, 1993, 1995, 1997, 1999, 2001 and 2003 were examined.

8. Specimen details: 1 shell, 95 mm ShL, SAM S3904, Strandfontein, False Bay, South Africa, coll. Mr van Rhyn, x.1976, det. M. Norman et al. 1997 as Argonauta cf. nouryi.