Patellogastropoda

Patinigera magellanica, photographed by Jan Delsing.

Belongs within: Gastropoda.
Contains: Patella, Scutellastra, Acmaeidae, Lepetidae, Lottiidae, Cellana.

The Patellogastropoda, true limpets, are a group of marine gastropods with cap-like shells bearing a horseshoe-shaped muscle attachment, and a docoglossate radula with few claw-like teeth in each row. Though generally believed to occupy a basal position in gastropod phylogeny, patellogastropods have a poor fossil record, probably due to most species occupying high-energy environments not conducive to preservation.

The mighty limpets
Published 27 October 2014
The limpet Nacella concinna on bull kelp Durvillea, copyright David Cothran.

I am Clamp the mighty limpet,
I am solid, I am stuck.
I am welded to the rockface
with my super-human suck.

The hero of Pam Ayres’ “Clamp the Mighty Limpet” is a misanthropic Napoleon, threatening would-be harassers with lost fingernails and the danger of attachment (if they would only be willing to stand in one place for two weeks). In reality, ‘limpet’ is a name that has been applied to a number of unrelated groups of gastropod with cap-like, more-or-less uncoiled shells. The most prominent group of limpets, however, and the one that Ayres almost certainly had in mind, is the ‘true limpets’ of the Patellogastropoda.

Owl limpet Lottia gigantea, copyright Jerry Kirkhart.

The Patellogastropoda are a mostly marine group of molluscs, though one species in south-east Asia, Potamacmaea fluviatilis, is found in rivers and brackish waters adjoining the Bay of Bengal (Lindberg 2008). Patellogastropods are particularly prominent in the intertidal zone, where they can be found clinging to rocky surfaces, but there are also many subtidal or deep-water limpets. Some limpets are specialised for living on macro-algae or marine vegetation; one such species, the North Atlantic Lottia alveus, has previously been mentioned on this site due to its unfortunate extinction as a result of the wasting epidemic that devastated sea-grass populations in the 1930s. Deep-water patellogastropods may be found on sunken wood, or they may live in association with hydrothermal vents or cold seeps. One such genus, Serradonta, is restricted to the tubes of vestimentiferan worms (Nakano & Sasaki 2011).

Whitecap limpet Acmaea mitra, copyright Mary Jo Adams.

Phylogenetically speaking, patellogastropods are a very interesting group indeed. Morphological studies have identified them as the sister group to all other living gastropods. They have a distinctive radula morphology, known as ‘docoglossan’, with each tooth-row of the radula containing a median tooth flanked by a small number of relatively simple lateral and marginal teeth (up to three pairs of each). This contrasts with the radulae of other gastropods, in which the teeth are more numerous and/or more specialised, but resembles the radula of other molluscan groups such as chitons. As such, patellogastropods may retain the plesiomorphic radula morphology of gastropods as a whole. Patellogastropods also have a shell microstructure that differs from that of other gastropods, and they have their gonads in a ventral position relative to the visceral mass instead of the dorsal position of other gastropods (Lindberg 2008). Some have even suggested that patellogastropods may represent a remnant lineage that never underwent the coiling that characterises other gastropods, but this seems unlikely. Patellogastropods do have some features, such as an asymmetrical position of the protoconch (larval shell) on the mature shell, that suggest coiled ancestors. Molecular studies, on the other hand, have been more equivocal in positioning the patellogastropods. Some have given results consistent with the morphological analyses, but a few have failed to place patellogastropods with the other gastropods at all (e.g. Giribet et al. 2006), while many have placed them in a more nested position deeper within the gastropods (Zapata et al. 2014).

Ringed blind limpet Cryptobranchia concentrica, copyright L. Schroeder.

At face value, the fossil record might actually appear to support a more nested position for patellogastropods. The fossil record for gastropods as a whole extends back to the Cambrian, but the oldest definite record of patellogastropods goes back no further than the late Triassic (Frýda et al. 2009). If patellogastropods were indeed the earliest surviving gastropod lineage to diverge, where were they hiding for the intervening 200 million years or so? One possibility is that they were there, but did not get preserved. Phylogenetic analysis of living limpets suggests that the immediate ancestors of the patellogastropods clung to rocks in high-energy environments, with deep-water lineages occupying more nested positions in the tree (Nakano & Sasaki 2011). Such environments are not favourable to the fossil record, as the shells of dead limpets tend to get broken up by wave action before they have the chance to be fossilised. Another, more likely, possibility is that we have failed to recognise the coiled ancestors of the Patellogastropoda for what they are. The Palaeozoic gastropod fauna included a number of groups that are not present in the modern day; it is quite possible that one of these groups gave rise to the patellogastropods. One group that has specifically been nominated as a possible relative of the patellogastropods is the euomphaloids. But for now, Clamp the Mighty Limpet is holding the secrets of his affinities well hidden, and it will not be easy prising them off him.

Systematics of Patellogastropoda
<==Patellogastropoda (see below for synonymy)BR17
    |--Eoacmaea Nakano & Ozawa 2007 [Eoacmaeidae, Eoacmaeoidea]BR17
    |    `--*E. profunda (Deshayes 1863) [=Patella profunda]BR17
    |--Patellidae [Patellaria, Patellinae, Retifera]NO04
    |    |--ProblacmaeaH96
    |    |--PatellaNO04
    |    `--ScutellastraNO04
    `--Lottioidea [Acmaeoidea, Lepetopsina, Lepetopsoidea, Metoptomatoidea, Nacelloidea, Neolepetopsoidea, Tecturoidea]BR05
         |--AcmaeidaeBR17
         |--LepetidaeBR05
         |--LottiidaeBR17
         |--Damilina Horný 1961BR05 [DamilinidaeBR17]
         |    `--*D. subrotunda (Perner 1903) [=Lepetopsis subrotunda]BR17
         |--Neolepetopsis McLean 1990BR05 [NeolepetopsidaeBR17]
         |    `--*N. gordensis McLean 1990BR17
         |--Metoptoma Phillips 1836BR05 [MetoptomatidaeB79]
         |    `--*M. oblonga Phillips 1836KC60
         |--Pectinodonta Dall 1882BR05 [PectinodontidaeBR17, Pectinodontinae]
         |    |--*P. arcuata Dall 1882KC60
         |    `--P. aupouria Marshall 1985AH96
         |--Lepetopsis Whitfield 1882 [Lepetopsacea, Lepetopsidae]BR05
         |    |--*L. levettei (White 1881) [=Patella levettei]BR17
         |    |--L. campannaeformis (Münster 1841)TTE93
         |    |--L. costulata (Münster 1841)TTE93
         |    |--L. dainellii Greco 1937B79
         |    |--L. petricola (Kittl 1895)TTE93
         |    |--L. petsus Mansuy 1913B79
         |    `--L. stefaninii Greco 1937B79
         `--Nacellidae [Nacellinae]BR17
              |--CellanaNO04
              |--Patinigera Dall 1905 [incl. Patinella Dall 1871 non Gray 1848]KC60
              |    |--*P. aenea [=Patella aenea]P61
              |    |--P. kerguelenensis (Smith 1879)P61
              |    |--P. macquariensis (Finlay 1927)P61
              |    |--P. magellanica (Gmelin 1791) (see below for synonymy)KC60
              |    `--P. terroris (Filhol 1880)P61
              `--Nacella Schumacher 1817BR05
                   |--N. mytilina (Helbling 1779) [=Patella mytilina; incl. *N. mytiloides Schumacher 1817]KC60
                   |--N. compressaC64
                   |--N. concinna (Strebel 1908)NO04
                   |--N. delesserti (Philippi 1849)F27
                   |--N. depictaC64
                   |--N. fuegiensis (Reeve 1855)F27
                   |--N. incessaC64
                   |--N. kerguelenensisF27
                   |--N. macquariensis Finlay 1927F27
                   |--N. paleaceaC64
                   |--N. peltoidesC64
                   |--N. redimiculum (Reeve 1854) [=Helcioniscus redimiculum]F27
                   |--N. strigilis (Hombron & Jacquinot 1841) [=Helcioniscus strigilis; incl. N. illuminata (Gould 1846)]F27
                   |--N. subspiralis Carpenter 1864C64
                   `--N. terroris (Filhol 1880)F27

Patellogastropoda [Docoglossa, Heterocardia, Nacellina, Onychoglossa, Patellacea, Patellida, Patelliformes, Patelliformii, Patelloidea, Patelloidei, Phyllidiobranchia, Stereoglossata]BR17

Patinigera magellanica (Gmelin 1791) [=Patella magellanica, Nacella (Patinigera) magellanica, *Patinella magellanica]KC60

*Type species of generic name indicated

References

[AH96] Angerer, G., & G. Haszprunar. 1996. Anatomy and affinities of lepetid limpets (Patellogastropoda=Docoglossa). In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 171–175. Oxford University Press: Oxford.

[B79] Batten, R. L. 1979. Gastropods from Perak, Malaysia. Part 2. The trochids, patellids and neritids. American Museum Novitates 2685: 1–26.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

[F27] Finlay, H. J. 1927. A further commentary on New Zealand molluscan systematics. Transactions and Proceedings of the New Zealand Institute 57: 320–485.

Frýda, J., P. R. Racheboeuf, B. Frýdová, L. Ferrová, M. Mergl & S. Berkyová. 2009. Platyceratid gastropods—stem group of patellogastropods, neritimorphs or something else? Bulletin of Geosciences 84 (1): 107–120.

Giribet, G., A. Okusu, A. R. Lindgren, S. W. Huff, M. Schrödl & M. K. Nishiguchi. 2006. Evidence for a clade composed of molluscs with serially repeated structures: monoplacophorans are related to chitons. Proceedings of the National Academy of Sciences of the USA 103 (20): 7723–7728.

[H96] Healy, J. M. 1996. Molluscan sperm ultrastructure: correlation with taxonomic units within the Gastropoda, Cephalopoda and Bivalvia. In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 99–113. Oxford University Press: Oxford.

[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

Lindberg, D. R. 2008. Patellogastropoda, Neritimorpha, and Cocculinoidea. In: Ponder, W. F., & D. R. Lindberg (eds) Phylogeny and Evolution of the Mollusca, pp. 271–296. University of California Press.

[NO04] Nakano, T., & T. Ozawa. 2004. Phylogeny and historical biogeography of limpets of the order Patellogastropoda based on mitochondrial DNA sequences. Journal of Molluscan Studies 70: 31-41.

Nakano, N., & T. Sasaki. 2011. Recent advances in molecular phylogeny, systematics and evolution of patellogastropod limpets. Journal of Molluscan Studies 77 (3): 203–217.

[P61] Powell, A. W. B. 1961. Shells of New Zealand: An illustrated handbook 4th ed. Whitcombe and Tombs Limited: Christchurch.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

Zapata, F., N. G. Wilson, M. Howison, S. C. S. Andrade, K. M. Jörger, M. Schrödl, F. E. Goetz, G. Giribet & C. W. Dunn. 2014. Phylogenomic analyses of deep gastropod relationships reject Orthogastropoda. Proceedings of the Royal Society of London Series B 281: 20141739.

Leave a comment

Your email address will not be published. Required fields are marked *