Alvania

Alvania bermudensis, from the Muséum national d’histoire naturelle.

Belongs within: Rissooidea.

On Alvania
Published 13 October 2018

It’s a general rule with organisms that species diversity increases as size decreases (at least down to about the millimetre range, below which things get a bit more complicated). That’s certainly the case with molluscs, whose range clearly favours the tiny.

Alvania cimex, copyright Alboran Shells.

Alvania is a cosmopolitan genus of marine gastropods, found in most parts of the world except the Antarctic and sub-Antarctic (Ponder 1984). The average Alvania species is less than five millimetres in total length, and other members of the family they belong to, the Rissoidae, are similarly wee. The shell of Alvania species varies from elongate-conical to more squatly conical in shape, and generally has a sculpture of both axial and spiral ridges. In some species the axial and spiral ribs are both similarly prominent; in others, the spiral ridges are more strongly developed.

Rissoids may be found crawling on seaweed or sheltered amongst stones or other rubble. Alvania species seem to be more likely to be found in the latter habitat than the former. Alvania have a smaller mucous gland on the rear of the foot than species of Rissoa, a related genus that is more likely to be found on the weeds. The mucus produced by this gland assists rissoids in clinging to their substrate or the surface film, and its reduction in Alvania is presumably connected to their preference for the low life. Rissoids are grazers on microalgae or deposit feeders; those species found on seaweeds will feed on diatoms and the like growing over the seaweed rather than on the seaweed itself. Among European species, A. punctura is known to selectively pick out diatoms and dinoflagellates from among detritus when feeding whereas A. jeffreysi may be less discriminating in what it swallows.

Alvania subcalathus, copyright H. Zell.

The greater number of Alvania species are planktotrophic as larvae, and as described in some of my previous posts on turrids, their shells have protoconches to match. Nevertheless, the genus also includes some direct-developing species with fewer protoconch spirals. The Mediterranean species A. cimex and A. mammillata are almost indistinguishable when mature except by features of the shell apex, which is broader with fewer spirals to the protoconch in the latter (Verduin 1986). If A. mammillata is a direct developer while A. cimex has a planktotrophic larva, it would tally up with the situation elsewhere seen among turrids.

Systematics of Alvania
<==Alvania Risso 1826 [Alvaniidae, Alvaniinae, Alvanioidea]BR17
    |--A. (Alvania)RM88
    |    |--*A. (A.) europea Risso 1826BR17
    |    |--A. (A.) abyssicolaO27 [=Rissoa abyssicolaO27, A. subsoluta var. abyssicolaN00]
    |    `--A. (A.) colombiana Romer & Moore 1988RM88
    |--A. (Flemellia) guesti Faber & Moolenbeek 1987BC01
    `--A. (Simulamerelina) bermudensis Faber & Moolenbeek 1987BC01
Alvania incertae sedis:
  A. acutilirata Carpenter 1866O27
  A. aequisculpta Keep 1887O27
  A. alaskana Dall 1886O27
  A. almo Bartsch 1911O27
  A. aurivillii Dall 1886O27
  A. bakeri Bartsch 1910O27
  A. burrardensis Bartsch 1921O27
  A. californica Bartsch 1911O27
  A. cancellata (Da Costa 1778)O96
  A. carpenteri Weinkauff 1885O27
  A. castanella Dall 1886O27
  A. cimex (Linné 1758)O96
  A. compacta Carpenter 1865O27
  A. cosmia Bartsch 1911O27
  A. dalli Bartsch 1927O27
  A. dinora Bartsch 1917O27
  A. discors (Allan 1818)O96
  A. dorbignyi (Andouin 1827)BD86
  A. elegantissima (Monterosato 1875)O96
  A. filosa Carpenter 1865O27
  A. hirta Monterosato 1844O96
  A. iliuliukensis Bartsch 1911O27
  A. isolata (Laseron 1956)JG19
  A. kyskaensis Bartsch 1917O27
  A. lineata Risso 1826O96
  A. litoralis (Nordsieck 1972)O96
  A. mamillata Risso 1826O96
  A. montaguiPP64
  A. montereyensis Bartsch 1911O27
  A. oldroydae Bartsch 1911O27
  A. purpurea Dall 1871O27
  A. reticulata Carpenter 1864C64
  A. rosana Bartsch 1911O27
  A. rudis (Philippi 1844)O96
  A. sanjuanensis Bartsch 1921O27
  A. subsoluta (Aradas 1847)BM88
  A. testae (Aradas & Maggiore 1844)O96
  A. trachisma Bartsch 1911O27
  A. tumidaC64

*Type species of generic name indicated

References

[BD86] Barash, A., & Z. Danin. 1986. Further additions to the knowledge of Indo-Pacific Mollusca in the Mediterranean Sea (Lessepsian migrants). Spixiana 9 (2): 117–141.

[BM88] Bieler, R., & P. M. Mikkelsen. 1988. Anatomy and reproductive biology of two western Atlantic species of Vitrinellidae, with a case of protandrous hermaphroditism in the Rissoacea. Nautilus 102 (1): 1–29.

[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.

[BC01] Boyko, C. B., & J. R. Cordeiro. 2001. Catalog of Recent type specimens in the Division of Invertebrate Zoology, American Museum of Natural History. V. Mollusca, part 2 (class Gastropoda [exclusive of Opisthobranchia and Pulmonata], with supplements to Gastropoda [Opisthobranchia], and Bivalvia). Bulletin of the American Museum of Natural History 262: 1–170.

[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.

[JG19] James, D. J., P. T. Green, W. F. Humphreys & J. C. Z. Woinarski. 2019. Endemic species of Christmas Island, Indian Ocean. Records of the Western Australian Museum 34 (2): 55–114.

[N00] Norman, A. M. 1900. British Amphipoda: families Pontoporeidae to Ampeliscidae. Annals and Magazine of Natural History, series 7, 5: 326–346.

[O27] Oldroyd, I. S. 1927. The Marine Shells of the West Coast of North America vol. 2 pt. 3. Stanford University Press: Stanford University (California).

[O96] Oliverio, M. 1996. Contrasting developmental strategies and speciation in N.E. Atlantic prosobranchs: a preliminary analysis. In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 261–266. Oxford University Press: Oxford.

[PP64] Peres, J. M., & J. Picard. 1964. Nouveau manuel de bionomie benthique de la mer Mediterranee. Recueil des Travaux de la Station Marine d’Endoume, Bulletin 31 (27): 5–137.

Ponder, W. F. 1984. A review of the genera of the Rissoidae (Mollusca: Mesogastropoda: Rissoacea). Records of the Australian Museum Supplement 4: 1–221.

[RM88] Romer, N. S., & D. R. Moore. 1988. A new species of Alvania (Rissoidae) from the West Indian region. Nautilus 102 (4): 131–133.

Verduin, A. 1986. Alvania cimex (L.) s.l. (Gastropoda, Prosobranchia), an aggregate species. Basteria 50: 25–32.

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