World Congress of Malacology Antwerp ... - Unitas Malacologica

Evolution of spermatophore ornamentation in the land snail genus Thapsia (Stylommatophora,
Helicarionoidea): a role for sexual selection?
de Winter, Anton. J.
National Museum of Natural History Naturalis, P.O. Box 9517, 2300 RA Leiden, The Netherlands,
Email: winter@naturalis.nnm.nl
Land snails of the genus Thapsia, like many other helicarionoid snails and slugs, are simultaneous
hermaphrodites, which can mate with different partners within a period of a few days, thereby
reciprocally exchanging a large, rigid, chitinous spermatophore. These spermatophores consist of a
voluminous sperm-filled ampulla, followed by a long, convoluted tail. The tail portion is a narrow,
hollow tube with an opening at the posterior end, and is ornamented by a variety of thorns, branched
spines and other spiny outgrowths. Details of the elaborate tail ornamentation appear to be species
specific, or at least population-specific. Spermatophores constitute a serious investment in terms of
quantity of sperm as well as nutritional (protein) resources needed to produce the chitinous material
from which the spermaphore is moulded. A sperm-filled spermatophore weighs approximately four
to six times as much as a freshly laid egg. It seems therefore unlikely that a spermatophore is a
"cheap" commodity and that the ornamentation is selectively neutral. However, it proved difficult to
ascribe a function to the various thorns and spines in efficient fertilization of the partner. Comparing
spermatophore morphologies of different closely-related species in combination with the orientation
of freshly exchanged spermatophores in the distal female genital tract suggests that the evolution of
the ornamentation might be better explained as the result of a kind of sperm competition (i.e postcopulatory
sexual selection) arising from conflicting interests between the sexes of the snail: female
control over fertilization of her eggs and male maximizing the fertilization success of his sperm.
Natural hstory of Doto koenneckeri Lemche, 1976 (Gastropoda, Nudibranchia, Dendronotacea)
in the Ría of Ferrol (NW Iberian Peninsula)
Díaz-Agras, Guillermo 1 ; Urgorri, Victoriano 1,2 ; Corral, Eva 2 ; Botana, Alba G. 2 ;
Señarís, Marcos P. 2 & Candás, María 1
1 Universidade de Santiago de Compostela, Estación de Bioloxía Mariña da Graña, Rúa da
Ribeira 1, 15590-Ferrol, Spain,
Email: ebmgwily@usc.es
2 Universidade de Santiago de Compostela, Departamento de Zooloxía e Antropoloxía Física,
Facultade de Bioloxía, Spain
Doto koenneckeri is a Dendronotacea nudibranch of the family Dotoidae that has some very clear
distinctive features: a characteristically cone-shaped apical tubercle, larger than the rest of the ceratal
tubercles, that takes up 1/3 or even ½ of the total length of the cerata; some comma-shaped carmine
red marks on the inner side of the ceratal tubercles and depigmented areas on the base of the cerata.
This species lives exclusively on the plumularid hydroid Aglaophenia pluma dichotoma, from which
it feeds itself and on which it spawns. The spawn has the shape of a long band, is folded up and has a
white or yellowish-white color.
Since the study about the nudibranchs of the Ría of Ferrol started in 1977, a special attention has
been paid to the nudibranchs of the family Dotoidae, by collecting specimens of different species at
any time of the year and in different localities of the ría, using always autonomous diving equipments
for their collection and observation, what provided us with a wide information and a large collection
of specimens of different sizes and ages. Besides, during the years 1996 and 1997 a specific study
was carried out about the biology of some nudibranch species that live associated to the hydroid
colonies throughout a complete annual cycle. A follow-up of the two most common species of the
Ría of Ferrol was carried out during thirteen monthly samplings: Doto koenneckeri and Doto
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