Molluscan Studies
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Journal of The Malacological Society of London Molluscan Studies Journal of Molluscan Studies (2012) 78: 185–196. doi:10.1093/mollus/eyr056 Advance Access publication date: 23 January 2012 MATING BEHAVIOUR AND COPULATORY MECHANICS IN SIX SPECIES OF PLANORBIDAE (GASTROPODA: PULMONATA) E. SOLDATENKO1 AND A. PETROV2 1E.V. Soldatenko, Smolensk State University, Przhevalskiy St. 4, Smolensk 214004, Russia; and 2A.A. Petrov, Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St Petersburg 199034, Russia Correspondence: A. Petrov; e-mail: [email protected] Downloaded from (Received 20 February 2011; accepted 31 October 2011) ABSTRACT Although Planorbidae are one the most common and diverse families of pulmonates, their mating be- http://mollus.oxfordjournals.org/ haviour is known only for a few species. This paper describes mating behaviour and copulatory mechanics in four species of the Planorbidae: Anisus vortex (Linnaeus, 1758), Bathyomphalus sontortus (Linnaeus, 1758), Choanomphalus riparius (Westerlund, 1865) and Planorbis planorbis (Linnaeus, 1758), and supplements previously published observations on two other species: Segmentina oelandica (Westerlund, 1885) and Planorbella (Seminolina) duryi (Wetherby, 1879). Patterns of musculature of the penial complex [in all species except P. (S.) duryi] were studied using fluorescent phalloidin dye specific for actin filaments. Choanomphalus riparius, P. planorbis and S. oelandica wereshowntomatebyshell mounting and display an elaborate courtship behaviour accompanied by shell-circling. Planorbella (S.) duryi mates in a face-to-face position; in this species, courtship is accompanied by mechanical stimulation of the partner’s plicae. Anisus vortex and B. contortus do not exhibit any distinct precopulatory behaviour by guest on November 13, 2016 and mate face-to-face. It is argued that Planorbidae show a relationship between gender expression (functional protandry vs simultaneous hermaphroditism) and mating behaviour (unilateral vs reciprocal mating). The taxonomic utility of the copulatory behaviour and penial musculature is discussed. INTRODUCTION In recent years, interest in the reproductive processes in fresh- water pulmonates has increased and experimental techniques Planorbidae are one of the most diverse and common worldwide have become more sophisticated (Boyle & Yoshino, 2000; families of basommatophoran pulmonates. These freshwater Vianey-Liaud & Dussart, 2002), but most studies (e.g. Koene & snails are considered to be simultaneous hermaphrodites and Ter Maat, 2005; Facon, Ravigne´& Goudet, 2008) are still have internal fertilization through direct copulation (Hyman, focused on reproduction in just a few model or parasitologically 1967; Minichev & Starobogatov, 1971). Most members of this important species, such as Biomphalaria glabrata, Bulinus globosus family are of small size (with shell diameter ,20 mm) and their and Lymnaea stagnalis. Some recent studies have provided a few copulatory behaviour typically has to be studied under a light preliminary generalizations concerning mating behaviour in microscope on experimentally paired individuals. This often pulmonates. For instance, it has been observed that the shell makes observation a challenging task and so there have been size influences gender role during copulation, i.e. individuals only a few studies dealing with reproductive behaviour in this with smaller shells act predominantly in the male role (DeWitt, group. Only a few of these are explicitly focused on mating be- 1996; Ohbayashi-Hodoki, Ishihama & Shimada, 2004; Norton, haviour and copulatory mechanics (Rudolph, 1979a, b; Trigwell, Johnson & Mueller, 2008); that flat-spired snails copulate recip- Dussart & Vianey-Liaud, 1997; Soldatenko & Petrov, 2009b); rocally and high-spired ones unilaterally (Asami, Cowie & most studies discuss mating only briefly as part of the reproduct- Ohbayashi, 1998); and that all basommatophorans mate by ive cycle (e.g. Kuma, 1975; Berezkina & Starobogatov, 1988)or shell mounting with unilateral intromission, and only as an ex- explore some of the more specialized aspects of the mating ception in some species is intromission simultaneously reciprocal process, such as reproductive physiology (e.g. Kruglov & (Jordaens, Dillen & Backeljau, 2009). Unfortunately, most gen- Berezkina, 1978) or the relationship between reproductive eralizations have been derived predominantly from observations anatomy and copulatory mechanics (Abdel-Malek, 1952; Pace, made for the Stylommatophora; in the Basommatophora, 1971) or between reproduction and ecological factors (Thomas, mating behaviour is known only in 15 out of 68 genera and Coldworthy & Benjamin, 1974; Boyle & Yoshino, 2000). Some these observations are often anecdotal or fragmentary. very brief observations on mating can also be found in faunistic Furthermore, there is now a growing body of evidence that chal- (Hazay, 1881) and taxonomic (Baker, 1945; Wu, 1972) accounts. lenges some long-held ideas about mating behaviour in # The Author 2012. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved E. SOLDATENKO AND A. PETROV freshwater pulmonates. For example, the notion that planorbids the larger containers. Mating was induced by an increase in do not display complex ritualized behaviour prior to copulation water temperature (Duncan, 1975; Smith, 1981); water was (precopulation or courtship) (Simroth & Hoffmann, 1908– heated with incandescent lamps up to 20–288C (except for 1928: 1119; Precht, 1936) has now been refuted (Trigwell et al., B. contortus, which copulates at temperatures not higher than 1997; Soldatenko & Petrov, 2009b). It is clear that proposed 208C). The copulating pairs were photographed and time generalizations should be tested on a broader empirical basis, intervals for the phases of the mating process were recorded. which implies studying copulation in a wider array of basomma- For each species the observations were repeated, for at least tophoran species. three to four groups per season. The aim of the present paper is to describe mating behav- Some individuals were marked with coloured nail varnish iour and copulatory mechanics in four species of the for identification. Several times during the mating season the Planorbidae: Anisus vortex (Linnaeus, 1758), Bathyomphalus experimental groups were replenished by freshly collected indi- contortus (Linnaeus, 1758), Choanomphalus riparius (Westerlund, viduals to sustain mating activity, which starts to decrease after 1865) and Planorbis planorbis (Linnaeus, 1758) and to supple- several days in captivity. ment previously published observations on two other species: A stopwatch was used to time different phases of the mating Segmentina oelandica (Westerlund, 1885) and Planorbella process; however, the time frames of the phases in some species (Seminolina) duryi (Wetherby, 1879). All six species live in the (e.g. the beginning of precopulation in A. vortex or intromission Palearctic region, although P. (S.) duryi is originally a tropical in B. contortus) were impossible to determine due to indistinct species and was only recently introduced to the temperate behaviour patterns (lack of stereotypic precopulatory behav- regions through the aquarium trade (Sitnikova et al., 2010). iour) or difficulty of direct observation (copulatory organs are An additional aim is to describe the musculature of the male obscured by other structures). In such cases, time intervals copulatory organs (penial complex) in these species [except were determined only approximately and the duration of in- Downloaded from P. (S) duryi] using confocal microscopy and fluorescent semination was not measured. The time intervals for mating phalloidin dye specific for actin filaments. and courtship rejection are summarized in Table 1. MATERIAL AND METHODS Morphological study Collection sites Three to five individuals of each species were prepared as un- http://mollus.oxfordjournals.org/ stained whole mounts. These whole-mount preparations were The snails (sexually mature individuals) were collected by the examined and photographed on a Leica DMLS-2 microscope senior co-author in 2008–2009 (June through October). equipped with a CCD camera; the line drawings were copied Collections were made from the following localities in the from photographs, retaining their original proportions. European part of Russia: (1) 558300N, 318470E: Smolensk For confocal microscopy, two specimens of each species Prov., Demidovskiy Distr., Smolenskoye Poozerye National [except P. (S.) duryi] were fixed for 1 h in 4% formaldehyde Park, near town of Przhevalskoye: lake Rytoye (A. vortex, buffered with 0.1 M phosphate-buffered saline (PBS) at room P. planorbis); temporary ponds in the outskirts of the Chistik temperature, rinsed in 0.1 M PBS (3 Â 15 min), permeablized Teaching Centre (Smolensk State University) (P. planorbis, for 1 h in PBS containing 0.2% Triton X-100, rinsed again Ch. riparius, S. oelandica); a pool at Kirovka village, temporary shortly in 0.1 M PBS and then transferred to ponds (Ch. riparius); a pool at Kirovka village, lake Mutnoye phalloidin-TRITC (Sigma-Aldrich) for 1 h. After that, the by guest on November 13, 2016 (B. contortus); a pool at Nikitenki village (S. oelandica); (2) specimens were washed again for 3 Â 15 min in 0.1 M PBS, 598580N, 308150E: Leningrad Prov., St Petersburg, ponds on mounted in 80% glycerol on glass slides and viewed with a Yelagin Island (B. contortus). The individuals of P. (S.)