Of Snails and Men: A Satirical Look at the Challenges of Privatization and Globalization

You may think of snails only as small mollusks that wreak havoc in your garden or crawl around on the sidewalk after rain. But in many parts of the world, including France, Germany, and Portugal, snails are actually a delicacy. They can be enjoyed cooked into a buttery hors d'oeuvre called escargot or fried in an Indian dish called sate kakul.

Of Snails and Men

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The protein content of snails is similar to the protein found in pork and beef, but snails come with a much lower fat content. In addition to containing significant sources of protein and low amounts of fat, snails are also good sources of iron, calcium, Vitamin A, and a number of other minerals.

Iron-deficient anemia can cause symptoms that include fatigue, weakness, pale skin, chest pain, headache, dizziness, and shortness of breath. Fortunately, eating snails may help relieve some of these symptoms by treating the underlying cause. Snails are an excellent source of iron, with one serving of snails containing 22% of your recommended daily allowance of iron.

The rat lung worm is a parasite that can get into snails if they come in contact with rat feces (poop). If you eat a raw snail with this parasite, you can become infected. Signs of infection include:

The violet sea-snail, Janthina janthina, uses a bubble raft to float near the surface of the water in the hope of encountering a man-of-war meal. These snails have dark purple undersides and are paler purple on top for camouflage. Because they float upside down, the darker purple faces up, helping them blend into the darker water below. When seen from beneath, their paler coloration blends in with the light coming from above.

When snails meet, the tasting and smelling continue, this time with full-body contact, sometimes for hours. Call it heavy petting or extreme vetting, snails take the time to get to know their partners.

When snails copulate, two penises enter two vaginal tracts. Both snails in a pairing transfer sperm, but whichever snail got in the best shot with the dart has a better chance of ultimately fertilizing eggs.

The data presented here reveal that these snails can donate and receive sperm several times within 24 hours, and that they have increased mating rates in larger groups (i.e. more mating opportunities). For mating pairs we show, by introducing novel mating partners after copulation, that animals do inseminate new partners, while they are no longer motivated to inseminate their original partners.

The great pond snail, L. stagnalis, is a simultaneous hermaphrodite that can mate in the male and female role, but within a single copulation one sexual role is performed (and roles can be swapped afterwards) [21]. These snails seem usually prepared to receive sperm [21], they can receive sperm multiple times within a breeding season [22], and they can store and use the received sperm from different partners [23]. However, they will only donate sperm after several days of sexual isolation [24]. Previous studies have demonstrated that this male motivation is determined by the amount of seminal fluid in the prostate gland [25]. The gland's volume increase is detected, via a nervous connection, by an evolutionarily conserved brain region controlling male behaviour in gastropod molluscs [26].

L. stagnalis' male behaviour comprises a fixed sequence of events. These events include shell mounting and circular locomotion over the partner's shell to eventually find the position on the edge of the shell from where the female opening is accessible. This is followed by probing with the everted preputium (penis carrying organ) and, once the female gonopore is found, penis intromission and transfer of a copious amount of semen [24]. That the male reproductive investment of this simultaneous hermaphrodite equals the energetic costs of female reproduction was demonstrated by experimentally eliminating male behaviour, which resulted in a doubling of egg production [27]. The above illustrates that these snails are expected to be prudent with their expensive male reserves. It would be prudent to use the sperm to inseminate different partners rather than the same partner several times, which we set out to test here.

24 hour observations of copulation activity in groups of 2, 4 and 8 snails. The mean number of inseminations per individual are shown, the error bars represent standard errors of the mean of the replicates. For clarity the replicates are pooled. Groups with different letters (a or b) differ significantly from each other.

In pairs of snails we subsequently tested experimentally whether the observed increase in insemination frequency in larger groups was due to the presence of new partners. We used a mixed model (nominal logistic REML procedure) to test for the fixed effects of treatment (New/Same partner) and test (Dirty/Clean aquarium) and the random effect of replicates (nested in treatment) on whether insemination occurred. Prior to the treatment, i.e. during the first 6 hours of the experiment, on average 39.25 ( 1.71 S.D., N = 4 replicates) of the 48 animals inseminated their partner. For this observation period no differences were found in the number of inseminations (treatment: χ2 df = 1, p = 1.00; test: χ2 = 0.31, df = 1, p = 0.57; interaction: χ2 = 0.07, df = 2, p = 0.96). In all cases where insemination took place after the treatment, i.e. during the second 6 hours, animals inseminated their partners only once. Significantly more new partners were inseminated than familiar partners (χ2 = 6.14, df = 1, p = 0.013). In a clean aquarium more copulations were observed than in an uncleaned aquarium (χ2 = 3.88, df = 1, p = 0.049), indicating that the presence of mucus is important for this effect. The interaction between the two factors was also significant (χ2 = 6.84, df = 2, p = 0.033), suggesting that the effect of a new partner depended on the factor Clean/Dirty. The percentage of animals performing an insemination during the second 6 hours is shown separately for the two replicates in the Dirty (Figure 2A) and the two replicates in the Clean aquaria (Figure 2B).

Dewsbury [4] predicted that in many species performing the male role will be a costly event. The high costs of the male function have previously been demonstrated in the simultaneously hermaphroditic pond snail L. stagnalis [27]. Hence, these snails can be expected to be prudent with their expensive male reserves (sperm and seminal fluid). We here suggest that they achieve a strategic allocation of their sperm by preferentially inseminating different partners, possibly via an inhibition of inseminating the same partner twice. The existence of such a preference is supported by our observation that the number of inseminations per individual increases with group size. More importantly, we show experimentally that the motivation to mate as a male is lower when the same partner is encountered than when a novel partner is encountered.

Based on the current data we cannot distinguish between whether pond snails can recognise trails from partners that they previously inseminated themselves or trails from individual snails. Although the former seems most parsimonious, in both scenarios either the chemical or textural composition of the mucus could mediate this response to sperm competition. Such a cue in the mucus trail could allow animals to detect the presence of competition. For a very different hermaphrodite, the flatworm Macrostomum lignano, Schärer and Ladurner [31] already suggested that a mechanism should be present to differentiate between previously mated and novel partners. L. stagnalis does not seem to recognize novel individuals by means of direct contact or water-borne chemical signals, but may rather recognise mucus trails of novel individuals. Chemical cues are known to affect other processes in hermaphrodites. For example, in the polychaete Ophryotrocha diadema sex allocation is shifted due to chemical cues [32]. In sea slugs of the genus Aplysia a pheromone is released from the egg cordon which attracts potential mates and stimulates them to lay eggs on the same site [33]. Such cues could also be involved in detecting previous partners or even in recognising individuals. That this is a possible function for the mucus, is supported by the ample evidence that gastropod mucus is used for a variety of purposes. Examples include homing [34], locating conspecifics [35], and finding prey [36]. Moreover, the directionality of own trails as well as conspecifics' trails can be detected [37, 38].

Our experiments reveal that great pond snails, L. stagnalis, perform more inseminations in larger groups and prefer to inseminate novel over familiar partners. Such higher motivation to copulate when a new partner is encountered is known as the Coolidge effect and has never been demonstrated in hermaphrodites. These hermaphroditic snails thus exhibit prudence in the allocation of their expensive male reserves, which is in line with recent work showing that this species also transfers different numbers of sperm depending on the partner's mating history [39].

To compare the effect of a novel partner on male motivation, with the effect of a second presentation of the same partner, a total of 96 pairs of snails were allowed to copulate for an initial 6 hours at the start of the light cycle. These animals were then treated according to either one of two protocols, termed "Dirty" and "Clean". In the "Dirty" protocol, all the snails were briefly lifted out of the aquarium and were returned either with the same partner (Same) or paired with a new partner (from another compartment; New) to their original compartment in the uncleaned aquarium. These pairs were then observed for another 6 hours. In the "Clean" protocol, the only difference in the experimental procedure was that all animals were transferred to a clean aquarium for the second 6 hours of observation. 2ff7e9595c