Indoor hibernation technological flow for the five case studies (Cs1–Cs5).
Abstract
The “Italian” outdoor snailfarming technology assumes that both mature and juvenile snails hibernate outdoor, protected by a thin sheet of unweaved coverlet (agryl sheet). In contrast, the “French” snailfarming technology implies that only mature brown garden snails (Helix aspersa) hibernate indoor, in strictly controlled microenvironmental parameters (temperature, humidity, and ventilation). This technology may also be viable for H. aspersa juveniles. Extremely high death rates occurring in Romanian outdoor snailfarms during colder winters (>80%) imposed the need to find alternative paths for a proper hibernation of H. aspersa. Using statistical analyses, close surveillance of technological flow, and controlled microenvironmental parameters, we assessed the possibility to adapt indoor hibernation for H. aspersa juveniles. The experiments lasted for 2 years (2006–2008) and were carried out on 34,000 H. aspersa juveniles and 15,000 mature ones, using different technological flows and microenvironmental parameters (temperature, humidity, and ventilation). They were performed in two stages and involved five case studies, conducted independently in three different locations: Floreşti (Mehedinţi county), Sântuhalm (Hunedoara county), and Muntenii de Sus (Vaslui county). The first stage tested the hypothesis in relation to survival rate of mature snails, H. aspersa, in the same conditions, whereas the second stage improved the technological flow, before its extensive application. We demonstrated that noncontrolled microclimate parameters (temperature, humidity, and ventilation) and the use of straw as hibernation support induced significant differences (P < 0.01) concerning death levels of H. aspersa juveniles as compared to their indoor hibernation in semicontrolled microclimate (temperature and ventilation). In the same hibernation microclimate, mature snails exhibited higher survival levels than the juvenile ones, irrespective of technological flow and origin (P < 0.0001). We also demonstrated that juveniles’ weight loss displays a relatively constant variation (16.33–20.51%). In addition, the correlations between the individual average weight before and after hibernation were described by the same logarithmic regression. Furthermore, significantly higher survival rates of H. aspersa juveniles (P < 0.0001) have been registered when they had not been awakened during hibernation. Finally, we proved that indoor hibernation of H. aspersa juveniles in strictly controlled microenvironmental parameters (temperature, humidity, and ventilation) could represent a viable technology that improves the technological flow in outdoor snailfarming during wintertime in colder climates.
Keywords
- microenvironment
- snailfarming
- hibernation
- technology
- monitored
1. Introduction
In a continental climate, characterized by higher rainfall levels than on countries with tradition in snailfarming (France, Italy, Spain, Greece), in Romania this activity registered a booming development during the 2003–2007 time period [1]. Thus, in 2006, according to the International Institute of Snail Farming from Cherasco (Italy), Romania ranked second in the world concerning the number of outdoor snailfarms (>1000) and their sown area. The “French” snailfarming technology implies that the snails are bred in captivity, and juveniles are introduced early in the spring in outside fattening pens, wherein they are fed primarily a combination of concentrated fodders [2]. As a result, most snails reach adulthood from 6 to 8 months, and in autumn they are sold as final product. Only a small proportion of adult gastropods is kept as reproductive herd for the next year productive cycle and hibernate in strictly controlled indoor environment [3]. The immature juveniles are not gathered; therefore, they are let to survive outside during wintertime, without any additional protection [4]. In contrast, the “Italian” snailfarming technology snails employs the biological cycle of raising and growing snails in open pastures of fresh vegetables [5]. A typical farm is organized in pens with precise destinations: 60% for breeding and 40% for fattening [6]. The fattening pens are used starting from the second year of activity onward, when after hibernation, snails are transferred from the breeding pens into the fattening pens [7]. When winter arrives, snail of many sizes, starting from hatchlings to adult ones, are found inside the pens [1]. The solution used for snail hibernation relies on trimming the vegetation inside the pens to 20 cm in height, whereas the pens are covered with unweaved coverlet (weight = 18–25 grams per square meters, i.e., g/m2)—material also known as agryl sheet [8, 9].
High death rates have occurred in snailfarms all around Romania during the winter of the year 2006, proving that the standard outdoor hibernation technology is not well suited for colder climates (temperate continental climate). As a result, our research focused on finding some alternative paths for a proper hibernation of
Then, we analyzed weight variation of
2. Materials and methods
The experiments of this pilot exploratory study were conducted in three snailfarms chosen based on their location, technological flow, and microenvironment parameters: Floreşti (Mehedinţi county; latitude, 44°75'; longitude, 22°92'), Sântuhalm (Hunedoara county; latitude, 45°85'; longitude, 22°96'), and Muntenii de Sus (Vaslui county; latitude, 46°70'; longitude, 27°76'). The farms were carefully monitored since their implementation: 2005 (Muntenii de Sus) and 2006 (Floreşti, Sântuhalm). The reproductive herd was imported from Italy. The data were carefully monitored and recorded into technological evidence files. Next, they were used for five case studies (Table 1) depending on location and snail size: Cs1 (Floreşti, juvenile
2.1 Hypothesis testing
First, two distinct locations were selected for these studies: Floreşti and Sântuhalm. Two lots were sampled from each location, one containing only juvenile
2.2 Technology optimization
The first stage data were used to optimize this technology in a study performed from October 2007 to March 2008 (Table 1) in a snailfarm located in Muntenii de Sus (Cs5). All the procedures were identical with those used in the study cases Cs1 and Cs3 (Table 1). The only exception was that the post-hibernal samples weighed about 75 g and not 50 g, like in the previous cases.
2.3 Statistical analysis
The hibernation efficiency (Table 2) was assessed based on the snail survival rate. To estimate the potential influence of origin and technological flow on juveniles’ weight loss during wintertime (Wl), we analyzed all the quantitative indicators (individual weight, weight loss, snail number/known weight) by descriptive (Figure 1) and nonparametric statistical tests. First, we assessed the distribution normality (Anderson-Darling test) for Wb, Wl, Wa, Na, and Nb for all the samples (df = 1,
Sampling data Number/(weight) | Intermediary control dead snails | Awakening (live snails) | T (°C) | U% | Ventilation | |
---|---|---|---|---|---|---|
Cs1 | November 17, 2006 5025 g (≈10,255 pcs.) | January 12, 2006 | March 13, 2007 3670 juveniles | Constant 2–5°C | Variable 60–75% | Partially controlled |
| ||||||
| ||||||
Cs2 | November 17, 2006 6500 pcs. | January 12, 2007 640 pcs. | March 13, 2007 5906 pcs. | Idem Cs1 | ||
Cs3 | November 11, 2006 5050 g (≈12,949 pcs.) | January 1, 2007 | March 7, 2007 724 pcs | Variable −1 → + 8°C | Variable 55–90% | Variable |
| ||||||
Cs4 | November 11, 2006 8500 pcs. | January 1, 2007 2000 pcs. | March 7, 2007 5800 pcs. | Idem Cs3 | ||
Cs5 | November 11, 2007 5, 050 g (≈10,100 pcs.) | — | March 18, 2008 6837 juveniles | Constant 2–5°C | Constant 70–75% | Controlled |
|
Cs1 | Cs2 | Cs3 | Cs4 | Cs5 | |
---|---|---|---|---|---|
Before hibernation | |||||
Wb | 0.49 ± 0.06 | — | 0.39 ± 0.06 | — | 0.50 ± 0.04 |
Nb | 205.00 ± 25.77 | — | 262.20 ± 40.61 | — | 200.00 ± 14.98 |
After hibernation | |||||
Wa | 0.41 ± 0.04 | — | 0.31 ± 0.05 | — | 0.41 ± 0.03 |
Na | 123.40 ± 14.77 | — | 160.80 ± 21.47 | — | 175.6 ± 24.82 |
Wl | 0.087 ± 0.027 | 0.075 ± 0.023 | 0.089 ± 0.009 | ||
Wl% | 16.33% | 20.51% | 18.00% | ||
Intermediary control | |||||
Sli | — | 91.62% | — | 76.46% | — |
Dri | — | 8.38% | — | 23.53% | — |
Final control | |||||
Slf | 35.78% | 78.55% | 18.06% | 68.34% | 67.69% |
Drf | 64.22% | 21.45% | 81.94% | 31.66% | 32.31 |
Death rates were analyzed by using a
3. Results
3.1 Hypothesis testing (Cs1–Cs4)
The Anderson-Darling test proved an abnormal distribution (
where
The data recorded in the technological files revealed that, for Cs3 and Cs4, the problems started from January 1, 2007, when suddenly the outdoor temperature increased over 5°C and abundant rainfall (slushes) were recorded. Because the storage had no thermic insulation, the air humidity exceeded 85%, water condensated on the storage walls, the straw soaked, and the snails, especially the juvenile ones, started to awaken from hibernation. As a result, the straw were removed, and the dead snails were also drawn away. This action limited the death rate, but at the same time, it induced the restart of their metabolic cycle, especially for juvenile snails. This behavior of
At that time, no data were available in literature or in practice concerning the maximum period that allows juveniles to successfully survive during wintertime. Thus, Cs1 snails were awakened form hibernation on January 12, 2007. Next, they were fed with concentrated fodder and minced carrots, and after that, they were reintroduced to hibernation. After hibernation, the comparative statistical analyses revealed significant differences between Slf and Slo for the juvenile snails, in both locations: Cs1 (
3.2 Technology optimization (Cs5)
The same abnormal distribution (
Concerning Slf, Cs5 proved significant differences in comparison to both Cs1 (
This study demonstrated without doubt that indoor hibernation of
4. Discussion
The key factors triggering land snail dormancy are temperature decrease [16], photoperiod diminishing [17], and low humidity [18]. For
Oblomovism is well known in the world of mollusks [21]. This term came from the homonym novel written by Ivan Goncharov and is used to describe someone who exhibits the personality traits of sloth. Thus, during their life, snails pass through short periods of great activity, essential for building up their reserves, which alternates with frequent periods of inactivity, when they are sleeping or pending the favorable weather. Taylor [22] considered juvenile snails less sensitive to cold and thus less inclined to hibernation; therefore it was considered that they exhibit a partial oblomovism. However, recent studies proved that for
Our findings proved that juveniles displayed, regardless of the technology flow and origin, a relatively constant variation of weight after 100–110 days of indoor hibernation. Although in the wild, snails displayed variable losses of weight in relation to climatic factors [1], we considered that snail adaptation to hibernation throughout their long evolution and the controlled microenvironment allowed them to pass overwinter with a relatively constant weight loss during wintertime. Thus, we consider that this technology might be used in outdoor snailfarms located in colder areas with temperate continental climates as efficient alternative to the simple outdoor hibernation.
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