Contributions to Zoology, 82 (2) 85-94 (2013) Brooding in a temperate zone land snail: seasonal and regional patterns (original) (raw)
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Brooding in a temperate zone land snail: seasonal and regional patterns
Contributions to Zoology, 2013
The goal of this study is to assess if the reproductive strategy of a brooding land snail shifts along a climatic gradient. We focused on the following traits: timing and length of the reproductive season, brood size, ontogenetic dynamics of embryos, and reproductive mode (viviparity versus egg-laying). We dissected the central European door snail Alinda biplicata, collected monthly from eight populations covering the oceaniccontinental climatic gradient within the species’ distribution range. Forty percent of the 1706 dissected individuals were brooding. The species displayed a spring-summer reproductive activity pattern: intrauterine brooding was recorded between March and September; first embryos of a developmental stage that equals that of live-born neonates appeared in late April. Brooding started approximately when the mean daily temperature of a month exceeds ca. 5°C, thus the ontogenetic development of embryos is advancing earlier in populations under the influence of mild o...
Influence de la date d'échantillonnage sur la reproduction de l'escargot terrestre helix aperta maintenu en conditions contrôlées de température et de photopériode. -Les caractères reproductifs des escargots Helix aperta ont été étudiés sous quatre combinaisons de température et photopériode (20°C/16hL 8hd ; 20°C/8hL:16hd ; 15°C/16hL:8hd and 15°C/ 8hL:16hd). Trois échantillons ont été utilisés : Ech. 1 et Ech. 2 collectés à Annaba (Nord-Est Algérien) respectivement durant et après l'hibernation ; Ech. 3, précédemment analysé (données non publiées), collecté à Béjaïa (proche Nord-Est Algérien) durant l'estivation. Tous les escargots ont commencé à s'accoupler dès la 1 ère semaine et à pondre durant la 3 ème ou la 4 ème semaine de leur mise en conditions de reproduction. Ech. 1 et Ech. 2 se sont distingués par leur plus courte période de reproduction (4-6 semaines) en comparaison avec Ech. 3 (5-7 semaines). d'une manière frappante, bien que les escargots collectés durant ou après hibernation (Ech. 1 et Ech. 2) se soient accouplés, dans la plupart des cas, à des taux plus élevés (56-87 %) que ceux échantillonnés durant l'estivation (32-92 %), leurs taux de pontes ont été dramatiquement plus faibles (6-25 % contre 12-80 %). Autrement dit, parmi les escargots qui se sont accouplés dans Ech. 1 et Ech. 2, seulement 11-36 % ont pondu, contre 38-87 % dans Ech. 3. Les nombres moyens d'oeufs par ponte étaient plus élevés en Ech. 1 (293-323) et Ech. 3 (337-348) qu'en Ech. 2 (237-248) (P < 0.05). Inversement, les poids moyens des oeufs par ponte étaient plus élevés en Ech. 2 (17.5-17.8 mg) qu'en Ech. 1 (16.1-16.3 mg) et Ech. 3 (16 3-16.6 mg) (P < 0.05). Après la période de reproduction, en conséquence des rendements reproductifs différentiels, les poids moyens des escargots ont très significativement augmenté en Ech. 1 et Ech. 2 (P < 0.001) et significativement baissé en Ech. 3 (P < 0.05). Les performances reproductives étaient plus affectées et les taux de mortalité plus élevés sous basse température et courte photopériode. La meilleure combinaison de ces deux facteurs était souvent 20°C/16hL:8hd, plus proche des conditions sur le terrain en automne, surtout durant la nuit, phase d'activité des escargots. Après la période de reproduction, la mortalité devenait de plus en plus élevée et les survivants moins actifs ou essayant de s'enfouir dans le sol des pots de ponte. Tous ces arguments plaident que les escargots H. aperta sont mieux adaptés à se reproduire en automne (jours décroissants et températures plus élevées) après une longue estivation stimulant la gamétogenèse qu'au printemps (jours croissants et températures basses) après l'hibernation inhibant la gamétogenèse.
2012
3 Abstract: Eighty (80) adult or sexually mature land snails, A. marginata var. saturalis (P.), forty each of the black-skinned (BS) and white-skinned (WS) ectotypes with weight ranging from 56.22-67.38 g and 55.54-67.02 g for the BS and WS ectotypes respectively were reared in pairs (two snails) for twelve weeks to evaluate reproductive performance. Correlations between the traits of produced eggs were also estimated. Assessed reproductive traits included clutch size, mean egg weight at lay and weekly, mean egg length and width at lay and weekly, incubation period (days), number of hatched eggs, percent hatchability and hatchlings weights at hatch. Results of reproductive performance showed that considerable reproductive differences exist between snail ectotypes of a particular breed. This is because significantly different (P<0.05) variations existed between the number of eggs laid by the BS ectotypes and those laid by the WS ectotypes. The BS ectotypes were actually more proli...
Ecology and evolution, 2015
In a seasonal environment, the suitable time window for females to reproduce is restricted by both environmental conditions and the availability of males. In simultaneous hermaphrodites, which are female and male at the same time, selection on a trait that is solely beneficial for one sexual function cannot occur independently. Therefore, it is assumed that the optimal time window for reproduction is a compromise between the two sexual functions in simultaneous hermaphrodites, mediated by environmental conditions. We examined seasonal patterns of reproduction and the resulting paternity in a natural population of the simultaneously hermaphroditic land snail Arianta arbustorum. Adult and premature individuals (snails in a short protandric phase) were collected on four occasions over the entire active season. The snails were allowed to deposit eggs after which we assessed the level of paternity in their hatched offspring. Individuals mated throughout the reproductive season, whereas e...
2022
The purpose of this study was to investige the reproductive success of land snails (Cornu aspersum) without photoperiod during the non-breeding season in the Black Sea Region between December 2019 and January 2020. Snails, which were placed in cold storage for a hundred days, were awakened in December. The reproductive performances were assessed under semi-controlled laboratory conditions using the natural daylight cycle and the ideal temperature and moisture. The experiment was designed as a single group with 3 replications. The experiment was designed 3 replications, with 10 snails in each replicate in total of 30 snails. The reproductive performance of the snails was observed daily and the first mating took place on the 9th day of the study and the first egg-laying was detected in the second week of the study. In the study, the fecundity of the snails was 43%. Spawning activity was continued through to 3 weeks. The mean number of eggs, hatching rate and the number of offsprings were 151.13±22.02, 90.33±2.39% and 138.13±21.09, respectively. The mean egg and offspring live weights were 0.034±0.001 g and 0.03±0.007 g, respectively. The findings showed that the reproductive performance was low as 43%. As a in conclusion, reproductive performance is unsuitable for commercial snail production without the photoperiod treatment during the non-breeding season.
Reproductive Strategies of a Terrestrial Snail along an Altitudinal Gradient on an Oceanic Island
This study reports how the reproductive cycle of a land snail endemic from an oceanic island is shaped by abiotic factors over an altitudinal gradient of 800 m. In addition, the validity of two morphometric shell parameters (maximum diameter and total height) was assessed, as maturation diagnostic characteristics. The authors' findings suggest that, at Piedade (200 m), individuals are active and mature from October/November to March, and they exhibit dormancy in the remaining months, as a consequence of soil dryness. Thus, at low altitude, gonadal maturation was considered to be primarily influenced by photoperiod, rainfall and temperature. At Cabeço da Bola (1000 m), in turn, individuals are mature from March to July/August and they seem to have minimal gametogenic conditions throughout the remaining months of the year to reproduce. As soil moisture is never a limiting factor, gonadal maturation is mainly shaped by photoperiod and temperature at high altitude. The morphometric shell parameters under analysis were unable to diagnose gonadal maturation, as recently described for related Azorean species.
Journal of Molluscan Studies, 2019
Viviparity in land snails occurs mainly in species living in tropical or harsh mountain habitats, both of which are characterized by high humidity. The clausiliid Idyla bicristata (Rossmässler, 1839) is an exception. This viviparous snail inhabits the Mediterranean region, which is characterized by long, dry summers. Here, based on field and laboratory breeding observations and experiments, we describe the phenology and fecundity of I. bicristata in detail. The species follows a seasonal pattern of activity: snails are active from October until April (but not in January), and aestivate during the summer months. Reproduction occurs in autumn and spring, with a peak in October, when about 50% of adults were found to be gravid, with an average of 4.9 embryos/adult. In laboratory cultures, adults usually produced neonates twice a year, and the annual fecundity of a pair averaged 15.7 neonates. Reproductive maturity was attained 6.5-7 months after birth. We also investigated the effect of a two-month long experimental drought on gravid snails. We found that the reproductive period was long and flexible, with a low number of individuals being gravid at a given time (in comparison to other viviparous snails). This strategy may reduce the risk of failure and may be a response to demanding climatic conditions. The widespread occurrence of viviparous reproduction in related taxa, which inhabit mainly mountainous areas (the Mentissoideinae group), is also discussed.
Oecologia, 1986
Factors affecting oophagy among siblings in the land snail Arianta arbustorum were studied in 3 populations from different altitudes in Switzerland. The degree of egg cannibalism in A. arbustorum is a function of hatching asynchrony since the earliest hatched snails will devour the unhatched eggs in the same clutch. Clutch size, egg density and amount of vegetable food available to newly hatched snails did not affect the degree of cannibalism. Snails from 3 populations were similar in terms of incubation time and intrinsic hatching asynchrony of the clutches. However, they differed in degree of cannibalism when the hatching asynchrony had been experimentally increased. Snails from a lowland forest showed a higher degree of cannibalism than did those from an alpine mountain slope. The parent snails differed in terms of incubation time and hatching synchrony in their clutches. Under natural conditions, the length of the hatching spread and, as a result, the degree of cannibalism will depend additionally on the mode of oviposition (batches or single; clumped or dispersed), on the spatial heterogeneity of egg-laying places and on climatic conditions (e.g. drought).
Journal of Molluscan Studies, 2005
Xeropicta derbentina (Krynicki, 1836), a native of Eastern Mediterranean Europe, was introduced to southeastern France during the 1940s and is now widely spread across Provence. In summer it aggregates on plants, making its populations clearly visible. However, its life cycle within the Mediterranean basin is poorly documented. While X. derbentina in its native area exhibits an annual life cycle, this species has been found in Provence to have a biennial life cycle. Moreover, in southeastern France, field studies within a restricted area show variations in demographic structure. In consequence, the life cycle of X. derbentina and the demographic patterns observed require clarification. Five populations with various demographic structures were studied over 1 year in the same location, i.e. under the same climatic conditions. The field study was complemented by laboratory observations on mating, egglaying and hatching. Xeropicta derbentina appears to be a semelparous species, with an annual life cycle being found on four plots. The reproductive period begins at the end of summer and lasts until the beginning of winter. First egg-laying occurs within 1 week after mating and lasts up to 30 days. Hatching takes place 15 -20 days after egg-laying. Xeropicta derbentina possesses multiple mating and egg-laying sessions, involving successive hatching. Populations are mainly characterized by two growth stages, the first in spring when newly-hatched snails evolve into juveniles, and the second in late summer when they reach maturity. However, on the highest density plot, a biennial life cycle is observed for some newly-hatched snails that show an interrupted growth during summer and evolve into juveniles only in the second autumn. Moreover, this life cycle not only varies among plots but also at a 1-year interval within plots. Hence, the life span of X. derbentina is between 12 and 20 months, but can be extended up to 30 months according to whether hatching occurs early or late and whether they survive the first and second winters. Xeropicta derbentina is thus able to have various growth speeds and life spans, and appears to switch from an annual life cycle to a biennial cycle in response to population density or climatic conditions.