Influence of Egg Cannibalism on Growth, Survival and Feeding In
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Influence of egg cannibalism on growth, survival and feeding in hatchlings of the land snail Helix aspersa Müller (gastropoda, pulmonata, stylommatophora) C Desbuquois To cite this version: C Desbuquois. Influence of egg cannibalism on growth, survival and feeding in hatchlings ofthe land snail Helix aspersa Müller (gastropoda, pulmonata, stylommatophora). Reproduction Nutrition Development, EDP Sciences, 1997, 37 (2), pp.191-202. hal-00899950 HAL Id: hal-00899950 https://hal.archives-ouvertes.fr/hal-00899950 Submitted on 1 Jan 1997 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Original article Influence of egg cannibalism on growth, survival and feeding in hatchlings of the land snail Helix aspersa Müller (gastropoda, pulmonata, stylommatophora) C Desbuquois Laboratoire de zoologie et d’écophysiologie, UA InralUMR 6553 du CNRS, Faculté des science.r, université de Rennes 1, avenue du Général Leclerc, 35042 Rennes cedex, France (Received 10 September 1996; accepted 26 November 1996) Summary ― Under controlled conditions, growth, survivorship and several nutritional parameters (ingestion, egestion and assimilation) were measured weekly in hatchlings that either ate a conspe- cific egg after birth (cannibalistic) or not (non-cannibalistic) and in food-deprived individuals (con- trol group). Subsequently, the snails were fed on Taraxacum officinale. After 4 days, cannibalistic snails were 1.3 times heavier than food-deprived snails and 100% survived (75.8% in the control group and 40% of the non-cannibalistic individuals). Mortality, particularly in smaller snails, might be a con- sequence of food deprivation. Nutritional and energetic gains of oophagy increased both future sur- vivorship and growth. After 11 weeks, cannibalistic snails were 1.4 times heavier and had higher sur- vival rates than food-deprived ones although ingestion, egestion rates and assimilation efficiency were similar in both groups. The larger wet weight of cannibalistic snails after 4 days induced a higher food consumption and thus a higher growth rate. The influence of oophagy on life-history traits is discussed in relation to costs and benefits. nutrition / Helix aspersa / egg cannibalism / growth / survival Résumé ― Influence du cannibalisme des oeufs par les nouveau-nés sur la croissance, la survie et la nutrition chez l’escargot petit-gris Helix aspersa Müller (gastéropode, pulmoné, stylom- matophore). En condition contrôlées, la croissance, la survie et plusieurs paramètres nutritionels (ingestion, excrétion et assimilation) sont mesurés chaque semaine chez de jeunes H aspersa qui, pen- dant 4 jours suivant l’éclosion, ont consommé un oeuf de cette espèce (cannibales) ou non (non can- * Correspondence and reprints. Tel: (33) 02 99 28 61 56; fax: (33) 02 99 28 16 12; e-mail: secretariat-zoo-ecophy@univ- rennesl.fr nibales) et chez des individus ayant jeûné (témoins). Pendant 11 semaines, des feuilles de Taraxacum officinale sont utilisées comme aliment. Après 4 jours, les individus cannibales sont 1,3 fois plus lourds que les individus ayant jeûné et 100 % ont survécu (contre 75,8 % des témoins et 40 % des non can- nibales). La mortalité affecte particulièrement les petits individus. Les apports nutritionnel et éner- gétique de l’oophagie permettent une survie et une croissance plus importantes. Après I semaines, les individus oophages sont 1,4 fois plus lourds et présentent une meilleure survie que les escargots ayant jeûné. Les taux d’ingestion, d’excrétion et le rendement d’assimilation sont similaires. Ainsi, le poids plus élevé des individus oophages après 4 jours provoque une ingestion supérieure ulté- rieurement et donc une plus forte croissance. Les individus ayant jeûné pendant 4 jours ne peuvent pas compenser leur retard de croissance. L’influence du cannibalisme des oeufs sur « l’histoire de vie » est discutée en relation avec ses coûts et bénéfices. nutrition / Helix aspersa / cannibalisme des oeufs / croissance / survie INTRODUCTION fits of egg cannibalism (on growth and sur- vival) in newly born H aspersa. To high- The number of individuals surviving to the light the effect of egg cannibalism, which adult stage is a crucial factor in the dynam- might be hidden by nutrition differences ics of populations. Therefore juvenile sur- between cannibalistic hatchlings and non vival is very important and may be affected cannibalistic/control animals during their by intraspecific predation, ie, cannibalism. growth, I measured different nutritional One type of cannibalism, namely oophagy, parameters: feeding ingestion and faecal which concerns the consumption of egestion. Oophagy cannot be studied with unhatched eggs by hatchlings (Polis, 1981), egg-clutches kept in the soil because numer- has been studied in some land snail species ous uncontrolled factors might influence the (Baur, 1988, 1990a, b, 1992, 1994a; Baur eggs’ development under these conditions and Baur, 1986). and a single snail might cannibalize several In the land snail Helix aspersa Muller, eggs in the hatch. Thus, this experiment took Elmslie (1988) had noted that newly hatched place in small aluminium capsules, without snails may exhibit egg cannibalism. In this earth and under controlled conditions. species, eggs were laid in humid earth in a depth of some centimetres. A hatching asyn- chrony exists among eggs of the same MATERIALS AND METHODS clutch. This factor could promote oophagy as demonstrated in Arianta arbustorum L Biological materials (Baur and Baur, 1986). This phenomenon, combined with the period of time during Adults of the land snail H aspersa were collected which hatchlings remained in their nest after from salt-pans at Guerande (South Brittany, in France) and reared under the condi- 6 on average - following hatching - days (Herzberg tions to 20 °C and 1962) allow first born promote reproduction: temperature: Herzberg, might ± I; relative humidity: 80% ± 5; photoperiod: snails on unhatched in the nest feeding eggs 18/6 (L/D). Eggs, laid in humid earth, were (sibling cannibalism). In preliminary exper- washed before use. During 11 weeks, food con- iments, this feeding behaviour appeared to sisted of small discs (13 mm in diameter) of be common in H aspersa and to occur in leaves of Taraxacum officinale (Weber). The relation to some proximate factors (Des- plants were collected in the wild before use. They buquois and Madec, in preparation). were cut in the lamina without veins with a cork borer. T o,fficinale is known to be highly palatable The aim of the present study is to carry for H a.spersa and is abundant in numerous out a quantitative investigation of the bene- biotopes of this species. Moreover, this natural food had induced a low variability in the growth culate the egg consumption of each cannibalistic of H aspersa in preliminary experiments (Des- snail. 1991). buquois, Then each snail of both groups was placed in a separate Petri dish 11 mm; diameter 88 mm; surface: 152.1(height: cm ) under the same con- Experimental conditions ditions as before except for photoperiod: 16/8 (L/D)-chosen to be similar to natural one in spring. During 11 weeks, I tested the influence of A single hatch of H aspersa was divided into early egg cannibalism on the subsequent growth, two groups of equal size. One group was incu- survival and nutrition of the snails in relation to bated at 20 °C to obtain hatchlings for the tests starved snails. Petri dishes were sprayed with and the other at 15 °C to slow down the embry- distilled water twice a week. During the first 4 onic development of eggs which were used to weeks, one disc of leaf was given per week to feed animals of the treatment group (Baur, 1988, each snail; from week 5 to 9, two discs, and from 1990a, 1994a; Baur and Baur, 1986). According week 10 to 11, four discs per week. All the discs to Le Calve (1987), these conditions induce a were weighed before being given to the snails. of about 9 for the incu- hatching delay days eggs Each week, snails from both treatment groups bated at 15 °C. When the incubated at 20 °C eggs were food-deprived during the first 3 days and T each newborn snail was and hatched, weighed o!cinale leaf discs were given during the 4 last in a small aluminium placed individually cap- days. Faeces were removed the 3rd day of the sule 6 diameter: 20 surface: (height: mm; mm; following week, so that digestion was achieved 10.1 cm2). and faeces derived from the 4 days’ previous feeding. Several wet discs of T o!cinale were Two sets of replicates were constituted: hatch- weighed, dried to constant weight and weighed lings were fed with a conspecific egg (n = 43; again so that a regression between wet and dry treatment) or received neither an nor egg any weight of Taraxacum discs could be calculated. other food item (n = 33; control group). In natu- ral conditions, hatchlings can feed on organic matter present in the earth, but cannot consume plants because they remain several days in their Parameters used nest after hatching. I decided not to feed the con- trol group, because cannibalistic snails might Once a week, the number of surviving snails was equally consume earth and the aim of our exper- counted and the live weight (LW in mg) of each iment was to test and measure the effect of can- of them was measured. This measure is a suffi- nibalism only. In any case, in my preliminary cient parameter to estimate the growth of young laboratory experiments, hatchlings had not con- H aspersa (Lucarz and Gomot, 1985).