Differences on allocation of available resources, in growth, reproduction, and survival, in an exotic gastropod of Physidae compared to an endemic one

Abstract

ABSTRACT. Physa acuta Draparnaud, 1805 is an invasive gastropod that can affect local species. In Argentina, it is widespread and abundant, even in environments inhabited by the native species Stenophysa marmorata Guilding, 1828. Its predominance raises the question whether this could be explained by a more successful energy allocation in functional requirements (growth, reproduction and survival) compared to S. marmorata. This study was aimed at comparing growth rates, as well as survival and fecundity, between both species under laboratory conditions. Individuals born on the same day were grouped in four per aquaria and kept under controlled conditions of food, light, and temperature. Snails were weekly measured (maximum shell length), and growth rates were calculated using the Von Bertalanffy's equation. The number of eggs and survivors were grouped by week. Stenophysa marmorata was larger at birth than Physa acuta and invested more energy in growth, delaying sexual maturity. This resulted in a disadvantage in fecundity and survival compared to P. acuta, which had a lower growth rate but matured earlier and survived longer. Furthermore, the growth of P. acuta was not affected by reproduction, its reproductive period was longer, consequently with more eggs laid than S. marmorata. KEYWORDS.Fecundity, invasive species, longevity, Physa acuta, Stenophysa marmorata.RESUMEN. Diferencias en la asignación de los recursos disponibles en crecimiento, reproducción y supervivencia entre un gasterópodo exótico y uno endémico de la familia Physidae. Physa acuta Draparnaud, 1805 es un gasterópodo invasor que puede afectar las poblaciones de especies locales. En Argentina, se encuentra ampliamente distribuida y en altas densidades, incluso en ambientes habitados por la especie nativa Stenophysa marmorata Guilding, 1828. Su predominancia podría ser explicada por un uso más exitoso de la energía en las demandas funcionales (crecimiento, reproducción y supervivencia) con respecto a S. marmorata. El objetivo de este trabajo fue comparar las constantes de crecimiento de ambas especies, teniendo en cuenta también los valores de supervivencia y fecundidad, en condiciones de laboratorio. Los individuos nacidos el mismo día fueron agrupados de a cuatro por acuario y mantenidos en condiciones controladas de alimentación, luz y temperatura. La longitud máxima de conchilla de los caracoles fue medida semanalmente, y la constante de crecimiento fue calculada usando la ecuación de Von Bertalanffy. El número de huevos y sobrevivientes era contado cada semana. Los ejemplares de S. marmorata nacieron con un tamaño mayor que los de Physa acuta e invirtieron más energía en el crecimiento, retardando su madurez sexual. Esto se tradujo en una desventaja en fecundidad y supervivencia con respecto a P. acuta, la cual presentó una constante de crecimiento menor pero maduró más tempranamente y sobrevivió más tiempo. Además, P. acuta no vio afectado su crecimiento por la reproducción y presentó un período reproductivo más prolongado, depositando así ...

Life table estimates of the invasive snail Physa acuta Draparnaud, 1805, occurring in India

“…Although the shell length and body weight increments were higher for P. acuta observed in the present instance, the pattern of growth remained similar to those occurring in Argentina (Núñez, 2010(Núñez, , 2011. In comparison to the survival till 88 weeks with a maximum shell length of 9.08mm observed in Argentina, the P. acuta in the present study survived for 22 weeks but attended a shell length of 11.5 mm (and body weight of 47.08 mg).…”

“…The data on the survivorship was applied to generalised life table parameters (Krebs, 1999), and the age-specific survivorship (l x ) and life expectancy at age x (e x ) were calculated, whilst the growth of the snails was assessed through the changes in the shell length. The data on the shell length (SL, in mm) was portrayed as a function of time and subsequently judged for the compliance (Núñez, 2010) with the von Bertalanffy growth equation , where l t is the shell length of the snails at time t and l ∞ and k are the von Bertalanffy growth parameters. Assuming that the relation between l t+1 and l t will yield a straight line equation (y = a + bx), with the slope (b) being e(−k) and the intercept (a) being l ∞ = [1-e(−k)] = l ∞ (1− b), thereby enabling determination of l ∞ and k, the parameters of the von Bertalanffy growth parameters.…”

“…The invasive snail Physa acuta Draparnaud, 1805 (Gastropoda: Physidae) has spread through the continents of Asia (Ali, 1993), Africa (Brackenbury, Appleton, 1993;de Kock, Wolmarans, 2007;Appelton, Miranda, 2015), Australia (Zukowski, Walker, 2009), Europe (Semenchenko et al, 2008;Raković et al, 2016) and South America (Núñez, 2010) during the past few decades. In India, following the reports on the occurrence of P. acuta (Raut et al, 1995), little effort has been made to document the demography, life history and ecology, which are essential indicators to monitor the colonisation pattern in the native ecosystem (Aditya, Raut, 2002a,b,c;Devi et al, 2006Devi et al, , 2008.…”

“…This has been the basis for the assessment of the life history of invasive freshwater snails including P. acuta. Empirical studies on the growth and the reproduction of the snail in South Africa (Brackenbury, Appleton, 1993) and Argentina (Núñez, 2010(Núñez, , 2011 have been useful in comparative assessment of the population demography of the invasive snails in the respective geographical area. In Indian context, information on the life history features and the fecundity of P.…”

Characterisation of the multixenobiotic resistance (MXR) mechanism in the freshwater snailPhysa acutafrom Patagonia (Argentina)

“…Snails were given no food during the adaptation period and then were fed ad libitum with lettuce leaves (Núñez 2010).…”