Presence of Palaemon macrodactylus in a Europe estuary: evidence for a successful invasion of the Gironde (SW France)

Palaemon macrodactylus, an exotic shrimp native to the northwest Pacific Ocean, has been recorded in many estuaries along the Atlantic coast of Europe since the late 1990’s. In this study, a regular monthly survey, held since 1992 of the middle section of the Gironde estuary, revealed this species’ rapid and full colonization of the system since its appearance in samples during summer 1998. In the Gironde, the population of P. macrodactylus is self-sustaining and the species is now established there. Our study highlights two important elements that might explain its successful colonization: its ability to quickly invade a niche under-exploited by the similar native species and its greater reproductive output. The species’spatio-temporal distribution in relation to environmental variables was studied and compared with that of the native species P. longirostris. The exotic species was shown to mainly inhabit the polyhaline and mesohaline section of the estuary, which are sections generally under-exploited by females of the native species. Furthermore, fecundity analysis and larval abundance survey results revealed a higher potential fecundity and a greater proportion of larvae and juvenile stages for P. macrodactylus in the natural environment

Morphological anomalies in estuarine shrimp larvae

International audienceFor several years, major exoskeletal anomalies in two species of European estuarine shrimp of the genus Palaemon have been observed. The phenomenon has been described for P. longirostris and P. macrodactylus in the Gironde estuary (France) and affects all stages of the species’ life cycles: from juvenile to adult and in both wild and laboratory-reared individuals. In the present follow-up study, the effects of these anomalies in larval stages of the two species were investigated. Regular sampling across most of the saline estuary confirmed that the post-larval stages of both species were affected. The morphological anomalies (MA) observed in the larvae were of the same type as those described for the adult stages, although more limited and primarily affecting the rostrum and cephalothorax. Larvae were reared from hatching to the post-larval stage, and the appearance of the aforementioned anomalies was observed as early as in Zoea I. This was the case even in larvae whose mothers did not exhibit anomalies. For both species, the most advanced stage was the one most affected. Also, in the rearing experiment, a greater proportion of the P. macrodactylus larvae was affected than those of P. longirostris. No significant effects ofMA on size or growth rate were demonstrated for larvae of either species in this study. Nevertheless, it provides data on larval growth that were not previously available. Further rearing experiments should be considered in order to explore any demonstrable effects of these morphological anomalies.Deux espèces de crevettes estuariennes européennes du genre Palaemon sont affectées depuis plusieurs années par des déformations importantes de l’exosquelette. Ce phénomène a été décrit pour les espèces P. longirostris et P. macrodactylus de l’estuaire de la Gironde (France) et porte sur les stades juvéniles à adultes, provenant du milieu naturel et également suivis en élevage. Dans cette étude complémentaire, les stades larvaires de ces deux espèces sont étudiés. L’échantillonnage régulier des larves sur la majeure partie de l’estuaire salé a confirmé une atteinte des stades postlarvaires des deux espèces et ceci dans des proportions significatives. Les déformations observées sur les larves sont du même type que celles décrites pour les stades adultes, avec toutefois une expression morphologique plus restreinte touchant principalement le rostre et le céphalothorax. L’élevage des larves, depuis l’éclosion jusqu’au stade post-larve, a permis d’observer l’apparition de ces déformations dès le stade Zoé I, même chez les mères pourtant dépourvues de déformation. Chez les deux espèces, les stades les plus avancés sont les plus affectés. Aussi, nous avons montré, lors de l’élevage au laboratoire, qu’une plus grande proportion de larves de P. macrodactylus était affectée par rapport à P. longirostris. Aucun effet significatif des anomalies morphologiques sur la taille ou le taux de croissance des larves n’a pu être démontré pour les deux espèces. Cependant, des données sur la croissance larvaire des deux espèces sont apportées. D’autres expériences d’élevage en laboratoire devraient être envisagées afin d’explorer les effets de ces anomalies morphologiques

Exploration of ultimate gate patterning technologies: lithography and plasma etching

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Investigation of switching mechanism in HfO2-based oxide resistive memories by in-situ Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS)

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A stacked SONOS technology, up to 4 levels and 6nm crystalline nanowires, with gate-all-around or independent gates (Φ-Flash), suitable for full 3D integration.

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Physical Understanding of Program Injection and Consumption in Ultra-Scaled SiN Split-Gate Memories

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Physical Understanding of Program Injection and Consumption in Ultra-Scaled SiN Split-Gate Memories

International audienceIn this work, a detailed study of the physical mechanisms governing the Source Side Injection programming in ultra-scaled (down to 20nm) SiN split-gate memories is presented. Experimental measurements coupled to static and dynamic TCAD simulations are shown. In particular, we claim that adjusting the select gate voltage in moderate inversion allows for the optimization of the compromise between high electron injection and limited consumption. Then, we show that scaling the dimensions of the select gate can induce a higher consumption, while scaling the memory gate leads to lower programming energy (<1nJ) due to higher injection efficiency, suitable for low power applications