No abstract

With the intention of knowing if coral associates can be used as indicators of coral reef status, we studied organisms associated with live scleractinian corals on different sites located around Hoga and Kaledupa islands in the Tukang Besi Archipelago of the south-eastern coast of Sulawesi in the Banda Sea, in Indonesia. Twenty meter long line intercept transects were used to estimate the number of coral colonies infested by coral associates. The number of coral associates found on each coral colony on the transect was recorded and corals were identified to the most precise level. Massive and encrusting coral colonies were also measured in order to estimate the densities of infestation per square meter of coral colonies. To link the assemblages of coral associates observed with the characteristics of the benthic habitats, the coral cover was estimated using a 0.5 m point intercept transect method.Three hundred seventy-six colonies (45%) were infested by a total of 2,815 coral associates. In total, coral associates amounted to 2,062 lithophagid bivalves (73% of total coral infestations), 306 dwelling hermit crabs of the genus Paguritta (10.9%) and 242 vermetid snail Dendropoma maxima (8.6 %). The most infested colonies belonged to the genera Montipora, Pavona and Porites. They represented 33%, 23% and 18% of the total number of colonies infested respectively. The highest densities of infestation were found for the boring Lithophaga spp. for which a density of 88 ind/m2 was noticed in encrusting corals of the genus Pavona.The density of lithophagid bivalves and the number of infested colonies were high in the most impacted site (Sampela) and one of the intermediately impacted site (Pak Kasim's) whereas they were low in the most pristine site (Kaledupa). The other intermediately impacted site (Buoy 3) had an intermediate number of infestations. Despite the lack of any significant difference in biotic cover between the most pristine site and the intermediately impacted sites, a common gradient tends to emerge based on coral associates. Although having a high biotic cover, Pak Kasim's suffers from a similar level of infestation as Sampela suggesting process of reef degradation previously experienced by the most impacted site. Our results suggest that coral associates can be used as indicators of coral reef status.

Requ le 2 1 janvier 1992 Accept6 le 17 septembre 1992 SCAPS, P., RETICRE, C., DESROSIERS, G., et MIRON, G. 1993. Effets de la ration alimentaire, de la densitk intraspkcifique et des relations entre individus sur la croissance des juvkniles de l'espkce Nereis diversicolor (Annelida : Polychaeta). Can. J. Zool. 71 : 424-430.L'klevage, en laboratoire, de juvkniles du Nereis diversicolor sur alimentation a base de Tetramin a permis de quantifier les effets des variations de la quantitk de nourriture, de la densitk intraspkcifique et des relations entre individus sur la croissance. Une ration alimentaire de 3,33 mg d-' de Tetramin par individu assure une croissance optimale de la masse moyenne. Un effet marquk de dkpendance face h la densitk se manifeste non seulement par un ralentissement de la vitesse de croissance mais aussi par une diminution de la biomasse et des taux de survie, pour des valeurs supkrieures h 3000 individus/m2. Le stress provoquk par une manipulation trop frkquente des individus et par le choc thermodiffkrentiel qui en rksulte engendre les memes effets nkgatifs. La variabilitk de la rkponse h l'effet de groupement ou d'isolement est grande puisque des lots de juvkniles prklevks en pkriodes hivernale et printannikre rkagissent diffkremment : alors que la croissance de la masse chez les premiers n'est pas affectke par les conditions d'klevage, celle des seconds est plus importante dans le cas ou les individus sont maintenus isolkment. SCAPS, P., RETICRE, C., DESROSIERS, G., and MIRON, G. 1993. Effets de la ration alimentaire, de la densitk intraspkcifique et des relations entre individus sur la croissance des juvkniles de l'espkce Nereis diversicolor (Annelida : Polychaeta). Can. J. Zool. 71: 424-430. We studied the effects of food intake, intraspecific density, and interactions between individuals on the growth of laboratory-raised juveniles of Nereis diversicolor fed different quantities of Tetramin. A daily intake of 3.33 mg of Tetramin per individual resulted in an optimal mean mass gain. At densities above 3000 individuals/m2, not only was the growth rate reduced, but biomass and survival rates were also diminished. Frequent handling and the thermodifferential shock that ensured created a stress that had the same negative effects. Variations in responses to aggregation or isolation were high, as revealed by groups of juveniles captured in winter or in spring reacting differently: growth was not affected by the breeding conditions in the winter-caught worms but was faster in spring-caught individuals kept in isolation.[Journal translation]

Spatial analysis, laboratory experiments and field observations in the intertidal zone of La Ranee Estuary (northern coast of Brittany, France) of the infaunal polychaete Perinereis cultrifera indicate that the distribution and the abundance of this species appear to be related to the availability of cobbles. Individuals build U-shaped galleries with a surface gutter network protected by a cobble which acts as a roof. The study of spatio-temporal evolution of P. cultrifera burrows showed experimentally that density is important in space-sharing modalities within the sediment. Effects of increased density lead to modifications in the shape and size of the burrows. The absence of connections between burrows, as observed in ‘sandwich aquaria’ and in resin casts, suggest that the gallery is defended against intruders. The study of the distance between individuals in the laboratory did not reveal a regular distribution pattern. These results probably mean that the area around the burrow opening is not defended and, therefore, does not constitute a territory. Perinereis cultrifera is probably competing for burrow space while food may be shared. Territoriality is certainly the main factor involved in the organization and the spatial arrangements of individuals within a population.

Les Chilopodes et les Diplopodes présents au niveau de deux sites localisés dans le nord-est de l’Algérie (site anthropisé d’Annaba et site naturel d’El Tarf) ont été étudiés par piégeage durant une année (juin 2006 à mai 2007). Au total 901 Chilopodes et 411 Diplopodes ont été récoltés. Les diversités spatiotemporelles des deux taxons ont été évaluées. Nos résultats suggèrent que les paramètres physico-chimiques édaphiques tels que le taux de limon, le pourcentage de matière organique ou le pH mais aussi les paramètres climatiques tels que le volume de précipitation et le taux d’hygrométrie qui en résulte ont une influence significative sur l’abondance et la répartition spatiale des Chilopodes et des Diplopodes avec une nette différence de comportement entre les deux taxons. L’estimation de l’intensité des perturbations introduites par l’homme influençant la diversité écologique des deux taxons indique que la région d’Annaba, qui est plus anthropisée que celle d’El Tarf, subit une perte en matière de diversité concernant à la fois les Chilopodes et les Diplopodes.