Raúl E. Campos

Oviposition activity and seasonal pattern of a population of Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) in subtropical Argentina

Monthly oviposition activity and the seasonal density pattern of Aedes aegypti were studied using larvitraps and ovitraps during a research carried out by the Public Health Ministry of Salta Province, in Tartagal, Aguaray and Salvador Mazza cities, in subtropical Argentina. The A. aegypti population was active in both dry and wet seasons with a peak in March, accordant with the heaviest rainfall. From May to November, the immature population level remained low, but increased in December. Ae. aegypti oviposition activity increased during the fall and summer, when the relative humidity was 60% or higher. Eggs were found in large numbers of ovitraps during all seasons but few eggs were observed in each one during winter. The occurrence and the number of eggs laid were variable when both seasons and cities were compared. The reduction of the population during the winter months was related to the low in the relative humidity of the atmosphere. Significant differences were detected between oviposition occurrences in Tartagal and Aguaray and Salvador Mazza cities, but no differences in the number of eggs were observed. Two factors characterize the seasonal distribution pattern of Ae. aegypti in subtropical Argentina, the absence of a break during winter and an oviposition activity concomitant of the high relative humidity of the atmosphere.

Variation in the hatching response of Ochlerotatus albifasciatus egg batches (Diptera: Culicidae) in temperate Argentina

Egg hatching of winter-collected Ochlerotatus albifasciatus was studied for six months. Batches of eggs were divided into two groups, one of them was stored in the laboratory at 23 degrees C and 12:12 photoperiod, and the other in the field under dead leaves. Every month, from July to December, eggs from the two groups were flooded under both laboratory and field conditions. Unhatched eggs were returned to the original condition and flooded two more times separated by ten-day intervals. Results show that egg diapause is expressed in different intensities, not only on eggs exposed to different conditions but also in those exposed to the same condition, even when they were laid by the same female. Successive inundations yielded incomplete hatches of eggs, and favored the hatching response in the next flooding. Low environmental temperatures before and during the flooding depressed hatching response. This shows that eggs need a warm period before flooding as well as warm temperatures during flooding, to hatch. As drought period was longer hatching response increased, but this was also accompanied by warmer environmental conditions. The experiment performed in laboratory did not show that increment. Field studies showed that a layer of dead leaves protected eggs from extreme temperatures.

Cold season mortality and hatching behavior of Aedes aegypti L. (Diptera: Culicidae) eggs in Buenos Aires City, Argentina.

ABSTRACT: In temperate regions, populations of Aedes aegypti survive the cold season in the egg stage. In the present work, we studied the cold-season mortality of Ae. aegypti eggs and their subsequent hatching pattern in Buenos Aires city. Eggs were exposed during the winter season (three months) in three neighborhoods located along a gradient of distance toward the Río de la Plata River, coincident with a gradient of activity of Ae. aegypti. Results showed mortalities lower (30.6%) than those from tropical regions during the dry season. Significant differences were detected among the egg mortalities of each site with a maximum value at the site nearest the Río de la Plata River (50%), and a minimum value at the most continental site (9%). Post-experimental hatching response of eggs differed between sites, with the highest proportion of hatched eggs during the first immersion in the site nearest to the river and the lowest proportion in the most continental site. The hatching proportion also differed between age classes, with older (early-laid) eggs hatching later than new (late-laid) ones. Our results provide the first information of Ae. aegypti egg mortality in temperate South America and support the hypothesis that differences in egg mortality are associated with abundance patterns of Ae. aegypti in Buenos Aires city.

Eryngium (Apiaceae) phytotelmata and their macro-invertebrate communities, including a review and bibliography

The objective of this study was to determine how phytotelm communities differ in four Eryngium sp. of different morphologies. Macro-invertebrate communities from 320 individual plants of Eryngiumhorridum, E. stenophyllum, E.serra, and E. elegans were sampled in Buenos Aires Province, Argentina. The morphology and structure of each Eryngium specimen, and water volume and debris in their phytotelmata, were measured. Morphology indicated that E. elegans and E. serra are closely related and differ from E. horridum and E. stenophyllum. The latter two species are markedly different from E. stenophyllum, the biggest of the four. The communities differed among these Eryngium species, but a large number of generalist macro-invertebrates use all four phytotelmata. Canonical correlation analysis showed that diptera are inhabitants in E. horridum, and micro-crustaceans in E.serra and E. elgans. By contrast, no specific taxa were grouped in E. stenophyllum. Results of inter-specific association (C8 coefficient) show that species of Culicidae and Chironomidae are highly positive associations in E. horridum, by contrast with the negative association observed in E. stenophyllum. Culex renatoi (Culicidae) and Polypedilum sp. (Chironomidae) were highly likely to co-occur in the same plant of E. serra, but not with Metriocnemus eryngiotelmatus (Chironomidae). Larsia sp. (Chironomidae) was the species better associated with the other macro-invertebrates in E. elegans. The food web was constructed from Eryngium phytotelmata. This study includes an updated list of known aquatic and semi-aquatic invertebrates reported from Eryngium phytotelmata, and their bibliography.

Simple Indices Provide Insight to Climate Attributes Delineating the Geographic Range of Aedes albopictus (Diptera: Culicidae) Prior to Worldwide Invasion

ABSTRACT Aedes albopictus (Skuse) has expanded its distribution worldwide during the past decades. Despite attempts to explain and predict its geographic occurrence, analyses of the distribution of Ae. albopictus in the context of broad climatic regions (biomes) has not been performed. We analyzed climate conditions at its distribution sites in the range before the worldwide invasions (from the easternmost Hawaii through westernmost Madagascar) by using thermal and aridity-humidity indices descriptive of major biomes. A significant advantage of this approach is that it uses simple indices clearly related to the population dynamics of Ae. albopictus. Although Ae. albopictus has been regarded as a forest species preferring humid climate, in areas with significant human habitation, the distribution sites extended from the perhumid, rain forest zone to the semiarid, steppe zone. This pattern was common from the tropics through the temperate zone. Across the distribution range, there was no seasonal discordance between temperature and precipitation; at sites where winter prevents Ae. albopictus reproduction (monthly means < 10°C), precipitation was concentrated in warm months (> 10°C) under the Asian summer monsoon. Absence of the species in northern and eastern coastal Australia and eastern coastal Africa was not attributable solely to climate conditions. However, Asia west of the summer monsoon range was climatically unsuitable because of low precipitation throughout the year or in warm months favorable to reproduction (concentration of precipitation in winter).We hypothesized that Ae. albopictus originated in continental Asia under the monsoon climate with distinct dry seasons and hot, wet summer, enabling rapid population growth.

Long-term storage and viability of Ochlerotatus albifasciatus eggs (Diptera: Culicidae)

The viability of Ochlerotatus albifasciatus (Macquart) eggs stored at room temperature and at 5 degrees C was studied over 31 months. After 12, 18 and 31 months of storage, eggs were acclimatized at 22 degrees C for ten days, and then inundated twice every seven days. The effect of the storage period on the percentage of hatching was analyzed by one way ANOVA. Differences on the hatching response between the first and second flooding were analyzed by paired t-test. Differences on the hatching response between the two storage conditions were analyzed by Mann-Whitney rank test. Results showed that (1) Oc. albifasciatus eggs were able to survive and hatch over 31 months; (2) the percent hatching of eggs stored at 5 degrees C was higher than that of eggs stored at room temperature; and (3) low temperatures and long periods without water favor installment hatching.

Coleopterans associated with plants that form phytotelmata in subtropical and temperate Argentina, South America

Abstract A list of the most common plants that form phytotelmata and their associated coleopterans (aquatic, semi-aquatic and terrestrial) from the northeastern subtropical and temperate area of Argentina, South America with biological and behavioral observations is presented in this study. Species of Poaceae (n = 3), Bromeliaceae (5), Apiaceae (6), Araceae (2), Urticaceae (1), Marantaceae (1), Arecaceae (1), Dipsacaceae (1) and Cyperaceae (1) were identified as phytotelmata. Aquatic species of Scirtidae (2), Dytiscidae (2), and Hydrophilidae (4), semi-aquatic Chelonariidae (2), and terrestrial species of Carabidae (3), Staphylinidae (5), Histeridae (1), Elateridae (1), Cantharidae (1), Cleridae (1), Tenebrionidae (1), Meloidae (1), Anthicidae (1), Chrysomelidae (3), Curculionidae (7) and Apionidae (1) were identified from six species of Eryngium L. (Apiales: Apiaceae), two species of Guadua Kunth (Poales: Poaceae), Aechmea distichantha Lemaire (Poales: Bromeliaceae), and from fallen leaves of Euterpe edulis Martius (Arecales: Arecaceae) from the temperate and subtropical area. The highest species richness was recorded in Eryngium phytotelmata. Fifteen species of beetles inhabit Eryngium cabrerae Pontiroli, 11 in E. horridum Malme, 7 in E. stenophyllum Urban, 4 in E. aff. serra Chamisso and Schlechtendal., 3 in E. elegans Chamisso and Schlechtendal, 2 in E. eburneum Decne and E. pandanifolium Chamisso and Schlechtendal. From bamboo, 6 species of coleopterans were collected from Guadua trinii (Nees) Nees ex Ruprecht and 4 from G. chacoensis (Rojas) Londoño and Peterson. Three species of aquatic coleopterans were recorded from A. distichantha and only one from E. edulis.

The aquatic communities inhabiting internodes of two sympatric bamboos in Argentinean subtropical forest

Abstract In order to determine if phytotelmata in sympatric bamboos of the genus Guadua might be colonized by different types of arthropods and contain communities of different complexities, the following objectives were formulated: (1) to analyze the structure and species richness of the aquatic macroinvertebrate communities, (2) to comparatively analyze co-occurrences; and (3) to identify the main predators. Field studies were conducted in a subtropical forest in Argentina, where 80 water-filled bamboo internodes of Guadua chacoensis (Rojas Acosta) Londoño and Peterson (Poales: Poaceae) and G. trinii (Nees) Nees and Rupr. were sampled. Morphological measurements indicated that G. chacoensis held more fluid than G. trinii. The communities differed between Guadua species, but many macroinvertebrate species used both bamboo species. The phytotelmata were mainly colonized by Diptera of the families Culicidae and Ceratopogonidae.

Effect of diet composition on the development of the floodwater Mosquito Ochlerotatus (Ochletotatus) albifasciatus (Macquart) (Diptera: Culicidae)

One important step for the colonization of Ochlerotatus albifasciatus (Macquart) is to determine the optimal conditions for larval rearing, which makes possible the development of experiments comprising larval rearing in the laboratory. In this research the effect of diet composition on the development of O.albifasciatus was studied. For this purpose, cohorts of 20 first instars were reared using five diets: 1:1 mix of yeast and TetraMin(R), 1:1 mix of fine and coarse organic matter, grass cuts soaked in water for 1h or 24h before larvae incorporation, and 1:1:1 mix of grass cuts, fine organic matter and coarse organic matter. Survival was recorded for each cohort, while development time from first instar to pupa, and adult wing length were recorded for each individual. The effects of the diet on the observed traits were analyzed by one way ANOVA. Both survival and wing length were affected by diet, being significantly higher (79-100% and ~ 4.46 mm) on diets consisting of organic matter or organic matter plus grass than on those consisting of yeast plus TetraMin(R) or grass. Development time was not affected by the diet, although the shortest time (8.1 to 8.3 days) and lower variation between replicates were recorded when larvae were reared using organic matter or organic matter plus grass. Thus, it is concluded that the diets consisting of organic matter or a mix of it and grass are the most effective for O.albifasciatus rearing.

Phytotelmata colonization in bamboo (Guadua sp.) culms in northeast Argentina

ABSTRACT This study aimed to determine the susceptibility of stumps and internodes of bamboos to colonization by different types of macroinvertebrates and the formation of communities of different complexity. Semi-controlled field studies were carried out in a subtropical area of Argentina to analyse community structure, species richness of the aquatic macroinvertebrate communities and co-occurrences of predators and prey to delineate the food webs. Water-filled bamboos were sampled every season during a year by removing, without replacing, all water and macroinvertebrates. This study shows that the variation in the morphology of the container provides different resources, leading to segregation of species per container type, and allowing each of them to establish aquatic communities with differences in diversity. The Diptera was best represented in the communities of bamboos, where Culicidae showed the highest species richness and Ceratopogonidae were the most abundant numerically. Eleven taxa were present in both phytotelmata, 12 were unique in internodes and 13 in stumps. The community in internodes was composed of 21 taxa where mosquitoes were represented by Sabethini and Toxorhynchitini. By contrast, stumps were colonized by 24 taxa and Ceratopogonidae were numerically dominant. Regarding food webs established in stumps and internodes, no differences in length were found, except for the species that played equivalent roles in each of the studied phytotelmata.