Geometric morphometric differences between Panstrongylus geniculatus from field and laboratory

Abstract

The finding of Panstrongylus geniculatus nymphs inside a house in northeastern Antioquia, Colombia, and the reports related to their increasing presence in homes suggest the need for surveillance methods for monitoring the invasion processes. We analyzed the morphological differences between a wild population and its laboratory descendants, using the techniques of geometric morphometry, with the idea that such differences might parallel those between sylvatic and synanthropic populations. The analyses over five generations showed differences in size but not in shape. Head size and wing size were both reduced from sylvatic to laboratory populations, but the decrease in head size occurred only up to the second generation while the decrease in wing size proceeded up to the fifth generation. In contrast, although a decrease in sexual size dimorphism has been proposed as a marker of colonization in human dwellings, we did not detect any significant loss of dimorphism between sexes of P. geniculatus over the five generations studied. We conclude that size changes may have a physiological origin in response to a change of ecotopes, but more than five generations may be required for the expression of permanent morphological markers of human dwellings colonization.Key words: geometrical morphometry -isometric size -shape -Triatominae -Panstrongylus geniculatus -Chagas disease Panstrongylus geniculatus (Latreille, 1911) is one of the most widely distributed species of Triatominae (Hemiptera, Reduviidae) on the American continent, with a range known to extend from southern Mexico to northern Argentina, and including several of the Caribbean islands (Carcavallo et al. 1999). Its main habitats are the burrows and nesting places of marsupials, bats, rodents and birds, but adult specimens have also been collected from human peridomicile and homes -presumably attracted by light (Carcavallo et al. 1998). It has even been found in urban areas of Caracas, Venezuela (Pifano 1986) and in the city of Corrientes, Argentina (Carcavallo et al. 1998).Although Miles et al. (1981) reported that Amazon populations of P. geniculatus were difficult to rear in the laboratory, requiring 100% rh in their hands, peridomicile and synanthropic colonies of this species have since been reported from parts of southern Venezuela and the Brazilian Amazon (Valente et al. 1998) with evidence that it has been feeding on domestic pigs and on people. In the Ecuadorian Amazon P. geniculatus has also shown a tendency to establish peridomicile colonies in which they have exhibited the capacity of flying from their breeding places, in order to feed inside the dwellings during the night (Chico et al. 1997, Aguilar et al. 1999, Abad-Franch et al. 2001 and we were interested to study these populations in order to assess possible morphometric changes associated with the apparently recent trend to synantrophic behavior (Dujardin et al. 1999b, Schofield et al. 1999. Accordingly, we report here a comparison between natural populations of P. geniculatus and their labora...

Morphometric changes of Triatoma flavida Neiva, 1911 (Hemiptera:Triatominae) in the transition from sylvatic to laboratory conditions

“…When the rate is similar in each sex, no sexual dimorphism modification is expected. For instance no such evidence could be established after five laboratory generations of P. geniculatus 7 , although these authors could observe a significant decreasing in head or wing size.…”

“…These changes generally involved genetic drift effects 3 together with a reduction in average size and modification of sexual size dimorphism 4,6,7 . Although these observations are found in various genera (Rhodnius, Triatoma and Panstrongylus), more species have to be analyzed before accepting them as generalities for Triatominae.…”

“…Sexual dimorphism was not present at all for laboratory wings (Table 4, left part). 1,4,5,6,7,14 . It was thus also verified here for T. flavida with a significant decrease in almost all the characters measured in head, thorax and wings.…”

Genetic structure of Triatoma venosa (Hemiptera: Reduviidae): molecular and morphometric evidence

“…The wings were mounted on an inclusion medium between a slide and a cover slip (Jaramillo et al 2002). For the digitalization of images, a Nikon® 4500 digital photographic camera was used, adapted to a Nikon® SMZ800 stereomicroscope.…”

Evaluación de la estructura espacial de Triatoma maculata del centro-occidente de Venezuela y su viabilidad alimentado con sangre humana en condiciones de laboratorio

“…En triatominos se ha propuesto el uso de marcadores como el tamaño de las alas y las cabezas para discriminar entre poblaciones silvestres y de ambientes domiciliarios (8,(11)(12)(13)(14)(15)(16). La detección de la reducción del tamaño y del dimorfismo sexual podrían constituir marcadores de adaptación de estos insectos al domicilio (13).…”