Raúl Godoy-Herrera

Inter- and intrapopulational variation in digging inDrosophila melanogaster larvae

The digging behavior of larvae from the following strains ofDrosophila melanogaster was studied: Oregon R-c, taxi, yellow, and vestigial. It was found that the time of stay of preadults in the culture medium, the number of larvae, and the illumination conditions can modify this behavior. The presence of this characteristic depends on the genetic composition of the population: the larvae of each strain used exhibited their own particular pattern of dispersal throughout the culture medium, independent of the experimental conditions under which this behavior was surveyed.

The development of larval movement patterns in Drosophila

A survey in the development of larval movement patterns of D. melanogaster and D. simulans wild stocks was made. Larval movement patterns of four lines of D. melanogaster genetically selected for fast and slow feeding rate were also examined. The following behavioural elements were considered: locomotion, turning behaviour and number of larvae moving within a small area (“sitter” larvae). Because locomotion increases with larval age whilst turning does not substantially change between 24 to 96 hours of age, the larval movement pattern of Drosophila tends to be straighter as development proceeds. In the absence of food, Drosophila larvae increase locomotion and decrease turning. The opposite situation occurs when larvae are deposited on a nutritive substrate. However, larvae of a slow feeding line (SA) have a modified pattern of movement in the presence and in the absence of food. Orthokinesis and klinokinesis were more obvious in D. simulans larvae. Quantitative differences in the larval movement pattern of these two sibling species were greater on a nutritive medium. In both species the percentage of “sitter” larvae increases in the presence of food, particularly in D. simulans. This increase depends on larval age. Crosses between two D. melanogaster strains, which differ in larval turning, suggest that one pair of major additive genetic factors control this behaviour. The adaptative nature of larval movement patterns of Drosophila is discussed.

Drosophila pupation behavior in the wild

We investigated pupa distributions of D. simulans, D. buzzatii, D. melanogaster, D. immigrans and D. hydei on a number of natural breeding sites. Pupae of all five species showed aggregated distributions, which prompted us to examine these aggregations in a more detail for two species that commonly co-occur in breeding sites, D. simulans and D. buzzatii. We found that pupae of both species tend to be aggregated in conspecific clusters. Subsequent experiments revealed that both species are attracted to the odors of other larvae, though only D. buzzatii differentiated between conspecifics and heterospecifics (they preferred conspecific). Furthermore, third instar larvae of both species preferred more alkaline substrates. Altogether, our results demonstrate that Drosophila species form conspecific pupa aggregations in natural breeding sites, and that pupation site selection depends on interactions among conspecific and heterospecific larvae and on chemical characteristics of the breeding sites.

The development and genetics of digging behaviour in Drosophila larvae

Larval digging behaviour of Drosophila melanogaster and the sibling species Drosophila pavani and Drosophila gaucha differs quantitatively. Digging activity increases with age. Crosses between four strains of D. melanogaster indicate dominance and heterosis for digging; some non-allelic interaction is also suggested. Larval locomotion of a line with low digging behaviour is lower than that exhibited by larvae of a line with high digging behaviour. Larvae of the low digging line form puparia away from the medium, while those of the high digging line select places close to the substrate. However, larvae of a separate digger strain (the Oregon R-C strain) show similar locomotor behaviour to that of larvae of another non-digger strain (the vestigial strain). It is suggested that, besides locomotion, photoresponse of larvae may also influence the dispersal pattern within food. Dominance and heterosis towards high digging suggest possible evolutionary importance for this behaviour.

Abnormal development of the locomotor activity in yellow larvae of Drosophila: a cuticular defect?

The yellow (y) mutation of Drosophila melanogaster affects the development of behavior and morphology. We have analyzed some behavioral and morphological parameters during the development of y mutants. Wild-type third instar larvae move in straighter paths than larvae of the same age homozygous for the y mutation. At 96 h of age, the tracks of y larvae have 10 times as many loops as tracks of wild-type larvae, and at 120 h of age, y larvae show bending behavior about 2.5 times more frequently than do wild-type. Consequently, they do not disperse as much as wild-type larvae. Concomitant with the behavioral changes, the larvae present a defect in the morphology of large chaetae in the larval denticle belts, particularly of 2nd and 3rd instars, both with light and scanning electron microscopes. These results suggest that a cuticular defect is probably involved in the abnormal locomotor activity observed in y larvae of Drosophila melanogaster.

Selection for digging behavior inDrosophila melanogaster larvae

The genetics of the digging behavior ofDrosophila melanogaster larvae was studied through selective breeding. Selection for low digging activity was successful, but selection for high digging activity was not. Selection for low and high digging activity affected another behavior, namely the choice of a pupation site. Digging behavior appears to be under polygenic control.

Chemical cues influence pupation behavior of Drosophila simulans and Drosophila buzzatii in nature and in the laboratory.

In the wild, larvae of several species of Drosophila develop in heterogeneous and rapidly changing environments sharing resources as food and space. In this scenario, sensory systems contribute to detect, localize and recognize congeners and heterospecifics, and provide information about the availability of food and chemical features of environments where animals live. We investigated the behavior of D. simulans and D. buzzatii larvae to chemicals emitted by conspecific and heterospecific larvae. Our goal was to understand the role of these substances in the selection of pupation sites in the two species that cohabit within decaying prickly pear fruits (Opuntia ficus-indica). In these breeding sites, larvae of D. simulans and D. buzzatii detect larvae of the other species changing their pupation site preferences. Larvae of the two species pupated in the part of the fruit containing no or few heterospecifics, and spent a longer time in/on spots marked by conspecifics rather than heterospecifics. In contrast, larvae of the two species reared in isolation from conspecifics pupated randomly over the substrate and spent a similar amount of time on spots marked by conspecifics and by heterospecifics. Our results indicate that early chemically-based experience with conspecific larvae is critical for the selection of the pupation sites in D. simulans and D. buzzatii, and that pupation site preferences of Drosophila larvae depend on species-specific chemical cues. These preferences can be modulate by the presence of larvae of the same or another species.

Hybrid disadvantage in the larval foraging behaviour of the two neotropical species of Drosophila pavani and Drosophila gaucha

Flies from two populations of the Chilean endemic neotropical species Drosophila pavani and two populations of its sibling species Drosophila gaucha were crossed reciprocally to obtain intra- and interspecific hybrids. The developmental pathways of locomotor activity and feeding rate were analysed for eleven of twelve possible genotype groups. The hybrids showed reduced fitness indicated by a decrease in the measured traits. Hybrid disadvantage was strongest in interspecific hybrids, especially with respect to feeding behaviour. This evidence supports the contention that D. pavani and D. gaucha have evolved different coadapted gene pools controlling the developmental pathways for behavioural traits expressed during larval foraging; but genetic divergence affecting these behaviours has also taken place between locally adapted populations within each species.

The behaviour of Drosophila melanogaster larvae during pupation

Larval prepupation behaviour of Drosophila melanogaster was analysed to determine the behavioural mechanisms by which larvae select pupation sites. Mature larvae of D. melanogaster perceive and react to humidity, light and the surface texture and consistency of the substrate. These stimuli induce in the larvae hydro- and photoresponses and burrowing, all of which are involved in larval pupation site choice. A selection scheme was applied to understand the genetic bases of preferences for pupation outside and inside the food cup. Pupation outside the cup on a dry substrate was dominant over pupation inside the cup. The results also suggested the presence of additive genes. Larvae of the lines selected to pupate outside the cup formed puparia away from the cup; those selected to pupate inside the cup were found near the food cup. Larvae of the F1 generation obtained by crossing the selected lines had a norm of reaction for prepupation behaviour which was greater than those of the parental lines. It is argued that heterozygosity permits a greater amplitude of modifications for this behaviour than homozygosity.

Biometrical analysis of larval digging behavior inDrosophila melanogaster

Digging behavior of D. melanogaster larvae increases as larval development proceeds. Diallel crosses were made to analyze genetically digging behavior at 72 and 108 h of larval age. Additive and dominance variation was found, dominance being principally to dig. Dominance to dig is higher at 108 than 72 h of development; additivity does not substantially change between these two larval ages. At 72 h of larval age, depending on the cross, I found (i) dominance to dig, (ii) dominance to nondig, (iii) overdominance to dig, and (iv) no dominance to dig. At 108 h of larval development I detected (i) dominance to dig and (ii) overdominance to dig. Thus, diversity of response in the F1 was greater at 72 than 108 h of larval development. These age-related changes in larval digging behavior of D. melanogaster seem to reflect epigenetic changes in the patterns of gene expressions.