Received Date: 20/03/2018; Accepted Date: 11/04/2018; Published Date: 13/04/2018
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In order to explore new methods for the control of domestic pests at low cost and without human disturbance, we examined the diet of Hemidactylus frenatus from the stomach content analysis of 53 females and 47 males. The specimens were captured in ten urban areas of the state of Morelos, Mexico; where H. frenatus is well established and where interactions with humans are frequent. The diversity (H´) of the food, the variation between the components, and the overlap of the trophic niche between males and females were examined; as well as the differences between the rainy and dry seasons. The diet consisted of eleven arthropod groups, the most representative being Diptera (Culicidae) 23.73%, Araneae 20.45%, Hymenoptera (Formicidae and Cynipidae) 17.05%, Lepidoptera 14.20% and Coleoptera (Chrysomelidae) 10.80%. There were no significant differences in the diet by sex, nor between the dry and rainy seasons. The diversity of food consumed between males and females showed a high overlap value (Ojk=0.94709). Although it is true that the diet is opportunistic and is associated with the availability of food in urban areas; the increase in the consumption of Lepidoptera and hematophagous mosquitoes (Dipera) in the rainy season, to almost double that which occurs in dry, suggests that geckos can contribute to the control of these insects. Experimental studies are suggested to test this hypothesisa.
Diet, Mosquitoes, Hemidactylus
frenatus, Urban areas, Morelos, Mexico
Hemidactylusfrenatus geckos entered Mexico through the port of Acapulco, as a result of trade between Asia and Mexico between the years 1565-1815 [1,2]. Since its introduction, it has established itself in several regions of the Mexican Republic [3,4] and in almost all urban areas of the state of Morelos, at an altitude between 800 and 1,700 meters above sea level [5,6].
Because their populations have nocturnal activity and develop closely associated with human settlements, near artificial sources of light , we examine whether these lizards can contribute to the natural control of domestic insects such as cockroaches (Periplanetaamericana) and mosquitoes. Cockroaches are a problem because they contaminate cooking utensils and food , and mosquitoes are carriers of diseases such as yellow fever and dengue among others [9,10].
Natural control has been an efficient technique for reducing insect populations throughout the world, but ceased to be used due to the introduction of chemical control. However, because of the problems caused by pesticides, biological control has once again become a viable alternative .
In order to assess the potential use of these lizards as a possible means of insect control in urban environments, this paper describes the diet of males and females, the variation between dry and rainy seasons, and the amplitude and overlap of the trophic niche between the sexes.
Between dry and rainy periods, 53 females and 47 males were obtained in a twilight and nocturnal schedule, between 18:00 and 03:35, inside houses in 10 urban zones of Morelos, Mexico (Table 1).
18° 48’ 38” N
98° 57’ 24.43” O
18° 54’ 59” N
99° 13’ 54” O
18° 50’ 28” N
99° 11’ 5”O
18° 52’ 54” N
99° 10’ 26” O
18° 36’ 51” N
99° 10’ 35” O
18° 50’ 53” N
99° 13’ 31” O
18° 41’ 8” N
99° 7’ 2” O
18° 37’ 42” N
99° 9’ 38” O
18° 46’ 56” N
99° 18’ 48” O
18° 39’ 30” N
99° 11’ 21” O
Table 1: Number of Hemidactylus frenatus obtained by location, season and sex.
The specimens captured with adhesive traps, rubber bands and using a noose were individually conserved in plastic bags and labeled with the following data: location, date, and time of capture, sex and season of the year dry November-May, rainy June-October after were transported in a cooler, to be killed by cold. In the laboratory, we obtained the snout-vent length (SVL) of all the specimens, the stomachs were extracted by dissection and the content of each was identified taxonomically under a microscope [13,14]. The content of each stomach was homogenously extended in a Petri dish with millimeter grid (10× 10 mm), to estimate by the total number of frames covered by the food, 100% of the diet of each individual. The proportional consumption per group of food (Pi) was estimated with the expression:
Pi=(Total of frames covered with food/total of frames of the individual diet)x100 
The frequency of occurrence (FO) was calculated by FO=[ne/Ne] x 100
Where ne is the number of stomachs with a particular type of food and Ne the number of stomachs analyzed. The final value indicates the proportion of the food groups that make up the diet. The amplitude of the trophic niche was estimated with the Shannon diversity index (H´)
Where pi is the percentage of ingestion of each food group and ln pi the natural logarithm of pi. The overlap of the trophic niches, which produces a value of 0 for unused resources in common and a value of 1 as maximum overlap, was calculated with the expression of Pianka.
Where Ojk is the overlap between males-females; p2ij the total proportion of ingestion of resource i from the total resource used by species j (=females), p2ik the total proportion of ingestion of resource i of the total resource used by species k (=males), n total number of food resources.
A Mann-Whitney U test was used to estimate differences in the amount of diet components between the sexes and the dry and wet seasons. The differences in the magnitude of the trophic niche (H ') of males and females, was estimated with a T-student test.
Females have an average SVL of 46.04 mm (31.63-61.34, STD ± 5.95, n=53) and males 48.98 mm (32.86–58.45, STD ± 6.23, n=47), which are only 3.23 mm larger than females (T=2.41, P=0.0176).
The 94% of the stomachs examined contained food. Eleven groups of arthropods constitute the diet of H. frenatus, among them Diptera (22.73%, Culicidae), Araneae (20.45%, Salticidae), Hymenoptera (17.05%), Lepidoptera (14.20%) and Coleoptera (10.80%, Chrysomelidae) (Figure 1). Among the Diptera, 90% were mosquitoes of the genera Anopheles sp., Culex sp., and Aedes sp.; and among the Blattoptera only domestic Periplanetaamericana cockroaches were found.
The analysis of the frequency (FO) and percentage of food consumption between dry and rainy seasons showed that Araneae, Diptera, Hymenoptera, Coleoptera, Lepidoptera, and Blattoptera were the groups consumed most frequently by females (Table 2). All the components reveal a significant trophic diversity of the order of H´= -2.56 (T=3.40, n=12, P=0.0058). Similarly, Araneae, Diptera, Hymenoptera, Lepidoptera, Coleoptera, and Isopoda were also the groups most frequently consumed by males (Table 3); and these have a significant trophic diversity with a value of H´=-2.57 (T=3.79, n=11, P=0.0035).
|Frequency of Occurrence (FO) n=23 %||Percentage of Consumption
|Frequency of Occurrence (FO) n=30 %||Percentage of Consumption
Table 2: Components of the diet of female Hemidactylusfrenatus from Morelos, Mexico. Frequency of occurrence, percentage of consumption of each group of food consumed in drought and rains.
The Mann-Whitney U test did not reveal significant differences in the amount of components ingested between the rainy and dry periods (U=83, P≤0.938). The analysis of the overlap of the diet (Ojk=0.94709) between males-females was significant, especially in the consumption of Diptera, Araneae and Hymenoptera (Figure 1); that is, males and females consume practically the same groups of insects.
Variations of the order of almost double the consumption of Diptera (Anopheles sp., Culex sp., and Aedes sp.(Tables 2 and 3) between periods of drought rain, suggest that H. frenatus could help control these insects.
|Frequency of Occurrence (FO) n=27 %||Percentage of Consumption
|Frequency of Occurrence (FO) n=20 %||Percentage of Consumption
Table 3: Components of the diet of males Hemidactylus frenatus from Morelos, Mexico. Frequency of occurrence, percentage of consumption of each group of food consumed in drought and rains.
While it is true that the diet consisted of eleven groups of insects; those that stand out due to high consumption were Arachnids of the Salticidae family and Diptera of the Culicidae family (Culex sp., Aedes sp., Anopheles sp.). This contrasts with the diet of another population of H. frenatus in urban areas of Colombia, where the highest consumption concentrated on Hemiptera, Hymenoptera and Diptera. In Costa Rica, the highest consumption was of Lepidoptera, Orthoptera and Araneae moths ; very similar to that observed in urban areas of insular environments . This indicates an opportunistic diet that had previously been observed in H. frenatus and Phyllodactylusreissi[17,20].
The data obtained here allow us to establish that the diet is more associated with the fauna of arthropods that live in the vicinity of houses.
We suggest that the placement of traps with attractants in urban environments could facilitate the capture of domestic insects by geckos.
Because H. frenatus are the only lizards that live in close contact with humans, and have crepuscular and nocturnal habits as well, we suggest that they do not compete with other geckos of Morelos such as Phyllodctyluslaneiand Coleonyxelegansthat are typical inhabitants of tropical dry forest . However, for now we have no data on the possible dispersion from urban areas to natural environments and their effects on other lizards, making it necessary to evaluate this issue in the future.