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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 97, Num. 1, 2002, pp. 133-136
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Mem Inst Oswaldo Cruz, Rio de
Janeiro, Vol. 97(1) 2002, pp. 133-136
Activity of Tabanids (Insecta:
Diptera: Tabanidae) Attacking the Reptiles Caiman crocodilus (Linn.)
(Alligatoridae) and Eunectes murinus (Linn.) (Boidae), in the Central
Amazon, Brazil
Ruth LM Ferreira+, Augusto
L Henriques, José A Rafael
Coordenação de Pesquisas em Entomologia,
Instituto Nacional de Pesquisas da Amazônia, Caixa Postal 478, 69011-970
Manaus, AM, Brasil
+Corresponding author. Fax: + 55-92-643.3195. E-mail: ruth@inpa.gov.br
Financial support: PPI-1-3070 (MCT/INPA)
Received 7 May 2001
Accepted 24 July 2001
Code Number: oc02025
Tabanid females are better known as hematophagous
on man and other mammals, and linked to mechanical transmission of parasites.
The association between tabanids and reptiles is poorly known, but has been
gaining more corroboration through experiments and occasional observation in
the tropics. The present study was conducted at a military base (CIGS/BI-2),
situated 54 km from Manaus, Amazonas, in a small stream in a clearing (02°45'33"S;
59°51'03"W). Observations were made monthly, from April 1997 to March 1998,
during two consecutive days. At the same time, other vertebrate animals were
offered, including humans. However in this paper only data obtained on a common
caiman, Caiman crocodilus (Linn.), and an anaconda, Eunectes murinus (Linn.),
in diurnal observations from 05:30 a.m. to 18:30 p.m., will be discussed. A
total of 254 tabanid specimens were collected, 40 from the anaconda and 214
from the caiman. Four tabanid species were recorded on these two reptiles: Stenotabanus
cretatus Fairchild, S. bequaerti
Rafael et al., Phaeotabanus nigriflavus
(Kröber) and Tabanus
occidentalis Linn. Diurnal activities
showed species-specific patterns. The first three species occurred only in the
dry season. T. occidentalis occurred
during the whole observation period, and with increased frequency at the end
of the dry season. We observed preferences for body area and related behavior
of the host. Observations on the attack of tabanids on one dead caiman are also
presented.
Key words: Tabanidae - horse fly - hematophagy
- common caiman - anaconda - tropical forest - Amazon Basin
Blood-feeding of tabanids (Diptera: Tabanidae)
has been the subject of occasional observations and experiments in the tropics.
This is because the females of tabanids are known as ectoparasites of humans
and other mammals, and thus are likely to transmit pathogens mechanically during
interrupted feeding on different hosts. The association of tabanids with reptiles
was described briefly by Leclercq (1952) apud Oldroyd (1954). More recently,
Medem (1981) reported ten tabanid species attacking caimans in Colombia, but
only four fed exclusively or preferentially on caimans. Philip (1983) reported
one species attacking turtles in the Galapagos islands and in 1986 reported
four tabanid species attacking anacondas in the Tambopata River, Peru. Barros
(1996) observed one species flying around alligators at Corumbá, Brazil.
Oliveira (1998) collected three tabanid species flying around alligators near
the site were the present study was conducted. Henriques et al. (2000) recorded
four species attacking caimans in the Central Amazon.
The present study was undertaken to verify the
diurnal activity and seasonality of tabanids captured using two reptile host-species:
the common caiman, Caiman crocodilus (Alligatoridae) and the anaconda,
Eunectes murinus (Boidae). We observed parasite/host-specificity, frequency
of landing and blood feeding on different body parts, host defense behavior
and we studied the relationship between tabanid species occurrence, temperature
and relative humidity.
MATERIALS
AND METHODS
Fieldwork was carried out in cooperation with
the Brazilian Army at the Center for Instruction of Forest War (Centro de Instrução
de Guerra na Selva, Base for Instruction 2 (BI-2), about 54 km east of
Manaus, Amazonas on AM-010 highway (Fig. 1).
A small stream in a clearing around 500 m from the Base (02°45'33"S and
59°51'03"W) was selected for the experiment.
The local climate provides permanently hot and
humid conditions, classified by Köppen (1948) as a typical climate of the
Amazon basin. The vegetation surrounding the clearing is tropical humid "terra-firme"
forest, with trees reaching up to 40 m height (Lechtchaler 1956, Aubréville
1961).
Temperature and relative humidity were measured
at 30 min intervals in the experimental site.
The observations were conducted monthly from
April 1997 to March 1998, from 05:30 to 18:30 p.m. during two consecutive days.
The diurnal and annual activity was determined by the number of tabanid attacks
on the hosts. Collections were made using entomological nets. During the observation
period, the caiman was kept tied and the anaconda was kept in a cage, covered
with 2 cm mesh. Both were partially submerged in a small stream.
The descriptions of attacking behavior of the
horse flies, preference for landing places and host defense were made in field
observations. Captured tabanids were identified in the field by the second author,
mounted with entomological pins, labeled and deposited in the invertebrate collection
of the Instituto Nacional de Pesquisas da Amazônia.
RESULTS
AND DISCUSSION
During one year of observation, 254 tabanids
were collected, 40 on the anaconda and 214 on the caiman. Only four species
were recorded during the experiment: Stenotabanus cretatus Fairchild,
S. bequaerti Rafael, Fairchild & Gorayeb, Phaeotabanus nigriflavus
(Kröber) and Tabanus occidentalis Linnaeus, all attacking both hosts.
S. cretatus and T. occidentalis were the most abundant
species with 123 and 61 specimens respectively. The remaining species totalled
with 35 specimens each.
The majority of diurnal activity occurred in
the hours with lower humidity and higher temperature. S. cretatus was
an exception, because it was present throughout the day and increased in abundance
in the early evening (Fig. 2)
During the year the occurrence of all species
was almost completely restricted to the dry season. The only exception was T.
occidentalis, which occurred during the whole sampling period and was more
frequently observed at the end of the dry season (Figs 3,
4).
The preferred landing and feeding area on each
host was observed for the four tabanid species (Figs 5, 6). We observed that
S. cretatus was visually attracted to the reptiles, when seeking a blood
meal. After landing, it walked along the body of the animal, without defining
a feeding place. Frequently it was captured in the sucking position, always
on the head of the hosts, but it was never collected in a blood-filled state.
For all of the tabanid species, we observed circular
and fast flight before settling on the head or other place chosen for landing
and blood feeding. At the moment the tabanid selected the desired place and
started feeding, we noticed a tenseness of the host. Caiman near the water dived
or showed visible irritation, beating with the tail in an attempt to dislodge
the pest flies. This behavior was aggravated when four or five tabanids attacked
at the same time on the head and snout, as in the case of S. cretatus.
Anaconda appeared to be bothered and, if the snake began moving or dived to
dislodge, the tabanid resumed its attack immediately after the host reemerged.
The adult flight activity of the majority of
the species has been recorded from June to December, the dry season in the Central
Amazon Basin. In this season the water level of rivers and lakes is lower and
the reptiles are more easily seen. The feeding place on the hosts, head and
back, suggests that the tabanids can feed when the reptiles are in the water
because the head stays above the water surface.
Aditional observations on the attack of tabanids
on dead caimans were conducted in Cruzeiro do Sul, Acre 7°37'02"S,
72°46'15"W, in November 1996. A common caiman was captured to be used
as bait for tabanids, but was dead on the morning of the following day. At 09:30
we recorded the attack of T. occidentalis, at 09:40, Diachlorus curvipes,
at 12:30, two individuals of T. occidentalis and one of P.
nigriflavus, and finally, at 15:30 two individuals of T. occidentalis
and one of P. nigriflavus.
ACKNOWLEDGEMENTS
To the Centro de Instrução de Guerra
na Selva for logistical help. To Stefan Keppler and Flávia Costa for
suggestions on manuscript and João Vidal for field support.
REFERENCES
- Aubréville A 1961. Estude Écologique
des Principales Formations Vegetales du Bresil et Contribuition a la Connaissance
des Forets de L' Amazonie Bra-silienne, Centre Technique Forestier Tropical,
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- Barros ATM 1996. Seasonality of Phaeotabanus
fervens (Diptera:Tabanidae) in the Pantanal region, Brazil. Mem Inst
Oswaldo Cruz 91: 159.
- Henriques AL, Ferreira, RLM, Vidal JF, Rafael
JA 2000. Betrequia ocellata Oldroyd (Diptera, Tabanidae, Rhinomyzini)
blood feeding on Caiman crocodilus (Linnaeus) (Crocodylia, Alligatoridae)
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- Köppen W 1948. Climatologia com un
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as ectoparasites on caimans (Crocodylia: Alligatoridae) in eastern Colombia.
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- Oldroyd H 1954. The Tabanids (Diptera:
Tabanidae) of the Ethiopian Region. Vol. II, Tabanus and Related Genera,
British Museum (Natural History), London, 341 pp.
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na Amazônica Central, Brasil, Thesis, Instituto Nacional de Pesquisas
da Amazônia, Manaus, 38 pp.
- Philip CB 1983. A unique, divergent developmental
dependence of a Galapagos tabanid (Diptera, Tabanidae). Wasmann J Biol
41: 47-49.
- Philip CB 1986. A collection of four species
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© 2002
Instituto Oswaldo Cruz - Fiocruz
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