The Genus Gyrostigma Brauer (Diptera: Gasterophilidae)*
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Z. f. Parasitenkunde 22, 245--260 (1962) South African Institute for Medical Research, Johannesburg THE GENUS GYROSTIGMA BRAUER (DIPTERA: GASTEROPHILIDAE)* By F. ZUMPT With 12 Figures in the Text (Received July 14, 1962) I. History SJOSTEDT (1908) gave a short sketch of the early history of the Gyrostigma problem. In 1839, HOrE figured a larva which had been found in an African rhinoceros, and OWEN some time later simply designated it as "Oestrus Rhinocerontis", meaning Oestrus from the rhinoceros. JOLI mentioned this larva again in 1846 and reproduced HOPE's illustration, but thought it would belong to the genus Hypoderma. DELECORGUE in his "Voyage dans l'Afrique australe" (vol. 2, 1847, p. 356) described the rich animal life near the Vaal river in South Africa and said that the Black Rhinoceros [Diceros bicornis (L.)] there was found to be heavily infested with stomach bots. The White Rhinoceros, [Diceros simus (BuRCHELL)] however, harboured relatively few of these bots, and this was thought to be constant and typical. Nowadays rhinos no longer occur in this area of South Africa, but we can conclude that the difference in the grade of infestation of these two species was only a local one, or even only accidental. The White Rhinoceroses now pro- tected in the National Parks of Zululand are as heavily infested as those of the black species investigated by DEL~GORGUE. In his famous monograph on the Oestridae, BRAUER (1863) gave the first adequate description of the larva after HOPE'S figure, still under "Gastrophilus Rhinocerontis OWE~". This name has no nomenclatorial standing, but BRAUER wanted only to indicate that he was dealing with OWEN'S larva. However, he correctly stated for the first time that this larva was similar to Gasterophilus. In 1884, BRAUER founded the genus Gyrostigma on larvae recovered from an Asiatic Two-horned Rhinoceros [Didermocerossumatrensis (FISCKER)] which had died just after its arival in the Zooliogical Gardens of Hamburg. He found them to be different from the African larvae and named the species G. sumatrensis, the adults of which have until now remained unknown. * This paper has been partly financed by the South African Council for Scien- tific and Industrial Research, and forms part of a survey of Arthropod parasites in Africa south of the Sahara. 246 F. ZUMrT : In 1895, a paper appeared byCoRTI, in which he described from a single female a new oestrid species from Gallaland which he named Spathicera pavesii, and which he believed to be related to Gasterophilus. Due to the enormous size of the specimen, CORTI presumed that it was the adult of larvae living in elephants or rhinoceroses, and evidently belonged to the genera Cobboldia or Gyrostigma created by BI~AUEI~. CORTI sent the only specimen to BRAUER, who studied it once more (1895). He suggested that Spathicera might represent the adult stage of Gyrostigma, but he did not dare to synonymize the two genera. Two years later, BRAVER (1897) described and partly figured a third stage larva from a Black Rhinoceros, shot at Gurui in Tanganyika. He designated it as "Gyrostigma rhinocerontis bicornis", and apparently wanted to indicate only that it was found in "Rhinoceros bicornis". E~DERLEIN (1899), however, accepted this name as a nomenclatorial, valid designation, and it was listed as such by later authors, until ROD~AIN and BEQUAERT (1919) placed it into the synonymy of G. pavesii (CORTI). In the meantime EI~DERL:EIN(1901) had published an important paper, in which he described from the 3rd instar larva the new species Gyrostigma conjungens found in a Black Rhinoceros near Kilimandjaro, and discussed larval material of "Gyro- stigma rhinocerontis bicornis", pointing out the great variability in the shape of the slits in the posterior peritremes. A third species of Gyrostigma was then described by SJOSTEDT (1908), under the name Spathicera meruensis. He had shot a rhinoceros in the Kilimandjaro- Meru district and found in the stomach a great number of mature larvae, from which he succeeded in rearing one adult female. In another rhinoceros, he detected larvae which he assigned to BRAV~R'S "Gyrostigma rhinocerontis bicornis", and which he found to be different from his new species. SJ•STEDT, moreover, decided definitely to unite the genera Spathicera and Gyrostigma, but he treated Gyrostlgma as a synonym, because it was based on a species known only from the larval stage. ROD~AIN and BEQUAERT (1919), who synonymized BRAUER'S species with G.pavesii, accepted SJOSTEDT'S view of the specific difference of these two species. ZUMrT and PATERSO~ (1953) doubted "whether the larval characters given in the key of ROD~AIN and BEQUAERT are of significance" with respect to a specific separa- tion of G. meruensis and G. pavesii. They had seen quite a number of young and old 3rd instar larvae, but only one female fly from Zululand, which was "in some ways intermediate" between G. meruensis and G. pavesii. Since then, I have been able to study a great number of larvae and adults from various parts of Africa, and I have also seen a female fly from "Abyssinia" in the Paris Museum, which may be identical with the specimen mentioned by I~ODHAIN and BEQUAERT under G. meruensis. It is in my opinion conspecific with specimens which can be clearly referred to COnTI'S G. pavesii. The adult flies I saw show a pronounced variability which includes the features given in the descriptions for G. pavesii as well as for G. meruensis. The dark spots of the third larval stage of G. meruensis, to which SJOSTEDT and also RODHAIST and BEQUAERT called specialattention, may be characteristic of the mature larvae, and a similar appearance is known from several species of Oestrinae. The size and pigmentation of the larval denticles increase with the growing larvae, and on the other The genus Gyrostigma BRAUER (Diptera: Gasterophilidae) 247 hand, are fairly variable. Through the kindness of Professor BEIER, Vienna, I received an evidently paratypical specimen of the third larval stage of G. meruensis which is in my opinion not separable from BRAUP~R'S larvae. I believe therefore that it is justi/ied to place G. meruensis definitely into the synonymy o/ G. pavesii. The adult of G. con]ungens, which in the larval stage is clearly different from G. pavesii and G. sumatrensis, remained unknown to all former authors. A few years ago, I received for the first time several 3rd instar larvae from a Black Rhinoceros killed in the Makueni district of Kenya. On my urgent request to try to rear the adults of this larva, Mr. J. G. TREMLETT of the Department of Veterinary Services eventually succeeded in hatching two females which are now at my disposal, and are described later in this paper. They are quite different from G. pavesii and much more reminiscent of a Gasterophilus species, a fact which had already been stated by ENDERLEIN (1901) for the 3rd larval stage. But they nevertheless clearly belong to Gyrostigma, and it is not necessary to place this species into a distinct genus as proposed by ENDERLEIN (1911). The differences between these two Gyrostigma species are not greater than those between the species of Gasterophilus. Mr. TREMLETT reared the adults from larvae found in a Black Rhinoceros which had to be destroyed in June 1961 in the Tsavo National Park, Kenya. With respect to the biology of Gyrostigma species, very little is known. The second and third instar larvae are found attached to the wall of the stomach as observed by DELEGORGUE, apparently without causing severe pathological effects. The eggs were first discovered in the Congo by Mr. L. LEBRUN. They were firmly attached to the host's skin, mainly on the head, at the base of the ears, on the neck and the shoul- ders. RODHAIN (1915) obtained eggs from a caged fly and gave a descrip- tion and figure of the egg, and later he and BEQUAERT (1919) were able to describe the first larval stage which had been extracted from an egg. It is still unknown under what circumstances the larvae hatch and how they find their way to the stomach. The mature larvae are passed through the anus, but it is doubtful whether they are normally excreted together with the faeces. Frequent checking of the large heaps of dung accumulated by the regular use of the same defaecation places by a certain number of White Rhinoceroses in the National Parks of Zulu- land, have never resulted in finding the pupal cases. Perhaps the larvae leave their hosts more or less actively at their resting places. The pupal stage lasts about six weeks. II. The taxonomic position of the genus Gyrostigma When BBAUER in his monograph of the Oestridae in 1863 mentioned the stomach-infesting bots of the African rhinoceroses as "Gastrophilus Rhinocerontis", he correctly indicated their close relationship to those z. Parasitenk. Bd. 22 18 248 F. ZVMPT: bots which develop in the alimentary tract of equids. CORTI (1895) describing his Spathicera pavesii also stated that it was related to Gastero. philus. I~O])~AIN and BE QUAERT (1919) listed the genera Gasterophilus LEACH and Gyrostigma BRAUER under the Gasterophilinae, which he regarded as a subfamily of the Oestridae. TOWNSEND (1931) raised the subfamily to a distinct family and created the two tribes Gasterophilini and Gyrostig- matini I (see also TOWNSEND 1935). S~GU¥ (1937) then valuated these tribes as subfamilies, but placed both, widely separated from one another, into the family Muscidae. ZUMPT (1957) accepted their rank of sub- families, but listed both together again with the Cobboldiinae (parasites of elephants) under the distinct family Gasterophilidae. The discovery of the adult of Gyrostigma conjungens has revealed a great similarity of this species to Gasterophilus, which no longer seems to justify placing these two genera into different subfamilies or tribes.