Southwest Madagascar Research Articles

Australian Triassic lungfish skulls

Skull bones of Gosfordia truncata Woodward, 1891, from the Lower Triassic Hawkesbury Sandstone of New South Wales, Australia, are described for the first time. The skull roofing pattern suggests possible affinities between G. truncata and Paraceratodus germaini (Triassic, southwest Madagascar). A three-dimensional reconstruction of the skull of Ceratodus formosus Wade, 1935, based on the holotype, found in a Lower Triassic deposit at Brookvale in New South Wales, is included. This reconstruction indicates that this species is not closely related either to the recent Australian lungfish, Neoceratodus forsteri, or to the Triassic Ceratodus (Tellerodus) sturii from Nord Alpen in Austria, and it has no close affinities with G. truncata. A new genus, Ariguna, is therefore proposed to receive Ceratodus formosus Wade, 1935. Without associated tooth plate material, G. truncata and A. formosa cannot be defined more precisely.

Dispersal by Propithecus verreauxi at Beza Mahafaly, Madagascar: 1984-1991.

From 1984 to 1991, 126 males and females were marked and monitored in a wild population of Propithecus verreauxi in southwest Madagascar. Animals were assigned birth years, based on known birth date or degree of dental wear calibrated by recapture data. Twenty-one of 27 groups identified in 1984 persisted within stable home range boundaries, 6 groups disappeared, and 6 new groups formed. Only males transferred between existing groups, although individuals of both sexes left groups to form new groups. The home range of the group into which a male transferred usually overlapped that of his group of origin. On average, 35% of males aged 3-6 years transferred each year. Older males transferred at a lower rate. Three to 6-year-old males were more likely than older males to transfer two or three times. Most 3-6-year old males transferred into groups with a higher proportion and number of females, whereas older males were progressively more likely to transfer into groups with a lower proportion and number of females. New groups were formed by older males, whose mates had died or who had not been successful in joining an existing group, and by young, nulliparous females. Males have rarely been observed for more than 5 years in the same group. Dispersal by 3-6-year-old males appeared to be voluntary. Females helped evict non-natal males from the group but did not prevent new males from joining. Age at first reproduction was 5 years in this population. Forced secondary dispersal may occur when maturing females cease to tolerate males who may be their fathers. © 1993 Wiley-Liss, Inc.

Demography of Propithecus verreauxi at Beza Mahafaly, Madagascar: Sex ratio, survival, and fertility, 1984–1988

AbstractEighty‐five sifakas (Propithecus verreauxi) have been captured, marked, released, and monitored between September 1984 and August 1988 at the Beza Mahafaly Special Reserve in southwest Madagascar. Estimates are presented of the age and sex structure of this population and of age‐specific fertility and survival. Using data from this and other studies, it is shown that sifaka tertiary sex ratios do not depart significantly from 50:50, but that they do differ significantly from those of haplorhine primates, which have strongly female‐biased tertiary sex ratios. Two demographic mechanisms that could give rise to this distinction are considered: 1) intermittently male‐biased birth cohorts among sifakas and 2) different patterns of survivorship in haplorhines and sifakas.

Organic-geochemical characterisation of sediments from the Sakoa coalfield, Madagascar

Eleven coals and five mudstones of the Sakoa coalfield, southwest Madagascar, have been characterised by microscopy, Rock-Eval pyrolysis, and detailed analysis of C 12+-aromatic and C 15+-saturated hydrocarbon fractions of the organic extracts. Average vitrinite reflectance of 0.77% R r and T max of 439°C indicate moderate thermal evolution of the organic matter corresponding to the beginning of catagenesis, which is confirmed by molecular indicators based on aromatic hydrocarbons and saturated biological markers. The average Methylphenanthrene Index (MPI 1) of 0.69 corresponding to a calculated vitrinite reflectance ( R c) of 0.81% is in agreement with an isomerisation of selected steranes and triterpanes having not yet reached equilibrium. Maceral compositions and molecular distributions of saturated and aromatic hydrocarbons are typical of organic matter mainly derived from terrestrial higher plants with significant contributions of bacteria and a minor input of algae. The hydrocarbon potential in terms of Hydrogen Index (HI)-values of the coal samples varies between 83 and 284 mg hydrocarbons (HC)/g C org, i.e. in approximately the same range as that commonly observed for high volatile bituminous coals. Carbon-normalised concentrations of C 12+-aromatic and C 15+-saturated hydrocarbons generally are higher in the coals than in the mudstones, thus suggesting expulsion of heavier hydrocarbons was relatively ineffective in Sakoa coals.

Isolation of aromatic compounds from a coal extract by semipreparative HPLC

Two methyldibenzofuran isomers and a tetramethylnaphthalene isomer have been isolated from the organic extract of a Sakoa (southwest Madagascar) coal and were positively identified by IR spectroscopy. The isolation procedures were carried out on a semipreparative scale and included two to four normal-phase HPLC steps and a reversed-phase HPLC step. Reproducibility of the normal-phase fractionations on alumina was enhanced by an improved moisture-control system. Substantial enrichment of the compounds of interest was achieved in each step, as evidenced by capillary GC.

The morphology and systematic position of the Didiereaceae of Madagascar

The Didiereaceae, endemic to the arid south-west of Madagascar is one of the most remarkable plant families in the world. Four genera and 11 species are known, of which 3 have been described by the author: Decaryia (1 species), Alluaudiopsis (2 spp.), Alluaudia (6 spp.) and Didierea (2 spp.). The species show different growth forms, but their shoot-stem-systems are basically similar; they are all spiny, semi-succulent deciduous shrubs or trees, with a stem (shoot) system differentiated into long-shoots and short-shoots (brachyblasts). The long shoots bear normal leaflets, which soon fall off. In their axils, brachyblasts develop proleptically, which produce two types of leaves (1) thorns which develop proleptically in different numbers (1 in Alluaudia, 2 in Alluaudiopsis marnieriana and several Didierea)-, (2) leaves which are green, deciduous assimilation organs (2 per brachyblast in Alluaudia, several in Didierea). The stem organization is comparable to that of the Cactaceae of the New World. The brachyblasts of the Didiereaceae are homologous to the areoles of the Cactaceae, most obviously to those of the primitive members, the Pereskioideae. The affinities between the two families can be demonstrated by means of grafting. It is possible to graft Didiereas onto Pereskioideae and vice versa. The flower structure of Didiereaceae is very uniform. Flowers are unisexual and dioecious and show affinities to those of the Portulacaceae. The development of the gynoecium, the ovule and the female gametophyte as well as the presence of betalains in the flowers indicate that the Didiereaceae do not belong to the Sapindales as was sometimes assumed, but to the Centrospermae. They should be placed between Portulacaceae and Cactaceae. The ancestors of the Didiereaceae are not known.

Geology and Oil of Sakamena Basin, Malagasy Republic (Madagascar)

Structure and evolution of the Malagasy sedimentary belt were controlled, during Paleozoic and Mesozoic (Karroo) times, by north-northeast-south-southwest (East Coast)- and north-northwest-south-southeast (Bongolava)-trending faults. These two fault trends correspond to old lines of weakness (faults and flexures), which had a role in the Precambrian evolution of the Malagasy basement. In southwest Madagascar, the Manalobe, Ilova, and Iakomby (East Coast trend) fault lines are known to strike east-west, whereas the Andranopasy-Befandriana fault lines (Bongolava trend) strike southwestward. They were active during Karroo deposition, and they frame the region where Malagasy Karroo rocks are found. No Karroo formations are known southwest of the Andranopasy-Befandriana fault lines. On the northeast side of the fault lines a Lower Karroo basin (Sakoa) lies between the crystalline basement on the east and Manalobe en echelon lines on the west; Middle and Upper Karroo basins (Sakamena and Isalo) are between the basement on the east and the Ilova fault line on the west; a basin of mixed-facies sedimentary rocks of Middle Jurassic age (Dogger; Sakaraha basin) lies between the Ilova and Iakomby fault lines. West of the Iakomby fault a completely marine Liassic to Cretaceous series lies directly on the crystalline basement. The Sakoa, Sakamena, and Isalo basins originated by successive downward movements of the blocks outlined by the crystalline Precambrian backbone of Malagasy Island on the east and the Manalobe, Ilova, and Iakomby, Andranopasy-Befandriana faults, which always determined the western and southwestern boundaries of these basins. The Sakoa and Sakamena basins were of a mediterranean type, of restricted circulation. As indicated by several surface and subsurface hydrocarbon shows, naphthogenic conditions certainly existed within the Sakamena basin, and probably within Sakoa basin as well. From the structural and paleogeographic interpretation of Sakoa and Sakamena basins here presented, these basins, and particularly their cul-de-sac southern part, seem to deserve a reexamination from the point of view of oil exploration.

Comparative plague dynamics of tropicalLocusta(Orthoptera, Acrididae)

AbstractThe occurrence and causes of plagues of tropicalLocustaspp. are compared for the three major outbreak areas, Middle Niger of Mali (L. migratoria migratorioides(R. & F.)), south-west Madagascar (L. m. capito(Sauss.)), and Mindanao (Philippines) (L. m. manilensis(Meyen)). Multiplication and concentration are the two most important processes involved and may occur concurrently or sequentially depending on the outbreak area. In the Middle Niger and Madagascar heavy rainfall, through its effect of increasing multiplication, is the key density-disturbing factor, whereas on Mindanao the factor is drought leading to concentration of locusts. Variations in multiplication rates are determined by the response of eggs and hoppers to desiccation and by the density-dependent effects of fecundity and natural enemies. Concentration is caused by the restriction of favourable breeding habitats in relation to the seasonal population displacements and, because it occurs at different seasons in the three outbreak areas owing to their differing climates and geographies, profoundly modifies the timing of outbreaks. Man's modification of the environment, particularly in relation to the dry season survival ofLocusta, has caused outbreaks to occur in new areas. Long-term solutions to the problem of controlling such outbreaks lie in the field of management rather than in the continued use of insecticides because of the continued reinfestation from surrounding populations. The use of natural enemies does not as yet show any promise as a means of controlling outbreaks of tropicalLocusta.

Pluralité des Aires de Grégarisation de Locusta Migratoria Migratorioides

SummaryLast years'observations and studies seem to show that there is not one, but four outbreak areas of Locusta migratoria migratorioides (Reiche & Fairmaire, 1850) e.g.: flood plains of Mali, North-East State in Nigeria, Kassala and Blue Nile Provinces in Sudan, South-West of Madagascar.

Tenebrionidae Récoltés par Mr. L. Bigot dans le Sud-Ouest de Madagascar

SUMMARYList of the 23 species or forms of Coleoptera Tenebrionidae collected by Mr. L. Bigot in the South-West of Madagascar, and description of a new species and a new variety.

Effets édaphique et biotique de l'inversion pluviométrique des saisons, important facteur de pullulation des acridiens migrateurs dans le Sud-Ouest malgache

In South-West Madagascar, the area from which outbreaks ofLocusta migratoria capito (Sauss.) andNomadacris septemfasciata (Serv.) proceed, a seasonal pluviometric inversion (an unusual occurence) will mean successful and simultaneous hatches due to edaphic and biotic effects.

Subsurface Palynology in Madagascar: Permian, Triassic, and Jurassic of Morondava Basin: ABSTRACT

Palynological investigations are summarized for several hundred cores and cuttings samples from the Permian, Triassic, and Jurassic found in about 30 wells drilled by the Societe des Petroles de Madagascar in the Morondava Basin (southwest of Madagascar). The nature of the microflora, which includes about 300 forms of organic microfossils (numerous spores and End_Page 269------------------------------ gymnospermic pollen grains, a few Hystrichospheres and Dinoflagellates) is presented. Evolutionary trends of the associations and lateral variations and environmental influences are discussed. Choice of stratigraphical characteristics and zonation of the series, which have an aggregate thickness of several thousand meters, are indicated. Correlation is made between wells at distances extending to as much as 600 kilometers and across various deposits of continental, brackish, and marine facies. End_of_Article - Last_Page 270------------

Research Items

DUGONG FISHING IN MADAGASCAB.—M. G. Petit publishes in the Bull, et Mém. Société d'Anthropologie de Paris, T. 8, Sér. 7, fasc. 4-5-6, some further observations on the ritual of dugong fishing in south-west Madagascar. Small light outriggers, extremely mobile, are employed, the fishermen being two in number to each, a harpooner who stands in the bow being in command. Before setting out, the harpooner consults the Sitily as to whether conditions are favourable, and he is provided with a talisman (Ody). This is used first to consecrate a vessel of sea water, and is then placed in the prow and covered with a piece of old net to protect it. The sea water is used to sprinkle the canoe, while invocations are addressed to it, and to the harpoon and its ropes. It is also used to wash the head and hands of the fishermen. As soon as the day for fishing has been fixed, the fishermen must abstain from all contact with their wives, and must not touch food prepared or water drawn by them. The fishermen are in fact in a magical state, of which the serious nature is indicated by the fact that to miss the dugong not only entails misfortune for the village, but will be followed by the death of a member of the fishermen's family. When the animal has been brought to land, its body is scrupulously hidden from the sight of women and children. The body is dismembered by an old man, and the blood carefully collected and divided into three parts, one poured on the sand by the canoe, one into the sea, and the third smeared on the prow of the canoe, the harpoon and the rope. The flesh is eaten on the beach, first by men and, when they are satisfied, by women and children, but no knife, fork, or other utensil must be employed, nor must anyone spit or blow the nose. The carcase must be buried, this being done with ceremony, as neither beast nor bird, but only man, must eat the flesh or pick the bones. If the animal is female, connexion is enjoined on the fishermen, a custom which is found on the east African coast, and in a Chinese account of the Aino of Sakhalin in relation to women-fish, presumably seals.

VIII.—Descriptions of four new species of butterflies from south-west Madagascar, captured by Mr. J. T. Last, in the collection of H. Grose Smith

VIII.—<i>Descriptions of four new species of butterflies from south-west Madagascar, captured by Mr. J. T. Last, in the collection of H. Grose Smith</i>