By examining iron contents, it is demonstrated that the monogenean Ancyrocephalus mogurndae (Yamaguli, 1940) feeds on the blood of its host, the mandarin fish Siniperca chuatsi (Basilcwsky), The iron content and then the quantity of blood necessary to produce this amount of iron are found different in young and fully-matured worms. Young worms contain higher levels of iron and estimated amount of blood. It is suggested that/1, mogurndae may start to feed on host blood as attached on gills, and the amount of blood ingested by young worms may vary from 0.01 to 1.00 μΙ before reproduction. The difference between young and fully-malurcd worms may be accounted for by the elimination of haematin and change of food composition in matured worms and may also be affected by reproduction. Experimental infections of the monogenean may provide supportive information for explaining the difference, and further studies should also examine the effect of immune components in host blood or mucus on the intestines of the parasite.
Nine Pteromylaeus bovinus (F., Geoffroy St. Hilaire) (Euselachii: Myliobatinae) from the Tunisian coast were examined l'or ectoparasites during 1995, 1996 and 1997. A monogenean found on the gills of seven host specimens is described as a new species and a new genus, Heliocotyle, is proposed to accomodate it. The presence of a single sclerotized haptoral structure on the dorsal surface of the haptor leads us to place this species in the Heterocotylinae Chisholm, Wheeler ct Beverley-Burton, 1995. The genus Heliocotyle is characterized by a haptor with only one dorsal structure and seven loculi, six being subdivided by pseudosepta. Heliocotyle kartasi sp. n. is the type and the only species in this genus.
Backward Integrations of motion of the Halley-type comets, covering over 11,000 years, are used to investigate their librations around high-order resonances with Jupiter. These occur for comets moving in direct orbits with revolution periods between 50 and 90 years. The fact that about one halí of them is librating at a time explains the concentration of revolution periods in this range. The librations are of rather uniform period and amplitude, and tend to persist over about 200 revolutions of tho comet. Their presence implies that the lifetimes of these comets since their captures Into periodlc orbits of small perihelion distance mostly exceed 300 revolutions. Possible exceptlons among the 9 comets with present periods of 50 to 90 years are the already extinct P/Westphal, and also P/Halley, for whlch a close approach to the orbit of Jupiter 150 revolutions ago was identified.
Problems, methods and results are discussed to model finestructures of sunspots, plages and prominences from observed data. The very small scales of those structures prevents so far their full resolution in a spectrum. Thus, twocomponent models of other indirect methods are used to deduce model atmosphere, magnetic and velocity field within these finestructures.
The prototypical young cometary nebula NGC 2261, around the star R Mon, has been extensively observed with 20" resolution in the J=1-0 line of CO and 13CO by using the IRAM 30-m telescope (located on the Pico Veleta, near Granada, Spain). The molecular line maps are compared to optical observations in order to obtain
detailed information on the nature of this cometary nebula as well as on the kinematic structure of the gas. Our observations suggest that cometary nebula NGC 2261 is actually the brightest fan of a bipolar nebula. Furthermore, it appears that the optical nebula is a hollow cone which has been emptied by the action of winds from R Mon, the star located at the tip of the nebula. High velocity CO is
flowing along the cone walls. Toward the position of the star R Mon we observe a molecular maximum which could be due to residual material originated during the collapse process that led to the formation of the star.