Fine Structure of Human Malaria In Vitro*†

SYNOPSIS. The erythrocytic cycle of the human malaria parasite, Plasmodium falciparum, was examined by electron microscopy. Three strains of parasites maintained in continuous culture in human erythrocytes were compared with in vivo infections in Aotus monkeys. The ultrastructure of P. falciparum is not altered by continuous cultivation in vitro. mitochondria contain DNA-like filaments and some cristae at all stages of the erythrocytic life cycle. The Golgi apparatus is prominent at the schizont stage and may be involved in the formation of rhoptries. In culture, knob-like protrusions first appear on the surface of trophozoite-infected erythrocytes. The time of appearance of knobs on cells in vitro correlates with the life cycle stage of parasites which are sequestered from the peripheral circulation in vivo. Knob material of older parasites coalesces and forms extensions from the erythrocyte surface. Some of this material is sloughed from the host cell surface. The parasitophorous vacuole membrane breaks down in erythrocytes containing mature merozoites both in vitro and in vivo. Merozoite structure is similar to that of P. knowlesi. The immature gametocytes in culture have no knobs.     

Revision of Microlaimidae, Erection of Molgolaimidae fam.n., and Remarks on the Systematic Position of Paramicrolaimus (Nematoda, Desmodorida)

The family Microlaimidae contains Bolbolaiminae subfam.n. (Bolbolaimus syn. Pseudomicro-laimus) and Microlaiminae ( Calomicrolaimus, Ixonema and Microlaimus ). The new family Molgolaimidae contains Aponematinae subfam.n. ( Aponema gen.n.) and Molgolaiminae subfam.n. ( Molgolaimus and Prodesmodora ). The main differentiating characters applied are: structures of the head region, shape of the oesophagus, position of the excretory pore, shape of the tail, structure of the gonads and ornamentation of the cuticle. The significance of porids and preanal supplements as distinguishing characters is, discussed. Microlaimidae are closely related to Desmodoridae; Molgolaimidae related to Spiriniidae. Paramicrolaimus is transferred from Microlaimidae to Spiriniidae.–Six species from the Øresund, Denmark, are redescribed: Microlaimus punctulatus Gerlach, 1950 and M. acinaces Warwick & Piatt, 1973; Aponema torosus (Lorenzen, 1973) gen.n., comb.n. (syn. Microlaimus torosus Loren-zen, 1973); Molgolaimus allgeni (Gerlach, 1950) comb.n. (syn. Microlaimus allgeni Gerlach, 1950) and M. turgofrons (Lorenzen, 1972) comb.n. (syn. Microlaimus turgofrons Lorenzen, 1972); Paramicrolaimus spirulifer Wieser, 1959.     

OXYNOE AZUROPUNCTATA, N. SP., A NEW SACOGLOSSAN FROM THE FLORIDA KEYS (MOLLUSCA: OPISTHOBRANCHIA)

A new species of Oxynoe from the Florida Keys is described.It differs from the other Caribbean Oxynoe, O. antillarum Mörch,1863, in color, number and size of papillae, size increase ofradular teeth, diet, and type of development. The type of developmentis extended lecithotrophic. The larvae hatch about 4 weeks afterthe eggs have been deposited, and metamorphosis is completedafter about one additional week. Oxynoe azuropunctata n.sp.feeds on Caulerpa paspaloides, C. cupressoides and C. sertularioides.Details of the feeding process in Oxynoe are described for thefirst time. The junction of the oral tube and the pharynx isequipped with a complex muscular buccal apparatus, part of whichis everted during feeding. The protrusible parts of the buccalapparatus completely surround part of an algal filament, whichis then slit with the radula, and the cell sap is sucked out.The protrusible parts are retracted after the filament has beenreleased. ^*Present address: Ellebjergvej 22, 1 t.h., DK-2450 CopenhagenSV, Denmark (Received 13 November 1979;     

Population recovery of the sea urchin Lytechinus variegatus in a seagrass flat (Araruama Lagoon,Brazil): the role of recruitment in a disturbed environment

Summary

The size, structure, and density of a population of Lytechinus variegatus were recorded from a shallow seagrass bed (Halodule wrightii) at 40-day intervals from April 1994 to April 1995. A local mass mortality was observed in May 1994. The density declined from 0.57±0.10 to 0.06±0.05 ind.m^?2, mean size declined from 37.6±0.49 to 16.2±2.14 mm and maximum size from 75 to 40 mm. Ten months after mortality, the maximum and mean sizes had returned to initialvalues, but density had not (0.10±0.03 ind.m^?2). A second, smaller mass mortality occurred in April 1995. High values of gonad index were recorded before mortality (9.40±5.97) and after population recovery (11.96±5.74). Recruitment was continuous throughout the year, but reached a peak from August to October. This can he related to the patterns of upwelling in the region. Mass mortality is probably an annual event in this population that can be correlated with the occurrence of low tides during daytime in the fell. The population can recover during the summer when low tides occur during the night. The massive input of recruits prevents extinction of the population during the season of high mortality. Population recovery depends on the magnitude of recruitment.