A new species of Tunga perforating the osteoderms of its armadillo host in Argentina and redescription of the male of Tunga terasma

A new species of Tunga (Siphonaptera: Tungidae) collected from armadillos in Argentina is described. The new species is characterized by large and pigmented eyes, the presence of two bristles on antennal segment II, two bristles at the base of the maxilla, and a discoid neosome compressed anteroposteriorly. The gravid female is located in the carapace of the host, perforating the osteoderms. The new species resembles Tunga penetrans and Tunga terasma in general appearance. However, it differs by the greater anteroposterior compression of the neosome, a more angular head, and a manubrium with a pointed proximal end and convex ventral margin (the proximal end of the manubrium is rounded or slightly pointed in T. terasma, and the ventral margin is straight in both T. penetrans and T. terasma). In addition, specimens of T. penetrans have more bristles in antennal segments II and III, and lack bristles in the posterior tibia. This is the first report of a species of Tunga perforating the osteoderms of its host and thereby showing a high degree of specialization. Tunga terasma is recorded for the first time in Argentina; the male is described again and the characteristics of the species amended. This information may be useful in epidemiological studies of diseases caused by species of Tunga.     

High frequency of adventitious shoot regeneration from commercial cultivars of evening primrose (Oenothera spp.) using thidiazuron

Evening primrose (Oenothera spp.) is grown commercially for its seed oil that contains gamma linolenic acid (GLA), a valuable food supplement and pharmaceutical. There is considerable interest in the potential of genetic engineering to improve yields of GLA in evening primrose, and attention has focused on the current state of tissue‐culture knowledge in this species which is a prerequisite for genetic transformation. Published protocols for the regeneration of plants from leaf or cotyledon material of Oenothera spp. are available, but these prove unsatisfactory when applied to commercial cultivars used in this study. An efficient method for regenerating three commercial cultivars of evening primrose Rigel, Merlin and Vulcan was developed using thidiazuron (TDZ) as a growth regulator. Explants from one month old seedlings were cultivated in vitro; a large number of buds were induced directly from strips of leaves, cotyledons and stems when cultured on Murashige and Skoog (MS) basal medium containing TDZ and indole‐butyric acid (IBA). Shoots that were excised and placed onto MS basal medium, supplemented with IBA, rooted with 85–90% efficiency. Plantlets were transferred to soil after 6–8 wk. TDZ stimulated the regeneration process, and its effects were enhanced when combined with IBA or indole‐3‐acetic acid (IAA). The methods developed may be a useful advance toward improvement of this oil seed crop through genetic modification.     

Further evidence for cortical control over replication of the macronucleus and basal bodies in Stentor

This paper presents further evidence that the cortex controls macronuclear replication and basal body production during the cell cycle of Stentor. At the onset of cell division, basal body production occurs on the ventral side of the cell to form an oral primordium; this structure develops slowly into the oral apparatus destined for the posterior daughter cell. Meanwhile, a series of morphological changes in the macronucleus (coalescence, elongation, nodulation) doubles the number of nodes in preparation for division. When a cell undergoing oral development is grafted to a morphostatic cell of equal size, oral development is usually induced in the morphostatic component and the two members of the graft complex eventually become synchronized with respect to macronuclear morphology. However, primordium induction and nuclear synchronization usually do not occur when the 2 members of the graft complex are separated by cortical discontinuities which heal gradually, even though the graft components demonstrably share a common endoplasm throughout the experiment. These results suggest that the cell surface may control the replication of organelles such as the macronucleus and basal bodies which are normally kept “in step” with the cell cycle in such a way that they are not lost or reproduced too frequently.     

EFFECT OF ECDYSTERONE ON VITELLOGENIN CONCENTRATION IN HAEMOLYMPH OF MALE AND FEMALE SARCOPHAGA BULLATA

Using Polyacrylamide gel electrophoresis, cycloheximide, incorporation of ³H-labelled amino acids and immunological methods, we have demonstrated that injection of ecdy- sterone induces de novo synthesis and release of vitellogenin in both sexes of Sarcophaga bullata. Vitellogenin concentrations were measured by the Mancini-radial immunodiffusion technique. In males a dose as low as 1 ng always makes vitellogenin appear in the haemolymph but very reproducible results are only obtained when doses varying from 10 to 250 ng were injected. In this range, the dose-response curve was linear on a semi- logarithmic scale.

In females, vitellogenin concentration remained low until a few hours after liver feeding and thereafter it rose sharply and reached its maximum about 24 h after the protein meal. 100 μg 6-hydroxydopamine HCl, injected before liver feeding in 4-day-old females, inhibited vitellogenin synthesis and yolk deposition, probably by interfering with the release of a brain hormone. This inhibitory effect on vitellogenin synthesis, but not that on yolk deposition, could be overruled by injection of ecdysterone. Juvenile hormone was ineffective on both. Females, ovariectomized on day 2 or 3, accumulated vitellogenin in their haemolymph, indicating that the continuous presence of the ovaries was not required for vitellogenin synthesis. The possible relation between the gonadotrophs hormone from the brain, vitellogenin synthesis and moulting hormone metabolism is discussed.