Questions Regarding the Implementation of EU Mutagenesis Ruling in France.

The European Commission has asked EU Member States for comments on a French law notification demanding plant varieties produced with the help of in vitro mutagenesis have to be eliminated from the national catalog of approved varieties because of missing legal authorization deemed required by genetic engineering law. Primary target are herbicide-tolerant Clearfield oilseed rape varieties. The scientific reasoning is questionable, traceability is illusive, and law enforcement is likely to be impossible.

Ultrastructure of pigmented and unpigmented photoreceptors in cercariae of Trichobilharzia ocellata (Plathelminthes, Trematoda, Schistosomatidae): evidence for the evolution of parasitism in Neodermata.

The lens-covered pigment cup ocelli in free-swimming cercariae of Trichobilharzia ocellata were re-examined and the differentiation of the lenticular elements was studied in cercariae still enclosed in sporocysts. Each eye consists of a single rhabdomeric sensory cell, a single cup cell harboring pigment granules and the lens. This lens is developed step by step by the fusion of numerous dark platelets not enclosed by a bordering membrane. The material is presumably proteinaceous. There is no evidence that the lenses are of mitochondrial origin. Besides the pigment cup ocelli, a special type of unpigmented rhabdomeric photoreceptor was discovered. Three unicellular photoreceptors arranged in a three-dimensional configuration exist. These light-sensing organs show a principle of construction similar to that of phaosomous photoreceptors. We hypothesize that both types of photoreceptors are relevant for distinct reactions in the host-finding behaviour of the cercariae. The special type of lensing in the pigmented eyes seems to be restricted to Trichobilharzia species, whereas the phaosomous-like receptors may be more widespread in members of the Schistosomatidae. The obvious absence of any mitochondrial lensing in T. ocellata, and probably all other species of the Digenea, may be correlated with the evolution of endoparasitism in the Trematoda.

The syndermatan phylogeny and the evolution of acanthocephalan endoparasitism as inferred from 18S rDNA sequences.

The phylogeny of the Syndermata (Rotifera: Monogononta, Bdelloidea, Seisonidea; Acanthocephala: Palaeacanthocephala, Eoacanthocephala, Archiacanthocephala) is key to understanding the evolution of acanthocephalan endoparasitism from free-living ancestors. In the present study, maximum likelihood, distance/neighbor-joining, and maximum parsimony analyses have been carried out based on 18S rDNA data of 22 species (four new sequences). The results suggest a monophyletic origin of the Eurotatoria (Monogononta+Bdelloidea). Seison appears as the acanthocephalan sistergroup. Palaeacanthocephala split into an "Echinorhynchus"-and a "Leptorhynchoides"-group, the latter sharing a monophyletic origin with the Eoacanthocephala and Archiacanthocephala. As inferred from the phylogeny obtained acanthocephalan endoparasitism evolved from a common ancestor of Seison and Acanthocephala that lived epizoically on an early mandibulate. Probably, an acanthocephalan stem species invaded the mandibulate host, thus establishing an endoparasitic lifestyle. Subsequently, vertebrates (or gnathostomes) became part of the parasite's life cycle. In the stem line of the Archiacanthocephala, a terrestrial life cycle has evolved, with an ancestor of the Tracheata (Insecta, Myriapoda) acting as intermediate host.

The position of the Arthropoda in the phylogenetic system.

Traditionally, Panarthropoda (Euarthropoda, Onychophora, Tardigrada) are regarded as being closely related to Annelida in a taxon Articulata, but this is not supported by molecular analyses. Comparisons of gene sequences suggest that all molting taxa (Panarthropoda, Nematoda, Nematomorpha, Priapulida, Kinorhyncha, Loricifera) are related in a monophyletic taxon Ecdysozoa. An examination of the characters supporting Articulata reveals that only segmentation with a teloblastic segment formation and the existence of segmental coelomic cavities with nephridia support the Articulata, whereas all other characters are modified or reduced in the panarthropod lineage. Another set of characters is presented that supports the monophyly of Ecdysozoa: molting under influence of ecdysteroid hormones, loss of locomotory cilia, trilayered cuticle and the formation of the epicuticle from the tips of epidermal microvilli. Comparative morphology suggests Gastrotricha as the sister group of Ecdysozoa with the synapomorphies: triradiate muscular sucking pharynx and terminal mouth opening. Thus there are morphological characters that support Articulata, but molecular as well as morphological data advocate Ecdysozoa. Comparison of both hypotheses should prompt further thorough and targeted investigations. J. Morphol. 238:263-285, 1998. © 1998 Wiley-Liss, Inc.