On endostyle ultrastructure in two new species of doliolid-like tunicates

The endostyle is a glandular and ciliated groove lining the pharyngeal floor of tunicates. This paper describes the histological structure of this organ in two new species of doliolid-like animals, Doliopsis bahamensis and Paradoliopsis harbisoni, and compares it with that of Doliolum nationalis. The results confirm the distinction between the Doliolida and the other Thaliacea. Received: 7 November 1996 / Accepted: 6 December 1996     

Allele-specific amplification for preimplantation genetic diagnosis (PGD) of spinal muscular atrophy

We have developed a new allele-specific amplification method for the preimplantation genetic diagnosis (PGD) of spinal muscular atrophy (SMA; Werdnig-Hoffmann disease) from a single cell. This method is based on the detection of the deletion of exon 7 of the telomeric copy of the survival motor neurone (SMN^t) gene. An oligonucleotide was designed to be specific to the SMN^t nucleotidic sequence with exonic mismatch G (for SMN^t)→A (for SMN^c) at its 3′ end. This test produces reliable PCR products in 95% of single lymphoblasts (85/88) tested as well as in 16/16 blastomeres from normal controls. Specificity analysis showed that we were able to detect homozygous deletion of the SMN^t gene in 99% of single lymphoblasts (103/104) from a SMA patient. No contamination was detected in 68 blanks tested. Multiple cell and DNA dilution analysis revealed that the test is accurate and specific up to 100 pg DNA and should thus also be suitable for PGD at the blastocyst stage. This rapid procedure requires a single round of fluorescent PCR and no restriction digestion, while previously described single cell methods include nested PCR followed by restriction enzyme digestion. Two PGD cycles for SMA using this procedure were performed in our centre. Copyright © 2001 John Wiley & Sons, Ltd.     

New kind of polarotaxis governed by degree of polarization: attraction of tabanid flies to differently polarizing host animals and water surfaces

Aquatic insects find their habitat from a remote distance by means of horizontal polarization of light reflected from the water surface. This kind of positive polarotaxis is governed by the horizontal direction of polarization (E-vector). Tabanid flies also detect water by this kind of polarotaxis. The host choice of blood-sucking female tabanids is partly governed by the linear polarization of light reflected from the host’s coat. Since the coat-reflected light is not always horizontally polarized, host finding by female tabanids may be different from the established horizontal E-vector polarotaxis. To reveal the optical cue of the former polarotaxis, we performed choice experiments in the field with tabanid flies using aerial and ground-based visual targets with different degrees and directions of polarization. We observed a new kind of polarotaxis being governed by the degree of polarization rather than the E-vector direction of reflected light. We show here that female and male tabanids use polarotaxis governed by the horizontal E-vector to find water, while polarotaxis based on the degree of polarization serves host finding by female tabanids. As a practical by-product of our studies, we explain the enigmatic attractiveness of shiny black spheres used in canopy traps to catch tabanids.     

Life history and production of <Emphasis Type="Italic">Corophium urdaibaiense</Emphasis> (Crustacea: Amphipoda) in the Urdaibai estuary (NE Spain)

The population of species Corophium urdaibaiense has been studied for a year in the Urdaibai estuary (NE Spain). The new species is characterised by its preference for muddy sand sediments (15% of mud) and the long body size (with a maximum length of 10.24 mm). The maximum abundance occurs in November (11,600 ind m⁻²); it almost disappears at the end of spring. The juveniles represent 79% of the population and the recruitment is concentrated within the October–December period. The breeding period begins in May, when the temperature is above 15°C, and it ceases in November, when the temperature is below 15°C. Bivoltinism is probable, taking into account the latitude (43°), temperature range (12–25°C) and breeding period (May and August–October), but the data are not sufficiently consistent to confirm the hypothesis. The production ranges from 2.93 to 5.85 g m⁻² year⁻¹, considering one and two generations per year, respectively. Some aspects concerning the food availability, predation and intraspecific competition could have an influence on the dynamics of the population and are discussed.     

Phototaxis and polarotaxis hand in hand: night dispersal flight of aquatic insects distracted synergistically by light intensity and reflection polarization

Based on an earlier observation in the field, we hypothesized that light intensity and horizontally polarized reflected light may strongly influence the flight behaviour of night-active aquatic insects. We assumed that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of these insects than they would have separately. We tested this hypothesis in a multiple-choice field experiment using horizontal test surfaces laid on the ground. We offered simultaneously the following visual stimuli for aerial aquatic insects: (1) lamplit matte black canvas inducing phototaxis alone, (2) unlit shiny black plastic sheet eliciting polarotaxis alone, (3) lamplit shiny black plastic sheet inducing simultaneously phototaxis and polarotaxis, and (4) unlit matte black canvas as a visually unattractive control. The unlit matte black canvas trapped only a negligible number (13) of water insects. The sum (16,432) of the total numbers of water beetles and bugs captured on the lamplit matte black canvas (7,922) and the unlit shiny black plastic sheet (8,510) was much smaller than the total catch (29,682) caught on the lamplit shiny black plastic sheet. This provides experimental evidence for the synergistic interaction of phototaxis (elicited by the unpolarized direct lamplight) and polarotaxis (induced by the strongly and horizontally polarized plastic-reflected light) in the investigated aquatic insects. Thus, horizontally polarizing artificial lamplit surfaces can function as an effective ecological trap due to this synergism of optical cues, especially in the urban environment.