The incidence of the parasitic disease trichomoniasis and its treatment in reintroduced and wild Pink Pigeons Columba mayeri

The recovery programme for the endangered Pink Pigeon Columba mayeri Prévost, 1843 of Mauritius has involved intensive management to promote rapid population growth. As the Pink Pigeon population has increased in size and distribution, disease problems have emerged that have affected wild and reintroduced birds. Trichomoniasis first appeared in the remnant wild population in 1992, and became established in a reintroduced subpopulation on the offshore island of Ile aux Aigrettes. We aimed to control the disease by treating individuals and, on Ile aux Aigrettes, by routinely treating the population with medicated drinking water. On Ile aux Aigrettes, 49% of squabs were clinically diseased and only 27% of all squabs survived without treatment. Treatment of squabs that were not clinically diseased improved survival from 36 to 82%, suggesting that subclinical infections also affected survival. Subclinical infections were demonstrated by microscopy in 22% of Pink Pigeons and 17% of exotic doves on Ile aux Aigrettes. Clinical disease was observed in 4.5% of adults and 3.1% of juveniles, but more juveniles than adults died from the disease. It is likely that Trichomoniasis and other diseases will continue to affect the Pink Pigeon's recovery and the species may require long-term management to counteract the effects of disease and other limiting factors.     

Studies of Long-Range Density Effects on the Proliferation of 3T3 and RLCW Cells in Recirculated Medium

Swiss mouse 3T3 cells and rat liver-derived RLCW cells were grown in monolayers and perfused with culture medium. A flow-rate dependent increase in the growth rate was observed both by ³H-thymidine uptake and by a rise in cell numbers. The characteristics of the response were dependent on the recirculating volume and on whether serum was present in the culture medium. In RLC cultures perfused with serum-supplemented medium the growth promoting effect decreased with increasing density of the cells. In the absence of serum, recirculation of NCTC medium had no effect on RLCs but increased growth was observed in recirculated MEM. In 3T3 cultures, a linear response was observed over a limited density range in the presence of 10% serum-supplemented medium indicating that substances present in the serum substantially modify the behaviour of the monolayer to perfusion. In serum-free medium the effect of perfusion on 3T3 cultures was confined to a small density range and was consistent with the more rapid removal of a diffusible inhibitor from the pericellular environment by recirculating the medium. Treatment of the perfusing medium with immobilised proteinases (trypsin, chymotrypsin, protease) did not alter the response except in the presence of putrescine.     

Piecing together an integrative taxonomic puzzle: microsatellite,wing shape and aedeagus length analyses of Bactrocera dorsalis s.l. (Diptera: Tephritidae) find no evidence of multiple lineages in a proposed contact zone along the Thai/Malay Peninsula

Bactrocera dorsalis (Hendel) and B. papayae Drew & Hancock represent a closely related sibling species pair for which the biological species limits are unclear; i.e. it is uncertain if they are truely two biological species, or one biological species which has been incorrectly split taxonomically. The geographical ranges of the two taxa are thought to abut or overlap on or around the Isthmus of Kra, a recognised biogeographic barrier located on the narrowest portion of the Thai Peninsula. We collected fresh material of B. dorsalis s.l. (i.e. B. dorsalis s.s.+ B. papayae) in a north–south transect down the Thai Peninsula, from areas regarded as being exclusively B. dorsalis s.s., across the Kra Isthmus, and into regions regarded as exclusively B. papayae. We carried out microsatellite analyses and took measurements of male genitalia and wing shape, both used previously to separate the taxa. No significant population structuring was found in the microsatellite analysis, consistent with one, predominantly panmictic population. Both morphological datasets showed consistent, clinal variation along the transect, without disjunction. No evidence supported historical vicariance driven by the Isthmus of Kra, and no dataset supported the current taxonomy of two species. Rather, within and across the area of range overlap or abutment between the two species, only continuous morphological and genetic variation was recorded. Recognition that morphological traits previously used to separate these taxa are continuous, and that there is no genetic evidence for population segregation in the region of suspected species overlap, is consistent with a growing body of literature that reports no evidence of biological differentiation between these taxa.     

RELATIONSHIPS BETWEEN SHELL SHAPE, WATER RESERVES, SURVIVAL AND GROWTH OF HIGHSHORE LITTORINIDS UNDER EXPERIMENTAL CONDITIONS IN NEW SOUTH WALES, AUSTRALIA

The shell morphologies of the highshore littorinids, Littorinaunifasciata Gray and Nodilittorina pyramidalis (Quoy & Gaimard)have previously been shown to vary at a variety of spatial scales,including among replicate sites at the same height, from heightto height and from shore to shore. In this study, the relationshipsbetween morphology of the shell, the reserves of water heldwithin the shell, the size of the foot and survival on differentshores and rates of growth in different habitats were examinedfor L. unifasciata and, to a lesser extent, N. pyramidalis.Reserves of water were not consistently related to size or shapeof the shell, but did increase as relative weight of shell increased.This may be due to the relatively smaller body providing moreinternal volume for extra-corporeal water. Water reserves andthe amount of free water held in the shell were also not relatedto loss of water or survival during extended periods of emersion.Although the shape of the shell on sheltered and exposed shoreswas correlated with size of the foot, with the snails on anexposed shore having larger apertures and feet than those ona sheltered shore, transplant experiments did not show differentialmortality between morphs from the different shores. All translocatedand transplanted snails disappeared from the exposed shore ata greater rate than from the sheltered shore, but this was probablydue to the snails dispersing out of the experimental areas ratherthan due to mortality. Therefore, many of the large-scale modelsthat have previously been used to describe patterns of shellshape in intertidal gastropods do not appear to be importantin these highshore littorinids. Finally, field experiments ongrowth of juvenile L. unifasciata indicated that rate of growth,largely governed by opportunity to feed rather than type andquantity of food, is the most likely explanation for the small-and large-scale patterns of shell shape that have been previouslydescribed in this species. (Received 22 October 1996; accepted 19 February 1997)     

A field study of the pattern of local spread of ryegrass mosaic virus in mown grassland

In a field experiment at Hurley, small areas of old ryegrass sward, known to be infected with ryegrass mosaic virus (RMV) were partially surrounded by newly-sown Italian ryegrass. The experiment was harvested by mowing on five occasions. Samples of Italian ryegrass taken when it was 11 months old showed a very marked increase in the levels of RMV close to the areas of old sward. Thus, 84% of the Italian ryegrass plants bordering the old sward to the north contained RMV, compared with 63% of plants only 2.7 m away. The corresponding values to the south were 68% and 39%. The much higher values encountered to the north are presumed to be caused by the movement of the mite vector of RMV (Abacarus hystrix) in relation to the prevailing wind. Two different mowers were used, a rotary mower and a reciprocating knife mower. We could demonstrate no increase in the level of RMV as a result of mowing from the infected sward and on to the new sowing and could demonstrate no difference in the infection levels as a result of using the different mowers. We conclude that in mown swards migration by the mite is responsible for all or nearly all of very local spread of RMV.     

EXPECTATIONS AND STABILITY OF PREFERENCE CHOICE

When identical milk samples are presented, only 30% of participants respond with a “no preference” rating. Stability of the “no preference” rating was studied under a variety of conditions, having consumer panelists rate both identical and different pairs of milk samples with varying fat content. The proportion of participants choosing the “no preference” option, when the samples in the pair were identical, was largely consistent despite manipulation of pretest conditions and changes in test questions and answer formats. However, when the milk preference test was preceded by a same/different test, and those responding “same” were assumed to have no preference, the percent of “no preference” was two to three times larger for identical test samples (60–69%). Thus by branching the question, the “false preference” choice for identical milks was lowered. Among those responding “different” to identical milks, the false‐alarm rate increased to 91%, suggesting that perception of (spurious or momentary) differences is driving at least part of the preference choice.     

SOURCES OF ERROR AND THE NO-PREFERENCE OPTION IN DAIRY PRODUCT TESTING

When products are physically identical, consumers will choose a no‐preference option in a paired preference test only about 30% of the time, giving a nonintuitive result. We evaluated the no‐preference false alarm rate in dairy products and the potential sources of error in panelist behavior, including discrimination problems and poor repeatability of judgments. Paired preference tests were conducted with milk (2% versus nonfat or skim), with cottage cheese (4% versus nonfat) and with identical samples. Triangle, dual standard and same/different discrimination tests were also conducted. The no‐preference option was chosen by about 30% of the consumers when samples were identical, and less frequently when samples were different. Discrimination performance, although statistically significant, was poorer than expected with about 30% discriminators (d′ of 1.7) in most tests. Even in the dual standard tests on milk (visually obvious and with references present), performance was only 88% correct (76% discriminators). Repeatability in preference tests was also poorer than expected, with only 56% choosing the same preference option for different samples on repeat trials although the group preferences were stable. Same/different tests indicated that over 50% of the consumers called identical samples different, although this fell short of explaining the 70% average false alarm rate in preferences. Even with apparently discriminable consumer products, accurate discrimination of the samples and repeatability of preferences should not be assumed. Random responding may contribute to error variance and produce nonsensical results such as the expression of choice between identical samples.