Search publications of the members of the Royal Belgian institute of natural Sciences
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Food-induced body pigmentation questions the taxonomic value of colour in the self-fertilizing slug Carinarion spp.
- Body pigmentation is a popular taxonomic marker in slugs to discriminate closely related species. However, the genetic background of body pigmentation is known only for a few species, while in many others body pigmentation is influenced by age, food and/or climate. In this study, we investigated the effects of different food items on body pigmentation expression in two selfing pulmonate gastropods, Arion (Carinarion) silvaticus and Arion (Carinarion) fasciatus. Both species mainly differ in the distribution of yellow-orange granules on the body, which in A. fasciatus are concentrated in lateral bands, and in A. silvaticus are evenly scattered. Animals were raised individually under the same conditions, while they laid eggs as a consequence of selfing. This F1 generation was afterwards divided into two groups, which were fed with different food items. A diet of carrot, lettuce or paper had no effect on the distribution of the yellow-orange granules in A. silvaticus, but provoked a loss of the yellow-orange lateral bands in A. fasciatus so that externally these F1 specimens became similar to A. silvaticus. In both species, a diet of nettle resulted in a strong yellow-orange pigmentation, which often formed yellow-orange lateral bands. These results indicate that food can probably influence the 'species-specific' body pigmentation in Carinarion, and thus question the reliability of colour traits to distinguish A. silvaticus and A. fasciatus.
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Centipede communities in the forests of flanders
- During a year-round pitfall sampling campaign in 56 Flemish forest stands, a total number of 21 centipede species were caught. Community analyses on the basis of the species composition revealed that three distinct clusters of forests could be recognised which are separated geographically. The Campine Region with a lot of pine forests, which is characterised by its sandy soils, contained the lowest diversity of centipedes and only Lithobius forficatus and L. calcaratus were common. Sandy Flanders with a lot of oak forests contained more species including Cryptops hortensis, the most characteristic species of this region. The Loamy Region contained a lot of oak and beech forests and Cryptops parisi and Lithobius dentatus were especially characteristic for this region.
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Effects of metal contamination on the activity and diversity of carabid beetles in an ancient Pb-Zn mining area at Plombières (Belgium)
- Carabid beetles were monthly sampled with pitfall traps in the ancient Pb-Zn mining area of Plombières during one year. Based on the total soil concentrations of lead, zinc, cadmium and copper, it was expected that zinc would probably have the most adverse effects on the populations. Activity and species richness of carabid beetles were, however, not significantly correlated with total zinc concentration nor with the water soluble and the calciumchloride extractable concentration. In fact, despite the high soil concentrations, carabid beetles did not seem to be affected in the study area. The apparent lack of effects at the high observed zinc concentrations is probably caused by the low bioavailability of zinc to the beetles in the litter of the study sites which was also reflected in the low observed water soluble zinc concentrations.
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Echiuropus bekmanae n.sp. (Crustacea, Amphipoda, Carinogammaridae) from Lake Baikal, retrieved by a new deep-water sampling device
- Lake Baikal is well known for its exceptional diversity of gammarid amphipods, with 95\% of endemics from its 270 described species representing about 20\% of the world freshwater fauna. Echiuropus (Asprogammarus) bekmanae n.sp. was collected by an 'autonomous trap system', a sampling device thoroughly described here. Although not necrophagous itself, this new species was found in two baited trap samples (at 750 and more than 1600 m) from 1995 and 1996. This rather small (13 mm) deep water species is the eighth species of the subgenus Asprogammarus, of the Baikal endemic genus Echiuropus. Diagnoses of the subgenus and the closer species are given.
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Dolichopodid biodiveristy and site quality assessment of reed marshes and grasslands in Belgium (Diptera: Dolichopodidae)
- The conservation value of grassland and reed marsh habitats in Belgium was determined on the basis of dolichopodid communities (Diptera: Dolichopodidae). Four grassland and one reed marsh sites within the 'Bourgoyen-Ossemeersen' Nature Reserve (B.O.) (Ghent) were sampled with white water traps from March 1993 until March 1994. Subsequently, these soil faunas were compared with those of reed marsh habitats in 'Het Meetjeslandse Krekengebied' (M.K.) sampled in 1990. Comparisons of species communities were carried out by means of multivariate analysis techniques. The DCA and CCA on the B.O. sites produced a clear separation between the grassland and the reed marsh communities. Light intensity and soil humidity were among the most important factors determining species distributions. The comparison between the B.O. and M.K. communities revealed that sampling sites were clustered according to their geographical location rather than to habitat type. Overall species richness and diversity was not significantly different between grasslands and reed marshes. However, conservation quality estimates of the sites using the Site Conservation Quality Index (SCQI) indicated that reed marshes comprise a considerably larger number of rare and Red Data Book species. Moreover, besides typical reed marsh-inhabiting species, reed marshes also house species with other ecological affinities sometimes in rather high abundance. As a result, reed marshes are considered highly valuable for the survival of several wetland dolichopodid species.
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First evidence of possible outcrossing in the terrestrial slug Arion intermedius (Gastropoda: Pulmonata)
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Evolutionary convergence of body shape and trophic morphology in cichlids from Lake Tanganyika
- A recent phylogenetic analysis of mitochondrial DNA sequences from eretmodine cichlids from Lake Tanganyika indicated independent origins of strikingly similar trophic specializations, such as dentition characters. Because genetic lineages with similar trophic morphologies were not monophyletic, but instead were grouped with lineages with different trophic phenotypes, raises the question of whether trophic morphology covaries with additional morphological characters. Here, we quantified morphological variation in body shape and trophically associated traits among eretmodine cichlids using linear measurements, meristic counts and landmark-based geometric morphometrics. A canonical variates analysis (CVA) delineated groups consistent with dentition characters. Multivariate regression and partial least squares analyses indicated that body shape was significantly associated with trophic morphology. When the phylogenetic relationships among taxa were taken into account using comparative methods, the covariation of body shape and trophic morphology persisted, indicating that phylogenetic relationships were not wholly responsible for the observed pattern. We hypothesize that trophic ecology may be a key factor promoting morphological differentiation, and postulate that similar body shape and feeding structures have evolved multiple times in independent lineages, enabling taxa to invade similar adaptive zones.
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Lake level fluctuations synchronize genetic divergences of cichlid fishes in African Lakes
- Water level fluctuations are important modulators of speciation processes in tropical lakes, in that they temporarily form or break down barriers to gene flow among adjacent populations and/or incipient species. Time estimates of the most recent major lowstands of the three African Great Lakes are thus crucial to infer the relative timescales of explosive speciation events in cichlid species flocks. Our approach combines geological evidence with genetic divergence data of cichlid fishes from the three Great East African Lakes derived from the fastest-evolving mtDNA segment. Thereby, we show for each of the three lakes that individuals sampled from several populations which are currently isolated by long geographic distances and/or deep water form clusters of equally closely related haplotypes. The distribution of identical or equally closely related haplotypes in a lake basin allows delineation of the extent of lake level fluctuations. Our data suggest that the same climatic phenomenon synchronized the onset of genetic divergence of lineages in all three species flocks, such that their most recent evolutionary history seems to be linked to the same external modulators of adaptive radiation. A calibration of the molecular clock of the control region was elaborated by gauging the age of the Lake Malawi species flock through the divergence among the utaka-cichlid and the mbuna-cichlid lineages to minimally 570,000 years and maximally 1 Myr. This suggests that the low-lake-level period which established the observed patterns of genetic relatedness dates back less than 57,000 years, probably even to 17,000-12,400 years ago, when Lake Victoria dried up and Lakes Malawi and Tanganyika were also low. A rapid rise of all three lakes about 11,000 years ago established the large-scale population subdivisions observed today. Over that period of time, a multitude of species originated in Lakes Malawi and Victoria with an impressive degree of morphological and ecological differentiation, whereas the Tanganyikan taxa that were exposed to the same habitat changes hardly diverged ecologically and morphologically. Our findings also show that patterns of genetic divergences of stenotopic organisms provide valuable feedback on geological and sedimentological time estimates for lake level changes.
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Microsatellite data reveals weak population substructuring in Copadichromis sp. `virginalis kajose', a demersal cichlid from Lake Malawi, Africa
- Small but significant differences were found in allele frequencies among five populations (overall F ST estimate (θ)=0.004, P=0.006; overall R ST estimate (RHO)=0.019, P<0.00001) of the demersal cichlid Copadichromis sp. `virginalis kajose', collected from five locations in Lake Malawi. Pairwise F ST estimates revealed significant differences between the most southerly population (Cape Maclear), and the three most northerly populations (Mbamba Bay, Metangula and Chilola). Pairwise R ST estimates also revealed significant differences between some populations, but no geographical pattern was discernible. There was no evidence of isolation by distance using either the shortest straight-line distance between samples, or the distance around the shoreline following a 50 m depth contour. F ST, estimates were considerably lower than found in previous studies on the mbuna (rock-dwelling species), but higher than those found in a study of three pelagic cichlid species from Lake Malawi. Substructuring in C. sp. `virginalis kajose' appears to be on a similar scale to the Atlantic cod. © 2001 The Fisheries Society of the British Isles.
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Morphological variation within and between four closely related phyllotreta species: P. dilatata, P. flexuosa, P. ochripes and P. tetrastigma (Coleoptera: Chrysomelidae)
- Phyllotreta dilatata Thomson. 1866. P. flexuosa (Illiger, 1794) P. ochripes (Curtis, 1837) and P. tetrastigma (Comolli, 1837) are four closely related, morphologically similar flea beetle species which are usually distinguished according to elytral colour pattern and also show morphological differences in the genitalia. Here both uni- and multivariate analyses are used to study intra-and interspecific morphological variation for the four species. All species seem to differ in overall morphology and the results also support the idea of regarding P. tetrastigma and P. flexuosa as two different systematic entities.
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On the Cyprideis species flock (Crustacea, Ostracoda) in Lake Tanganyika, with the description of four new species
- Four new species, belonging to three genera, of ostracods from Lake Tanganyika are described: Mesocyprideis nitida sp.nov., Romecytheridea belone sp.nov., R. plegma sp. nov. and Cyprideis loricata sp. nov. The Cyprideis species flock of Lake Tanganyika now consists of 17 formally described species (16 endemic) in 6 genera (4 endemic). The geographical and ecological distribution of the four species is briefly discussed and some supplementary remarks on the radiation of the Cyprideis species flock in Lake Tanganyika are offered.
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Molluscan diversity in tidal marshes along the Scheldt estuary (The Netherlands, Belgium)
- The mollusc fauna of 64 sites in 31 tidal marshes was surveyed along a salinity gradient from freshwater to marine conditions in the river Scheldt (Belgium-The Netherlands). A total of 10 649 specimens involving 31 taxa were identified. Salinity turned out to be a major factor in mollusc assemblages in the Scheldt estuary, but other factors can not be excluded. In the marine part five species were common, compared to the brackish part where only Assiminea grayana was abundant. In the freshwater zone species richness was highest (24). There was a significant correlation between flooding frequency and species richness in the tidal freshwater marsh 'Durmemonding'. Finally, the survey confirmed the distribution of the amphibious hygromiid snail Pseudotrichia rubiginosa, a species which in Belgium only occurs in the marshes of the tidal freshwater part of the Scheldt and its tributaries.
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Ostracods and fore-reef sedimentology of the Frasnian-Famennian boundary beds in Kielce (Holy Cross Mountains, Poland)
- Four major microfacies have been recognized in the Psie Górki section and the bioclastic content indicates an open marine environment in the photic zone close to an algal shole. Sedimentological studies point to a regressive episode starting close to the Frasnian-Famennian boundary. The regressive microfacies pattern is revealed by the presence of semi-restricted algal microbreccias that compose all of the lower part of the Famennian. The regression was accompanied by meteoric water invasion as the sea level fell. Seventy-six ostracod species are recorded. The ostracod assemblage, dominated by podocopids, belongs to the Eifelian ecotype and is indicative of a well-oxygenated marine environment below fair-weather wave base in the Frasnian part of the section, and of shallower environments in the base of the Famennian. No ostracod assemblage characteristic of hypoxic or semi-restricted water conditions has been recorded. The rate of extinction of ostracod species (70\%) close to the Frasnian-Famennian boundary is comparable with that known on the same level in several other sections investigated in the world. Five new ostracod species are proposed by J.-G. Casier and F. Lethiers: Selebratina vellicata, Samarella? minuta, Bairdiocypris ventrorecta, Acratia pentagona, and "Bairdia" psiegorkiensis.
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Evaluation of a high-resolution time-of-flight mass spectrometer for the gas chromatographic determination of selected environmental contaminants
- A benchtop high-resolution time-of-flight mass spectrometer (TOF MS) was evaluated for the determination of key organic microcontaminants. The major advantage of the TOF MS proved to be the high mass resolution of about 0.002 Da (10 ppm). Consequently, the detectability of polar pesticides, polynuclear aromatic hydrocarbons and polychlorinated biphenyls is excellent, and detection limits are in the order of 1-4 pg injected mass. Best mass spectral resolution was obtained for medium-scale peaks. It is a disadvantage that the calibration range is rather limited, viz. to about two orders of magnitude. The high mass spectral resolution was especially useful to improve the selectivity and sensitivity when analyzing target compounds in complex samples and to prevent false-positive identifications. © 2002 Elsevier Science B.V. All rights reserved.
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Isolation and characterization of microsatellite loci in Galápagos caterpillar hunters (Coleoptera, Carabidae, Calosoma)
- Five microsatellite loci were isolated from the Galápagos caterpillar hunter Calosoma granatense. Polymorphism ranges from four to 14 alleles, and observed and expected heterozygosities range from 0.138 to 0.889 and 0.197-0.902, respectively. Cross-amplification of the developed primers was successful in the related species C. leleuporum.
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Some gastronomic aspects of bird species in still life paintings of Frans Snyders (Antwerp, 1579-1657)
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Post-mortem findings and causes of death of harbour porpoises (Phocoena phocoena) stranded from 1990 to 2000 along the coastlines of Belgium and Northern France
- Between the years 1990 and 2000, an attempt was made to determine the causes of death of 55 harbour porpoises stranded along the Belgian and northern French coasts. From 1990 to 1996, only five carcasses were collected as against seven in 1997, eight in 1998, 27 in 1999 and eight in 2000. The sex ratio was normal and most of the animals were juvenile. The most common findings were emaciation, severe parasitosis and pneumonia. A few cases of fishing net entanglement were observed. The main microscopical lesions were acute pneumonia, massive lung oedema, enteritis, hepatitis and gastritis. Encephalitis was observed in six cases. No evidence of morbillivirus infection was detected. Pneumonia was associated with bacteria or parasites, or both. The causes of death and the lesions were similar to those previously reported in other countries bordering the North Sea. The cause of the increased numbers of carcasses in 1999 was unclear but did not include viral epizootics or net entanglement. A temporary increase in the porpoise population in the southern North Sea may have been responsible. © 2002 Elsevier Science Ltd. All rights reserved.
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Multivariate morphometrics of soft body parts in terrestrial slugs: Comparison between two datasets, error assessment and taxonomic implications
- Ten flexible characters for two collections of a pulmonate land slug that differed in their method of preservation (ethanol or freezer/ethanol), were measured four times - twice with calipers and twice with a stage micrometer - by two different people. Repeated measurements were used to estimate the measurement error (ME) associated with the ten characters. ME ranged from 2\% to 90\% and differed significantly between the characters. Characters with low mean values and a high flexibility showed the largest ME. With the stage micrometer, one measurer obtained significantly higher ME, but both measurers obtained the same ME with calipers. There was no detectable effect of preservation method on the size and shape of characters, yet, results differed when characters were measured with either calipers or a stage micrometer. One measurer obtained significantly larger mean values for three characters with calipers. Additionally, presumed species differences between three Carinarian species (Arion fasciatus, A. silvaticus and A circumscriptus; subgenus Carinarian Hesse 1926) were tested using principal component analysis and canonical discriminant analysis. Despite possible measurer biases and high ME, the different datasets yielded highly similar results, indicating that biometrical data of soft, flexible structures may yield valuable and reliable data which can be examined statistically. Our results indicate that A. fasciatus is larger than the other two species, but it is hard to distinguish from both of the other species when size is not considered. Arion silvaticus and A. circumscriptus can be separated only when colour characters are used. © 2002 The Linnean Society of London.
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Mouthpart deformities and nucleolus activity in field-collected Chironomus riparius larvae
- Chironomid mouthpart deformities and aberrations of their polytenic chromosomes are sublethal responses to toxic stress. These endpoints have been used in several cases as bioindications for sediment pollution. In the present study we aimed to establish whether there was an association between mouthpart deformities and nucleolus activity in the polytenic chromosomes. Such information could be useful to gain insight into the mechanisms involved in the occurrence of mouthpart deformities and their consequences on the larvae. Third-instar larvae of Chironomus riparius were collected at a site downstream of a sewage treatment plant mostly contaminated by pesticides. Larvae were then raised in the laboratory in aquaria containing sediment and water from the study location. During a 16-day period, larvae ready to molt to the fourth instar were reared individually. Within a few hours of their molt, the larvae were preserved. The presence of mouthpart deformities (menturn, mandibles, and pecten epipharyngis) and the percentage of active nucleoli were assessed. Those larvae presenting menturn deformities had a significantly higher incidence of active nucleoli in their polytenic chromosomes than nondeformed larvae. Because a high number of active nucleoli generally indicates increased rRNA synthesis, deformed larvae seemed to exhibit a higher protein synthesis than normal individuals. The synthesis of additional proteins may increase deformed larva tolerance to toxicants.
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Isoelectric focusing as a tool to evaluate carabid beetles as predatory agents of the pest slug Arion lusitanicus
- Isoelectric focusing was investigated to detect esterases of the pest slug Arion lusitanicus in the crop contents of predatory carabid beetles. The method is exceptionally well suited for field studies, as it is fast, cheap, easy to apply, and almost species-specific. The identification of A. lusitanicus was enabled by four characteristic, stable esterase electromorphs. The profile clearly differed from the band patterns of the digestive enzymes of the carabid beetles, from esterases of other potential prey species and even from the enzymes of early developmental stages of the slug. To test the heaviest stained isoenzyme for its decay under controlled conditions, three carabid species were fed on a fixed amount of slug hepatopancreas. In Carabus cancellatus and Pterostichus melanarius the enzyme lost 35\% of its activity after 16 h, fitting a logarithmic curve, whereas in Carabus granulatus the same decay status was already reached after 8 h following a linear regression. Both, the similarities and differences between beetle species might be due to their mode of extra- versus intraintestinal digestion and the amount of hepatopancreas fed. The temperature during digestion was also influential, as the regression slopes of esterase activity between the two temperature regimes tested in C. granulatus were significantly different. The volume of crop contents decreased during digestion in both Carabus species, corresponding to the decline in esterase. In contrast, the crop volume of P. melanarius reached its maximum almost 4 h after ingestion. This was interpreted as an effect of its mode of ingestion and time-elapsed enzyme production. © 2002 Elsevier Science Ltd. All rights reserved.
