Comparison of sister species identifies factors underpinning plastid compatibility in green sea slugs

The only animal cells known that can maintain functional plastids (kleptoplasts) in their cytosol occur in the digestive gland epithelia of sacoglossan slugs. Only a few species of the many hundred known can profit from kleptoplasty during starvation long-term, but why is not understood. The two sister taxa Elysia cornigera and Elysia timida sequester plastids from the same algal species, but with a very different outcome: while E. cornigera usually dies within the first two weeks when deprived of food, E. timida can survive for many months to come. Here we compare the responses of the two slugs to starvation, blocked photosynthesis and light stress. The two species respond differently, but in both starvation is the main denominator that alters global gene expression profiles. The kleptoplasts'' ability to fix CO₂ decreases at a similar rate in both slugs during starvation, but only E. cornigera individuals die in the presence of functional kleptoplasts, concomitant with the accumulation of reactive oxygen species (ROS) in the digestive tract. We show that profiting from the acquisition of robust plastids, and key to E. timida''s longer survival, is determined by an increased starvation tolerance that keeps ROS levels at bay.     

The systematics of Porphyra: character evolution in closely related species

Isozymes, vegetative and reproductive morphology, seasonality, vertical and geographic distributions and chromosomes were compared for six pairs of putative sibling species of Porphyra (P. abbottae/P. torta, P. fallax subsp. fallax/P. fallax subsp. conwayae, P. amplissima/P. cuneiformis, P. fucicola/P. leucostica, P. miniata/P. variegata, P. umbilicalis/P. umbilicalis) and among five species in a complex (P. brumalis, P. kurogii, P. linearis, P. pseudolinearis, and P. purpurea.) Geographic distribution and zymograms for certain proteins showed the greatest change between species pairs: only one pair of species had identical distributions, and most species pairs were disjunct; every species had a different allozyme for GOT-1, whereas all species had apparently identical proteins for phycoerythrin. Seasonality and habitat exhibited moderate differentiation: Northeast Pacific sibling species were characterized by a high intertidal winter species pairing with a mid intertidal spring species, whereas all but one of the other species pairs exhibited nearly identical vertical distributions and seasonalities. There were few changes in morphology: most species pairs had essentially identical morphologies and coloration and the same arrangement of reproductive cells. Chromosome numbers and karyotypes were identical for species pairs and in the species complex. These results provide evidence for different rates of evolution of different characters in the genus Porphyra.     

双向电泳法在家蚕蛋白质分离中的应用

家蚕Bombyxmori(L.)既是重要的经济昆虫,又是鳞翅目昆虫研究的典型模式生物。开展家蚕蛋白质组研究,将有助于阐明家蚕绢丝蛋白的分泌机理,也是研究鳞翅目昆虫及其他生物生命本质的需要。双向电泳是蛋白质分离的关键技术。为探讨适宜家蚕蛋白质组研究的双向电泳条件,以家蚕丝腺、丝腺内容物、蚕卵和血液为材料,在不同条件下进行双向电泳,并对分离的蛋白点进行质谱分析。结果表明:通过改进的蛋白质裂解液辅以超声破碎制备的蛋白质,双向电泳后能够得到较好的2-DE图,也能满足进行MALDI-TOFMS分析的需要。因此本研究方法适用于家蚕不同组织中蛋白质的提取和双向电泳。     

DNA reassociation kinetics of closely related species

The kinetics of reassociation of the DNA of three groups of closely related organisms were examined. The laboratory mouse was compared to an Asiatic mouse, whose chromosome number is the same but whose chromosome organization is different. Chinese hamster (2N=22) was compared to Syrian hamster (2N=44), and Haplopappus gracilis (2N=4) was compared to H. ravenit (2N=8). It was found that the most highly repeated DNA fractions of the three comparative sets of organisms differ in their reaction rates. However, these fractions of the related hamsters, haplopappi, and probably the mice, do not differ in the amount of DNA composing the fractions. The intermediately fast reassociating DNA and the unique DNA do not differ between members of related pairs of organisms. The implication of these results is that a short sequence of DNA may be highly copied in one organism, while in a related organism a longer DNA sequence is repeated a fewer number of times, and the total amount of repeated DNA may be the same in both related organisms.     

General vs. local differentiation between two closely related white oak species

The geographical distribution of species differentiation throughout the natural range of two sympatric, closely related species of oaks, Quercus petraea (Matt) Liebl. and Quercus robur L., was investigated. By sampling species in pairs in different European regions, from Spain to Poland and Romania, the differentiation between the two species could be subdivided into general and local differentiation. Nine sequence characterized amplified region (SCAR) markers corresponding to genomic regions which discriminate the two species were analysed using single-strand conformation polymorphism (SSCP) or classical electrophoresis (double-stranded DNA on agarose gel) on PCR products providing, respectively, codominant and dominant markers. Similar levels of gene diversity ( H _E) within the two species were observed, varying generally from 0.3 to 0.5 for dominant markers and from 0.5 to 0.86 for codominant markers. SSCP loci exhibited numerous alleles that were differently involved in species differentiation. The geographical distribution of species differentiation is heterogeneous between the regions, the north-east populations exhibiting higher differentiation than the others. For most loci, general differentiation was higher than local differentiation and was interpreted as the result of historical causes, selection pressures, and intra- and interspecific gene flow.     

The acceptability of mosses as food for generalist herbivores, slugs in the Arionidae

Observations in the held suggest that moss shoots are seldom freely consumed by either vertebrate or invertebrate herbivores, but damage to immature capsules by slugs is abundant. Palatability of the mosses Mnium hornum, Brachythecium rutabulum and Funaria hygrometrica to the generalist herbivores, Arion subfuscus and A. rufus was investigated by offering the slugs four stages in the moss life cycle; protonema, leafy shoot, immature capsule and mature capsule. The slugs showed a preference for immature capsules and protonemata in all moss species tested. Consumption of shoots of M. hornum and B. rutabulum was negligible even after seven days starvation, but some shoots of F. hygrometrica were eaten in every overnight trial performed. Shoot extracts on starch-wafer substrate appeared to be more acceptable than intact shoots suggesting that the cell wall provides the barrier to free consumption. The form and location of a possible feeding deterrent is discussed.     

Patterns of introduction of non-indigenous non-marine snails and slugs in the Hawaiian Islands

The native snails of the Hawaiian Islands are disappearing. One cause is predation by introduced carnivorous snails. Habitat destruction/modification is also important, facilitating the spread of other non-indigenous snails and slugs. Eighty-one species of snails and slugs are recorded as having been introduced. Thirty-three are established: 12 freshwater, 21 terrestrial. Two or three species arrived before western discovery of the islands (1778). During the nineteenth century about one species per decade, on average, was introduced. The rate rose to about four per decade during the twentieth century, with the exception of an especially large number introduced in the 1950s as putative biocontrol agents against the giant African snail, Achatina fulica. The geographical origins of these introductions reflect changing patterns of commerce and travel. Early arrivals were generally Pacific or Pacific rim species. Increasing trade and tourism with the USA, following its annexation of Hawaii, led to an increasing proportion of American species. More general facilitation of travel and commerce later in the twentieth century led to a significant number of European species being introduced. African species dominated the 1950s biological control introductions. The process continues and is just part of the homogenization of the unique faunas of tropical Pacific islands.     

The influence of azadirachtin on the feeding behaviour of cereal aphids and slugs

The probing behaviour of Rhopalosiphum padi (L.) and Sitobion avenae (F.) and the feeding behaviour of several slug species, (Deroceras reticulatum (Müller), Arion distinctus Mabille, Agriolimax caruanae Pollonera, Maximus sp.) were assessed on seedlings of winter barley (Hordeum marinum) treated with different concentrations of azadirachtin. Settling behaviour of both aphid species was strongly biased towards the untreated seedlings or those treated with low concentrations of azadirachtin. Concentrations of <500 ppm were effective with topical application and probing activity was reduced for at least 4 days after application. Systemic activity of azadirachtin against cereal aphids was also demonstrated. Feeding behaviour of the slug species, as seen by the amount of leaf eaten compared to the controls, was not affected by the presence of azadirachtin at those concentrations which deterred aphids from feeding. The relevance of these results to crop protection is discussed.     

Terrestrial slugs (Gastropoda, Pulmonata) in the NATURA 2000 areas of Cyprus island

Terrestrial slugs of the Island of Cyprus were recently studied in the framework of a study of the whole terrestrial malacofauna of the island. The present work was carried out in the Natura 2000 conservation areas of the island in 155 sampling sites over three years (2004-2007). Museum collections as well as literature references were included. In total six species are present in the Natura 2000 areas of the island, belonging to three families: Limacidae, Agriolimacidae and Milacidae. One of the species, Milax riedeli, is a new record for the island. The distribution of the species across the island and in the surrounding areas is discussed.     

Respiration rates of two closely related species of carabids in Australia

Abstract The respiration rates of Notonomus gravis (Chaudoir) and N.philippi (Newman) (Coleoptera: Carabidae) were measured at temperatures between 10°C and 45°C. Mature males of both species had higher respiration rates than mature females. There was no difference between the rates of teneral male and female beetles at 30°C. The difference in respiration rates between the sexes is attributed to the maternal behaviour, and decreased surface activity, of mature females.     

Homology of Balbiani Ring DNA in two closely related Chironomus species

Cytogenetic analysis indicates that Balbiani Ring 2 (BR 2) in the two sibling species Chironomus tentans and Chironomus pallidivittatus arises from identifically banded segments in the salivary gland polytene chromosomes, although chromosomal rearrangements have occurred. In situ hybridization of BR 2 RNA to the polytene chromosomes of each individual species, as well as their F1 hybrids, reveals that the repetitious BR 2 DNA in the two species has, within the limits of the technique, retained identity of nucleotide sequences and degree of repetition. The DNA of the naturally expressed BR 1 and BR 3 in both species and that ot the galactose induced BR 6 in C. pallidivittatus did not hybridize with BR 2 RNA, indicating that these BR's are different from BR 2 with regard to sequence content.     

Characterization of microsatellite loci in two closely related Lissotriton newt species

We have developed eight di- and tetranucleotide Lissotriton microsatellite markers. Eight loci were polymorphic in the palmate newt Lissotriton helveticus and six were polymorphic in the smooth newt L. vulgaris. Polymorphism detected in 33 and 37 individuals per species ranged from 3 to 15 alleles. These markers are suitable for the investigation of population structure, genetic variation and taxonomic identification in the two focal species, and may also be of use in other Lissotriton–Triturus species.     

The separation of Liriomyza huidobrensis (Diptera: Agromyzidae) from related indigenous and non-indigenous species encountered in the United Kingdom using cellulose acetate electrophoresis

The non-indigenous pest leaf miner Liriomyza huidobrensis and its close relatives L. bryoniae and L. strigata belong to a natural group. These species can be separated from one another by means of protein electrophoresis on a cellulose acetate membrane. The protocol for this diagnostic assay involves staining for two enzymes, glucose-6-phosphate dehydrogenase (G6PDH) and leucine-glycine peptidase (PEP). Other leaf miner species that might also be found under glass, Chromatomyia syngenesiae, C. horticola and the non-indigenous L. trifolii and L. sativae , are clearly distinguishable from the L. huidobrensis group of species by this assay. The effect of parasitism on L. huidobrensis by Dacnusa sibirica was investigated and shown unlikely to cause misidentification of the leaf miner host. Results obtained from practical use of the assay to identify unknown specimens from ports and nurseries are compared with those obtained from flies kept in laboratory culture and used during development of the assay. No new variation was found for G6PDH. New PEP variation was found for both L. huidobrensis and L. bryoniae but this did not affect the integrity of the assay. A biochemical key to these agromyzid leaf miners is presented.     

Isozyme criteria in the testing of phyletic relationships between species of Gobius and related eastern Atlantic-Mediterranean genera (Teleostei: Gobüdae)

Horizontal starch gel electrophoresis was employed to investigate allozyme variation at 19 isozyme loci, in nine closely-related Atlantic-Mediterranean gobiid fish species, to assess genetic relationships, and to compare this with a phyletic hypothesis based on morphological apo-morphies. The species examined were Gobius niger, G. auratus, G. cruentatus, G. paganellus, Mauligobius maderensis, Zosterisessor ophiocephalus, Thorogobius ephippiatus, Padogobius martensii and P. nigricans . Various phenetic and cladistic analyses were performed on isozyme and morphological data. The phenetic and cladistic results from morphological data, and the cladistic results from isozyme data, were largely comparable, with P. martensü and P. nigricans forming a sister group to all the other taxa, species of Cobius forming a crown group within the latter, and stem lines formed by Mauligobius, Zosterisessor and Thorogobius , respectively. The isozymic estimates of genetic distance differed from these chiefly in the relative positions of Zosterisessor and G. auratus , which appear less similar to other species of Gohius. G. auratus shows many alleles which are unique within the genus Gobius ; possible explanations for this are put forward. The position of nigricans as congeneric with Padogobius martensü is confirmed by both phenetic and cladistic analyses of isozyme data.     

Aquatic versus terrestrial locomotion: comparative performance of two ecologically contrasting species of European natricine snakes

One indicator of ecological differences between species is differential locomotory performance in different media. In this study, we compare locomotory speed of two species of natricine snakes on land and in water at a range of temperatures in the laboratory. As expected, both species moved more quickly at higher temperatures and both swam faster than they moved on land. However, the difference between aquatic and terrestrial speed was much greater for the aquatic species, Natrix maura , than for the semi-aquatic Natrix natrix . Furthermore, although N. maura was significantly faster than N. natrix in water, the opposite was true on land. In fact, N. maura was reluctant to move very far on land at all and would not complete a 2 m terrestrial course. Although we found no evidence of a negative correlation between the aquatic and terrestrial speeds of individual N. natrix , this interspecific comparison is consistent with the notion of a tradeoff between performance abilities on land and in water.     

Expression of esterases during ontogenesis of the flour beetle Tribolium castaneum (tenebrionidae; coleoptera)

Two electrophoretically fast-migrating, nonspecific esterases were detected in two strains of the flour beetle Tribolium castaneum and designated F (fast) and S (slow) according to their relative migration distances. Both isozymes are associated with the alimentary canal and display ontogenetic changes. Their activity is very low in the egg stage, increases in the larva, and declines dramatically in the pharate pupa and pupa. The overall activity in the pupal stage is low, yet increases gradually throughout this period. In the adult, the activity of the esterases rises sharply. The larval and adult F and S isozymes were found to hydrolyze - and -naphthylacetate and -naphthylpropionate with almost equal capacity. -Naphthyl laurate was cleaved by the F enzyme of both larvae and adults. The F and S were insensitive to inhibitors of arylesterases and cholinesterases and were markedly inhibited by the organophosphate diisopropylphosphorofluoridate (DFP) and could be classified as carboxylesterases. Differential sensitivities of larval and adult esterases to urea and heat treatment as well as to DFP may indicate the expression of different genes during metamorphosis.     

Consequences of competition on the reproduction and mortality of three species of terrestrial slugs

The interaction of three species of terrestrial slugs was studied in six field cages containing monocultures and 2-way combinations. A. columbianus and A. ater were non-aggressive species and L. maximus was highly aggressive during the summer. All three species were similar in body design and resource utilization. Reproduction (egg size, eggs/batch, number of batches, wet-weight productivity) and mortality were monitored through the 1977 season. L. maximus drastically reduced reproductive success of the non-aggressive slugs and increased their mortality. There were also significant interactions between the non-aggressive species. Compared to other invertebrates, the life history characteristics of A. columbianus are strongly K-selected and probably evolved through intraspecific exploitative competition in predictable, stable forest habitats. A. ater is best classified as a refuging r-selected species adapted to less predictable, unstable field environments. L. maximus appears to be α-selected and its overall design is suited to density-dependent regulation in fields.     

Competitive relationships existing between two closely related species of Argemone living in the same area

Summary The present paper deals with the reaction of two closely related species of Argemone L., A. mexicana L. and A. ochroleuca Sweet, to its own density in pure stands and a comparison of this with its reaction to the density of the associated species. The results of the pure culture studies indicate that whilst each of the two species reacted to an increase in its own density by higher mortality and a striking reduction in vegetative and reproductive growth, A. mexicana was more susceptible to intraspecific effect than A. ochroleuca. On the other hand, mixed culture studies indicated that A. mexicana was more successful when in competition with A. ochroleuca. Further, that species which was in a majority in the mixture suffered most compared to the minority species. Such a density dependent differential behaviour in pure stands and frequency dependent differential behaviour in mixed cultures along with the reversal in superiority of the two species in pure and mixed cultures was considered to be responsible for the cohabitation of the two species and their relative population sizes in nature.     

The use of electrophoresis of the water-soluble (sarcoplasmic) proteins of fish muscle to differentiate the closely related species of hake (Merluccius sp.).

1. Electrophoretic separation patterns of water-soluble proteins of five species of hake, Merluccius merluccius; M. australis; M. productus; M. bilinearis and M. angustimanus, have been examined. 2. The patterns were reproducible within each species and distinguishable from one another. 3. The frequency distribution of numbers of vertebrae and of gillrakers were obtained for the same fish. 4. Only the electrophoretic patterns gave an unequivocal identification of the species.