Molecular Systematics of Middle American Cichlid Fishes and the Evolution of Trophic-Types in ‘Cichlasoma(Amphilophus)’ and ‘C.(Thorichthys)’

The majority of Middle American cichlids are placed in the informal assemblage ‘Cichlasoma.’ The group is divided into eight sections which appear to be based primarily on trophic morphology. Although several members of ‘Cichlasoma’ have been used in ecomorphological, behavioral, and biogeographic studies, no phylogenetic hypotheses for the group exist. In an attempt to develop a better understanding of the phylogenetic relationships of ‘cichlasomine’ cichlids, we examined the evolution of the trophic specialization, substratum-sifting, in two sections, ‘Cichlasoma(Thorichthys)’ and ‘C.(Amphilophus),’ to determine whether the trait reflects common ancestry. We sequenced the complete mitochondrial cytochromebgene for 19 cichlids representing six sections of ‘Cichlasoma,’ and representatives of other Neotropical Cichlidae. Additional cichlid, and noncichlid outgroup sequences were included for a total of 22 taxa. The molecular phylogeny supports the recognition of the section ‘C.(Thoricthys)’ as a natural group, and we place those cichlids in the genusThorichthys.The phylogeny also depicts ‘C.(Amphilophus)’ as paraphyletic, with substratum-sifters and generalized predators forming separate nonsister clades. We recommend that the substratum-sifting clade of the section ‘C.(Amphilophus)’ be placed in the resurrected genusAstatheros.The generalized predator clade of ‘C.(Amphilophus)’ contains only two species, ‘C. (A.) citrinellum’ and ‘C. (A.) labiatum,’ which we place in the genusAmphilophus.The phylogenetic hypotheses generated indicate that the substratum-sifting generaThorichthysandAmphilophusdo not share a common ancestor. Reconstruction of the evolution of substratum-sifting is equivocal, requiring either the independent evolution of the trait on two separate occasions or its presence in a more inclusive clade and subsequent loss in nonsubstratum sifting species.     

Parental Investment and Division of Labor in the Midas Cichlid (Cichlasoma citrinellum)

The Midas cichlid (Cichlasoma citrinellum) is an aggressive, monogamous fish living in the Great Lakes of Nicaragua. Its breeding success rates are low due to intense competition for breeding sites and high levels of predation on the young. Male Midas cichlids devote a small portion of body weight to gonads and gametes compared with females. Males produce relatively small amounts of sperm perhaps because cichlid fertilization is very efficient and the male has a high certainty of paternity. While pair members invest equal amounts of time in parental care over the course of the breeding cycle, there is a clear division of labor. Males invest more in territorial protection than do females, whereas females provide more nurturance. Both parents are active over the course of the cycle but the male invests more intensely in the early stages of the cycle. About the time the eggs hatch, the burden of care shifts to the female and she continues to invest significantly more than the male over the remainder of the cycle. Females invest much more than do males when tissue investment and parental behavior are combined. Females also assume more of the burden of care as the brood matures. The male is not free to take advantage of this and leave his mate to initiate other broods because two parents are needed to defend the breeding site and brood. Monogamy with biparental care results.     

Comparison of gastropod mollusc (Apogastropoda: Hydrobiidae) habitats in two crater lakes in Nicaragua

The aquatic gastropod mollusc, Pyrgophorus coronatus, may perform an important role in the transmission of an emergent ocular pathology among fishes in Lake Apoyo, Nicaragua. This disease emerged after an introduction of tilapia (Oreochromis niloticus) and the subsequent loss of Chara sp. beds in the lake. We compared the mollusc population densities in three habitats (sandy/muddy substrates, rocks, and Chara vegetation) at varying depths (1.5, 10, 20, and 30 m) in two volcanic crater lakes in Nicaragua: Lake Apoyo and Lake Xiloa. where lower numbers of affected fishes were found and tilapia has not been introduced. Duplicate samples at 1.5 m depth were taken in each habitat monthly for a year, and triplicate samples for bathymetric analysis of snail populations were performed during August, 2005. Samples of fixed surface area were filtered in a 0.4 cm size screen and live snails were counted from each sample. The preferred snail habitat in both lakes, Chara beds, was vastly reduced in Lake Apoyo via consumption by introduced Nile tilapia (Oreochromis niloticus). Structureless sandy substrates (mean +/- standard error 3.1+/-1.3 ind/m2) had lower population densities than other habitats in Lake Xiloa (rocks 590.9+/-185.3 ind/m2; vegetation 3 686.5+/-698.2 ind/m2; ANOVA 1, p<0.01 in both cases) but this difference was attenuated in Lake Apoyo (sand 384.4+/-111.1 ind/m2; rocks 1 480.4+/-384.8 ind/m2: 0.0 1相似文献   

Molecular analysis of two genes between let-653 and let-56 in the unc 22(IV) region of Caenorhabditis elegans

Summary A previous study of genomic organization described the identification of nine potential coding regions in 150 kb of genomic DNA from the unc-22(IV) region of Caenorhabditis elegans. In this study, we focus on the genomic organization of a small interval of 0.1 map unit bordered on the right by unc-22 and on the left by the left-hand breakpoints of the deficiencies sDf9, sDf19 and sDf65. This small interval at present contains a single mutagenically defined locus, the essential gene let-56. The cosmid C11F2 has previously been used to rescue let-56. Therefore, at least some of C11F2 must reside in the interval. In this paper, we report the characterization of two coding elements that reside on C11F2. Analysis of nucleotide sequence data obtained from cDNAs and cosmid subclones revealed that one of the coding elements closely resembles aromatic amino acid decarboxylases from several species. The other of these coding elements was found to closely resemble a human growth factor activatable Na⁺/H⁺ antiporter. Pairs of oligonucleotide primers, predicted from both coding elements, have been used in PCR experiments to position these coding elements between the left breakpoint of sDf19 and the left breakpoint of sDf65, between the essential genes let-653 and let-56.     

Neoechinorhynchus (Neoechinorhynchus) chimalapasensis n. sp. (Acanthocephala: Neoechinorhynchidae) from the freshwater fish Awaous banana (Valenciennes) (Gobiidae) in Mexico

Neoechinorhynchus (Neoechinorhynchus) chimalapasensis n. sp. (Eoacanthocephala: Neoechinorhynchidae) is described from the intestine of Awaous banana (Valenciennes) (Pisces: Gobiidae) collected in the Río Negro, a tributary in the upper Río Coatzacoalcos basin, Santa María Chimalapa, Oaxaca State, Mexico. It is the third species of Neoechinorhynchus Stiles & Hassall, 1905 described from Mexican freshwater fishes, although 36 other species are known from freshwater fishes in the Americas. Like four other species of Neoechinorhynchus from freshwater fishes in North America and Mexico, N. (N.) limi Muzzall & Buckner, 1982, (N.) rutili (Müller, 1780) Stiles & Hassall, 1905, N. (N.) salmonis Ching, 1984 and N. (N.) roseus Salgado-Maldonado, 1978, males and females of the new species are less than 20 mm in length, lack conspicuous sexual dimorphism in size, have a small proboscis of about 0.1 mm in length with the largest hooks being the anteriormost, about 30–90 μm in length and of equal size, and have subequal lemnisci, larger than the proboscis receptacle but still relatively short and, in males, generally restricted to a position considerably anterior to the testes. The new species is closest to N. (N.) roseus, but it is distinguished from it by having: (1) a slightly larger cylindrical proboscis with almost parallel sides versus a globular proboscis with a rounded tip which is shorter and somewhat wider in N. (N.) roseus; (2) smaller but robust anterior proboscis hooks that do not reach the equatorial level or extend beyond the hooks of the middle circle as in N. (N.) roseus; and (3) the female gonopore situated ventrally subterminal, as opposed to being a significant distance anteriorly to the posterior extremity in N. (N.) roseus.     

Female Choice Predicts the Best Father in a Biparental Fish,the Midas Cichlid (Cichlasoma citrinellum)

The Midas cichlid is a monogamous, biparental species. It breeds in a highly competitive system where pairs have a low probability of raising fry to independence. Both parents must cooperate to retain the territory and protect the fry from predation. Previous experiments showed that females prefer large, aggressive and sexually experienced males as mates but males do not display any consistent preferences. Here I present the results of two experiments designed to see whether qualities preferred by females correlate with increased success in retaining territories and in providing parental care. Pairs with either large or aggressive males had an advantage in appropriating and holding a breeding territory; reproductive experience conferred no advantage in usurping a territory. Aggressive and reproductively experienced males had an advantage in defending the brood from predators of fry, but size had no effect. Thus, the qualities preferred by females confer advantages both in holding territories and in protecting fry. In contrast, males need not be selective because females, once in possession of a brood, defend it equally well regardless of size, aggressiveness, or reproductive experience. The system is one of mutually enforced monogamy based on female choice; females drive the system because they provide more investment than do males (combining gametes and time) and because this investment is a reliable resource to the male.     

Differential regulation of the two rice ferritin genes (OsFER1 and OsFER2)

Iron is essential to plants. However, when free and in excess, iron can catalyze the formation of oxygen free radicals. Ferritin, a protein capable of storing up to 4500 atoms of iron, can act as an iron buffer inside plant cells. Using a strategy based in amplicon size difference, we were able to analyze the expression profile of the two rice ferritin genes (OsFER1 and OsFER2). Both genes are expressed, although with different regulation and organ distribution. Exposure to copper, Paraquat, SNP and excess iron led to accumulation of ferritin mRNA, remarkably of OsFER2. The iron-induced expression was abolished by treatment with GSH, indicating that the induction observed is dependent of an oxidative step. OsFER2 mRNA levels in rice flag leaves and panicles at different reproductive stages were higher than OsFER1 mRNA levels. No ferritin mRNA was detected in rice seeds. However, imbibition under light led to ferritin expression, which was abolished when seeds were kept in the dark, suggesting a light-regulated induction. Ferritin mRNA accumulation was seen in the dark only when seeds were germinated in the presence of externally supplied iron. We suggest that the primary role of rice ferritins is related to defense against iron-mediated oxidative stress.     

Der Gesangsaufbau von Braunkehlchen(Saxicola rubetra) und Schwarzkehlchen(S. torquata) im Vergleich

Zusammenfassung Braunkehlchen und Schwarzkehlchen verfügen über ein großes individuelles Repertoire (über 100 Elementtypen), das sich in 12 gemeinsame Lautklassen gliedern läßt. In der Bevorzungung der einzelnen Klassen traten große individuelle Unterschiede auf. Das gesamte Repertoire beider Arten kann man in Strophenklassen einteilen, die nach Übereinstimmung der Anfangslaute oder ganzer Elementsequenzen definiert werden. Das Schwarzkehlchen singt meist mehrere Strophen der gleichen Klasse hintereinander, das Braunkehlchen wechselt die Strophenklasse nach jeder Strophe. Um den abwechslungsreichen Klangeindruck des Braunkehlchengesanges und den eher monotonen Eindruck des Schwarzkehlchengesanges näher zu bestimmen, wurde der Tonhöhenwechsel zwischen aufeinanderfolgenden Lauten quantitativ untersucht. Da die lineare Darstellung im Sonagrammbild nicht der akustischen Auflösung des menschlichen Gehörs entspricht, werden die Frequenzunterschiede in Quotienten umgerechnet und in Klassen eingeteilt. Die gebildeten Klassen sind zur Anschaulichkeit nach den in der Musik gebräuchlichen Intervallen benannt; sie stellen somit keinen reinen Melodieverlauf dar, sondern stehen für ganze Intervallbereiche, die benutzt werden. Beim Schwarzkehlchen finden sich insgesamt kleinere Intervalle als beim Braunkehlchen, welches sowohl größere Intervalle zwischen den Elementen bildet, als auch wesentlich mehr Elemente im unteren Frequenzbereich singt. Dadurch entsteht ein melodiöser Eindruck.

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Comparison of Whinchat's and Stonechat's songs(Saxicola rubetra, S. torquata)

Summary To study the organization and the species specific basic pattern of the whinchats' and stonechats' songs data from several birds in West Germany were compared to records made in different parts of Europe. Both species have a rather large repertoire, consisting of about 100 different utterances (see fig. 2). The repertoire can be classified in twelve common basic categories (see fig. 5). A high percentage of whistle-like structures occur in both species. However, there is a considerable variation in terms of the use of this categories in different individuals (see tab. 2). Phrases consisting of identical or similar sequences of elements are called song-type. Whinchats regularyly change the song-type from one phrase to another, whereas stonechats often repeat the same song-type in consecutive phrases (see fig. 4). Songs of whinchats sound melodious to human ears, compared to the more monotonous songs of the stonechats. To asses this quantitatively, the degrees between consecutive notes were studied: according to human auditory sensation a logarithmic rather than linear measurement was used. The quotients between the end of the preceeding and the beginning of the succeeding note were calculated (see fig. 7). The occurring quotients of frequency were classified; for reasons of clearness the resulting classes were named after the corresponding melodic intervals in music. In the stonechats' songs small melodic intervals in the range of the second degree mostly occur and larger melodic intervals are less frequent (see fig. 9). In the songs of whinchats no preferences for small melodic intervals appear and larger intervals (range of octave and larger) were used more frequently (see fig. 9). One of the fundamental differences between the two species is found in the arrangement patterns of similar vocal structures: whinchats sing within a larger frequency band (between 2,5 cps—8 cps) compared to the stonechats, which sing between 3 cps and 7 cps.

     

Teleomorph of Erysiphe necator var. necator on Vitis vinifera and Ampelopsis brevipedunculata var. heterophylla (Vitaceae) newly found in Japan

 The teleomorph of Erysiphe necator var. necator [≡Uncinula necator var. necator], hitherto unknown in Japan, was found on Vitis vinifera and Ampelopsis brevipedunculata var. heterophylla (Vitaceae) in Okayama, Japan. Morphological characteristics of the fungus are described and illustrated. Received: December 13, 2002 / Accepted: January 22, 2003 Correspondence to:Y. Nomura     

Kreuzung spanischer Haus-(Passer domesticus) und Weidensperlinge(Passer hispaniolensis) in Gefangenschaft

Summary A male bird of the F₁-generation of a successful hybridization experiment between House Sparrows(Passer domesticus) and Spanish Sparrows(Passer hispaniolensis) exhibited intermediate phenotypical characters between both parental species, being similar to a Nord-African flückigeri-type Sparrow.     

Speciation of two sympatric coastal fish species, Girella punctata and Girella leonina (Perciformes, Kyphosidae)

Girella punctata and Girella leonina are sympatric sister species showing extensive distributional overlap in shallow rocky reefs in the Pacific Ocean south of the Japanese Islands. Differences between the two species in external morphological characters, such as number of pored lateral line scales, colour of opercular flap and shape of caudal fin, are congruent with genetic divergence. Nucleotide identity between the two species in the 3.3 kbp region of partial mitochondrial DNA containing the D-loop region, in 12S and 16S ribosomal RNA (rRNA) and transfer RNA genes is 95%. To estimate divergence time, Bayesian analysis was conducted using a dataset comprising concatenated nucleotide sequences from the two rRNA genes of three girellid and nine other fish species. Using the Elopomorpha – Clupeocephala split (265 million years ago (mya)) as a calibration point, divergence between G. punctata and G. leonina is estimated as having occurred 6.0±1.4 mya. Speciation is suggested to have been caused by geographical isolation associated with formation of the Japanese Islands, which resulted in disjunction of Girella habitat.     

The distribution and abundance of Lernaeocera lusci (Copepoda) on hake (Merluccius merluccius) and bid (Trisopterus luscus) (Teleostei)

Distribution patterns, mean intensity and prevalence of Lernaeocera lusci (Copepoda, Pennellidae) in its 2 hosts Trisopterus luscus (Teleostei, Gadidae) and Merluccius merluccius (Teleostei, Merlucciidae) were examined, together with parasitic abundance and aggregation in relation to the size of the host. The mean parasite abundance and the variance to mean abundance ratio increased with host size, suggesting that the accumulation of this parasite had no noticeable impact on the structure of either host population. Merluccius merluccius being a newly colonized host in the Mediterranean, these results are discussed in relation to current ideas on the evolution of pathogenicity in heterospecific associations.     

Ecophysiological responses of salt cedar (Tamarix spp. L.) to the northern tamarisk beetle (Diorhabdacarinulata Desbrochers) in a controlled environment

The northern tamarisk beetle (Diorhabda carinulata Desbrochers) was released in several western states as a biocontrol agent to suppress Tamarix spp. L. which has invaded riparian ecosystems; however, effects of beetle herbivory on Tamarix physiology are largely undocumented and may have ecosystem ramifications. Herbivory by this insect produces discoloration of leaves and premature leaf drop in these ecosystems, yet the cause of premature leaf drop and the effects of this leaf drop are still unknown. Insect herbivory may change leaf photosynthesis and respiration and may affect a plant’s ability to regulate water loss and increase water stress. Premature leaf drop may affect plant tissue chemistry and belowground carbon allocation. We conducted a greenhouse experiment to understand how Tamarix responds physiologically to adult beetle and larvae herbivory and to determine the proximate cause of premature leaf drop. We hypothesized that plants experiencing beetle herbivory would have greater leaf and root respiration rates, greater photosynthesis, increased water stress, inefficient leaf nitrogen retranslocation, lower root biomass and lower total non-structural carbohydrates in roots. Insect herbivory reduced photosynthesis rates, minimally affected respiration rates, but significantly increased water loss during daytime and nighttime hours and this produced increased water stress. The proximate cause for premature leaf drop appears to be desiccation. Plants exposed to herbivory were inefficient in their retranslocation of nitrogen before premature leaf drop. Root biomass showed a decreasing trend in plants subjected to herbivory. Stress induced by herbivory may render these trees less competitive in future growing seasons.     

Environmental determinants of fish abundance in the littoral zone of gravel pit lakes

Hydrobiologia - The type and extent of habitats along the shoreline specify the distribution of fish in the littoral zone of lakes, but effects are likely species and size-specific and might be...     

Arthromyces and Blastosporella, two new genera of conidia-producing lyophylloid agarics (Agaricales, Basidiomycota) from the neotropics

Two new genera encompassing three new species of lyophylloid agarics that produce conidia on the basidiomata are described. Arthromyces is a genus comprised of two very different arthrospore-producing mushroom species found in the Greater Antilles and Central America. Blastosporella is a monotypic genus with spherical balls of blastospores covering the pileus surface with age and is known from Hispaniola and Colombia. A key to the species of Arthromyces is included.     

The chitinase gene (Bbchit1) from Beauveria bassiana enhances resistance to Cytospora chrysosperma in Populus tomentosa Carr.

The Chinese white poplar (Populus tomentosa Carr.) is susceptible to infection by plant diseases which severely affect its growth and substantially decrease its economic value. A chitinase gene (Bbchit1) from Beauveria bassiana was introduced into Chinese white poplar (Populus tomentosa Carr.) by Agrobacterium-mediated transformation. The T-DNA of plant transformation vector contained the β-glucuronidase reporter gene (GUS) under the control of CaMV 35S promoter and the neomycin phosphotransferase selection marker gene (NPTII) driven by the nos promoter. GUS activity was detected in most of the kanamycin-resistant plants tested. Stable integration of transgenes in the plant genome was confirmed using PCR. RT-PCR analysis showed that the Bbchit1 gene was transcribed in the transformed plants. When evaluated for resistance to poplar fungal pathogens with an in vitro assay, crude extracts from leaves and shoots of transgenic lines were inhibitory against the pathogenic fungus Cytospora chrysosperma (Pers.) Fr. Similarly, Bbchit1 overexpression enhanced disease resistance to C. chrysosperma in the transformed poplar plants, indicating that is gene is potentially useful to protect the trees against fungal diseases.