摘要:

Sexing individuals in a population is important in many ecological and life‐history studies. Since many bird species are monomorphic, non‐invasive tools are necessary for sex determination. In this study we utilized flow cytometry to sex individuals in a moorhen population of northern Italy. By improving previous laboratory protocols, we were able to obtain clear and repeatable measures of DNA content from field blood samples. The per cent difference in nuclear content between male and female moorhens was among the highest values reported for birds. We also utilized a discriminant analysis of seven morphological measures to investigate whether birds can be sexed on the basis of biometry. Tarsus and foot lengths were the most influential variables in gender discrimination. However, only 13 females and 10 males (77%) were correctly sexed, while six females and two males were wrongly assigned. When juvenile moorhens were excluded the discriminant analysis correctly sexed 90% of the birds. Since morphometric comparisons with English moorhen populations showed that discriminant bio‐metrical values are geographically different, and thus not useful as universal sexing tools, we recommend the use of the cytometry technique for sex determination.

ISSN:1125-0003    

DOI:10.1080/11250009909356229

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The idea that tetracycline may have antifilarial properties was first proposed in 1960. Data were subsequently published on the effects of tetracycline on the development and reproduction ofBrugia pahangiin both the mosquito and mammalian hosts. These studies were apparently ignored until recently. In 1998, it was suggested that the antifilarial properties of tetracycline may derive from the presence of the bacterial endosymbiontWolbachiain fi‐larial worms. In view of this renewed interest, we would like to highlight an old study on the prophylactic activity of tetracycline against three filarial species. Although this work was performed at the begining of the seventies, and presented at a congress in 1973, it has never been published. This study showed that tetracycline had a prophylactic effect against infection of the mammalian host (the gerbilMeriones unguiculatus) withB. pahangiandLito‐mosoides sigmodontis. On the other hand, no significant prophylactic effect of the drug was observed againstAcanthocheilonema viteaein the same host. The new data on the distribution and phy‐logeny ofWolbachiaendosymbionts in filarial nematodes, showing thatA. viteaeis uninfected and thatB. pahangiandL. sigmodontisare infected, suggest that the activity of tetracycline on the latter two species is related to the presence ofWolbachia.

ISSN:1125-0003    

DOI:10.1080/11250009909356230

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The authors present the first TEM observations on the head organ, a multicellular structure housing solid inclusions discovered in 1996 by Rota & Erséus in the proximity of the brain inGrania.The cellular components, their spatial organisation and their relationships to the inclusions are described. The ultrastructural data confirm the sensory nature of the organ and corroborate its interpretation as a georeceptor. There are four receptor cells, each giving off a whorl of 50 cilia with (8+1)×2 microtubular pattern and no rootlets. The solid inclusions are opaque to the electrons and have the appearance of amorphous aggregations. They contact the sensory cilia within separate extracellular compartments lined by extensions of glial cells, whose perikarya are located on the lateral aspects of the organ. The head organ is unprecedented in annelids and its structure is probably unique among invertebrates. Cells with similarly modified cilia were known in the central nervous system of enchytraeids and also occur inGraniain the region between the head organ and the cerebral ganglion proper (here called “rostral territory"). The derivation of the head organ from this type of ciliated cells is suggested. Original light microscopy observations on the central nervous system of enchytraeids are also included.

ISSN:1125-0003    

DOI:10.1080/11250009909356231

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Meiotic metaphases II from archival slides were studied in male house mice caught near Rome in a hybrid zone between a population with nine monomorphic centric fusions‐ (CD: 2n = 22) and one with the standard karyotype (2n = 40). The segregation pattern was investigated: it was found that chromosomes of the same form tended to cosegregate.

ISSN:1125-0003    

DOI:10.1080/11250009909356232

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The African grass rat,Arvicanthis sp., from Benin shows sex‐chromosome polymorphism for the presence in the karyotype of three X‐chromosome forms: subtelocentric (Xst), submetacentric (Xsm), and metacentric (Xm). Here we report statistically significant differences of diploid genome size (g.s.) among individuals, from 6.22 ± 0.06 pg to 6.80 ± 0.10 pg, depending on the X‐chromosome form. The evaluation of the total and X‐chromosome heterochromatin content alone (Xst: 2.16 ± 0.22%; Xsm: 5.02 ± 0.22%; Xm: 6.54 ± 0.28%), supports this suggestion. DNA base‐pair preferential staining revealed that heterochromatin of both autosome and sex chromosomes is AT‐rich. Digestion of genomic DNA with sixteen restriction enzymes produced DNA bands representing the repetitive fraction of the genome. When these were used as probes for fluorescencein situhybridization (FISH), two hybridization patterns were found: a) FISH positive signals localized in the pericentromeric areas of every chromosome of the complement and b) chromosome specific signals co‐localizing with both the pericentromeric regions of every chromosome and the heterochromatic regions of Xsm and Xm, but not on the Xst chromosome. FISH performed with a (TTAGGG)n probe revealed a telomere‐only pattern.

ISSN:1125-0003    

DOI:10.1080/11250009909356233

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The cytogenetic profile of two Nearctic and one Paleartic treehole mosquitoes belonging to theCoelodiazesisgroup,Anopheles barberi, Anopheles judithae, andAnopheles plumbeus, was outlined by means of standard banding techniques andin situhybridization. Results indicate that, during the evolution of this species group, several rearrangements have occurred including inversions, translocations, and loss of heterochromatic material and rRNA genes copy number. The karyotype ofA. barberi ismarkedly different from the other two species, in spite of morphological similarities with the other North American species,A. judithae. This latter species has retained part of a more ancestral karyotype still shared with the PalearticA. plumbeus. Chromosomal repat‐terning inA. barberihas probably facilitated isolation and divergence of the two Nearctic species, impairing introgressive hybridization withA. judithae.

ISSN:1125-0003    

DOI:10.1080/11250009909356234

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

White muscardine is a common disease of the silkwormBombyx moricaused by an insect mycopathogenBeauveria bassiana. The present study revealed the germination, penetration, and invasion ofB. bassianaon the larval integument ofB. mori. The NB18strain ofB. moriwas surface inoculated with concentrations of 1×106conidia/ml. Each conidium, germinated approximately 8 h after inoculation, forming an appressorium within 24 h and the hypha entered the cuticle by forming a clear circular hole. The hyphae reached the haemocoel, where they grew and multiplied extensively, forming a mycelial complex, causing death of the host larva in about five‐six days. This occurred with minimal breakdown of the internal tissues. Death of the host was followed by ramification of the fungus through the mesodermal and epidermal tissues, leading to larval mummification about six days post‐inoculation. Extensive fungal outgrowths followed, mostly through the intersegmental regions of the larva, and formed aerial hyphae, which gave rise to branched conidiophores forming a confluent white fungal mat over the entire larval body in six‐seven days. The life‐cycle of the fungus onB. mori wascompleted in seven‐eight days.

ISSN:1125-0003    

DOI:10.1080/11250009909356235

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Feeding habits in a population ofSalamandra lanzaiwere studied at an Alpine meadow at 2020 m a.s.l. in the Cottian Alps, NW Italy. Adult specimens underwent stomach flushing was applied to in June and September 1992, and in July 1993.Salamandra lanzaiproved to be an opportunistic predator, feeding on invertebrates within a broad range of categories and sizes. Ground‐dwelling insects (especially carabids) constituted the main part of the diet. AlthoughS. lanzaiis commonly believed to be a completely terrestrial species, some individuals were observed to feed on aquatic Trichoptera larvae. The utilization of prey taxa by number of specimens consumed and volume consumed varied seasonally. Mean ingested volume per salamander averaged 173–76 ± 449.31 mm3, i.e., about 1.39% of the average salamander mass (12.56 ± 3.43 g; range 6.0–22.5 g). Prey mass and predator mass were positively correlated in males, which most likely are more active than females. The prey mass to predator mass ratio was not significantly correlated with log predator mass, neither for males nor for females.

ISSN:1125-0003    

DOI:10.1080/11250009909356236

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Quantitative samples of sediment for the study of the meiofau‐na were collected monthly beweenMar1996 andFeb1997 from a 7‐m‐deep site in the Meloria Shoals, Livorno Italy. In the Tuscan Shoals, 16 species of tardigrades were found belonging to the families Stygarctidae, Halechiniscidae, and Batillipedidae.Megastygarctides orbiculatusandActinarctus doryphorusare reported for the first time in the Mediterranean Sea, and a re‐description ofBatillipes similisis proposed. Global density of the Tardigrada population fluctuated between 8 ind./10 cm2in May 1996 and 285 ind./10 cm2in January 1997. The lowest value of the Shannon‐Wiener biodiversity index (H’ = 1.09) was found in September 1996, whereas the highest score (H’ = 2.46) was obtained inMar1996. Pielou's evenness index (J) fluctuated between 0.40 and 0.88, values attained in January 1997 andMar1996, respectively. The study confirms the notion that the organogenic detritus of the Shoals represents a very favourable environment for meiofaunal organisms in general, and Tardigrada in particular.

ISSN:1125-0003    

DOI:10.1080/11250009909356237

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The tadpole of the endemic Corsican painted frogDiscoglossus montalentiiLanza, Nascetti, Capula & Bullini, 1984 is described on the basis of two samples obtained in captivity from in‐traspecific breeding. Tadpoles of this species possess a ventral spiraculum, dorsal eyes and nares, and a relatively long tail which is rounded at the end. The oral disk is completely bordered by a single series of marginal papillae and, in advanced larval stages (i.e., from stage 35), the two anterior and the three posterior ker‐atodont rows usually comprise three or four subrows. In Corsica, whereD. montalentiiandD. sardusare often found in syntopy, the identification of their tadpoles appears relatively easy only if the developmental stage is taken into account: the tadpole ofD. montalentiialways possesses a complete series of marginal papillae, a higher total number of keratodont subrows, a larger body size, and a differently shaped tail. These characters permit identification of CorsicanDiscoglossustadpoles. The results have important implications for both in ecological and management strategies necessary to the preservation of the endemic Corsican painted frog.

ISSN:1125-0003    

DOI:10.1080/11250009909356238

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor