摘要:

Three examples of recent findings illustrating the intricacy of inter‐relationships between mechanisms responsible for gas exchange and transport and salt and water balance are described: 1) Divalent cations raise the oxygen affinity of crustacean hemocyanins (Hcs). At low salinity the respiratory consequences of a loss of Ca++from the blood of an estuarine crab are offset by a concomitant and compensatory rise in blood pH and a shift in intrinsic oxygen binding properties, possibly brought about by a change in composition of the constituent subunits of the He molecule. The net result is a return to the original oxygen affinity during normoxia but not hypoxia, when anaerobic metabolism results in acidosis due to the accumulation of acidic end products. The acidosis requires compensation by allosteric actions of L‐lactate, the chief end product, and Ca++, a product of acid dissolution of the exoskeleton. The combined actions of these two effectors restores oxygen affinity to the original level. 2) Oxygen carrying capacity of He‐containing bloods of the arthropods are low because of the low blood pressures that accompany the replacement of a fluid with a solid skeleton. Hydrostatic pressures in the sinuses surrounding the excretory organ, the site of extracellular volume regulation, now barely exceed the colloid osmotic pressures of the extracellular oxygen carrier. Natural selection has promoted the formation of high molecular weight He polymers having 6–48 active sites/‐osmotically active particle. Nonetheless the excess of hydrostatic over colloid osmotic pressure, which permits primary urine formation and net fluid output from a hyperosmotic animal, is very small. Colloid osmotic pressure, and thus oxygen carrying capacity, could be no higher and the degree of polymerization could be no smaller without impairing fluid balance with the medium. 3) Divalent cations lower the oxygen affinity of gastropod He. Within the ecological range the loss of Ca++and Mg++from the blood of an osmoconforming conch is not great enough to influence oxygen affinity but it does lower cooperativity and thus the oxygenation of the blood at the gill. Oxygen uptake goes down at low salinity and the animal does not survive mesohaline waters.

ISSN:0373-4137    

DOI:10.1080/11250008609355474

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0373-4137    

DOI:10.1080/11250008609355473

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The historical aspects of the renin‐angiotensin system (RAS) were summarized by Peach (1977) as well as the sequence of biochemical events revealing that renin itself is an enzyme that catalyses the formation of a decapeptide (Angiotensin I), which is further modified to form an octapeptide (Ang. II) and other biologically active (Ang. III) and inactive products. The knowledge on the phylogeny of the physiological actions of the RAS is scanty. Several approaches may be considered particularly illuminating comparative anatomy and ontogeny of the RAS as well its biochemistry and adaptive evolution of related endocrine systems are reviewed. The localization of renin producing cells and the components of the juxtaglomerular apparatus are different among the vertebrates, the functional significance of these anatomical structures are well known in mammals, however in non‐mammalian vertebrates definitive observation are lacking and renin release control is not clearly understood. The biochemistry of renins and angiotensins well known in mammals has been investigated in other vertebrates but not extensively. Comparative studies as well as studies on the ontogeny may add clarification to the physiology of the RAS. Angiotensin is in mammals a potent dipsogenic factor and there are only a few reports of dipsogenic actions of angiotensin in non‐mammalian vertebrates. Although there may be a long phylogenetic history for such actions, the problem is not far from the control of glomerular filtration rate in marine and fresh water teleosts. Eventually the analysis of the functional evolution of the RAS may extend the knowledge on the basic mechanisms of the system also in mammals and in human beings.

ISSN:0373-4137    

DOI:10.1080/11250008609355475

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The meiotic and mitotic chromosomes of the five recognized species ofSolatopupaPilsbry 1917 are described and compared. Meiosis is of a standard type. The karyotype ofS. psarolena(Bourguignat) with 2n=56 chromosomes and a conspicuously large metacentric pair is compared with those ofS.pallida(Rossmässler) andS.simonettae(Giusti) having 2n=58 chromosomes, and with that ofS.similis(Bruguière) which has 2n=60. A Robertsonian fusion could be linked with the splitting ofS.psarolenafrom a common ancestor with the congeneric species. The diploid value 2n=58 is most probably the ancestral one.

ISSN:0373-4137    

DOI:10.1080/11250008609355476

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The chromosome complement ofChamelea gallinais n = 19 and 2n = 38. In both males and females meiosis shows chiasmata. Karyotype mainly contains submetacentric and metacentric chromosomes. No heterotypic or supernumerary chromosomes result from the analysis of meiotic and of mitotic chromosomes.

ISSN:0373-4137    

DOI:10.1080/11250008609355477

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The variations of cell area and number inDrosophilawing compartments following heat‐shock at different developmental stages have been studied in two unrelated stocks. In spite of different sensitivity to heat‐shock treatment, similar trends of response are exhibited by the two strains. At developmental stages when mitotic activity occurs, a general decrease of compartment areas is observed after treatment. The effect on the wing area appears to be mainly determined by the decrease of cell number, however cell area seems to compensate for cell number variations in the posterior compartment. The posterior compartment appears to respond earlier, than the anterior, possibly due to the different growth rate of the two compartments. We suggest that the genes for wing area determine the growth strategy of the wing compartments through pleiotropic effects on the genes for cell area and the genes for cell number.

ISSN:0373-4137    

DOI:10.1080/11250008609355478

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A femaleAlopecosa albofasciata(Brullé, 1832) with two well developed epigynes placed side by side was collected near Trento, Northern Italy. This case appears to be different from the three other occurrences of this abnormality hitherto known, since the two epigynes do not result from presumable duplication of abdominal segments. This abnormal duplication is likely to be due either to secondary subdivision of the uterus or to lack of fusion of the two oviducts; the development of the two epigynes could be induced by the two underlying gonoducts.

ISSN:0373-4137    

DOI:10.1080/11250008609355479

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The fat cells of females ofDaphnia obtusahave a well developed rough endoplasmic reticulum, free ribosomes and small Golgi complexes. When the ovaries contain growing parthenogenetic oocytes, the fat cells show few scattered glycogen granules, whereas they show abundant glycogen when the ovaries contain one vitellogenic amphigonic oocyte. The latter case could be explained by the fact that the fat cells synthesize little vitellogenin since the yolk of amphigonic oocytes is mostly endogenous.

ISSN:0373-4137    

DOI:10.1080/11250008609355480

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The study refers to the composition of the zoobenthos in submerged macrophytes in Lake Nemi, subject to an organic pollution caused mainly by domestic wastes. The fauna, sampled in five stations in the period 1981/82, was composed of 18 zoological groups, including 60 taxa. Cladocera, represented almost exclusively by the microfiltratorChydorus sphaericus, constituted by far the dominant group in all stations. Oligochaeta, comprising 14 taxa, was the most diversified group and their maximum percentages ware found in the Genzano village discharge. Other detritivorous groups, such as Chironomidae and Ostracoda were also abundant, while Hydroida and some Cyclopidae were the most common predator organisms. Owing to the eutrophication process, we can observe: a) abundance of species having wide ecological valence; b) low diversification and reduced abundances in most of the zoological groups; c) prevalence of a detritus food chain.

ISSN:0373-4137    

DOI:10.1080/11250008609355481

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The mauthner apparatus is described for the first time in a selachian fish,Squalus acanthias. Its size and relative growth have been measured. The function and the evolution of this structure are discussed.

ISSN:0373-4137    

DOI:10.1080/11250008609355482

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor