摘要:

The influence of egg size and composition on the size, quality and survival of lapwing chicks was examined on two farmland study sites in the Midland Valley of Scotland. Eggs comprised 33.1% yolk, 61.3% albumen and 5.6% shell. Whereas the yolk and shell proportions decreased with increasing egg size, the albumen proportion increased. Most variation in egg size was attributable to differences between females but was also influenced by clutch number (eggs in replacement clutches on the rough grazing, but not the arable, site were smaller), clutch size (eggs were smaller in smaller clutches), maternal body condition (females in good condition produced larger eggs) and habitat (since females on the arable site fed more successfully, they were in better condition and laid larger eggs). Chick size, weight and survival were all influenced by egg size. The incubation period varied between 21 and 28 days (mean = 25.2) and was shorter in clutches laid later in the season.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03747.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Baseline haematological data were obtained through routine analyses of blood samples from 31 wild black rhinoceroses captured in the Mana Pools National Park, Zimbabwe. Additional tests showed that the haemoglobin of this population is unstable; this observation helps explain the attacks of acute intravascular haemolysis documented in captive animals.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03748.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Female coypusMyocastor coypusin captivity produce more litters than expected by chance following days when they are undisturbed and less after they are disturbed. The observed distribution can be explained using simulations which assume that females can delay parturition for up to three days, depending on the level of disturbance on a previous day. The advantage of delay for wild coypus may be that parturient females can delay parturition if detected by a predator and move to a safer location. The main cost of delay is an increase in the average proportion of young that die in the last few days of pregnancy and in the days following parturition. These costs and benefits may be similar to those involved in the evolution of gestation periods.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03749.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Representatives of all seven stages in the metamorphosis of the parasitic lampreyGeotria australisand the nonparasitic lamprey Lampetra planeri have been used to describe the way in which the heart and associated blood vessels are modified or lost during metamorphosis from the larval (ammocoete) to adult condition. Attention is focused on discussing the possible functional significance of these alterations and on resolving major anomalies in the literature regarding the adult circulation. The metamorphic changes to the heart and associated blood vessels do not commence until external signs of transformation are apparent and, despite the different modes of adult life of the two species, they subsequently undergo a similar pattern of modification and loss. While the left duct of Cuvier has disappeared by the end of Stage 5, the right duct remains and its walls increase in thickness throughout metamorphosis. The small left dorsal hepatic vein, and also often the right dorsal hepatic vein which in ammocoetes enter the left and right ducts of Cuvier, respectively, are lost during metamorphosis. The median ventral hepatic and prominent inferior jugular veins, which both pass into the ventral region of the sinus venosus at the same level, remain in the same position as in the ammocoete. By Stage 4, the larval hepatic portal vein, which in the ammocoete entered the posterior dorsal tip of the liver, has undergone extensive degeneration and the new adult hepatic portal vein passes into the mid‐dorsal region of the liver. The pericardium develops during metamorphosis through a forward and upward growth of connective tissue on the anterior face of the liver and from connective tissue on the ventrolateral, dorsolateral and dorsal inner surfaces of the body wall. The development of cartilage can be detected in parts of this structure as early as Stage 3. The loss of certain blood vessels, the development of a pericardium and the alterations in the position and structure of the chambers of the heart and associated blood vessels which occur during metamorphosis, are all interpreted as adaptations for accelerating blood flow and increasing the pumping efficiency of the heart. These features would be of advantage to adult lampreys, which are more active than ammocoete

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03750.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Radio‐tagged hedgehogs were studied on an area of traditionally managed farmland to obtain information about distances travelled and range areas used per night in this habitat. Data from five animals were obtained on 62 hedgehog/nights. Twelve of the data sets were eliminated owing to their incompleteness; observations of three animals (totalling 45 hedgehog/nights of acceptable data) were critically examined to establish basic procedures for future comparative studies. The concept of ‘home range’ is discussed in relation to the duration of study pe

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03751.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A first‐time account is given of the parenchymal subdivisions and related duct system of the pancreas inDidermocerus, DicerosandCeratotherium.In each of these rhinoceros forms a small, superficial portion only of the caput pancreatis is drained by a Santorini duct opening directly into the duodenum. The remainder of the pancreatic parenchyma is drained principally by a transverse and an ascending duct, from whose union arises a short Wirsung duct which enters the duodenum through an intermediary Vaterian ampulla situated within a prominent papilla duoden

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03752.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The vascularization of the choroid plexus of the lateral ventricle of the turtle (Pseudemys scripta elegans) has been studied by means of vascular corrosion casts and transmission electron microscopy (TEM). A single arterial supply via the choroidal artery and a two‐fold venous drainage was found. By its form the plexus was subdivided into two parts: the body, and numerous villi projecting out of the body. The body consists of large convoluted arteries and veins which are covered by a network of vessels always greater than 15 μm in diameter. The villi are composed of a head consisting of vessels with a diameter of 16–50 μm and a stalk represented by one arteriole and one or two veins, which unite at the base of the stalk. An arteriovenous shunt occurs occasionally at the base of the stalk. By their angioarchitecture, six types of villi can be discerned: simple, club‐shaped, flat, wrinkled, glomus‐like and basket‐like villi. Garland vessels were present around arteries only. In ultrathin sections the vessels of the head of a villus possess a thin endothelium with tentacle‐like flaps which protrude into the lumen and many pinocytotic vesicles. These vessels were surrounded by a very fragmentary basement membrane and a dense layer of collagen fibrils.It is suggested that the different areas in the plexus, i.e. the various villi and the body, represent areas with different physiolog

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03753.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A small geographically isolated population of the Barbary macaque inhabits a high‐altitude fir forest habitat (Abies pinsapo) in the Ghomaran region of the Rif mountains of northern Morocco. The climate of this region is Mediterranean, but the altitude (1600–2100 m) causes winters to be cold (as low as ‐8.0 d̀C) with snow occurring from November to May (snowfall as deep as 1.5 m). The primary winter feeding adaptation is the ability to ingest high quantities of fir foliage; in spring, the macaques took a high diversity of leafy food items from all vegetation layers; in summer, the macaques foraged terrestrially for a high diversity of food items including seeds, small fruits, bulbous geophytes, and animal foods (including tadpoles from small streams); in autumn, the macaques returned to arboreal foraging, primarily feeding on oak acorns (Quercus ilex), fir seeds and yew fruit (Taxus baccata). The macaques were capable of ingesting 100 of 195 (51%) of all identified plant species in the region, although during the four‐month winter, the macaques only averaged 12.5 common food items. A comparison of the study area with the prime habitat of the Barbary macaque‐the high‐altitude cedar forests of the Moroccan Moyen Atlas‐indicates that climate and vegetation physiognomy are highly similar in both regions. Correspondingly, there is a high degree of similarity in macaque diet in both regions in terms of feeding behaviour by season, food diversity and specific feeding techniques. In the Ghomara, the winter feeding adaptation of fir foliage eating parallels that of the Barbary macaque in cedar forest (winter foraging for cedar foliage). This enables the Barbary macaque to exploit the Ghomaran fir forest habitat during the cold, snowy winters much the same as it does cedar forest habitat throughout a major portion of its geog

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03754.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Octopus dofleini(Wulker) drills holes in mollusc shells, enabling it to introduce venom. Boreholes in the bivalveSaxidomus giganteus(Deshayes) were generally irregular. Thick shells were more likely to have incomplete boreholes, and the diameter of completed boreholes was larger than in thin shells. A comparison of boreholes to fractured and artificially drilled surfaces suggests thatO. dofleiniemploys chemical dissolution of the shell during drilling.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03755.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Cichlid fishes of the great East African lakes have been the subject of many evolutionary studies over the last decades. Over 100 haplochromine species have been described from Lake Victoria alone, many of which are endemic to that lake. Two recent studies, using enzyme electrophoresis, could not detect any genetic differentiation among the examined species. Consequently, it was concluded that the gene loci which were scored in these studies were not relevant to the genetic changes which occurred during speciation. Analyses of general protein electrophoretic patterns, however, does reveal differentiation on the supraspecific level. Three basic species groups can be discerned, each associated with ecological characteristics of these species such as diet and substratum. Implications for haplochromine evolution and taxonomy are discussed. Our data seem to support the hypothesis that trophic differentiation may have occurred within habitats, implying the possible importance of sympatric speciation in haplochromine evolution in Lake Victoria.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb03756.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY