摘要:

The cuttlefish ingests much skeleton from the crustaceans and fish it preys upon. The skeletal pieces are relatively large and their dimensions bear a close relationship to the length of the buccal mass and diameter of the oesophagus. The structures of the buccal mass are instrumental in the breakdown of prey and orientation of long pieces of skeleton to ensure their entry into the oesophagus. Many pieces of skeletal material present in the stomach contents still have attached muscles, showing that there is little, or no, external digestion. Skeletal material may be important for long‐term maintenance of youngSepiain captivit

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04716.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The intrinsic rate of natural increase (rmax) is calculated for 58 primate species. It is found that this parameter is negatively correlated with body weight, so that larger primate species consistently have a lower rmaxthan do smaller species. Although there is no apparent link between the raw value of rmaxand environmental predictability, a relationship between a high rmax, relative to body weight, and an unpredictable environment is found to exist. However, there is no relationship between a predictable environment and either the raw value of rmax, or the relative rmax. After body size effects are removed, rmaxis not correlated with basal metabolic rate (BMR). Pre‐natal maternal investment (MI) is found to correlate highly with BMR, even after the removal of body weight effects. MI does not correlate either with rmaxor with environmental predictability. Diet appears to have little influence either on rmaxon MI, but there is some indication that folivores have both a high relative rmaxand a high relative MI. These results are discussed in the light of theories of life‐history strategy evolut

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04717.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The reproductive performance, including survival, growth and mature egg production, ofMoniliformis moniliformiswas studied experimentally during primary infections in rats given 10 cystacanths each. Four isoenergetic purified diets containing either 1, 3, 6 or 12% fructose (w/w) were used and the amounts of fructose in the intestinal lumen of rats fed on these diets were measured. It was concluded that, while dietary composition had no effect on parasite establishment, there were associations between diet and the survival, growth and fecundity of the parasite. The host diet containing 3% fructose was considered to be more favourable for the worms than the others; 12% fructose was associated with a curtailment of survival time without any compensatory production of eggs. Female worms from rats fed on diets containing 3 or 6% fructose grew larger, and consistently carried more ovaries and produced more eggs than those from rats fed on the 1% fructose diet. It was concluded that these and other findings might be mediated not only through the amount of available fructose in the intestine for worm metabolism, but also by the responses of the host's intestinal physiology to the varying concentrations of fructose in the diet.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04718.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Skull characters of wildcats (Felis silvestris), classed as ‘old’, ‘recent’ or ‘modern’, depending on collection date, were compared with those of domestic cats (F. catus) and hybrids, using Fisher Linear Discriminant Functions, Principal Component Analyses and Canonical Variates. A key is derived for classification of individual (unknown) skulls. All analyses indicate that ‘recent’ and ‘modern’ wildcats were different from those collected earlier, and implied marked changes in the rate of hydridization during this century. We suggest that the older wildcat populations were a relatively ‘pure’ form but more recent populations contain a significant hybrid component. Although there may be a trend towards re‐establishment of the earlier type, an alternative conclusion is that the ‘pure’ form of wildcat is ef

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04719.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The systematic status ofPriotrochusFischer, 1879 and the taxonomy of its type species,Trochus obscurusWood, 1828, are discussed. Although previously regarded as a subgenus ofMonilea, observations on the radula and external anatomy reveal little similarity withMonileaand the Umboniinae as a whole. Greater similarity exists with members of the Monodontinae and a position, at generic level, in that subfamily is suggested. The extinctTrochus ponsonbyiSowerby, 1888, is maintained as a subspecies ofPriotrochus obscurus.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04720.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The reproductive biology of Nilgiri tahr (Hemitragus hylocrius) was studied in Eravikulam National Park, Kerala, India from August 1979 to September 1981.The rutting season occurred during the monsoon (July and August) and the main birth season was January to mid‐February. Gestation was estimated at 179 days.Three females which lost their first young in 1981 conceived 18 to 21 days post‐partum. One female conceived of her second young while the first was 15 days old. The remainder of the individually identified females gave birth to one young (n=40) or none (n=4).Infant mortality was highest during the first two weeks after birth. Young born during the monsoon also had a high mortality rate (0.50/week).Oestrus during the rut was discontinuous in 1980 and 1981. Periods of frequent oestrus corresponded with periods of low rainfall with a mean lag time of 4.9 days.The ultimate factor determining the birth season in Nilgiri tahr appears to be weather. The main birth season is timed so as to minimize thermal stress.Several proximal factors may be important in stimulating reproductive activity. These include photoperiod, temperature, the presence of males in mixed groups, and nutrition. The photoperiod response is unusual in that Nilgiri thar evidently respond to the abrupt decrease in apparent day length associated with the onset of the monsoon.The inverse correlation of rainfall and oestrous activity may have been effected through the sudden decrease in thermal stress on the females or heavy rainfall (5.7 cm/day) masking pheromonal stimulation.The pattern of lactation anoestrus observed in Nilgiri tahr approximates results obtained from some studies of domestic Caprini.Nilgiri tahr females are presumably able to increase their lifetime reproduction by giving birth twice in one year. However, this strategy seemed counterproductive in 1981 as survival was low for second offspr

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04721.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Results of ultrastructural investigations (SEM and TEM) of the formation and structure of eggshells in the water mite,Limnochares aquatica, are presented. The material of the vitelline envelope is secreted in two stages by the oocyte commencing vitellogenesis. The vitelline envelope is later transformed into endochorion and during the passage through the reproductive tract it becomes covered with exochorion, produced by the female reproductive accessory gland. The exochorion swells in water to acquire a foamy structure.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04722.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Major osteological landmarks were used to prepare idealized drawings of mammalian and reptilian lower jaws. Measurements from these drawings allowed the average output or bite force, along the entire jaw, to be calculated for many different anteroposterior positions of the input or muscle force. In the mammalian drawing, the maximum average bite force is exerted when the resultant force is located at about 30% of the way along the jaw from the joints. Because of geometric differences in the reptilian drawing, a resultant positioned at 20% of the way along the jaw exerts the maximum average bite force; a maximum force that is smaller than that in the mammalian case. The estimated location of the muscle resultant in actual cases corresponds to these calculated positions. Therefore, in real animals, the muscles are located in the position that produces the largest average force for any jaw length. The geometric changes necessary to transform the idealized reptilian drawing, with a smaller maximum average bite force, into that of the mammalian drawing, with a larger maximum force, are the same as those changes seen in the fossil record of the reptile/mammal transition. This finding suggests that the morphological changes that occurred in the jaws increased the average bite force in the primitive mammals.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04723.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The manner of operation of the mysticete olfactory apparatus is described and its source of activation is indicated.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04724.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Aspects of the reproductive performance ofMoniliformis moniliformiswere investigated in rats allowed to feedad libitumon a purified diet containing 1% (w/w) fructose as an energy source for the worms. The rats were infected with either 10, 20, 40 or 80 cystacanths each with the intention of investigating density‐dependent effects on worm fecundity. The establishment of the worms in the gut was independent of dose, but survival, growth and reproductive performance generally were shown to be related to the infective dose given to the rats. The effects could not be related to the absolute numbers of worms present in the small intestine atpost‐mortemexamination. In general, some unidentified regulatory process appeared to operate to create severe density‐dependence in survival so that surviving parasites were not present in numbers expected to generate competition. Attainment of sexual maturity, growth and the production of mature eggs by worms from rats given doses of 80 cystacanths each were delayed compared with worms from rats given the other doses, but eventually the performance of the high‐dose worms caught up. Worms attached more anteriorly in the small intestine grew bigger and produced more mature eggs. Possible mechanisms responsible for the observed effects are di

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb04725.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY