摘要:

Ideally, diurnal orb‐web spiders should be able to ignore problems of insolation when siting their webs and should be able to operate such webs without the necessity of retiring into shade. Postures that minimize the surface area of the spider exposed to insolation may help to free the spider from the danger of overheating. Such postures are here described for the first time forArgiope argentataand three species ofGasteracantha. Experiments with deadNephila clavipesshow that postures described as thermoregulatory do, in fact, reduce absolute temperatures (and the rate of temperature increase) compared to normal predatory postures.Metalic or other reflectant coloration occurs in many species of diurnal orb‐web spiders. These are partly listed herein. Experiments with one such species,Argiope argentata, show that overpainting the silver parts increases both the rate of temperature increase and the absolute temperatures reached when naturally coloured and black‐painted spiders are exposed to the same radiant heat sources.It is suggested that these results on the probable thermoregulatory function of metallic coloration can provide insights into the probable habitat distributions of species whose coloration is known but whose ecology is presently unknown. The general question of adaptive coloration in spiders is discussed in the light of these re

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01060.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Laboratory experiments were performed on the schooling and feeding behaviour ofTrichogaster fasciatus. There was a tendency on the part of individuals of similar size to school together; the instinct being stronger in younger specimens. Unavailability of similar‐sized individuals led to schooling by members of different size‐groups. Column feeding was exhibited by the fish. While feeding at the bottom, the fishes formed angles varying from 30°90°. Larger individuals formed a right angle more often than younger members of the species. Optimum degree of crowding seemed necessary for active feeding as confinement of single individual, or overcrowded condition, both resulted in a decline of feeding act

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01061.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Investigations were made on the existence of size‐hierarchy in specimens ofEsomus danricus(Ham.) belonging to the same year‐class, and the variations in condition factor of the different size‐groups. Divergence in the growth rates of individual fish resulted in the development of size‐hierarchy in the population. Marked changes seemed to occur in condition factor of the different size‐groups. A multitude of factors operating simultaneously in the pond environment appeared to govern the condition facto

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01062.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

D. corallinacewnforms sheet‐like colonies at Mean Low Water (MLW) on exposed rocky shores:S. natalensisforms loose aggregations under stones below MLW in more sheltered situations. Both species released young from July— December.D. corallinaceunhas single embryos in capsules brooded free in the mantle cavity;S. natalensishas 20–40 embryos per capsule, the latter being attached to the roof of the shell and hanging through a dorsal slit in the mantle. The morphology of the crawling young is similar in both species, resembling adult errant prosobranchs.D. corallinaceumhas a stouter, more streamlined protoconch thanS. natalensiscorrelated with the more turbulent water of its habitat. The crawling young secrete a sticky mucous trail for adhesion to the substratum. They are strongly photopositive until settlement.D. corallinaceumcan settle within 24 hours but may delay settlement to 4–5 days if suitable substrata are absent. Metamorphosis is complete 2 days after settlement.D. corallinaceumprefer to settle on Lithothamnion which is easily eroded by the radula to provide a groove for rapid, firm attachments to the substratum. Both species feed from mucous nets,S. natalensishaving a slower feeding rhythm commensurate with its larger size. Contiguous pairs of S.natalensishave synchronised feeding rhythms, probably to reduce mutual net robbing. Particles are also filtered out of suspension; many particles are rejected in the pseudofaeces but some are ingested.D. corallinaceumandS. natalensishave many similar ecologically equivalent species throughout the warm temperate and tropical seas of th

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01063.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The Harderian gland of the rockhopper penguin,Eudyptes crestatus, lies in the orbit ventral and anteromedial to the eyeball. It is classed as a type II avian Harderian gland as it is similar to that of the duck, differing only in the possession of acini and small amounts of lipid in the epithelial cells of the tubules. Histologically it is a lobulated, compound tubulo‐acinar structure surrounded by a thin connective tissue capsule. Plasma cells and Mott cells are presen

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01064.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The distribution of freshwater shrimps in Jamaica is presented.Atya innocous, Atya lanipes, Atya scabra, Micratya poeyiandMacrobrachium heterochiruswere found only in the high‐gradient streams characteristic of eastern and north‐eastern parishes.Macrobrachium acanthurus, Jonga serrei, andPotimirim mexicanawere found only in the low‐gradient streams characteristic of western and southwestern parishes.Macrobrachium faustinum, Macrobrachium carcinus, andXiphocaris elongatawere distributed throughout Jamaica. Oxygen, temperature, and current speed were the physical features of the streams most likely influencing this distribution. It was observed that species in high‐gradient streams had larvae which required high salinity for development, and those in low‐gradient streams had larvae with low salinity requirements. It is argued that larval salinity preferences during the marine planktonic stage of the life history could allow larvae to select an appropriate river prior to its being invaded by

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01065.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Blue crabsCallinectes latimanus(Rath.) trapped from two lagoons were sexed, measured and weighed. The eggs of the mature females were counted to determine fecundity, and the spermatophores of the males were counted to determine the size of sexual maturity. Sizes at maturity of both male and female crabs were determined. The methods employed and the results are discussed.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01066.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Tropifer laevisGould is redescribed from new material, and tentatively placed in the family Coleiidae of the decapod Crustacea. Other fragmentary crustacean remains are described and assigned to the order Isopoda. The palaeoecology of these forms is briefly considered with reference to the Rhaetian Bone Bed, from which they came.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1978.tb01067.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY