摘要:

Reproductively inactive, winter dormant femaleAnolis carolinensiswere exposed to a stimulatory environmental regime while in socially stable or unstable male‐female groups. In a second experiment, winter dormant females were exposed to varying amounts of male courtship and male‐male aggression. Results indicate that (1) the presence of a stable dominance hierarchy among group males is necessary for male facilitation of environmentally‐induced ovarian recrudescence (OR) (an unstable dominance hierarchy inhibits OR), (2) the behaviour patterns responsible for the facilitation and inhibition of environmentally‐induced OR are courtship and male‐male aggression, respectively, and (3) ovarian development is graded in accordance to the amount of male courtship to which the female is exposed. It is proposed that male courtship insures normal gonadotropin (GT) secretion while the absence of male courtship results in subnormal GT secretion and the presence of male‐male aggression suppresses environmentally‐induced GT secretions. The functional significance of the inhibition of environmentally‐induced OR by male‐male aggression and its possible relation to differential vernal emergence in temperate‐zone re

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04377.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The effects of heterotypically conditioned media on the growth and natality rates ofBiomphalaria glabratahave been studied under conditions which prevented the assay snails from being stimulated by tactile and visual signals from other snails. It was demonstrated that increasing the density of snails producing the conditioned medium up to a critical threshold resulted in enhancement of growth and natality rates. Further increases in density beyond the optimum level caused a reduction in growth and natality rates. Possible explanations for these effects, which were caused by chemical conditioning, are discussed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04378.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The exoskeletal surface of the body of the terrestrial isopod,Porcellio scaberhas been examined with the scanning electron microscope as part of a study of the structural changes associated with the transition from sea to land in the Isopoda. No sexual differences are apparent. The dorsal cuticular surface is characterized by large tubercles, minute plaques and pits, separated by amorphous areas. Apart from the eyes the only structures of apparent sensory function are relatively large setae which occur near the antero‐lateral and posterolateral edges of each epimeron, and sensilla squamiformia (tricorns). Tricorns are extremely numerous on the dorsal surface and appear to be formed from the fusion of a plaque and a sensillum which arises from a pit. Much of the ventral body surface is covered with closely‐set plaques, tricorns being restricted to the epimera. Along the sides of the mid‐ventral sternal groove occur numerous small tubercles each surmounted by a single seta. Similar, though smaller structures are found in a single row along the outer edge of the epimera. The water capillary system of this species is formed from spines which arise from plaques around the pereopodal sockets and along the junctions between the epimera and sternites. Most of the sensilla described appear to be mechanosensory and are probably associated with the thigmokinetic and proprioceptive responses of the wood

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04379.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The phthirapteran parasites occurring on the flamingoes are listed and their distribution discussed. New species ofAnaticolaandAnatoecusare described.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04380.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

A study of the mayflyPovilla adustaNavas in five West African lakes showed at least one population (in Barombi Mbo) with a clear lunar periodicity of emergence, and at least one without, at Kainji Lake. The seasonal distribution ofPovillaeggs in fish stomachs at Kainji implies a delayed effect of lake level on adult numbers. The relatively small size and short generation time (probably three months) ofPovillain Barombi Mbo, by comparison with the same species in Lake Victoria, may be related to the higher temperature of Barombi Mbo. The eggs of bdelloid rotifers were found attached toPovillalarvae from some of the lakes.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04381.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

In the epidermis of frog skin, most nerves are situated at the top of the basal layer. More superficial nerve fibres are usually adjacent to flask cells; it is concluded that this is not a functional association, but a consequence of the pattern of moulting. There are nerve fibres in the walls of the granular glands; mucous glands appear to have no intrinsic innervation although nerves pass within a short distance of their walls. The smooth muscle bundles of the dermis are innervated, and have a physical attachment to the overlying epidermis.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04382.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

D. maximumis a dominant species of outer reef flats in the Red Sea, reaching densities of about 22/m2and biomass of 15.8 g dry tissue/m2. A few individuals attached to loose rocks are found inside the breaker zone but they may have been dislodged by heavy seas from the outer reef flat.D. maximumfeeds from a mucus net which is spread by wave action over the substratum. Hauling the net occurs at approximately 13 minute intervals throughout the 24 hours and lasts about two minutes. Neighbours with overlapping nets stimulate each other to haul and reduce feeding efficiency. The net is grasped by a pair of lateral jaws, tugged free of the substratum by rotation of the body and ingested by a zipper‐like action of the lateral and marginal radula teeth. The robust, central and lateral teeth become worn, possibly while channelling out the substratum to accommodate new shell. Defaecation occurs about 2.4 times an hour, amounting to 10450 kcal/m2/y. Females may brood simultaneously at least 11 egg capsules at various stages of development, which are suspended by stalks from the roof of the shell and pass through a dorsal slit in the mantle. Each capsule contains–500 embryos which develop into larvae with simple, coiled shells 0.33 mm in diameter. There is no planktonic phase. Adult shells amount to 2.5 kg/m2on the outer reef flat, while dead shells are often occupied by blennies. AlthoughD. maximumis not a specialized filter feeder, the highly developed ciliary mechanisms suggest that filtering may be an auxiliary feeding met

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04383.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04384.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The experiments investigated the effects of a school of live prey fish on the hunting behaviour of squid, cuttlefish and pike (ambush predators) and perch (a chasing predator). The hunting behaviour of all species is described, including some previously unrecorded actions.For all species the increasing shoal size from one fish to six, to 20, decreased the success of the predators' attacks per encounter with a prey. This was partly because attacks on larger shoals lasted longer, and fish became increasingly difficult to catch as a hunt went on. However, for some of the species there was a clear effect of the shoals at the start of the hunt. For other species it was less conclusive.The disruptive effect of the shoals was shown to act for the ambush predators by interfering with the “optimal” sequence of an attack and causing avoidance actions together with so‐called irrelevant behaviour. For the perch, shoals seemed to disrupt by forcing the predator continually to switch targets during his pursuit.The artificiality of the experiments is discussed in relation to field observations. The relatively high incidence of avoidance and irrelevant behaviour seems to be an artefact, but the main results are quite compatible with field studies. In nature fish predators may be able to get sufficient food by restricting their attacks to individuals which are conspicuous either by an abnormal appearance or by becoming separated from the school. An individual prey fish no doubt gains a considerable advantage from the school by burying itself in the crowd. Our experiments show that a shoal can provide further protection in hampering the attack of a pre

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04385.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY