摘要:

Population samples of algae‐grazing, mountain stream characins of the genusSaccodonof Panama and northwestern South America are reported with up to four sharply differentiated dental morphs. The morphs differ strikingly in the form and numbers of functional teeth and of preformed replacement teeth. Recognition of the polymorphic nature of these variations necessitates new concepts of taxa at species and generic levels. Two species with similar polymorphism are involved,Saccodon dariensisfrom Panamá and Colombia, andSaccodon wagnerifrom the Guayas basin on the Pacific coast of Ecuador. A total of rive morphs have been discovered, three of which are homologous in the two speci

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04117.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The genitalia of the maleCheiridium museorumLeach consists of a cup‐shaped ejaculatory canal atrium which opens into a simple saccate genital atrium. Associated with the genital atrium are a number of thickened regions of the cuticle: the dorsal apodeme, lateral apodemes and lateral rods. These both support the genital atrium and provide regions for muscle attachment. Two pairs of accessory glands, anterior and posterior dorsal glands, are present.The genital atrium of the female is divided into a median and two lateral diverticula. Lateral apodemes are present, as are two sets of accessory glands, lateral and median glands.The possible function of the genitalia of the male is considere

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04118.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The chance of encounter—and hence mating—between two animals may be limited by social as well as spatial factors, thus dividing a population into a series of discrete territories with little movement between them. Only within the sub‐units will random mating take place, and drift may cause a considerable amount of non‐adaptive genetical change if the units are very small. Work on House mouse (Mus musculus) populations in the laboratory and particular ecological situations have suggested that the effective breeding size of these units may be as small as four. This would mean that a considerable amount of random change would be expected in mouse populations. However, a six year study (1964–69) of movement and territoriality on the 244 acre (100 ha) Welsh island of Skokholm during which over 3000 animals were marked and released, showed that more than 20% of individuals breed in an area other than the one in which they were born, i.e. a considerable amount of population churning takes place. This conclusion is supported by evidence of the spread of three rare biochemical variants in the population. Chance seems to play little part in the determination of the genetical constitution of the Skokholm mice. In general, estimates of the size of effective breeding units must always be qualified by an understanding of the ecology of the population in

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04119.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Octopus joubiniRobson were hatched and reared in a closed circulating sea‐water system. Mortality was greatest during the period of hatching. The longest surviving octopus lived for 128 days—it had increased its weight × 5, from 0·04–0·19 g, mantle length × 3, from 3–9 mm, head width × 2, from 3–5 mm. Observations of (1) general behaviour, (2) feeding behaviour, (3) social behaviour of the newly hatched octopuses (0–3 days) and the three longest surviving octopuses (93–119 days) are described. In particular it was observed that the older octopuses would readily grasp and eat small live crabs when these were made to touch the suckers or arms. On no occasion did the attacks appear to be visually elicited. This result is discussed with reference to the memory and learning experiments usingO. vulgaris.Possible reasons for the limited survival

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04120.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The phenomenon of fighting was investigated under laboratory conditions using polecats (Mustela putorius, M. furoand interspecific hybrids). Diadic interactions between male polecats were recorded on 16 mm cine film in an unfamiliar area of 16 m2, one individual having been introduced ten minutes before its opponent.The behaviour patterns involved in fighting are described and their frequencies of occurrence, duration and average bout lengths specified. Biting, which occupied 41% of the animal's time in fighting, and attacking, which made up 27% of the bouts of behaviour, were the most important actions involved in fighting. Polecats most commonly bite their opponent's neck and bites in this region were the longest in duration. Success in gaining a bite was influenced by the opponent's behaviour at the time of the attack.Polecats fight when one individual bites its opponent and the opponent retaliates by biting; bite was shown to be the commonest response to being bitten. The length of a fight appears to be determined by the levels of motivation to bite of the two opponents, while biting and being bitten operate as a positive feed back mechanism. The fight terminates when the more aggressive opponent ceases to make spontaneous attacks. The reasons why one individual wins a fight are that it consistently spends more time than its opponent in biting, it persists for longer in making spontaneous attacks and its method of attacking is more efficient.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04121.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Pieces of shell from 19 species of molluscs exhibiting various microstructures were tested for tensile strength, modulus of elasticity in bending and modulus of rupture. In tensile strength most shells with cross‐foliated, foliated, homogeneous and crossed‐lamellar structures did not exceed 60 MNm2but prismatic and nacreous structures often exceeded this value. Nacreous structure was generally superior to all others in modulus of rupture tests; that ofTurbobeing about equal to bone. Values of modulus of elasticity were more uniform between structures. There is a general relation between mechanical properties, microstructure and the life style of each animal. Nacreous structure, which is very strong but not widely used, apparently evolved earlier than the less strong but widely used crossed‐lamellar stru

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04122.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Rhabdosargus holubiis a marine teleost endemic to south east Africa. The juveniles occur mainly in estuaries but the adults are largely confined to the sea. Stomach contents of over 2000 juvenileR. holubiwere examined from fish captured in the open Kowie and Msikaba estuaries, and from the closed West Kleinemond and Kasouga estuaries. JuvenileR. holubifeed mainly on aquatic vegetation. The fish cannot, however, digest the vegetation eaten due to the absence of a cellulase or a method of breaking up the plant tissue. Therefore, the plant material is passed out in an undigested state. Epiphytic diatoms and sessile ectoprocts (Bryozoa) are, however, removed from the macrophytes or multicellular algae in the stomach, and are subject to digestion. Diatoms may form up to 50% of the dry weight of the plants consumed. A variety of animals was also eaten. Maximum total food consumption was estimated at 1·9% of body weight per day although this is probably an underestimate. Feeding only took place during daylight hours. The teeth of juvenileR. holubiare specialized for grazing aquatic plants and differ from those of adultR. holubi.Adults consume mainly bivalves and large crustaceans. It is suggested that the different food requirements of the adults and juveniles determine at what stage this species enters and leaves estuaries

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04123.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Lipids in various tissues ofLacerta viviparawere measured at three times of the year: immediately after hibernation, mid‐season, and immediately prior to hibernation. Lipid deposits in the abdominal fat bodies and the caudal fat bands fluctuated seasonally, but at any time showed a marked positive allometry with body length and weight; the functional significance of this relationship is not known. Carcass lipid and liver weight were isometric with body length and weigh

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04124.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The mechanism of extrusion of a representative terrestrial pulmonateHelix pomatiahas been investigated using pressure recording devices. Extrusion is essentially a hydraulic process which is achieved in a step‐wise manner; each step, consisting of two distinct phases, being an exaggeration of a respiratory cycle apparent in the extended animal. The effect of extrusion, retraction and respiratory movements on the distribution and circulation of blood has also been investigated. Extrusion in other gastropods, factors affecting cardiac output and the adaptations which facilitate retraction, are discusse

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb04125.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY