摘要:

A diminution in function of the masticatory muscles of the rat was produced by feeding upon an abnormally soft diet. As compared with a control group fed on a hard diet, this resulted in a 12% decrease in the mass of the cranium and mandible together with a reduction of some 1 to 2% in the overall dimensions of the cranial and facial skeleton. This contrasted with a decrease of some 4% in the length of the angular process of the mandible which is specifically associated with muscular insertion.The differences in cranial dimensions of the two groups of rats were unlikely to have resulted from differences in overall body weight.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05205.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The morphological and histological structure of the post‐pharyngeal gut, liver and exocrine pancreas are described. InPoeciliathe gut comprises only oesophagus and intestine and lies folded in the body cavity, while inGasterosteusthe straight gut also includes a true stomach.In both species the oesophagus is lined by a stratified epithelium containing many saccular mucus cells. The oesophageal musculature consists of bundles of striated fibres.The wall of the post‐oesophageal gut comprises the following layers: simple epithelium, sub‐epithelial connective tissue, circular and longitudinal smooth muscle, and serosa. A muscularis mucosae is not present in any part of the digestive tract in either species.The stickleback stomach is lined by a simple columnar superficial epithelium. Gastric tubules, present only in the anterior half, are lined by pyramidal secretory cells of a single type, presumed to secrete both acid and pepsin.In both species columnar absorbing cells possessing a striated border and mucussecreting goblet cells are the most numerous cell types in the intestinal epithelium.The liver of each species is made up of tightly packed polyhedral hepatic cells with blood sinusoids running at random between them.Both species have a diffuse pancreas. Acini sheath the mesenteric blood vessels. The choledochal and pancreatic ducts open together into the anterior inte

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05206.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The morphology of the osteocranium and the Weberian apparatus of 14 representatives of Tachysuridae (= Ariidae) has been described and compared. It has been shown that these features are characteristic of the family Tachysuridae (= Ariidae) and can also distinguish the genera and the species of this family. A key to the intergeneric and interspecific characters has been provided. A few characters of morphological interest have been recorded. It has been shown that the erection of different genera for some species of the genusTachysurus(=Arius) by Munro (1955) is arbitrary and lacks support from morphology. The features of the oesteocranium and the Weberian apparatus support the fact that Tachysuridae are not primitive siluroids; they are at least more specialized than Siluridae, Plotosidae, and Bagridae. The advanced features of Tachysuridae are described. The morphological relationship of the superficial bone and its associated trough‐like bony structure with the swim‐bladder show that these bony formations develop from the tunica externa of the lat

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05207.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

A study of two distinct forms ofChaetogaster limnaei(Baer) was carried out in a population ofLymnaea pereger.One form inhabits the kidney of freshwater snails and the other lives on the external surface of these molluscs. Various differences between the two forms were studied.The outer form possesses a significantly greater number of setae per bundle than the kidney form and those of the kidney form are also shorter than those of the outer form. The stomach and intestinal epithelia are considerably thicker in the outer form than in the kidney form.The contents of the stomach and intestine of both forms was recorded from samples taken over a period of 12 months. It was seen that whilst the outer form fed on various planktonic organisms, the kidney form fed exclusively on cells derived from the kidney. Kidney forms would not under any of the experimental conditions feed on the planktonic organisms normally taken by the outer form.Both forms were found to be specific in their habitat in that if removed from their host and introduced to another, kidney forms always colonized the kidney and outer forms always remained on the outer surface. Neither lack of planktonic food nor conditions of drought could induce the outer forms to enter the kidney.Both forms showed a positive reaction to the mucus of their host but that of the outer form was by far the most pronounced. It was shown that the mucous trail left by the host snail assisted the outer form in finding a new host in that if the right direction was taken initially it would follow this trail, overhaul the snail and attach itself to it. The outer form also had greater ability to survive free living than the kidney form. Outer forms were kept alive for a maximum of seven weeks and kidney forms for only three weeks.It was suggested that the kidney form be considered a subspecies ofChaetogaster limnaeiand that it be known asChaetogaster limnaei vaghini.A brief description of the new subspecies is given.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05208.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Poeobius meseresHeath was found off Southern California in tows which reached depths from 350 to 1300 metres. It is not strictly confined to the sub‐Arctic water mass. Sensory papillae are found randomly scattered over the anterior and posterior ends of the gelatinous sheath. Isolated sensory cells are distributed over the head epidermis. A group of projections which are granular depositions from the epidermis encircles the extended head. The coelom is divided into three parts by two complete septa. The coelomic diverticula are branched extensions of the anterior coelom into the gelatinous sheath. The palpal coelom is a paired, tubular structure which lies in the head region and reaches between the ventral cavities of each palpus. The coelomic funnels are a pair of lateral tubes placing the middle coelom in communication with the exterior and probably function in gamete emission. The coelomocytes are associated with excretion. They are capable of spreading out within the epidermis of the head regions to dispose of excretory wastes. The nephridiopores are anterior to the tentacles. Excretory concretions may be found within the nephridia. The buccal pad is composed of an anterior tongue‐like portion and a more posterior bulb. The bulbous portion governs food intake by controlling the extent to which the oral aperture is opened. Absorption spectra show that the blood is a haem‐protein and probably a chlorocruorin. Respiration is achieved by the tentacles which contain a vascular loop, and is possibly aided by the highly ciliated and vascular anal area. The septa are ruptured when animals are fully ripe so that the gametes extend throughout the entire coelomic system (except the palpal coelom). Gametes escape through the coelomic funnels. The first two cleavages are holoblastic. Some eggs show an abnormal tri‐astral formation in the second meiotic division. Some gravid females are found in a disintegrated condition due to an unknown cause. The sperms ofPoeobiusare of the primitive type. Fertilization is external. Three main pairs of nerves arise from the brain to innervate the dorsal part of the nuchal organ, the lateral portion of the nuchal organ, and the palpi and the sub‐esophageal ganglia. The nuchal organs and palpi are sensory.Poeobiusdisplays features primitive to the Polychaeta. It is an early offshoot of the archiannelid line, derived from benthic forms, and resembles the flabelligerids in several

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05209.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

An analysis is made of the abundance, vertical occurrence and taxonomy of calanoid copepods from 29 samples. The samples were obtained in the northeast Atlantic between approximately 30° and 60°N and at intervals from the surface to a depth of 5000 m.The zooplankton is found to be more abundant in the upper 1000 m of the water column and below 2000 m the concentration is extremely small. The mean size of adult copopods is greater between 500 and 2000 m than in other depth intervals and the greatest number of species occurs in the upper 1000 m. Two new genera, 17 new species and the previously unknown males of three species are described and illustrated. Twenty‐one other species are discussed and five species are reported for the first time from the Atlantic Oc

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05210.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY