摘要:

The food of twenty‐six species of non‐cichlid fishes in the Lake Victoria basin is described. Most species, for which data were sufficient to show this, are facultative feeders, their food being determined by their size, their feeding grounds, and the age of the moon. The size of an organism and its position in the aquatic environment usually determine its importance as prey, and this is considered a reason why so many fishes in the lake are insectivorous. Only three species of non‐cichlid are extensively piscivorous: these feed heavily onHaplochromis, slightly onEngraulicypris, and hardly at all onTilapia.Several birds and fishes feed onEngraulicypris, but otherwise there are few natural predators of non‐cichlids. Ontogenetic changes in feeding behaviour ofMormyrus kannumeandBagrus docmacsupport the hypothesis (recently confirmed forB. docmac) that in the lake juveniles of these two species live on rocky shores. The evolutionary stages involved in the colonization of lakes from rivers are discussed, with particular reference to breeding habits and food. The non‐cichlids in Lake Victoria are considered not to have progressed far towards becoming adapted to a lacustrine en

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1961.tb06080.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Enterobius nycticebiBaylis, 1928 andE. callithricisSolomon, 1933 are briefly redescribed and the oxyurid parasites of primates are discussed, additional morphological evidence being presented on many of them when necessary. The parasites are regrouped into two genera, with two subgenera each, thus:EnterobiusLeach, 1853 withEnterobiusandProtenterobiussubgen. nov. (type speciesE. nycticebi);TrypanoxyurisVevers, 1923 withTrypanoxyurisandParaoxyuronemaArtigas, 1937. A trend from a three‐lipped mouth opening to a two‐lipped is demonstrated within the genusTrypanoxyurisand a trend from a “doubled” to “single” spicule is demonstrated withinEnterobius.It is pointed out that although the trend inEnterobiusparallels the phylogeny of the hosts in part it does not necessarily establish a phylogeny particularly as there are relatively few records of the parasites. This is clearly demonstrated by recording from which of the genera of living primates oxyurid parasites have been reported. It is argued that “Cameron's Hypothesis”—one species of parasite (EnterobiusorTrypanoxyuris): one genus of host—appears to hold good in the wild and that there is a tendency in the genusEnterobiusfor the parasites most like the parasites of man to occur in the hosts phylogenetically nearest man. The subfamily Oxyurinae is reviewed and two tribes, Oxyurini and Heteroxynematini, are recognized. It is reported thatCallistoura brygooiChabaud and Petter, 1958 does not have a spicule and that the structure described by Chabaud and Petter as such is a modified gubernaculum similar to that found inOzolaimusand related genera. The great similarity between the male tail ofC. brygooiandOzolaimusis noted and it is suggested thatCallistourashould be treated as a genusincertae sedisuntil a full study of the subfamily Pharyngodoninae, to which it is clearly related, can be undertaken. Several new synonyms are demonstrated, thus:Buckleyenterobius deniataSandosham, 1950=Enterobius lemurisBaer, 1935;Oxyuris parallelaLinstow, 1908=O. polyoonLinstow, 1909 and is referred toEnterobius; Oxyuris armataKreis, 1940=Primasubulura dist

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1961.tb06081.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The cyclical testicular events in the tropical weaver‐finchQuelea queleaare basically the same as those of temperate zone species but are modified for a xerophilous mode of life. Photostimulation is not necessary for the development of the sexual cycle and immediately the abbreviated regeneration period is overQ. queleawill again achieve spermatogenesis under an unchanging 12 hr. 25 min. daylength. An abnormally long photoperiod of 17 hrs. influences gonad growth during the pre‐nuptial acceleration phase and causes premature metamorphosis. It has no influence, however, on the duration of the regeneration phase. SomeQ. queleamaintained in captivity develop a black plumage. This induced melanism is briefly repor

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1961.tb06082.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The history and replacement of crocodile teeth are described. A new tooth erupts with only a short root which grows downwards into the socket as the pulp cavity in the crown begins to be occluded by the further deposition of dentine. After the root has become fully extended, it is gradually resorbed at its base to make room for an enlarging successional tooth which has been forming on the lingual side of the socket. The successional tooth eventually moves to a position within the partly resorbed functional root and directly under the functional crown. Progressive reduction of the functional root now occurs to accommodate the continuously enlarging successional tooth and, when resorption is largely complete, the functional tooth falls away, allowing the successional tooth, with a short, incomplete root, to take its place. As a result of this successional cycle it is found, within certain limits, that at any given time the form and condition of a functional tooth is related to the size and condition of its successor lying below.Consideration of various measurements made on a series of twenty‐four skulls of different sizes indicates that a regular and continuous replacement of teeth occurs throughout a large part of a crocodile's life. It is estimated that in a crocodile which is thirteen feet long, each tooth is likely to have been replaced forty‐five ti

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1961.tb06083.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Adults of several species of both solitary and colonial ascidians are capable of slow crawling, involving the progressive formation of new attachments and tearing or dissolving the old ones. The ampullae play a leading part. A moving colony may divide into two, or two adjacent colonies may fuse: true fusion has been observed only once, inTrididemnum tenerum.BothCiona intestinalisandDiplosoma listerianummay metamorphose by attachment to the surface film and are capable of post‐metamorphic attachment to a solid surface for a prolonged period. In such attachment the ampullae play a leading role. A free‐swimming (unattached) colony ofDiplosomatakes on the form of aPyrosomacolony. Such colonies have been reared in the laboratory forming cigar‐shaped, jet‐propelled bodies up to 1 cm. long with as many as fifty

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1961.tb06084.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1961.tb06085.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY