摘要:

The lengths and widths of at least 100 spicules from each of 126 specimens, comprising at least 12 species of haplosclerid sponges, mainly from Church Island and Rhosneigr, Anglesey, North Wales have been measured. It was found that spicule dimensions by themselves would be unreliable in the identification of species. The sample means, medians and maxima, when plotted using width and length axes, form specific clusters that overlap, sometimes to a considerable extent. The correlation coefficients for width against length varied widely, even when single species were considered. The variation arises from differences in the numbers of juvenile spicules in various samples. The best correlation coefficients exceeded 0.8 and the regression constants for linear correlation in such samples could be useful in the diagnosis and taxonomy of the species. The coefficients of variation for length and width also yielded parameters for species characterization. In general the coefficient for length tended to increase as the mean length increased, whereas that for width tended to decrease with increasing mean width. Some species stood apart from the general trends, however. The coefficients varied widely from one sample to another of the same species, identified using a variety of diagnostic features. To some extent the variation was linked with the date of collection. When all the data were combined, the average coefficient for width decreased markedly in May. The same was true for two species that were separately considered. The decrease was not simply caused by a change in mean width, changes in standard deviation also being involved. There was a tendency for certain species, in particularReniera roseaandGellius angulatus, to produce thin spicules in the spring, which became incorporated distally in the primary spicule bundles in July‐Augus

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01976.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Non‐cryptic didemnid ascidians containing the prokaryoteProchloronare abundant on the intertidal flat of many Pacific reefs. Species with sheet‐like colonies (e.g.Diplosoma similis, Trididemnum paracyclops) are characteristic of high wave energy situations and clean hard surfaces; didemnids in which the colony divides repeatedly into small cormomeres (e.g.Diplosoma virens, D. multipapillata, Lissoclinum voeltzkowi) are in less exposed situations, often on algae or unstable substrata. The unusual back‐reef cascade habitat ofD. multipapillataon a Fijian fringing‐reef is described. In Fiji, replicative division leads to population build‐up between June and October, with a hot season decline in November‐December. The effects of torrential rain in April 1980 are described. StudyingL. voeltzkowiin permanent quadrats has shown that the populations of cormomeres are dynamic, with much movement occurring. The process of colony division is described inDiplosoma virmsfrom the Great Barrier Reef. Possible advantages of didemnid dynamism discussed include maximization of periphery to area (perhaps increasing the efficiency of feeding and/or growth), the exclusion of competitors, and the mingling of clones to facilitate cross‐

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01977.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The present review considers the structure, site of formation and functions of protochordate blood cells/coelomocytes. Details of the circulatory and coelomic system are also given where appropriate. In the hemichordates, blood cells are absent but a single type of amoebocyte is present in the coelomic cavity. A similar situation exists in cephalochordates and these cells appear to play an important role in maintaining the animal free from infection. In the urochordates, several morphologically distinct types of blood cells (haemocytes) exist, some of which store vanadium. At present little is known concerning the phylogeny and ontogeny of the different cell types in these groups.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01978.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The marine piscicolid leechCalliobdella knightjonesisp. nov. from the Oregon coast is described and illustrated. Mature individuals do not exceed 10 mm in length, have faint reddish‐brown segmental pigment bands, small pulsatile vesicles, six pairs of testisacs and a well‐developed seminal receptacle connected to the posterior portion of the bursa by paired tissue strands. The leech lacks eyes and oce

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01979.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The Hirudinea have a number of arthropod‐like characters, including a true haemocoel and compound eyes. This ‘arthropodization’ may have bearing on the origin of the arthropod phylum Uniramia. Certain traits shared by Clitellata and Uniramia are interpreted as primitive and compatible with the view that a monophyletic link exists between these two groups: ‘internal’ fertilization, egg protected by cocoon/chorion, egg yolky with direct development not invoking a planktotrophic larval stage, formation and fate of presumptive areas in early embryology, uniramous lobopodial‐like structures and the presence of uniramous mouthparts. Still other traits shared by Hirudinea and Hexapoda are interpreted as advanced and evidence for a paraphyletic relationship between leeches and pterygote insects: oogenesis with nurse cells, cephalization and segmental constancy. It is proposed that a major theme in uniramian evolution is the invasion of land from freshwater by a pre‐lobopodial clitellate‐like ancestor, the lobopodium being an adaptation to terrestrial locomotion. These views give new significance to the poorly studied fossil segmented worms from freshwater and terrestrial

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01980.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Limb movements of restrained stage VI nauplii ofLepas pectinatawere studied by cine‐photography. Outline drawings were made of successive limb positions in both swimming and grooming activity. The antennae appeared to act as leaky paddles performing both propulsion and food gathering. Free‐swimming nauplii averaged 120 limb beats min‐1and a speed ofc.4 mm s‐1. Grooming occurred every 7–20 beats.It was concluded that lack of streamlining favours filtration at the expense of propulsion. The grooming sequence differs from that of balanid nauplii and is one method of transferring food to the vicinity of the mouth, where sorting and rejection take place prior to ingestion. Fine‐ and coarse‐mesh filters presumably exploit different plankton types. The overall behaviour pattern is well‐designed for exploitation of scarce food in the oligotrophic conditions of the ocean

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01981.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The movement of carbon and nitrogen fromAmphiscolops langerhansi, fed on14C‐ and15N‐labelledTigriopus japonica, to its algal endosymbiontAmphidinium klebsiiis examined in a series of experiments designed to detect both sources in the host and utilization by the symbiont. Data for carbon indicate that.1.klebsiiutilizes host carbon primarily as respired CO2taken up in photosynthesis. Data for nitrogen suggest that translocation takes place primarily through the excretion of ammonia, and that uptake and incorporation by the alga is light‐depe

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01982.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A functional view of growth inevitably leads one to consider how it is controlled. There is much information on control mechanisms that regulate growth at different levels of organization within an organism. Some evidence is presented to establish that different types of control exist. However, our interest is in how the operation of these different control mechanisms might be co‐ordinated, as it is clear that the can not operate autonomously. We consider a hierarchical arrangement of control systems, some of the implications for understanding normal growth processes, how it might have evolved and an interpretation of system failur

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb01983.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY