摘要:

Parahaploposthia thiophilusis described as a new species of the acoel turbellarian family Haploposthiidae. AlthoughP. thiophilusexhibits strong anatomical similarities to other members of the genusParahaploposthia, notably in the male copulatory organ, the male gonads and the frontal organ, this new species differs from all other members of its genus by the possession of a bursa. We have broadened the generic diagnosis ofParahaploposthiato include this feature, a measure that we prefer to the erection of a new genus based on a character (the bursa) of uncertain validity in the present system of acoel taxonomy. This species description is based primarily on information gleaned from the observation of living specimens by phase contrast microscopy, in order to illustrate the utility of an often neglected method that reveals important information not available from fixed and sectioned specimens, and which also may provide for more rapid and simple identification of acoel turbellarians by nonspecialists.

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00016.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The fine structure of rhabdomeric photoreceptors ofCirrifera aculeuta, Monocelis fuscaandNematoplana coelogynoporoidesis described. The existence of one receptor cell and one pigmented or unpigmented mantle cell is thought to be a basic feature of the Neoophora at least. The existence of a pigment shield formed by many cells is derived, in addition to one receptor and one unpigmented mantle cell, in the eyes ofMonocelis fuscu.

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Melanodrymia aurantiacagen. et sp.n., a conispiral archaeogastropod of trochacean affinities, occurs on chimneys and stacks of polymetallic sulphide deposits at hydrothermal vents on the abyssal ocean floor at 21°N Latitude off Baja California, Mexico. The shell is unique in its combination of reflexed growth lines, strongly prosocline aperture, discordant sculpture, discoidal geometry and pattern of apertural angulations. The similarity in form with Paleozoic euomphalaceans and pleurotomariceans is considered superficial and the unusual shell form and simplification of shell microstructure are interpreted as evolutionary correlates of small size. The radula is unusual, but it shares many features with the rhipidoglossan radulae of four undescribed limpet‐shaped species from hydrothermal vents on the East Pacific Rise. It is hypothesized that the adaptive radiation occurredin situ, late in the Tertiary or Quaternary, and from a coiled ancest

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Eleven species are now known to belong to theCopidognathus pulchergroup, viz. C.extensus, C. loricifer, C. magnipalpus(with the subspeciesmagnipalpusandponticus), C. manicatus, C. pachypus, C. pulcher, C. scitus, C. suezensis, C. triops, C. milliporusand C.uniscutatus, C. milliporussp.n., found in Caribbean waters, andC. uniscutatussp.n., from the Philippines, are described. The geographical distribution of thepulchergroup is summarized in a figure.

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Hemicyclops columnarissp.n. is described from the scleractinian coralPorites lobataDana on the Pacific coast of Panama. The new species may be distinguished from its 23 congeners by a combination of the body size and the shape of the genital segment in the female. Although certain members of the genusHemicyclopsare associated with crustaceans, polychaetes and other marine invertebrates, this is the first record of a species of this genus from a hard coral.

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The cornea in most stomatopods is divided into two halves by a band of specialized ommatidia, the middle band. This band is absent in the Bathysquilloidea, but present in the three other superfamilies. It is two facets wide in the Squilloidea and six facets wide in the Lysiosquilloidea and Gonodactyloidea. This differentiation must have occurred very early in the evolutionary history of the group.

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00021.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Two new Isopoda Anthuridea(Paranthura longitelsonsp.n.,Mesanthura nubiferasp.n.) from the Pacific coast of Mexico are described. A redescription of the hitherto poorly known speciesMesanthura occidentalisMenzies&Barnard is presented.

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Morphological and ultrastructural observations inElectra pilosu(L.) andMembranipora membranacea(L.) show that the diaphragm which closes the tentacular atrium is formed by the juxtaposition of folds of the tentacle sheath around its apical sphincter and another row of folds of the vestibulum. Double desmosomes bind the epithelium and cuticle at the base of vestibular folds to the collagen layer of the sheath. The continuity of parietal and polypidian cellular layers during the morphogenesis of the aperture is discussed. Several cellular types are differentiated in the microvillous epithelium of the sheath at the edge of the atrial orifice. The sphincter is innervated by twin motor branches of the mixed peripheral nerves. An efferent cluster of axonal fibres arises from bipolar neurons which are vitally stained by methylene blue within every vestibular lobe, with a slender dendrite reaching to the cuticle. The ramified dendritic ending encloses the kinetosomes and aborted root of a vestigial cilium. Interdigitation of the dendritic ramifications and marginal vesicles of adjacent epithelial cells which also contain a single reduced cilium is observed, although no particular junction implying a functional couple was found. Vestibular folds around the atrial orifice are interpreted as sensory papillae with either a mechano‐ or chemoreceptive functio

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The histology of premaxillary teeth ofColossomasp. from the Solimöes Formation of Northern Brazil is described, in comparison with Recent material. Analysis by light and scanning electron microscopy shows that they share with those of the serrasalminids, histological (though not anatomical) features of carnivorous fishes. The enameloid in both groups displays surface‐parallel images of calcified fibres along the periphery of the teeth while internally, these images present a random distribution. Such similarities suggest that both the serrasalminids and myleinids may have evolved from carnivorous ancestors. The serrasalminids remain carnivorous, while the herbivorous habit of the myleinids may have been acquired secondarily. This change of diet is probably related to changes in the shape of the teeth which are used for crushing fruits, seeds and leaves. The teeth in adultColossomaare unicuspid, though not conical. The molar or incisive form of these teeth may have evolved independently from the conical‐shaped primitive dentition of the characoids, without passing through any stage of fusion of dental papillae, which is observed in the ontogenetic development of other charac

ISSN:0300-3256    

DOI:10.1111/j.1463-6409.1984.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY