摘要:

Based on protochordates and extant fish, the earliest Palaeozoic vertebrates were microphagous suspension‐feeding animals that pumped food‐carrying water very slowly and thus required highly concentrated suspensions. Such conditions exist in benthic (not open water) aquatic environments. Feeding modes which on the basis of extant fish are closely related to benthic microphagous suspension feeding include deposit feeding, epilithic algal scraping, and macrophagous suspension feeding; early jawless vertebrates are predicted to have included all these feeding types. The gnathostome condition is predicted to have followed an initial switch from feeding on suspensions to taking tiny individual food particles (microphagous suspension‐feeding → microphagous particulate‐feeding → macrophagous particula

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb00643.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The zoeal morphology ofLiocarcinus arcuatus, L. corrugatusandL. depuratoris described from laboratory reared material and the larvae ofL. holsatus, L. puber, L. pusillusandL. marmoreusare reexamined from specimens deposited in the BM (NH). No single meristic character was found that would adequately separate the seven described species ofLiocarcinus.Characters that may facilitate separation of later zoeal stages only are listed.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb00644.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The skull and trigeminal jaw adductor musculature of the lizard families Gekkonidae, Pygopodidae and Xantusiidae are described. The external jaw adductor shows a different structure in the Gekkonidae and Pygopodidae than is observed in other lizards, approached only by the Xantusiidae and Feyliniidae. Paedomorphosis seems to be involved in the differentiation of the jaw adductor musculature in the Gekkonidae. The Gekkonidae and Pygopodidae may be hypothesized to form a monophyletic group, the Gekkota, on the basis of numerous synapomorphies. Within the Gekkota, the Pygopodidae are the sister‐group of the Gekkonidae and retain some plesiomorphous features which are absent in the latter. The Xantusiidae share few synapomorphies with the Gekkota on the one hand, and some with scincomorph lizards on the other, especially with the Lacertida

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb00645.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A study of certain aspects of two man‐made lakes at the University of Zambia Lusaka Campus was carried out. The three species of cichlids with which the lakes were stocked:Tilapia rendalli(Boulenger, 1896);Oreochromis(formerlyTilapia)macrochir(Boulenger, 1910) and O. (formerlyT.)andersonii(Castelnau, 1896) were examined for helminth parasites.The most numerous wasCichlidogyrusPaperna, 1960; followed byAcanthogyrus (Acanthosentis) tilapiaeBaylis, 1948. A few metacercarial cysts ofClinostomanLeidy, 1856; a few cysticercoids ofParadilepis delachauxiFuhrm, 1909 and a single specimen of a probable new genus of Monogenea (nearDiplozoonNordmann, 1832) were also found.The prevalence and seasonal variation in numbers of the two most common parasites are discussed in relation to parasite loads in different ages and sexes of the host fis

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb00646.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Previous uncertainty concerning the number of larval stages in a strepsipteran (Elenchus tenuicornis) was resolved by transmission and scanning electron microscope observations. The first larval instar (triungulinid) is free‐living: after entering the host (a delphacid) it undergoes a normal ecdysis. The resulting second instar larva undergoes two further apolyses without ecdysis. In the male, the cuticle of the fourth instar larva tans to form the puparium, while the female becomes sexually mature without a further moult after extrusion of the cephalothorax through the host cuticle. The discarded exuviae of the triungulinid remain in the host abdomen; subsequent larval staging is made possible by the retention of the exuviae ensheathing the larva as each apolysis is accomplishe

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1984.tb00647.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY