The growth rate of the aragonitic skeleton of the Caribbean 'sclerosponge' Ceratoporella nicholsoni has been studied by in situ staining of specimens with calcein in a reef tunnel, 28m depth, near Discovery Bay, Jamaica. Experiments were performed up to five times from 1984 to 1997 on a population of 10 specimens ranging from 10-20cm maximum diameter. In each experiment small skeletal samples were removed from the periphery of sponges, and specimens were left in place for further studies on growth and regeneration. Perpendicular sections, ground to a thickness of about 10μm, were photographed by fluorescence microscopy. Annual skeletal growth rates were calculated from measurements of the linear extension between calcein stained lines along growth axes. Data indicate that although average annual growth rates remained in the same range for different periods (214.6±54.5-233.3±33.0μm yr -1), significant differences occurred from one individual to another within the same period. The annual growth rate of a given individual also varied significantly in time (191.1±30.0-269.9±37.0μm yr -1). A second population of smaller individuals, measured after a single period of one year, revealed a strikingly lower average annual growth rate (124.4±35.0μm yr -1). Regeneration of the skeleton of injured specimens was also characterised by an initial slower growth rate. Nevertheless, after the first year, it was comparable to normal growth, and exceeded it slightly thereafter. This first long term study of Ceratoporella provides important information on the variability in growth rates, with implications on the use of sclerosponges as paleoenvironmental proxies.
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Remains of sturgeons (Acipenser sturio and A. oxyrinchus) are regularly found on western European archaeological sites. The identification of these isolated bones should ideally be carried out with the aid of a comparative skeletal collection, consisting of modern specimens of different sizes. Because such reference material of sea sturgeons (A. sturio and A. oxyrinchus) is relatively rare and dispersed over many different museums and institutes, a practical guide is presented here as an aid to the identification of the most commonly found archaeological sturgeon remains. This guide, which is based on observations made on 64 individuals housed in 13 different natural history collections, should allow identifying most archaeological sturgeon remains from western European sites. Presented are the morphological characteristics of the bones of the skull roof and circumorbital region (posttemporal, dermopterotic, parietal, frontal, dermosphenotic, postorbital, jugal and supraorbital), bones of the braincase (parasphenoid), opercular series (subopercle and branchiostegals), the palatoquadrate and associated bones and lower jaw (palatopterygoid, dermopalatine and dentary), the hyoid and gill arches with the hyomandibula, the isolated skeletal elements from the pectoral girdle (clavicle, cleithrum and supracleithrum), the bones of the fin and fin supports (pectoral fin spine, fin rays and fulcra) and the dorsal, ventral, lateral and accessory scutes. For each element, descriptions and pictures are provided of modern and archaeological specimens. Regression equations allowing fish length reconstructions on the basis of single bone measurements are given for 14 elements and the scutes. Finally, criteria for species identification are provided. In the case of the dentary, dermopalatine and palatopterygoid, these are differences in shape of the skeletal elements, whereas for the dermal bones the external surface pattern is diagnostic when reconstructed fish length is over one meter.
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Résumé Ce guide fournit l’information taxonomique pour les 68 espèces d’oligochètes dulçaquicoles connus à l’heure actuelle au Maghreb, au sens strict, c’est-à-dire la région d’Afrique du nord qui regroupe le Maroc, l’Algérie et la Tunisie. Au niveau du Grand Maghreb, ce guide est potentiellement valable pour la Libye mais pas pour la Mauritanie. Une introduction est faite au milieu dulçaquicole du Maghreb et sa spécificité pour les oligochètes, ainsi qu’une présentation de la biologie et la diversité globale des oligochètes. Les récentes avancées dans le domaine de la nomenclature et de la classification du groupe sont intégrées. Un panorama détaillé des familles maghrébines d’oligochètes est dressé, précédé par des introductions à l’anatomie générale et aux caractères taxonomiques des oligochètes. Les aspects pratiques liés à l’échantillonnage et les techniques de préparation des spécimens et leur conservation sont détaillés, ainsi que les étapes à suivre pour les identifier. Une clé d’identification au niveau spécifique est fournie pour chaque famille, valable uniquement pour les oligochètes connus à l’heure actuelle au Maghreb, mais en précisant les espèces susceptibles d’y être rencontrées en raison de leur distribution biogéographique présente. Enfin, ce guide donne la description d’Aktedrilus yacoubii (Naididae, Phallodrilinae), espèce nouvelle pour la science et le Maghreb. Mots-clés – Clitellata, oligochètes dulçaquicoles, Maghreb, clés d’identification, taxonomie, liste d’espèces, échantillonnage, préparation de spécimens. Abstract This guide provides taxonomical information for the 68 freshwater oligochaete species known to date in Maghreb sensu stricto, namely this region of Northern Africa that includes Morocco, Algeria and Tunisia. At the “Grand Maghreb” level, the guide is potentially valid for Libya as well but not for Mauritania. An introduction to the freshwater environment of Maghreb and its peculiarity vis-à-vis the oligochaetes is given, as well as a presentation of the biology and general diversity of oligochaetes. Recent nomenclatural and classification advances are integrated. A comprehensive overview of Maghrebin oligochaete families is given, preceded by introductions into the general anatomy and taxonomic traits of oligochaetes. Practical aspects of sampling, and techniques of specimen preparation and conservation are detailed, as well as steps required for their identification. An identification key, at the species level, is provided for each family, only valid for oligochaetes presently known from Maghreb; however, species likely to be found in the future, because of their current biogeographic distribution, are also mentioned. Lastly, this guide gives the description of Aktedrilus yacoubii (Naididae, Phallodrilinae), a species new for science and Maghreb. Keywords – Clitellata, freshwater oligochaetes, Maghreb, identification keys, taxonomy, species list, sampling, specimen processing.
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