ALBERT

Beschreibung: Based on collections assembled by Dutch expeditions to the Northwest African region, including the offshore islands in the neighbouring Atlantic, a taxonomic monograph of sponges of the genus Mycale is presented. Additional material from the region borrowed from the Zoologisk Museum of the University of Copenhagen and incidental samples made by individual collectors were also included. The combined collections contained sixteen species, nine of which are new to science: Mycale (Aegogropila) syringosimilis spec. nov., Mycale (Aegogropila) tenerifensis spec. nov., Mycale (Arenochalina) africamucosa spec. nov., Mycale (Carmia) atropha spec. nov., Mycale (Carmia) guineensis spec. nov., Mycale (Naviculina) cruzi spec. nov., Mycale (Paresperella) janvermeuleni spec. nov., Mycale (Rhaphidotheca) verdensis spec. nov. and Mycale (Zygomycale) sierraleonensis spec. nov. We briefly reviewed six Mycale species known from the region, but not represented in our material, making the faunal diversity twenty-two species. We present a key to all species of Northwest Africa and the neighbouring offshore Atlantic islands. The regional diversity of Mycale species is discussed in comparison to those of other regions.

Beschreibung: Recent (1998) collecting off the coasts of Oman in the course of the EC-MAS3 funded \xe2\x80\x98Symbiosponge\xe2\x80\x99 project yielded three species of the genus Biemna Gray, 1867 (Demospongiae, Poecilosclerida, Mycalina, Desmacellidae) not previously known from the area. One of these appeared to be new to science and is described as Biemna omanensis n.sp.. Its distinguishing features comprise the possession of oxea megascleres, which is of rare occurrence in Biemna, and a full complement of microscleres including microxeas, sigmas, commata, all of which are divisible in two non-overlapping size categories, and raphides. One of the other two species conformed to an earlier described species Biemna ciocalyptoides Burton, 1959, which was discovered to be a junior synonym of Biemna ehrenbergi (Keller, 1889) (new combination). The third species is the common and widespread Biemna tubutata Dendy, 1905.

Beschreibung: The Sultanate of Oman harbours rich populations of sponges, especially in the four coral reef areas (Musandam Peninsula, Muscat coast & Daymaniyat islands, coasts of Masirah Island, and the Khuriya Muriya Islands). Up till now, apart from a few incidental samples, the sponges of Oman were known only from five dredge stations made by the John Murray Expedition 1933-1934 off the south coasts of Oman, near the Khuriya Muriya Islands, between 13.5 and 1415 m. Descriptions of the sponges obtained in these dredges were published by Burton (1959) and the specimens are deposited in the collections of the Natural History Museum, London. To complement these dredge samples, we recently obtained samples collected by SCUBA and shore collecting, mostly from the northern part of Oman, deposited in the collections of the Zoological Museum of the University of Amsterdam. We studied the combined Oman collections of the Amsterdam and London Museums. In the present contribution we treat the species belonging to the tetractinellid and hadromerid Demospongiae. The sponges of the Zoological Museum of Amsterdam are fully described and illustrated, those of the John Murray Expedition are annotated and illustrated here with habit photographs, as these were entirely lacking from Burton\xe2\x80\x99s (1959) report. The collection studied here contains 30 species, two of which are new to science, six are up till now known only from Oman waters, while the remaining 24 species are shared with other areas. The Indian subcontinent shares the most species with Oman, followed by East African areas, while the nearby Arabian coasts share only few species, probably due to the poor knowledge of sponges from this region.

Beschreibung: We present a review of astrophorid species possessing calthrops megascleres as structural megascleres (including species with dichotriaene modifi cations, but excluding mesotriaene and trichotriaene bearing species). Radiating oxeas characteristic of most astrophorids are lacking in such sponges, but auxiliary oxeas are apparently present in some species. Th ese sponges are currently assigned to two families, Pachastrellidae with four nominal genera Dercitus, Stoeba, Dercitancorina, Halinastra (the latter two generally considered junior synonyms of Stoeba), and Calthropellidae with nominal genera Calthropella, Corticellopsis (usually considered a junior synonym), Pachataxa and Pachastrissa. Our review of many original specimens and extensive new material demonstrates the existence of considerable morphological similarity in megasclere shape and arrangement, and possible overlap of some microscleres of these sponges: pseudasters in Dercitus resembling euasters in Calthropella, ataxasters and other modifi ed types in Calthropellidae resembling rhabds in a species of Dercitus. Pachastrellid representatives are proposed to be united in a single genus Dercitus, recognizable as (dicho–)calthrops bearing sponges with sanidaster–like microrhabds. Th ree subgenera, Dercitus s.s., Stoeba and the revived Halinastra are distinguished to accommodate species groups sharing additional characters. Dercitancorina is merged with Dercitus (Stoeba), because the type species, D. lesinensis was found to be barely distinct from D. (S.) plicatus. Similarly, the calthropellid representatives are proposed to be united in a single genus Calthropella recognizable as calthrops bearing sponges with oxyasters. Th ree subgenera, Calthropella s.s., Pachataxa and Corticellopsis are distinguished to accommodate species groups sharing additional characters. Th e calthropellid genus Pachastrissa is considered a junior synonym of Calthropella s.s. because its type species, Pachastrella geodioides, is barely distinct from the type species of Calthropella, C. simplex. Two species previously assigned to Dercitus or Stoeba (Dercitus loricatus and Stoeba natalensis) are excluded from the genus Dercitus as they do not fi t with the emended and improved defi nition of the genus. One species assigned to Calthropella, C. digitata, is excluded from that genus and assigned to the ancorinid genus Stelletta. Based on the similarity of the megascleres and their structure-less arrangement, we predict that the two reviewed genera will be found to be closely related and eventually will need to be accomodated in a single family, but independent molecular evidence is awaited before changes in the family classifi cation, including a verdict on the validity of the family Calthropellidae, will be proposed. Our review included 38 valid species among which fourteen species and one subspecies appear to be new to science. Four of these were represented by insuffi cient material for a proper description, but the remaining ten are described as new species: Dercitus (Stoeba) senegalensis sp. n., Dercitus (Stoeba) verdensis sp. n., Dercitus (Stoeba) fi jiensis sp. n., Dercitus (Stoeba) bahamensis sp. n., Dercitus (Halinastra) berau sp. n., Dercitus (Halinastra) japonensis sp. n., Dercitus (Halinastra) arubensis sp. n., Dercitus (Halinastra) sibogae sp. n., Calthropella (Calthropella) xavierae sp. n., and Calthropella (Pachataxa) pyrifera sp. n. Th e new subspecies, Dercitus (Dercitus) bucklandi lusitanicus ssp. n. is described for southern East Atlantic populations of the nominal species. Several specimens assigned to existing species were found to be deviating to the extent that they are likely members of further undescribed species. Th ese are briefl y discussed to facilitate further studies of the diversity of the two genera. Species of both genera and the six subgenera, including deviating or insuffi ciently characterized specimens belonging to species not yet properly described, are keyed out. Distribution patterns are discussed.