Mikkelsen p m (48 risultati)

The Veliger 44: 271-293, 22 figs 4to, offprint.

Malacologia 46: 473-501, 33 figs, 1 tab 8vo, offprint.

Malacologia 46: 503-544, 15 figs 8vo, offprint.

Malacologia 46: 545-623 8vo, offprint.

Soft cover. , paperbound 0.0.

Ultrastructural features of the ovotestes, spermatogenesis, and the mature sperm are described for three galeommatid bivalves, Divariscintilla yoyo, Divariscintilla troglodytes, and Scintilla sp., from stomatopod burrows in eastern Florida. All three species yielded similar results except with respect to mature sperm dimensions. The ovotestis contains three types of somatic cells within the testicular portion: flattened myoepithelial cells defining the outer acinal wall; underlying pleomorphic follicle cells containing abundant glycogen deposits; and scattered, amoeboid cells containing lysosomal-like inclusions which are closely associated with developing sperm. Early spermatogenesis is typical of that reported from other bivalves. In contrast, the late stages of spermiogenesis involve the migration and gradual rotation of the acrosomal vesicle, resulting in a mature acrosome tilted about 70? from the long axis of the cell. The mature sperm possesses an elongated, slightly curved nucleus; a subterminal, concave acrosome with a nipple-like central projection; five spherical mitochondria and two centnoles in the middlepiece; and a long flagellum. The rotational asymmetry and the presence of perimitochondrial glycogen deposits in these sperm are unusual in the Bivalvia and may be associated with fertilization specializations and larval brooding common among galeommatoideans. 13 pp., 29 figs, gr. 8.…

In July 1999, green mussels were seen for the first time at Tampa Electric Company s (TECO) Gannon Station Power Plant (Gulf of Mexico, Hillsborough Bay portion of Tampa Bay, western coast of Florida) during routine maintenance of the seawater intake system. The mussels were identified as Perna viridis (Linnaeus 1758) based on shell and anatomical characters. This identification has been confirmed by cytological analysis. Perna viridis had previously not been found in the United States or in the Gulf of Mexico. Perna viridis is a native species in the Indian and Pacific Oceans and was discovered in the Caribbean Sea in Trinidad in 1990 and in Jamaica in 1998. The populations are widespread locally and well established; the largest specimen collected was estimated to be 15 months of age. This is the second species of Perna introduced to the Gulf of Mexico, joining Perna perna (Linnaeus 1758), which was discovered in Texas in 1990. Since the initial discovery of Perna viridis in Tampa Bay, range surveys have found it as far north as John s Pass in St. Petersburg, Pinellas County, Florida and as far south as Boca Grande, Charlotte County, Florida. 7 pp., 3 figs, 4.…

29 pp., 13 figs, 4.

33 pp., 8 figs, 4.

21 pp., 32 figs, gr. 8.

20 pp., 7 figs, gr. 8.

23 pp., 2 figs, 8.

23 pp., 27 figs, 4.

24 pp., 14 figs, 4.

24 pp., 33 figs., 4.

24 pp., 4.

76 pp., gr. 8.

Two western Atlantic vitrinellids, Cyclostremiscus beauii (Fischer, 1857) and Circulus texanus (Moore, 1965) new combination are redescribed based on a study of live snails from the burrows of the stomatopod crustacean Lysiosquilla scabricauda (Lamarck, 1818). Anatomy and reproductive biology are emphasized, with the first recorded description of spawn and larval development in the family. Synonymies are given, and a lectotype is selected for Cy. beauii. Literature data concerning anatomy are reviewed for the marine near-planispiral rissoaceans; Vitrinellidae (including Cyclostremiscus and Circulus, with Circulidae as a synonym) is considered distinct from Tornidae. Unusual morphological aspects of Cy. beauii are discussed, including external ciliation patterns, pallial tentacles (which are functionally and morphologically different from each other), and stomach morphology {with a large posterior chamber). Protandrous sequential hermaphroditism in Cy. beauii is inferred (for the first time in the Rissoacea) from morphological evidence of sex change correlated with size. 29 pp., 68 figs, 4.…

32 pp., 32 figs, gr. 8.