On the structure of the pulmonate osphradium

Summary The cellular organisation of the osphradium of Planorbarius as revealed by the previously described light microscope studies is confirmed in the present study. A third epithelial cell type, the basal cell, is described. Perception is carried out by dendritic processes from osphradial sensory neurones, forming free nerve-endings in the sensory region of the osphradial epithelium. Ciliated cells and secretory cells of the osphradial epithelium are concerned with the transport of material in the osphradial canal. Many of the ultrastructural features of molluscan central ganglia are present in the osphradial ganglion, including inter-axonal chemical synapses. Neuromuscular junctions are present in the sheath surrounding the organ and these may be involved in a behavioural response of the organ. The need for further electrophysiological studies is emphasised.     

Initial analysis of immunochemical cell surface properties, location and formation of the serotonergic apical ganglion in sea urchin embryos

In the present study it was found that serotonergic apical ganglion (SAG)-forming cells in plutei of the sea urchin, Hemicentrotus pulcherrimus, possessed a characteristic pear shape with broad apical sides and a pointed basal side in the acron epithelium. The basal side extended axons through the space between the epithelium and the basal lamina toward the midline of the embryo that aligned parallel to the embryonic anteroposterior axis. Serotonergic apical ganglion-forming cells had epithelial cell surface-specific proteins on their entire surface. The SAG in 4-arm plutei was composed of a 4-cell trunk region that aligned at right angles to the embryonic anteroposterior axis, and forked into two branches of one to two cells at both ends. Two branches extended toward the oral and the other two toward the aboral region, respectively. Double-stained immunohistochemistry using antiserotonin antibodies and oral ectoderm-specific anti-Ecto V monoclonal antibody or aboral ectoderm-specific anti-Ars antibodies indicated that SAG was in the aboral ectoderm region. Serotonergic apical ganglion cells were first detected in late gastrulae and increased in number rapidly between 36 and 48 h after fertilization, and then slowly afterwards. A 5-bromo-2-deoxyuridine incorporation study indicated that none of the increased SAG cells were in the S phase during the aforementioned period, suggesting that SAG cells do not proliferate by cell division, but acquire the property in particular cells by transdifferentiation using a mechanism that has yet to be elucidated.     

Veligers from the nudibranch <Emphasis Type="Italic">Dendronotus</Emphasis><Emphasis Type="Italic">frondosus</Emphasis> show shell growth and extended planktonic period in laboratory culture

The planktonic period of planktotrophic veliger larvae from the nudibranch Dendronotus frondosus was characterized by laboratory culture methods. Larvae in culture successfully metamorphosed at 73–86 days after hatching. These veligers have Type 2 (Thompson) larval shells that significantly increased in length over the first 7–14 days after hatching. Direct observations of the development of nudibranch larvae with Type 2 protoconchs are limited, and these data help clarify previous attempts to correlate shell type and growth with minimum planktonic periods. Although these are not absolute values for the planktonic period of D. frondosus larvae, these data show the potential for extended larval dispersal and may help explain reports of an extensive geographic range in north-temperate waters for this species.     

Reproduction and development of the limpet Limalepeta lima (Dall, 1918) (Gastropoda: Lepetidae) from Peter the Great Bay, Sea of Japan

Reproduction and larval development of the limpet Limalepeta lima (Dall, 1918) were studied under laboratory conditions for the first time. L. lima breeds in early July; it exhibits external fertilization and the pelagic lecithotrophic type of development. Larvae, juvenile, and adult specimens have different shell sculptures. Development from fertilization to settling and metamorphosis continues for 4–5 days at a water temperature of 16°C.     

Revision of the genus Thetidos Hedley, 1899 (Gastropoda: Conoidea: Raphitomidae) in the Indo-Pacific with descriptions of three new species

The genus Thetidos was established to accommodate a single species Thetidos morsura, a minute turriform conoidean with an unremarkable paucispiral protoconch, but possessing characteristic globose whorls of the teleoconch and three strong denticles on the inside of outer apertural lip. Subsequently, Thetidos was considered synonymous with Lienardia, and has rarely been mentioned in literature until the recent discovery of a remarkably similar species Thetidos tridentata, though it is different in protoconch morphology. Both molecular data and protoconch morphology unequivocally suggested placement of the new species in Raphitomidae. Examination of shells from the Indo-Pacific identified a number of similar forms, all referable to the genus Thetidos. Six species are now recognized within the genus; of them three, Thetidos puillandrei n. sp., Thetidos minutissima n. sp., Thetidos pallida n. sp., are here described as new. Thetidos species are now known from subtidal depths from the Philippines and Sulawesi to French Polynesia. Thetidos morsura is the only species of the genus that possesses a paucispiral protoconch suggestive of a non-planktotrophic development, although it displays a wide geographic range and a high morphological variability.

http://zoobank.org/urn:lsid:zoobank.org:pub:1F2001CC-6BEA-4B26-AFB8-6B337E101FDB     

Plant stem cells and their regulations in shoot apical meristems

Stem cells in plants, established during embryogenesis, are located in the centers of the shoot apical meristem (SAM) and the root apical meristem (RAM). Stem cells in SAM have a capacity to renew themselves and to produce new organs and tissues indefinitely. Although fully differentiated organs such as leaves do not contain stem cells, cells in such organs do have the capacity to re-establish new stem cells, especially under the induction of phytohormones in vitro. Cytokinin and auxin are critical in creating position signals in the SAM to maintain the stem cell organizing center and to position the new organ primordia, respectively. This review addresses the distinct features of plant stem cells and focuses on how stem cell renewal and differentiation are regulated in SAMs.     

Loss of planktotrophy and speciation: geographical fragmentation in the deep-water gastropod genus Bathytoma (Gastropoda,Conoidea) in the western Pacific

Dispersal capabilities are crucial in how speciation patterns are determined in marine invertebrates. Species possessing a long-living planktonic larva apparently have a dispersal advantage over those with non-planktotrophic development, and their distant populations may exchange genetic material, maintaining a broad geographical range for the species. Recent species of the gastropod genus Bathytoma (Conoidea) are all characterized by non-planktotrophic development, having most probably lost a free-swimming larva in the pre-Pliocene, as Miocene fossils have protoconchs indicating planktotrophic larval development. All have a bathyal distribution (100–1500 m), which implies that their capability for direct expansion on the bottom is restricted by both deep-sea basins and shallow-water areas, especially in insular West and South-West Indo-Pacific. Therefore, it can be hypothesized that Bathytoma populations should represent numerous, mostly allopatric taxa restricted to a single or contiguous island groups. We tested this hypothesis using molecular and morphological characters independently. One hundred and thirty-eight specimens from the Philippines, Solomons, Vanuatu, and the Coral Sea were sequenced for one mitochondrial (COI) and one nuclear (ITS2) gene, and 14 operational molecular units were recognized. When these molecular units are overlaid over shell characters, 13 species (11 unnamed) and one form of uncertain status are recognized: three occur in the Philippines, six in the Solomons and one in New Caledonia. Broad distributions (inter-archipelagic) are uncommon (three species). On the whole, the phylogeographic pattern of the diversity in the genus is rather complex and probably also reflects processes of sympatric and fine-scale allopatric speciation, and local extinctions. The eleven new species are described and named.     

植物干细胞培养研究进展

植物干细胞位于分生组织,是处于未分化状态的细胞,液泡化程度低,具有较高的线粒体活性,遗传稳定,具有很强的自我更新和再生能力。植物干细胞培养在下游制药和功能性食品以及化妆品行业具有广泛的应用潜质。文中综述了植物干细胞的基本培养技术、鉴别技术,为该领域的深入研究提供参考。     

Reproduction and larval development of the gastropodAlaba vladivostokensis in Vostok Bay, the Sea of Japan

The reproduction and development of the prosobranch gastropodAlaba vladivostokensis Bartsch were studied. In Vostok Bay,A. vladivostokensis reproduces in the warmest season at water temperatures of 19–23°C. The females lay egg masses in the shape of flat, coiled bands on eelgrass leaves and on sargosso thalluses. The total period of development from egg laying to larval settling takes 25–27 days. The reproduction and development patterns and larval morphology ofA. vladivostokensis are similar to that ofAustralaba picta (A. Adams), which inhabits the coast of Japan. It is suggested that the population ofA. vladivostokensis in Peter the Great Bay should considered as part of the wide geographical range ofA. picta.