Hoagland k e (26 Ergebnisse)

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4 pp., 4.

11 pp., 5 figs, 4.

Examination of museum specimens verified the existence of at least 3 distinct species of the marine gastropod genus Crepidula off the coast of southern Brazil: C. protea, C. plana and C. aculeata. Specimens of C. protea were collected alive by dredging. They carried broods of larvae that appeared ready to be released in the veliger stage. Unlike other Crepidula, the larvae were imbedded in the matrix of the egg capsule material. Other character states distinguishing C. protea and C. plana are discussed, as well as the population structure of C. protea. The distribution of C. protea is limited compared with that of C. plana. 5 pp., 1 figs, 4.…

Twenty-two type lots of Crepidula from the Paris Museum are discussed in terms of synonymy and type-locality. Seven are valid species, 13 are synonyms and 2 are nomina dubia. Three type lots of Calyptraeidae that have been confused with Crepidula are also discussed. 8 pp., 9 figs, gr. 8.

Illustrated Wrappers. Zustand: Near Fine. First Edition. 64 Pp. Illustrated Wrappers. Near Fine, Slight Rubbing, No Marks Or Discoloration.

We rediscovered Tricula montana Benson 1843, a species not found since it was described. Tricula montana is the type species for Tricula by Benson s original designation. Anatomical data show that Tricula s.s. comprises the T. bollingi species group previously known from northwest Thailand and Yunnan, China. A new genus, Neotricula Davis, is here described for the Tricula aperta species group, species of which are distributed from northwest Thailand to the lower Mekong River in Thailand, Laos, and Cambodia. Phylogenetic relationships and relevance of these genera to transmission of schistosomes are discussed. New taxon: Neotricula n. gen. 17 pp., 10 figs, gr. 8.…

8 pp., 7 figs, 4.

Poecilogony, defined as more than one mode of reproduction within a single species, has been reported in various invertebrates, including mollusks and polychaetes. Many cases that have been described involve planktotrophic and non-planktotrophic development in allopatric populations, or instances of planktonic larval stages and benthic juveniles being found together, but not associated with adults. There is always the possibility of mis-assignment of larvae to adults of the wrong species. Most cases that offer these kinds of evidence are now known to involve cryptic species, not poecilogony. There are a few species in which release of young occurs both at metamorphosis and a day or so before. There may be cases in which extracellular yolk or nurse-egg production is variable and allows the release of larvae at different stages, but no actual instance is known. A few instances are known of allopatric populations with different modes of development and other differences in reproductive characters that lack reproductive isolation when brought into the laboratory. The polychaetes Streblospio benedicti, Cirriformia tentaculata, Boccardia proboscidea, and the opisthobranch Elysia chlorotica are in this category. All examples of poecilogony require further genetic substantiation. Despite the scarcity of proven examples of poecilogony, the presence of more than one mode of reproduction within a genus is the rule in most invertebrate phyla. The evolutionary and ecological significance of these patterns is discussed. 17 pp., 4.…

17 pp., 1 fig., gr. 8.

22 pp., 2 figs, gr. 8.

Anatomical studies of living Fenouilia kreitneri (Neumayr), done in Yunnan, China, show that this species is a member of the Pomatiopsidae: Triculinae: Triculini. Multivariate and cladistic analyses demonstrate the close relationship of this species to Tricula bollingi Davis and to Lacunopsis. Fenouilia, endemic in a few lakes of Yunnan, China, and collected for this study from Lake Er Hai, gives insight into the evolution of Lacunopsis of the Triculinae: Lacunopsini from stock giving rise to the Tricula bollingi species group. This study solves a long-standing problem concerning the classification of Fenouilia, and probably (in part) the classification of the genera Delavaya and Parapyrgula. They are not cerithiaceans as previously proposed. Anatomical, geological and zoogeographical data are consistent with Davis hypothesis of the origin and direction of evolution of the Triculinae (Davis 1979, 1980, 1981). 23 pp., 12 figs, 4. …

27 pp., 10 figs, 7 tabs, gr. 8.

Illustrated Wrappers. Zustand: Good. First Edition. 64 Pp. Illustrated Wrappers. Rubbing, Wear Along Sipne Edge.

Two new species of the rissoacean prosobranch genus Stenothyra (S. khongi and S. huaimoi) are described, six other phenotypically similar species are redescribed and sources of confusion among species are pointed out. Phenetic relationships among populations and species are assessed using multivariate statistical techniques. The species are differentiated primarily by shell size and proportions, secondly by pigmentation and sculpture, and thirdly, by characteristics of the aperture and body whorl. The most variable characters are shell sculpture and some elements of shell shape. The distribution of character states among the species indicates that unidirectional evolutionary change has not occurred. Instead, we postulate that speciation has occurred following isolation of populations in the various tributaries and island regions of the Mekong River system, in a process of positive rheotropism. S. mcmulleni has the greatest range and abundance while S. huaimoi, S. khongi, S. fasciata, S. wykoffi, and S. confinis are each narrowly distributed in a different river. At least one species is found in every river of the Mekong drainage. Each species reaches maximum abundance in a different locality, but overlap occurs. The phenetically most similar species are generally allopatric. Sympatry usually occurs between species that differ in size, but there are two exceptions involving S. ovalis. The constant relationship of shell length to width and the inconsistent relationship between shell size and aperture size, and between shell size and size of the body whorl, implies that ecological differences rather than scaling factors dictate shell proportions among the eight species. Trends of intraspecific variation in shape are distinct for several of the species. 40 pp., 72 figs, stapled gr. 8.…

38 pp., 7 figs, 20 tabs, gr. 8.

In order to determine the relationships between Succinea ovalis Say, S. ovalis chittenangoensis Pilsbry of Chittenango Falls, New York, and specimens of uncertain affinity from Minnesota, electrophoretic studies of allozymes were conducted. Oxyloma retusa Lea and O. decampi gouldi Pilsbry of Chittenango Falls were included in the analysis for comparison. Via electrophoresis and shell morphometrics, we found yet another taxon at Chittenango Falls, Succinea sp., with shell shape similar to Succinea putris (Linnaeus) of Europe. Subsequent collection yielded two unknown species discovered by noting differences in mortality rate in the laboratory, considerable anatomical differences, and later, electrophoretic data. Anatomical studies were done on the above Succinea, including S. putris of Holland, and a population of Succinea from Philadelphia that also has a shell shape similar to S. putris. Because we could not find living topotypical S. ovalis from Philadelphia, we dissected topotypical material collected in 1923 to confirm the anatomy of S. ovalis. Succinea chittenangoensis is indistinguishable electrophoretically from S. ovalis, but has anatomical and shell-morphological differences worthy of species status. The Minnesota specimens belong to two closely-related taxa, probably subspecies, that in turn are specifically distinct from but in the same species group as S. ovalis and S. chittenangoensis. These taxa are relegated to the genus Novisuccinea Pilsbry. The two Oxyloma taxa group as a genus distinct from Succinea, as expected. Based on electrophoresis, the Succinea spp. of Chittenango Falls and Philadelphia are members of Succinea s.s., more closely related to Oxyloma than to Novisuccinea. Within Succinea s.s., one population from New York was referrable to S. pennsylvanica Pilsbry; the other, along with the population from Philadelphia, grouped with the S. putris species complex. We conclude that N. chittenangoensis is a valid species and a member of the N. ovalis species complex along with the species from Minnesota. S. putris in Europe is probably a species complex, i.e. a superspecies, with some members found in North America. 60 pp., 60 figs, stapled gr. 8.…

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