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1
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Types of vitellocytes and vitellogenesis in the Cestoda in relation to different types of embryonic development, ovoviviparity and life cycles

100%
Swiderski Z., Xylander W. E. R.
Wiadomości Parazytologiczne
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1998
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tom 44
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nr 3
2
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
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Ovoviviparity in freshwater snails - advantages and disadvantages

86%
Jakubik B.
Folia Malacologica
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2016
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tom 24
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nr 1
3

Is ovoviviparity rightly advertised?

72%
Pokryszko B. M.
Folia Malacologica
|
1998
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tom 06
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nr 1-4
4
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Egg retention in the clausiliid Balea (Pseudalinda) fallax (Rossmassler, 1836) from Roztocze (S. E. Poland)

58%
Sulikowska-Drozd A., Maltz T. K., Stachyra P.
Folia Malacologica
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2012
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tom 20
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nr 1
Adults of Balea fallax sampled monthly from the Roztocze Upland were dissected to examine the occurrence of uterine egg retention. Developing eggs were found in snails collected between May and August. In June more than 60% of the studied individuals were gravid, while in other months egg-retaining snails constituted less than 10% of the sample. The number of retained eggs ranged from 3 to 17 (mean 12.3) and was not related to the adult shell size. In June the majority of eggs contained shelled embryos (maximum shell size1.1 whorl). The reproduction mode of B. fallax is compared with those of other ovoviviparous clausiliids of Central Europe.
5

Ultrastructure of intrauterine eggs: Evidence of early ovoviviparity in the caryophyllidean cestode Wenyonia virilis Woodland, 1923

58%
Mlocicki D., Swiderski Z., Mackiewicz J. S., Ibraheem M. H.
Acta Parasitologica
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2010
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tom 55
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nr 4
349-358
Ultrastructural evidence for early intraurerine embryonic development of Wenyonia virilis is presented. At the initial stage of egg formation, the fertilized oocyte or ovum is surrounded by numerous vitellocytes and newly formed eggshell. Individual vitellocytes undergo progressive fusion into a vitelline syncytium. During cleavage divisions, three types of blastomeres are formed: macromeres, mesomeres and micromeres. Two large macromeres contain a large nucleus with spherical nucleolus and numerous small heterochromatin islands dispersed in moderately electron-dense nucleoplasm. The granular cytoplasm shows a few large mitochondria. Medium-sized mesomeres contain a spherical nucleus with numerous heterochromatin islands, adjacent to the nuclear envelope, and a prominent electron-dense nucleolus. Their nuclei are embedded in granular cytoplasm with a few large and numerous small mitochondria and Golgi complexes. The small micromeres are characterized by presence of spherical nucleoli with large areas of highly condensed heterochromatin and a few islands of granular electron-lucent nucleoplasm. Their granular cytoplasm shows a few small lipid droplets and several spherical mitochondria. Majority of micromeres give rise to the hexacanth but many of them also undergo degeneration or apoptosis. Both mesomeres and macromeres are engaged in the formation of the oncospheral envelopes. The outer envelope is formed by a fusion of two macromeres whereas the inner envelope originates from a fusion of mesomeres. The intrauterine eggs of W. virilis usually contain an embryo at the early preoncopheral phase of development and possesses three primary envelopes: (1) thick eggshell; (2) thin cytoplasmic layer of the outer envelope and (3) inner envelope. Based on embryonic development, egg type and life-cycle characteristics, caryophyllideans tend to show closer affinities to spathebothriideans than to the former pseudophyllideans.
6

Life history of Alinda biplicata (Montagu, 1803) (Gastropoda: Pulmonata: Clausiliidae) based on five-year laboratory observations

58%
Maltz T. K., Sulikowska-Drozd A.
Annales Zoologici
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2012
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tom 62
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nr 4
The maturation, growth and reproduction of Alinda biplicata in the laboratory were studied over a five-year period. The snails were kept in pairs and groups of a few individuals. The initial material came from two populations from SW. Poland. The snails reproduced during the whole year, more intensively in the spring and autumn. We confirmed the ovoviviparity of A. biplicata: the whole embrynic development takes place in eggs retained in the parent's uterus. The snails gave birth to juveniles (no egg-laying was observed), and the uteri of dissected individuals contained from 3 to 15 eggs. The number of juveniles per litter was 1 to 8. The snails produced 3 to 20 juveniles in 2-9 batches per year. The neonate shells had 2.1-2.9 whorls and height of 1-1.6 mm. Growth to adulthood lasted 20 to 56 weeks and the time increased with increasing density of snails. The snails became sexually mature 5-6 months after completeion of shell growth and formation of the closing apparatus. The juvenile mortality ranged from 16.7% to 60.6% and increased with density. The life span in the laboratory was 220 to 295 weeks (4 to 6 years). These results are compared with those for other species; A. biplicata resembles other large ovoviviparous Clausiliidae species.
7
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Coelacanths from the Middle Triassic Luoping Biota, Yunnan, South China, with the earliest evidence of ovoviviparity

58%
Wen W., Zhang Q.-Y., Hu S.-X., Benton M. J., Zhou C.-Y., Tao X., Huang J.-Y., Chen Z.-Q.
Acta Palaeontologica Polonica
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2013
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tom 58
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nr 1
The fossil record of coelacanths is patchy, with very few taxa known from the Triassic of Asia. We report here two new genera and species of coelacanths from the Luoping Biota, a recently found site of exceptional fossil preservation from Yunnan, South China. The first new taxon, Luopingcoelacanthus eurylacrimalis, is based on four specimens, which to− gether show most aspects of the anatomy. One specimen shows two small coelacanths inside the ventral portion of the ab− dominal cavity, and these are interpreted as intrauterine embryos, close to birth size, based on comparisons with previ− ously reported embryos of the fossil coelacanths Rhabdoderma and Undina, and the extant genus Latimeria. Our new find extends the evidence for ovoviviparity in coelacanths back from the Late Jurassic to the Middle Triassic. The second new taxon, Yunnancoelacanthus acrotuberculatus, is based on one specimen, and differs from Luopingcoelacanthus in the dentary, lachrymojugal, number of rays of the first dorsal fin, and especially in the ornament on dermal bones and scales. Acladistic analysis shows that the new taxa are closest relatives to the derived clade Latimerioidei. The relatively high di− versity of coelacanths in the Early Triassic, and adaptations of living Latimeria to low−oxygen conditions, suggests that the group may have included ‘disaster taxa’ that benefited from anoxic and dysoxic ocean conditions in the aftermath of the end−Permian mass extinction.
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