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| 2. |
- Elofsson, Rolf
(författare)
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Some observations on the internal morphology of Hansen's nauplius Y (Crustacea)
- 1971
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Ingår i: Sarsia. - : Informa UK Limited. - 0036-4827. ; 46, s. 23-40
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Tidskriftsartikel (refereegranskat)abstract
- The internal morphology of the crustacean larval form that Hansen (1899) called nauplius y has revealed a remarkably advanced early nauplius. The nervous system is well developed and differentiated. It is connected with the anlagen of the compound eyes. A presumed filamentous base of the SPX-organ connects with these. The nauplius eye is present in a three-partite form with two retinula cells in each cup. The alimentary canal consists of the ectodermal oesophagus with an inner layer of longitudinal muscles and an outer circular layer, and of the endodermal midgut with cells having microvillous borders against the lumen. There is no proctodeum or anus present. There is a well-developed muscular system. The head contains a large gland with a paired ventral outlet. A new dorsocaudal organ of doubtful function is described.The morphological facts presented in this investigation indicate that the nauplius y, as knowledge stands today, is close to the Cirripedia.
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| 3. |
- Elofsson, Rolf
(författare)
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The larvae of Pasiphaea multidentata (Esmark) and Pasiphaea tarda (Kröyer).
- 1961
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Ingår i: Sarsia. - : Informa UK Limited. - 0036-4827. ; 4, s. 43-53
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Tidskriftsartikel (refereegranskat)abstract
- Pasiphaeid larvae collected in the Korsfjord, western Norway, were found to split up into two groups. Mainly two characteristics separated the larvae viz. the size of the larvae and the number of telson spines. The group with small larvae (8 to 10 mm) and the larger number of telson spines is referred to Pasiphaea multidentata and that with large larvae (10 to 12 mm) and fewer telson spines to Pasiphaea tarda. Embryos ready to hatch from an ovigerous female of Pasiphaea multidentata were dissected and it is shown that they resemble the small larvae above.
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| 4. |
- Elofsson, Rolf
(författare)
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The nauplius eye and frontal organs in decapoda (Crustacea)
- 1963
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Ingår i: Sarsia. - : Informa UK Limited. - 0036-4827. ; 12, s. 1-68
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Tidskriftsartikel (refereegranskat)abstract
- The present investigation concerns the nauplius eye and frontal organs in decapod Crustaceans. Representatives from all groups of the Decapoda are included. Some of the more important results are abstracted.The nauplius eye in several families within the Eucyphidea is more complicated than generally believed. It consists of a nauplius eye s. s. with three cups and three sensory cells in each and the incorporated dorsal frontal organ, which functions as an eye. The sensory cells are everse.The dorsal frontal organ is thus intimately connected with the nauplius eye s. s. and must not be mixed up with the eye papilla and the sensory pore X organ.The dorsal frontal organ is subjected to a considerable degree of variation. As part of a nauplius eye s, 1. as mentioned above it is an eye. In many species all over the Decapoda the frontal organ is reduced. A line of transformation can be shown from eye appearance through intermediate stages to “globuli” cells situated in the ganglion layer of the brain.The ventral frontal organ is more common than formerly believed and its paired nature is stressed.The author acceds to Hanström's hypothesis (1926) concerning the phytogeny of the frontal organs.
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| 5. |
- Elofsson, Rolf
(författare)
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The nauplius eye and frontal organs in Malacostraca (Crustacea).
- 1965
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Ingår i: Sarsia. - : Informa UK Limited. - 0036-4827. ; 19, s. 1-54
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Tidskriftsartikel (refereegranskat)abstract
- The nauplius eye and frontal organs in the Malacostraca have been investigated. The present work is a direct continuation of the author's investigation of the same organs in decapod malacostracans (Elofsson, 1963). The results obtained confirm the recognition of a nauplius eye sensu iatu and a nauplius eye sensu strictu. The former is a combination of the latter and the dorsal frontal organ. It occurs together with the ventral frontal organ in the Decapoda and the Stomatopoda. The nauplius eye s. s. and the dorsal frontal organ, though separated, occur in the Anaspidacea. The nauplius eye s. s. and the ventral frontal organ, separated as is always the case in the Malacostraca, occur in the Euphausiacea. The Mysidacea have only the ventral frontal organ, The remaining orders of the Malacostraca investigated have none of these organs. The results obtained are discussed in morphological and phylogenetic terms. The morphological problems are the homologies and criteria of the organs. The criteria established in 1963 are confirmed. The results obtained lead to interesting phylogenetic considerations. A rearrangement of supposed relationships among the Malacostraca is proposed; the metaphor of the phylogenetic tree, however, should be used with great caution.
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| 6. |
- Elofsson, Rolf
(författare)
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The nauplius eye and frontal organs of the non-Malacostraca (Crustacea).
- 1966
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Ingår i: Sarsia. - : Informa UK Limited. - 0036-4827. ; 25, s. 1-128
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Tidskriftsartikel (refereegranskat)abstract
- The present work is a continuation of the morphological studies of the nauplius eye and frontal organs of the Crustacea. The previous papers on this topic comprised the Decapoda (ELOFSSON, 1963) and the Malacostraca (ELOFSSON, 1965). Its has been found that the nauplius eye and frontal organs of the Crustacea are separated into four different types. These comprise the Phyl-lopoda, Anostraca, Maxillipoda-Ostracoda and Malacostraca. Frontal organs do not appear in the maxillopod-ostracod group, but are present as paired dorsal and ventral frontal organs in the Malacostraca, paired ventral frontal organ in the Anostraca, and paired distal and unpaired posterior medial frontal organ in the Phyllopoda. The frontal organs of the different groups are not homologous. Their nature as reduced frontal eyes is maintained. The nauplius eye (and frontal organs when present and developed as eyes) shows, for instance, the following dissimilarities. The sensory cells of the eyes of the Malacostraca are everse with rhabdomeres at their sides combining into rhabdoms. The remaining groups have inverse sensory cells and rhabdomeres around the distal tip of the cells. Each cup in the maxillopod-ostracod line has tapetal and lens cells which are not found in the other types. The phyllopod group has a unique arrangement of the eye and frontal organs, depending on the typical and special development of the organs. Due to the structural dissimilarities and lack of transitional forms the frontal eyes (= nauplius eye and frontal organs) of the four different groups are considered non-homologous, and this view is discussed with regard to morphological, phylogenetical and functional viewpoints.
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| 7. |
- Hallberg, Eric, et al.
(författare)
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An ascothoracid compound eye (Crustacea)
- 1985
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Ingår i: Sarsia. - : Informa UK Limited. - 0036-4827. ; 70, s. 167-171
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Tidskriftsartikel (refereegranskat)abstract
- The ultrastructure of the compound eye of an ascothoracid larva — the only known occurrence of compound eyes in the Ascothoracida — is described. The ommatidia of apposition type consist of a crystalline cone composed of three cells and up to six retinular cells. Poor fixation of the scarce material allows no safe judgement about the number of retinular cells and the nature of two distal cells surrounding the crystalline cones. The structure of these compound eyes most closely resembles the cirriped compound eye.
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| 10. |
- Spicer, J. I., et al.
(författare)
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Metabolic responses to low salinity of the shipworm Teredo navalis (L.)
- 2003
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Ingår i: Sarsia. - 0036-4827. ; 88:4, s. 302-305
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Tidskriftsartikel (refereegranskat)abstract
- It has long been thought that shipworms are sensitive to salinity changes, but few studies have investigated this possibility. The oxygen uptake of excised gill tissue from individuals of a population of the shipworm Teredo navalis from southwest Sweden decreased with decreasing salinity. The greatest fall occurred between S = 4 and 8 PSU. Excised gill tissue showed little effect of salinity on ciliary beat rate at S greater than or equal to 3-4 PSU, but below this beating ceased. Individuals withdrew their siphons and sealed their bur-rows at S = 4-8 PSU. Burrows could remain closed at S < 4 PSU for at least 6 days at 22 degreesC. Siphons re-emerged within minutes of a return to S > 4 PSU. We conclude that a salinity range of 4-8 PSU is critical for this population of T. navalis. This fits well with information on salinity tolerance from other populations of this species.
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