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- Boisvert, Catherine, 1978-
(författare)
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The humerus of Panderichthys in three dimensions and its significance in the context of the fish-tetrapod transition
- 2009
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Ingår i: Acta Zoologica. - : Wiley. - 0001-7272 .- 1463-6395. ; 90:suppl 1, s. 297-305
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Tidskriftsartikel (refereegranskat)abstract
- The humerus of Panderichthyshas been considered to represent a transitionalform between that of tetrapodomorph fish such asEusthenopteronandtetrapods such asAcanthostega. The previous description was based onflattened material and was analysed in the context of the few fossils known atthe time. Since then, several new forms have been described such asGogonasus,Tiktaalikand an isolated humerus from the Catskill Formation. The humeralmorphology ofPanderichthys rhombolepisand its interpretation in this newcontext are therefore reassessed with the help of a three-dimensional modelproduced with themimicssoftware based on a computed tomography scan ofan unflattened specimen as well as comparisons with the originally describedmaterial. The humerus ofPanderichthysdisplays a combination of primitive,derived, intermediate and unique characteristics. It is very similar to themorphology ofTiktaalikbut when it differs from it, it is most often morederived despite the more basal phylogenetic position thatPanderichthysoccupies. What emerges from this study is a much more gradual transformationof the humerus morphology from fish to tetrapods and the ability to distinguishautapomorphies more easily. The picture is more complex than previouslybelieved, with many morphological specializations probably reflecting thebreadth of ecological specializations already present at the time.
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- Borg, Bertil, et al.
(författare)
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The Parapineal Organ of Teleosts
- 1983
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Ingår i: Acta Zoologica. - : Wiley. - 0001-7272 .- 1463-6395. ; 64:4, s. 211-218
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Tidskriftsartikel (refereegranskat)abstract
- A parapineal organ was found to be present in 21 teleost fishes belonging to 20 different families, but was absent in poecilids and cyprinodontids. The parapineal organ was situated on the left side of the brain and sent a nerve tract to the left habenular nucleus, except in Gadus, where a “parapineal organ” appeared to send a nerve tract into the pineal stalk. The parapineal organ of adult Gasterosteus consisted of glial elements and parapinealocytes. The latter were small neurons which sent off the unmyelinated axons that formed the parapineal tract. A single photoreceptor cell was found in a stickleback parapineal organ. 1983 The Royal Swedish Academy of Sciences
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- Dymek, Jakub, et al.
(författare)
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Micro- and macro-morphology of the olfactory organ of Syngnathus typhle (Syngnathidae, Actinopterygii)
- 2021
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Ingår i: Acta Zoologica. - : John Wiley & Sons. - 0001-7272 .- 1463-6395. ; 102:2, s. 206-219
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we describe the micro- and macro-morphology of the olfactory organ in broad-nosed pipefish (Syngnathus typhle) with a comparison of this organ between males and females during breeding season. With 8 adult males, 8 females, and 7 pregnant males collected during the breeding season from the Baltic sea as our samples, our research was conducted using light and electron (TEM, SEM) microscopes and immunohistochemistry methods to distinguish the olfactory sensory neurons. The interior of the olfactory chamber lacked an olfactory rosette. Instead, olfactory receptor epithelium covered the inner walls of the olfactory chamber and, to varying degrees, the inside of the anterior and posterior nostrils. All types of olfactory sensory neurons (ciliated, microvillus, and crypt) were present within the olfactory sensory epithelium, although the crypt sensory neurons were limited to the pregnant and non-pregnant males). The olfactory sensory neurons were present in the areas where the density of the non-sensory epithelium cells was reduced. No significant differences in morphology of the olfactory organ between sexes were found. Nevertheless, only in males crypt sensory neurons were presented in olfactory epithelium, which indicates that sense of smell could play a little role during mating.
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- Ekström, Peter, et al.
(författare)
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The Monoaminergic Paraventricular Organ in the Teleost Ictalurus nebulosus LeSueur, with Special Reference to Its Vascularization
- 1982
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Ingår i: Acta Zoologica. - : Wiley. - 0001-7272 .- 1463-6395. ; 63:1, s. 45-54
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Tidskriftsartikel (refereegranskat)abstract
- Specific, fluorescent, subependymal perikarya were found in the pars anterior of the paraventricular organ (PVOpa), in the nucleus recessus lateralis (NRL) and in the nucleus recessus posterioris (NRP). No fluorescent perikarya were present in the nucleus lateralis tuberis (NLT). Fluorescent nerve tracts connect the PVOpa and the NRL with the NRP, and interconnect the paired NRP. The nucleus preopticus (NPO) and the NLT receive a large input of aminergic nerve fibers. The monoaminergic nuclei are well vascularized, and their vascular plexes seem to be connected. A capillary plexus is situated dorsal to the NRP and exhibits no contact with the pituitary. It is surrounded by the prominent fluorescent tracts connecting the aminergic nuclei. 1982 The Royal Swedish Academy of Sciences
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- Elofsson, Rolf, et al.
(författare)
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Compound eyes of some deep-sea and fiord crustaceans
- 1977
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Ingår i: Acta Zoologica. - : Wiley. - 0001-7272 .- 1463-6395. ; 58, s. 169-177
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Tidskriftsartikel (refereegranskat)abstract
- The compound eyes of the deep-sea mysid Boreomysis scyphops and the two mysid species Amblyops abbreviata and Pseudomma affine, which are indigenous to deep fiords in Norway, have been investigated. The eye stalks are greatly transformed, but contain hypertrophied retinas. The ommatidia of all three species lack a dioptric apparatus, possessing only retinular cells, which are arranged in a cylinder-like fashion. Folds from the retinular cells project into the “cylinder” and are covered with microvilli. The arrangement is explained functionally by an increase in the photopigment-bearing surface as an adaptation to low-light intensities. The orderly arrangement of microvilli in most arthropod compound eyes has been lost, and the arrangement is thus multidirectional in these mysids. With the photopigment dipoles arranged along the microvillar axis, the disorderly arrangement of microvilli signifies a more efficient capture of non-polarized light. It is concluded that the mysid compound eyes show adaptations to low-light intensities probably acquired during the species' evolutionary descent into deep-sea habitats. Amblyops abbreviata and Pseudomma affine, belonging to genera with entirely transformed eyes and with an ultrastructure less “normal” than that of Boreomysis scyphops are believed to be earlier descendants into the deep-sea habitats than the latter species, which belongs to a genus in which most of the species have well-developed eyes.
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