Zoologischer Anzeiger - A Journal of Comparative Zoology, 2001
This study provides a detailed description of the cephalic sensory organ (CSO) of four species of... more This study provides a detailed description of the cephalic sensory organ (CSO) of four species of the cephalaspid genus Haminoea (Opisthobranchia, Gastropoda), based on light and electron microscopical investigations of complete serially sectioned larvae. The organ, which is present in all species investigated, exhibits the characteristic elements of gastropod CSOs: Two ciliary tuft cells; four to six ampullary cells showing intracellular lumina filled with bundles of tightly packed cilia; three para-ampullary cells interspersed medially and positioned laterally; a modified thickened microvillar border. A ciliary tuft is present in the planktotrophic developer Haminoea cymbalum, H. exigua and the intracapsular developer H. navicula, while it is lacking in the poecilogonous developer H. callidegenita. The number of ampullary cells ranges from 4 (H. cymbalum, H. exigua) to 6 (H. navicula, H. callidegenita). In general no clear correlation of development mode (e.g. planktotrophic vs. intracapsular) and organization of the organ can be found. Most structures, except ciliary tufts and number of ampullary cells, are very similar among the investigated species. The CSO cells of Haminoea are compared with those of other gastropods in the literature. The organ as a whole as well as its cellular components of Haminoea can clearly be homologized with such structures in other gastropods. The CSO's relationship to apical organs with regard to homology and the function is discussed.
Ultrastructural features of spermatozoa and spermatogenesis are described for the first time in a... more Ultrastructural features of spermatozoa and spermatogenesis are described for the first time in a monoplacophoran and compared with data for other conchiferan molluses. Spermatozoa of Laevipilina antarctica Warén and Hain, 1992, are of the structurally simple, aquasperm type, featuring a conical acrosome, a compact nucleus with lacunae, a short midpiece and a single flagellum. The acrosomal vesicle shows an electron-dense
The Journal of the Acoustical Society of America, 2000
Tuna fishers in the eastern Pacific Ocean often exploit an association between a few genus of dol... more Tuna fishers in the eastern Pacific Ocean often exploit an association between a few genus of dolphin (Stenella and Delphinus) and yellowfin tuna (Thunnus albacares) to locate and capture the tuna. Identification of a mechanism which facilitates the tuna/dolphin bond may provide a means of exploiting the bond and capturing tuna without catching dolphin. To investigate if tuna may be attracted to low-frequency sounds produced by dolphins, source levels of bottlenose dolphin (Tursiops truncatus) jaw pops, breaches, and tail slaps were experimentally measured and used to estimate the maximum range at which yellowfin could detect similar sounds produced by pelagic species. The effective acoustic stimulus to the tuna was defined as the maximum one-third-octave level between 200 and 800 Hz, the frequency range where T. albacares is most sensitive. Spherical spreading was assumed to predict transmission loss with range. Breaches and jaw pops produced maximum one-third-octave source levels between 200 and 800 Hz of 153 (+/-4) and 163 (+/-2) dB re: 1 microPa-m, respectively, which resulted in estimated detection ranges of 340-840 and 660-1040 m, respectively. Tail slaps had lower source levels [max. 141 (+/-3) dB re: 1 microPa-m] and a maximum detection range of approximately 90-180 m.
The apical area of larvae of four primitive pulmonate species was investigated by means of serial... more The apical area of larvae of four primitive pulmonate species was investigated by means of serial ultrathin and light microscope sections. Cephalic sensory organs (CSOs) were found in the larvae of Onchidium cf. branchiferum (Onchidiidae) and Laemodonta octanfracta (Ellobiidae), while no trace of the organ was present in the larvae of Ovatella myosotis (Ellobiidae) or Williamia radiata (Siphonariidae). TEM investigation revealed very similar CSOs in O. cf. branchiferum and L. octanfracta, with characteristic putative sensory cell types: ampullary cells with an internal ampulla containing densely packed cilia, para-ampullary cells with external cilia parallel to the surface, and ciliary tuft cells, bearing short ciliary tufts. The epithelium covering the organ has a thick microvillar border with microvilli laterally bearing a pair of electron-dense accumulations and a glycocalyx with interspersed flat plaque-like elements. While homologues of all major elements of the CSO can be found in other gastropod taxa, for example caenogastropods and opisthobranchs, the homology of the ampullary cell with similar cells in nongastropods appears unlikely. The CSO of L. octanfracta is associated with an additional structure, an epithelial external protrusion, lying ventral to the CSO. The absence of the organ in W. radiata weakens hypotheses on the organ's function of examining settlement conditions and velar control.
ABSTRACT The anatomy of the neopilinoid limpet Micropilina arntzi (Warén & Hain, 1992, Th... more ABSTRACT The anatomy of the neopilinoid limpet Micropilina arntzi (Warén & Hain, 1992, The Veliger 35: 165–176) is described on the basis of graphic reconstructions of semithin serial sections. Hard parts, anatomical features and reproductive biology of the minute species differ considerably from those of all other anatomically known neopilinoid species. Therefore, Micropilinidae fam. nov. is erected for this genus.Micropilina arntzi may be considered as partly paedomorphic with respect to the seriality of ventilatory (ctenidia), excretory or genital organs, or may represent an archaic condition within the Tryblidiida. Ontogenetic and comparative anatomical data strongly suggest that the serial repetition of the various organ systems should be regarded as one of several autapomorphic features of the Neopilinoidea (Tryblidiida).
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2001
This study provides a detailed description of the cephalic sensory organ (CSO) of four species of... more This study provides a detailed description of the cephalic sensory organ (CSO) of four species of the cephalaspid genus Haminoea (Opisthobranchia, Gastropoda), based on light and electron microscopical investigations of complete serially sectioned larvae. The organ, which is present in all species investigated, exhibits the characteristic elements of gastropod CSOs: Two ciliary tuft cells; four to six ampullary cells showing intracellular lumina filled with bundles of tightly packed cilia; three para-ampullary cells interspersed medially and positioned laterally; a modified thickened microvillar border. A ciliary tuft is present in the planktotrophic developer Haminoea cymbalum, H. exigua and the intracapsular developer H. navicula, while it is lacking in the poecilogonous developer H. callidegenita. The number of ampullary cells ranges from 4 (H. cymbalum, H. exigua) to 6 (H. navicula, H. callidegenita). In general no clear correlation of development mode (e.g. planktotrophic vs. intracapsular) and organization of the organ can be found. Most structures, except ciliary tufts and number of ampullary cells, are very similar among the investigated species. The CSO cells of Haminoea are compared with those of other gastropods in the literature. The organ as a whole as well as its cellular components of Haminoea can clearly be homologized with such structures in other gastropods. The CSO's relationship to apical organs with regard to homology and the function is discussed.
Ultrastructural features of spermatozoa and spermatogenesis are described for the first time in a... more Ultrastructural features of spermatozoa and spermatogenesis are described for the first time in a monoplacophoran and compared with data for other conchiferan molluses. Spermatozoa of Laevipilina antarctica Warén and Hain, 1992, are of the structurally simple, aquasperm type, featuring a conical acrosome, a compact nucleus with lacunae, a short midpiece and a single flagellum. The acrosomal vesicle shows an electron-dense
The Journal of the Acoustical Society of America, 2000
Tuna fishers in the eastern Pacific Ocean often exploit an association between a few genus of dol... more Tuna fishers in the eastern Pacific Ocean often exploit an association between a few genus of dolphin (Stenella and Delphinus) and yellowfin tuna (Thunnus albacares) to locate and capture the tuna. Identification of a mechanism which facilitates the tuna/dolphin bond may provide a means of exploiting the bond and capturing tuna without catching dolphin. To investigate if tuna may be attracted to low-frequency sounds produced by dolphins, source levels of bottlenose dolphin (Tursiops truncatus) jaw pops, breaches, and tail slaps were experimentally measured and used to estimate the maximum range at which yellowfin could detect similar sounds produced by pelagic species. The effective acoustic stimulus to the tuna was defined as the maximum one-third-octave level between 200 and 800 Hz, the frequency range where T. albacares is most sensitive. Spherical spreading was assumed to predict transmission loss with range. Breaches and jaw pops produced maximum one-third-octave source levels between 200 and 800 Hz of 153 (+/-4) and 163 (+/-2) dB re: 1 microPa-m, respectively, which resulted in estimated detection ranges of 340-840 and 660-1040 m, respectively. Tail slaps had lower source levels [max. 141 (+/-3) dB re: 1 microPa-m] and a maximum detection range of approximately 90-180 m.
The apical area of larvae of four primitive pulmonate species was investigated by means of serial... more The apical area of larvae of four primitive pulmonate species was investigated by means of serial ultrathin and light microscope sections. Cephalic sensory organs (CSOs) were found in the larvae of Onchidium cf. branchiferum (Onchidiidae) and Laemodonta octanfracta (Ellobiidae), while no trace of the organ was present in the larvae of Ovatella myosotis (Ellobiidae) or Williamia radiata (Siphonariidae). TEM investigation revealed very similar CSOs in O. cf. branchiferum and L. octanfracta, with characteristic putative sensory cell types: ampullary cells with an internal ampulla containing densely packed cilia, para-ampullary cells with external cilia parallel to the surface, and ciliary tuft cells, bearing short ciliary tufts. The epithelium covering the organ has a thick microvillar border with microvilli laterally bearing a pair of electron-dense accumulations and a glycocalyx with interspersed flat plaque-like elements. While homologues of all major elements of the CSO can be found in other gastropod taxa, for example caenogastropods and opisthobranchs, the homology of the ampullary cell with similar cells in nongastropods appears unlikely. The CSO of L. octanfracta is associated with an additional structure, an epithelial external protrusion, lying ventral to the CSO. The absence of the organ in W. radiata weakens hypotheses on the organ's function of examining settlement conditions and velar control.
ABSTRACT The anatomy of the neopilinoid limpet Micropilina arntzi (Warén & Hain, 1992, Th... more ABSTRACT The anatomy of the neopilinoid limpet Micropilina arntzi (Warén & Hain, 1992, The Veliger 35: 165–176) is described on the basis of graphic reconstructions of semithin serial sections. Hard parts, anatomical features and reproductive biology of the minute species differ considerably from those of all other anatomically known neopilinoid species. Therefore, Micropilinidae fam. nov. is erected for this genus.Micropilina arntzi may be considered as partly paedomorphic with respect to the seriality of ventilatory (ctenidia), excretory or genital organs, or may represent an archaic condition within the Tryblidiida. Ontogenetic and comparative anatomical data strongly suggest that the serial repetition of the various organ systems should be regarded as one of several autapomorphic features of the Neopilinoidea (Tryblidiida).
Uploads
Papers by Kurt Schaefer