Zoomorphology

Gruhl, Alexander

doi: 10.1007/s00435-009-0084-xpmid: N/A

A growing body of data from nervous systems of marine invertebrate larvae provides an ideal background for comparisons among higher taxa. The currently available data from Bryozoa, however, do not allow for a consistent hypothesis of an ancestral state for this taxon, which would be necessary for phylogenetic inferences. The larval nervous systems of the four gymnolaemate species Flustrellidra hispida, Bugula fulva, Alcyonidium gelatinosum, and Bowerbankia gracilis are examined by means of antibody staining against the neurotransmitters serotonin and FMRFamide, as well as against acetylated α-tubulin. Despite considerable variation, a comparison reveals a common pattern of the distribution of serotonin. The neurotransmitter is found in at least two cells in the apical organ as well as in paired axial and lateral nerves emerging from a central nerve nodule. A ring nerve is present below the corona and at least two serotonergic cells are found between the corona cells. Serotonergic coronal cells might represent unique bryozoan features, whereas the remaining elements show resemblance to the situation found in most spiralian taxa. The data do not provide support for a closer relationship of Bryozoa to Phoronida or Brachiopoda.

Ivanović, Ana; Sotiropoulos, Konstantinos; Džukić, Georg; Kalezić, Miloš

doi: 10.1007/s00435-009-0085-9pmid: N/A

We explored the phylogenetic signal of skull size and shape in alpine newts from the Balkans, a group of European newts that, in spite of their considerable phylogeographic substructuring (as inferred from previous DNA analyses), maintain a conserved phenotype. In terms of skull shape disparity, geometric morphometrics show that the dorsal cranium carries a significant phylogenetic signal, the most notable evidence in this present study. On the contrary, no phylogenetic signal in the shape of the ventral cranium was found. This result indicates that the variation in the shape of the ventral cranium is more prone to other factors and processes, such as adaptations to local environments rather than phylogenetic constraints. Variation in skull size within alpine newts seems to be independent from phylogenetic constraints.

Hochberg, Rick

doi: 10.1007/s00435-009-0086-8pmid: N/A

The platyhelminth reproductive system is a complex series of canals, glands, and sclerotic components that figure prominently in our understanding of reproductive physiology, taxonomy, and evolution of the Platyhelminthes. Yet, there is limited information on its innervation, especially for free-living species of Rhabdocoela, the most speciose and ecologically diverse assemblage. Here, innervation of the reproductive system in the common marine kalyptorhynch, Gyratrix hermaphroditus, is studied using confocal laser scanning microscopy (CLSM), fluorescent phalloidin, and antibodies to serotonin (5HT) and small cardioactive peptide b (SCPb). Results show that portions of the female atrial system (uterus, female gonopore) are innervated by peptidergic (SCPb) neurons that may function to control muscles involved in egg movement. In contrast, portions of the male atrial system (male atrium, male gonopore) are innervated by both peptidergic and serotonergic neurons. These neurons form a complex series of hoops around the musculature of the male atrium that houses prostate stylet type II. It is hypothesized that 5HT is the primary myoexcitatory neurotransmitter, and that it acts either synergistically with SCPb to trigger muscle contractions of the male atrium and protract the copulatory stylet, or that SCPb plays an inhibitory role during contraction of the male atrium. A comparison of the distribution of peptidergic and serotonergic neurons in G. hermaphroditus with other free-living species and parasitic rhabdocoels (Neodermata) reveals similarities in innervation of comparable (though probably not homologous) reproductive organs. These results suggest that the atrial systems of phylogenetically diverse species may share a common neuronal physiology despite their structural differences and potential independent evolutionary origins within the Platyhelminthes.

Sperone, Emilio; Bonacci, A.; Brunelli, E.; Tripepi, S.; Jamieson, B.

doi: 10.1007/s00435-009-0087-7pmid: N/A

The first morphological and ultrastructural description of testis, Wolffian duct, spermatophore, and spermatozoon of Lissotriton italicus is provided. The male reproductive system of this species consists of a pair of monolobed testes, fat bodies, efferent ductules, paired Wolffian duct, and the cloaca. The Wolffian duct is pseudostratified, consisting of an epithelium composed of an alternation of ciliated cells and non-ciliated secretory cells, with scattered basal cells. Melanocytes are found in the basal lamina of the Wolffian duct. Spermiogenesis is of the discontinuous type. In the early spermatid nuclear elongation, flagellar extrusion and development of a large acrosomal vesicle occur. Soon the perforatorium develops and the flagellum elongates. In the late spermatid gradual chromatin condensation and nuclear elongation is noticeable. At the end of spermiogenesis the flagellum develops marginal filament and undulating membrane. The mature sperm of L. italicus consists of a distinct head (acrosome, perforatorium, nucleus and nuclear ridge, plus the apical acrosomal barb) and a tail with axoneme, undulating membrane, and axial fiber. Nuclear ridge and apical acrosomal barb are two autapomorphic characters found in the Urodela. Several apomorphic characters for Salamandroidea are also present: elongation of the connecting piece, an apically modified acrosome vesicle, trifoliate axial fiber within the principal piece, elongate annulus, elongate midpiece, and the gentle merging of the axial fiber/principal piece into the endpiece. The spermatophore of L. italicus is formed by a cap consisting of randomly distributed spermatozoa surmounting a short pedicel. A membranelike structure involving the spermatophore is absent.

Stach, Thomas; Kirbach, Andreas

doi: 10.1007/s00435-008-0083-3pmid: N/A