榛属（桦木科）花序及花的形态发生

在扫描电镜下观察了桦木科榛属榛、毛榛和滇榛的花序和花的形态发生过程。榛属雌花序由多个小聚伞花序螺旋状排列组成;每个小花序原基分化出1枚初级苞片和一团小花序原基分生组织,由小花序原基分生组织分化形成2个花原基;每个花原基分化出2个心皮原基,形成二心皮雌蕊;雌蕊基部有2层花被原基,内层花被原基环状,外层花被发生于花原基近轴面和远轴面,近轴面和远轴面的花被不均等分化,外层花被发生早于内层花被。雄花序为柔荑状,由多个小聚伞花序螺旋状排列组成。每个小花序原基分化出1枚初级苞片和一团小花序原基分生组织,由小花序原基分生组织分化出2枚次级苞片和4。6个雄蕊原基,形成4—6枚雄蕊,每个雄蕊具4个药囊,在雄蕊原基分化形成4药囊雄蕊过程中．出现雄蕊原基纵裂。并且花丝纵裂至基部。为进一步全面探讨桦木科属间系统演化关系提供了证据。     

Cretaceous origins of the vibrotactile bill-tip organ in birds

Some probe-foraging birds locate their buried prey by detecting mechanical vibrations in the substrate using a specialized tactile bill-tip organ comprising mechanoreceptors embedded in densely clustered pits in the bone at the tip of their beak. This remarkable sensory modality is known as ‘remote touch’, and the associated bill-tip organ is found in probe-foraging taxa belonging to both the palaeognathous (in kiwi) and neognathous (in ibises and shorebirds) clades of modern birds. Intriguingly, a structurally similar bill-tip organ is also present in the beaks of extant, non-probing palaeognathous birds (e.g. emu and ostriches) that do not use remote touch. By comparison with our comprehensive sample representing all orders of extant modern birds (Neornithes), we provide evidence that the lithornithids (the most basal known palaeognathous birds which evolved in the Cretaceous period) had the ability to use remote touch. This finding suggests that the occurrence of the vestigial bony bill-tip organ in all modern non-probing palaeognathous birds represents a plesiomorphic condition. Furthermore, our results show that remote-touch probe foraging evolved very early among the Neornithes and it may even have predated the palaeognathous–neognathous divergence. We postulate that the tactile bony bill-tip organ in Neornithes may have originated from other snout tactile specializations of their non-avian theropod ancestors.     

Lateral organs in sedentary polychaetes (Annelida) – Ultrastructure and phylogenetic significance of an insufficiently known sense organ

Lateral organs are sense organs visible as densely ciliated pits or papillae between the noto‐ and the neuropodia in certain taxa of sedentary polychaetes. Ultrastructural studies in about 10 species of the following taxa Maldanidae, Opheliidae, Orbiniidae, Paraonidae, Magelonidae, Spionidae, Poecilochaetidae and Terebellidae have been designed to evaluate whether these organs are homologous among polychaetes. In spite of great external diversity, the investigations revealed an overall ultrastructural similarity. Differences between species investigated mainly concern the size of the organs as well as the number and arrangement of cells. The organs comprise supportive cells and uniciliated penetrative sensory cells. Their dendrites are closely arranged and thus their cilia may resemble multiciliated cells. There are two types of sensory cells: one type possesses no or mainly thin microvilli of which usually only a few reach the cuticular surface, and in the other type the cilium is consistently surrounded by 10 strong microvilli, which form a pore‐like opening in the cuticle. Further differences occur in the structure of the rootlet system. Basally, a retractor muscle attaches to the organ. The systematic significance of these organs within Annelida is discussed with respect to the conflicting phylogenetic hypotheses explaining the relationships of annelid taxa.     

Photoreceptive organs in larvae of Spionidae (Annelida) and Sipuncula

A pair of spherical unpigmented ocelli in addition to pigmented eyes have been observed in the anterior part of the prostomium in larvae of more than 40 species of Spionidae examined alive with light microscopy. Ocelli become visible in larvae at the one- to three-segment stage, increase in size as growth proceeds, and probably disintegrate in the course of metamorphosis because they were not observed in adults and settled juveniles. One pair of transparent, spherical bodies is also found in the anterior part of the head of planktotrophic pelagosphera larvae of Sipuncula. These bodies are in a similar position and have a similar appearance and size to unpigmented ocelli in Spionidae larvae. A pair of epidermal invaginations, densely covered with short cilia, is also observed antero-laterally in the head in pelagospheras of one species. These invaginations appear similar to the nuchal organs present in many polychaete larvae. Photoreceptive organs so far reported for sipunculan larvae comprise only pigmented eyes. Unpigmented ocelli and nuchal organs have never been reported in pelagospheras. Further ultrastructural investigations on sipunculan larvae are encouraged to clarify the composition, function and morphogenesis of transparent, spherical bodies and ciliated invaginations in the anterior part of the head. Such investigations may help to better understand the nature of photoreceptive structures and nuchal organs in Sipuncula, and also contribute to phylogenetic hypotheses regarding relationships of the Sipuncula and Annelida.     

Irregular chiasm-C-roughest, a member of the immunoglobulin superfamily, affects sense organ spacing on the Drosophila antenna by influencing the positioning of founder cells on the disc ectoderm

We describe a role for Irregular chiasmC-roughest (IrreC-rst), an immunoglobulin (Ig) superfamily member, in patterning sense organs on the Drosophila antenna. IrreC-rst protein is initially expressed homogeneously on apical profiles of ectodermal cells in regions of the antennal disc. During specification of founder cells (FCs), the intracellular protein distribution changes and becomes concentrated in regions where specific intercellular contacts presumably occur. Loss of function mutations as well as misexpression of irreC-rst results in an altered arrangement of FCs within the disc compared to wildtype. Sense organ development occurs normally, although spacing is affected. Unlike its role in interommatidial spacing, irreC-rst does not affect apoptosis during antennal development. We propose that IrreC-rst affects the spatial relationship between sensory and ectodermal cells during FC delamination. Received: 19 January 1999 / Accepted: 10 May 1999     

Modelling spatial dynamics of fish

Our ability to model spatial distributions of fish populations is reviewed by describing the available modelling tools. Ultimate models of the individual's motivation for behavioural decisions are derived from evolutionary ecology. Mechanistic models for how fish sense and may respond to their surroundings are presented for vision, olfaction, hearing, the lateral line and other sensory organs. Models for learning and memory are presented, based both upon evolutionary optimization premises and upon neurological information processing and decision making. Functional tools for modelling behaviour and life histories can be categorized as belonging to an optimization or an adaptation approach. Among optimization tools, optimal foraging theory, life history theory, ideal free distribution, game theory and stochastic dynamic programming are presented. Among adaptation tools, genetic algorithms and the combination with artificial neural networks are described. The review advocates the combination of evolutionary and neurological approaches to modelling spatial dynamics of fish.     

TESTING HYPOTHESES OF NEURAL EVOLUTION IN GYMNOTIFORM ELECTRIC FISHES USING PHYLOGENETIC CHARACTER DATA

In this paper, we propose a method to test alternative hypotheses of phenotypic evolution. The method compares patterns observed in phylogenetic character data with patterns expected by explicit models of evolutionary process. Observed patterns of character-state diversity are assessed from four properties of character-state change derived from a phylogenetic analysis: the sequence and correlation of transformations on a cladogram and the spatial and functional localization of these transformations to parts of an organism. Patterns expressed in terms of the localization of transformations are compared with the expectations of null models that the number of transformations is proportional to measures of size or complexity. Deviations from the values expected by the null models are then compared with qualitative expectations of the models. The method is applied to characters in the nervous system of gymnotiform electric fishes. Patterns in the diversity of 63 reconstructed character-state changes are compared with the expectations of 10 published models of neural evolution. A total of 63 expectations are reviewed, of which 33 (52%) are found to be consistent with the gymnotiform neural data. In general, the models reviewed are not successful at making global predictions, in part because they have been cast in excessively general terms. The data support the conclusion that evolution in the nervous system of gymnotiforms has involved a mosaic of processes, each operating differentially on functional and developmental systems and at different spatial and temporal scales. The results also indicate that more refined models are required, each making more explicit predictions.     

The coxal glands of geophilomorpha (chilopoda): Organs of osmoregulation

Summary The organs terminating at the coxal pores of the tug-legs of Geophilomorpha are not repugnatorial glands, but possess typical transport epithelia with deep apical and basal infoldings of the cell membranes, between which numerous large mitochondria are located. Many transport vesicles are found in the basal region but fewer in the apical cytoplasm. The apex is characterized by bundles of longitudinally oriented microtubules, sparse endoplasmic reticulum and free ribosomes. Single neurosecretory axons with synaptoid areas are scattered among the cells. It is suggested that the coxal organs have a diuretic function in moist habitats and an antidiuretic effect in arid environments. The switch-over is evidently controlled by a neuroendocrine mechanism.     

Scanning and transmission electron microscopy of the subfornical organ of the grass frog (Rana pipiens)

Summary The ventricular surface of the subfornical organ of the frog is made up of ependymal cells with numerous apical microvilli, occasional cytoplasmic protrusions and many vacuoles projecting into the lumen of the third ventricle. Between these cells dendrites of cerebrospinal fluid-contacting neurons reach the ventricle to terminate in bulbous enlargements. In addition, flask-shaped encephalo-chromaffin cells, containing granulated vesicles and aggregates of filaments in their cytoplasm, project into the cerebrospinal fluid. Surrounding the centrally located capillaries are enlarged dendrites and axons of heterogeneous morphology, some of which appear to originate within the subfornical organ, intermingled with dendrites and axons of normal structure. The glial cells in this region, especially the microglial cells, often contain large lipofuscin inclusions, suggestive of degeneration and subsequent phagocytosis of some of the enlarged dendrites and axons. The normally scarce neurosecretory peptidergic axons become more evident and form typical Herring bodies in stalk-transected animals. Neuronal perikarya of varying morphology are predominantly located peripheral to the region of enlarged dendrites and axons. Supraependymal macrophages are particularly numerous on the subfornical organ.Abbreviations used CSF cerebrospinal fluid - SEM scanning electron microscope, scanning electron microscopy - SFO subfornical organ - TEM transmission electron microscope, transmission electron microscopy Supported, in part, by NIH grant NB 07492The skillful technical assistance of J.G. Linner and the secretarial assistance of Ann Gerdom are gratefully acknowledged. The SEM studies were made possible through a grant from the Graduate College of Iowa State University and the use of the SEM facility in the Department of Botany     

On the ampullary organs of the South-American paddle-fish Sorubim lima (Siluroidea,Pimelodidae)

Summary Ampullary organs were found in the epidermis of the paddle-fish Sorubim lima; they are distributed all over the skin surface of the fish but are particularly densely grouped in the head region and on the dorsal surface of the paddle. Histological and electron microscopical observations show that their structure is similar to the type of cutaneous ampullary organs characteristic of other Siluroidea. Composed of a relatively large mucus-filled ampulla, the organ possesses a short and narrow canal which leads to the outer epidermal surface. The wall of the ampulla is formed of several layers of flat epidermal cells. In general four sensory cells, each one surrounded by supporting cells, compose the sensory epithelium at the bottom of the ampulla. The inner surface of the sensory cells in contact with the ampullary mucus bears only microvilli. The contact between the nerve endings and the sensory cells show the characteristic structure of an afferent neuro-sensory junction. Two ampullae are innervated in some cases by the same afferent nerve fibre.The author expresses her gratitude to Dr. Szabo for his scientific advice during her stay in Gif sur Yvette