Posterior Fin Research Articles

Sagitta chilensis nueva especie de quetognato en fiordos australes chilenos (Chaetognatha, Aphragmophora, Sagittidae)

A new species of Chaetognatha, Aphragmophora, is described for the first time for the Chilean fjords. The specimens were collected between the mouth of the Guafo and Pulluche channel, in November 2002. Noteworthy mor- phological differences with other relates species, such as a sharp pointed structure in the collar and fins; shape of anterior and posterior fins; position of the seminal vesicles and the presence of rounded vesicles in the caudal fi n, were present.

The zebrafish fgf24 mutant identifies an additional level of Fgf signaling involved in vertebrate forelimb initiation.

The development of vertebrate limb buds is triggered in the lateral plate mesoderm by a cascade of genes, including members of the Fgf and Wnt families, as well as the transcription factor tbx5. Fgf8, which is expressed in the intermediate mesoderm, is thought to initiate forelimb formation by activating wnt2b, which then induces the expression of tbx5 in the adjacent lateral plate mesoderm. Tbx5, in turn, is required for the activation of fgf10, which relays the limb inducing signal to the overlying ectoderm. We show that the zebrafish fgf24 gene, which belongs to the Fgf8/17/18 subfamily of Fgf ligands, acts downstream of tbx5 to activate fgf10 expression in the lateral plate mesoderm. We also show that fgf24 activity is necessary for the migration of tbx5-expressing cells to the fin bud, and for the activation of shh, but not hand2, expression in the posterior fin bud.

A functionally conserved homolog of the Drosophila segment polarity gene hh is expressed in tissues with polarizing activity in zebrafish embryos

The segment polarity gene hedgehog (hh) encodes a novel signaling protein that mediates local cell-cell interactions in the developing Drosophila embryo. Here we describe the existence of an hh-related gene family in the zebrafish, Brachydanio rerio. One of these genes, sonic hedgehog (shh), is expressed in the notochord, floor plate, and posterior fin mesoderm, tissues associated with polarizing activities in various vertebrate embryos. The pattern of shh expression in zebra-fish mutants affecting axial structures, together with the consequences of its ectopic expression in normal embryos, is consistent with a role for shh in floor plate induction. By expressing shh in transgenic Drosophila embryos, we also demonstrate a strong functional conservation between the fish and fly hh genes.

Development of the larval tunic in a compound ascidian: morphogenetic events in the embryos of Distaplia occidentalis

The larval tunic of Distaplia occidentalis is a complex investment consisting of extracellular filaments and an amorphous ground substance. The principal elements of the tunic are two thin cuticles and two subcuticular compartments. Compacted filaments and small amounts of ground substance characterize the cuticles. Dispersed filaments and large amounts of ground substance distinguish the compartments. The cells of the embryonic epidermis apparently secrete both the filaments and the ground substance. The elements of the larval tunic differentiate sequentially over a period of approximately 2 weeks. The outer cuticle appears 3–4 days after neurulation and it gradually lifts from the surface of the epidermis as the outer compartment forms. Tapered folds of the outer cuticle and extensions of the outer compartment produce the dorsal, ventral, and posterior fins of the larva. Test cells, occupying the perivitelline space around the embryo, release multigranular "ornaments" that adhere to the external surface of the outer cuticle. The inner cuticle and the inner compartment arise during the 4 days prior to hatching. The inner compartment over the truncal epidermis expands significantly to accommodate cells which emigrate from the body cavity (hemocoel).

Effect of ethyl linoleate, ethyl linolenate and ethyl esters of highly unsaturated fatty acids on essential fatty acid deficiency in rainbow trout.

In order to determine if essential fatty acid (EFA) is necesary for rainbow trout as it is for mammals, the fish raised on a fat-free diet long enough to manifest deficiency symptoms were given ethyl esters of linoleic, linolenic and highly unsaturated fatty acids and the following effects were observed.1. The posterior part of fish fed only the fat-free diet for 3 months was discolored and hardened. The posterior fin was worn out. In the extreme cases, the fin had almost disappeared, leaving the terminals of spiral column. Many of the fish died in this group. These symptoms might be caused by EFA deficiency. The fat-free diet was inferior to the diets containing fatty acid esters for weight gain and for efficiency of the diet.2. Among the three fatty acid esters, highly unsaturated fatty acid esters were the best in the accumulation and efficiency of the diet, showing minimum mortality. Ethyl linoleate was the next and ethyl linolenate was the last of the three. Of each ester a 200μg dose was better than 50μg.3. In this experiment, fish fed the diets containing more than 50μg esters per g of body weight per day, failed to cause deficiency symptoms, though a further experiment may be necessary to determine the minimum requirement of these fatty esters.4. A recovery test was carried out with rainbow trout which had been fed the fat-free diet for two months. In the fat-free diet group, the symptoms of the deficiency could still be observed, but in the groups containing the 3 kinds of esters at the rate of 500μg per g of body weight per day, such symptoms were not observed.

Effects of CO and Methylene Blue upon O2 Consumption of Shark (Mustelus) Blood.

The purpose of this experiment was to see if methylene blue had any effect upon the O2 consumption of shark (Mustelus) red blood cells in the presence of carbon monoxide or air. Since these red blood cells are nucleated and have a considerable rate of respiration, it was thought of interest to test Barron's conclusions that the action of methylene blue in increasing oxygen consumption is less marked, or even nil, in nucleated erythrocytes or leucocytes as contrasted with such non-nucleated erythrocytes as mammalian. In addition it was also thought of interest to find out whether methylene blue antagonizes the effects of CO on the respiration of these nucleated erythrocytes. The blood was collected fresh for each experiment into tubes by cutting the dorsal posterior fin of the shark. In some experiments the blood was centrifuged and the erythrocytes were subsequently washed several times in 1.1% NaCl and in others whole blood was used. No difference in the results was noted. Aliquot portions of 2 cc of blood were placed in the bottom of cups of Warburg respiration apparatus, temp. 20°C. Either 100% CO or air was used in the system. CO2 was absorbed by KOH in the insets in the usual way. The concentration of methylene blue added was .004% made in 1.1% NaCl. Tests were made to see if complete darkness affected the results with CO. No such effects were noted. The material was found to be remarkably uniform in behavior, and remarkably resistant to hemolysis in a wide range of NaCl concentrations. This table shows (1) that Mustelus blood has a considerable rate of respiration: (2) that in air methylene blue causes an increased O2 consumption of 151% over the controls in 2 to 4 hours under the conditions of the experiment—this does not confirm Barron's conclusions that methylene blue has little or not effect upon the respiration of nucleated red blood cells; (3) that CO produces a decrease to 61% (it was not determined in these experiments whether this change in the manometric readings was due to residual oxygen remaining after the atmosphere was saturated with CO, or actual CO consumption); (4) that methylene blue counteracts this decrease, increasing the rate to 86%. This increased rate in CO is about the same in percent as that produced by methylene blue in air.

2. On the Anatomy of the Amphioxus lanceolatus of Yarrell

After a short statement of the labours of Yarrell, Couch, Retzius, and Müller, the author gave a detailed description of the structure of Amphioxus, as observed in the dissection of one of two specimens taken by Mr Forbes in the Irish Sea. The abdominal folds, and the anterior and posterior anal fins, were described, and the existence of a fin in front of the anus illustrated by an observation made by Professor Agassiz, of the temporary existence of a similar fin in the embryos of certain fresh-water fishes.The osseous system presented two divisions,—the true or neuro-skeleton, and the intestinal or splanchno-skeleton. The true skeleton consisted of a chorda dorsalis, equally pointed at both extremities, without the slightest trace of a cranium, and destitute of any of the peripheral vertebral elements, with the exception of a row of cells—germs of interspinous bones and fin-rays —along the base of the dorsal and anal fins.

On the function of the medulla oblongata and medulla spinalis, and on the excito-motory system of nerves

The author begins by observing that a former memoir of his, entitled, “ On the Reflex Function of the Medulla Oblongata and Medulla Spinalis,” published in the Philosophical Transactions for 1833, has been translated into German, and favourably spoken of by Professor Muller, of Berlin. He states that his object in the present paper is to unfold what he calls a great principle in physiology j namely, that of the special function, and the physiological and pathological action and reactions of the true spinal marrow, and of the excito-motory nerves. The two experiments which he regards as affording the type of those physiological phenomena and pathological conditions, which are the direct effects of causes acting in the spinal marrow, or in the course of the motor nerves, are the following :— 1. If a muscular nerve be stimulated, either mechanically by the forceps, or by means of galvanism passed transversely across its fibres, the muscle or muscles to which it is distributed are excited to contract.—2. The same result is obtained when the spinal marrow itself is subjected to the agency of a mechanical or galvanic stimulus. The following experiment, on the other hand, presents the type of all the actions of the reflex function of the spinal marrow, and of the excito-motory system of nerves, and of an exclusive series of physiological and pathological phenomena :—If in a turtle, from which the head and sternum have been removed, we lay bare the sixth or seventh intercostal nerve, and stimulate it either by means of the forceps or galvanism, both the anterior and posterior fins, with the tail, are immediately moved with energy. Hence the author infers the existence: 1st, of a true spinal marrow, physiologically distinct from the chord of intra-spinal nerves; 2ndly, of a system of excito-motory nerves, physiologically distinct from the sentient and voluntary nerves; and, 3rdly, of currents of nervous influence, incident, upwards, downwards, and reflex with regard to the spinal marrow. A review is then taken of the labours of preceding physiologists relative to the functions of the nervous system : in which the author criticises the reasonings of Whytt, Legallois, Mr. Mayo, Dr. Alison, and Professor Muller; and illustrates his own peculiar views by several experiments and pathological observations, which appear to him to show that muscular movements may occur, under circumstances implying the cessation of sensation, volition, and every other function of the brain; and that these phenomena are explicable only on the hypothesis that impressions made on a certain set of nerves, which he terms excitomotory , are conveyed to a particular portion of the spinal marrow belonging to that system, and are thence reflected, by means of certain motor nerves, upon certain sets of muscles, inducing certain actions. The same actions may also be the result of impressions made directly either on the spinal marrow or on the motor nerves. He accordingly considers that the whole nervous system may be divided into,— 1st, the cerebral , or the sentient and voluntary; 2ndly, the true spinal, or the excitor and motor; and, 3rdly, the ganglionic, or the nutrient, the secretory. The excito-motory system presides over ingestion and exclusion, retention and egestion, and over the orifices and sphincters of the animal frame: it is therefore the nervous system of respiration, deglutition, &c., and the source of tone in the whole muscular system. The true spinal system is the seat or nervous agent of the appetites and passions, but is also susceptible of modification by volition. This theory he proceeds to apply to the explanation of several phenomena relating to the motions of the eyelids, pharynx, cardia, larynx, muscles of inspiration, sphincter animal expulsors of the faeces and semen, to the tone of the muscular system generally, and to actions resulting from the passions. Lastly, he considers its application to various diseased states of the same functions, as manifested in cynic spasm, vomiting, asthma, tenesmus, strangury, crowing inspiration, convulsions, epilepsy, tetanus, hydrophobia, and paralysis.