Your use of this PDF, the BioOne Complete website, and all posted and Key words: Hemichordata, acorn worm, Balanoglossus, new species. Abstract: In this study, for the first time, 2 species (Balanoglossus Key Words: Hemichordata, Balanoglossus clavigerus, Glandiceps talaboti. Balanoglossus is marine and inhabits the shallow coastal waters all over the world. Balanoglossus lives in burrows made in sand or mud. The burrow is usually.
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PDF | The morphology and development of a new species of the genus Balanoglossus belonging to the family Ptychoderidae are described in. PDF | We describe development from fertilization to metamorphosis of the enteropneust hemichordate Balanoglossus misakiensis. This is the. These are aquatic, aerial or terrestrial. 2. Their bodies are small to large, bilaterally symmetrical and metamerically segmented. 3. They have paired pharyngeal.
Habitat[ edit ] Balanoglossus is a tuberculos or burrowing and exclusively marine animal. It is found in shallow waters between tide marks along the coast of warm and temperate oceans. Balanoglossus clavigerus is a U-shaped excavated in a sandy bottom Affinities with Nemertinea[ edit ] Proboscis worms Nemertines resemble flatworms and possess a long protrusible proboscis. Balanoglossus shows similarity with nemertine in burrowing and feeding habits. The proboscis of nemertines is compared with proboscis of Balanoglossus. These similarities are superficial as the proboscis of Balanoglossus.
FGF signaling induces mesoderm in the hemichordate Mesoderm is specified Balanoglossus kowalevskii, and of the morphology of the enteropneusta. Click here to view. Go to Agassiz A.
The history of Balanoglossus and tornaria. Memoirs of Flag for inappropriate Priya : I wanted to get into medicine and excel in it. Diversity, abundance and distribution of intertidal URL www. A regression line and equation was calculated in Microsoft Excel and the The Archivio Moncharmont a Pioneering Biodiversity Excel, presentations and drawings.
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Tornaria larva of Balanoglossus leads a benthonic life. The fragments were observed every day during the first month and every few days during the following months under a light microscope. Figure 1 Open in figure viewer PowerPoint Overview of the acorn worm Balanoglossus simodensis and its regenerating fragments.
A An intact worm.
B Branchiogenital individual lower, big fragment and regenerand upper, small fragment. C Regenerating hepatic individual. Histology For histological observation, some worms were allowed to defecate their gut contents by keeping these worms without sand. Results In the present paper, as a matter of convenience, we defined the terms of asexual reproduction and regeneration as following: asexual reproduction is the process through a fragmentation of worm by autotomy and subsequent body repair; and regeneration is the process of body repair after an artificial cut.
The body repair after the induced fragmentation is also defined as the asexual reproduction. Fragmentation In the natural habitat, we found three kinds of fragmented individuals.
Fragmented individuals were collected only from June to December, but never at other times when B. Because these fragments were morphologically identical to the fragments undergoing asexual reproduction in the species described in previous reports, we followed the nomenclature for the three fragments as described by Gilchrist and Packard The posterior end of the genital region is elongated in this fragment.
All three kinds of fragments contained yellow granules in their gonads. The functions and composition of the yellow granules are still unknown, but they probably relate to the maturation of this species. Although some enteropneust species secrete a large amount of mucus and build distinct burrows Duncan , B.
Despite this situation, a pair of branchiogenital and hepatic individuals along with several regenerands in different regeneration stages were collected from the same mucous mass. This suggests that the regenerands are produced serially from the branchiogenital individual. To confirm that regenerands bud off from the branchiogenital individual, we kept branchiogenital individuals in aquariums in a laboratory.
A few days after transferring the individuals to the lab tanks, we observed that regenerands were produced from the posterior end of the branchiogenital individual through autotomy one by one.
We observed 17 regenerands formed from three branchiogenital individuals, with a frequency of one regenerand every 1 or 2 days.
The average length of the regenerands was 7. In the course of examination of the regeneration ability of artificially cut fragments as mentioned below , we found that autonomous fragmentation can be induced by the following method the process of fragmentation is shown in Fig.
Both the anterior and posterior fragments were nearly the same as the two fragments produced by fission, the branchiogenital individual and the hepatic individual Fig. When the anterior half of the cut fragments the branchiogenital individual was kept in an aquarium with sand, the posterior end of the branchiogenital individual elongated Fig.
About 1 week after cutting, the first regenerand was produced from the posterior end of the branchiogenital individual by fission Fig. After that, new regenerands were produced every 1 or 2 days. When the genital region of the branchiogenital individual became shorter, the branchiogenital individual stopped producing regenerands and began to regenerate its posterior body part.
Finally, all fragments, the branchiogenital and hepatic individuals and the regenerands, regenerated their lost body parts Fig.
The total number of produced regenerands varied by each individual, depending on the length of the branchiogenital individual and regenerands. Even in the case of long worms, the number of produced regenerands was small if it produced only long regenerands.
Regenerands were never formed when the anterior fragment was kept in an aquarium without sand or when the worm did not contain yellow granules in the gonads.
In these cases, the branchiogenital individual began to regenerate only the posterior lost parts soon after the worm was cut. An intact worm divides into two fragments: the branchiogenital individual and the hepatic individual Step 1. Each fragment regenerates into an intact worm Step 4. We think that this artificially induced autotomy is comparable to what occurs in the natural habitat because the size and number of the regenerands and branchiogenitals are quite similar to those found in the mucus of the natural habitat.
More importantly, autotomy only occurred when individuals were cut at the posterior end of the genital region and never occurred when cut at different positions. Thus, we decided to observe the details of the asexual reproduction process by using the artificially induced regenerands. Morphogenesis of the regenerand First, to define the stages of asexual reproduction, we observed the external morphology during the growth of the regenerands.
Furthermore, we examined the details of the internal morphology at each stage Fig. The wounds at the posterior end of the branchiogenitals and anterior end of the regenerands closed about 1 day after being cut, regardless of being cut artificially or by autotomy through the connection between the epidermis and intestinal epithelium. After wound healing, a blastema was formed on the dorsal side of the regenerand gut Fig. In this stage, distinct epithelial cells emerged on the gut side between the epidermis and gut epithelium, which contained vacuoles Fig.
This region would be the esophageal epithelium and stomochord in which cells are morphologically identical in an intact worm Fig. In an intact worm, a thick layer of nerve fibers forms under the proboscis epidermis Fig. The epithelial layer of nerve fibers then began to form Fig. Four days after fission, two projections of the blastema fused into a single projection that became the proboscis Fig.
At this stage, internal structures of the proboscis began to differentiate Fig. The proboscis coelom formed as a cavity inside of the proboscis Fig. The features of the stomochord cells, containing prominent vacuoles basally and nuclei more apically, became more distinct. Undifferentiated cells were located on the periphery of the proboscis coelom, associated with the developing nerve layer Fig.
This is because de novo epidermal cells probably differentiated in this stage and the epidermal cells have not contained vacuoles yet. Figure 4 Open in figure viewer PowerPoint External morphogenesis during regeneration of regenerands in Balanoglossus simodensis.
Anterior is at left, and the dorsal view is presented. A Stage 1. Just after fission: the wound is still open. B Stage 2. One day after fission: the wound is healed. C Stage 3. Two days after fission: a blastema with two projections has formed. D Stage 4. Four days after fission: the two projections of the blastema have fused to become a single projection. E Stage 5. Six days after fission: the proboscis has differentiated from a single projection of the blastema and the collar primordia are formed at the lateral edges.
F Stage 6. Eight days after fission: the inset shows the newly formed gill pores arrow. G Stage 7. Two weeks after fission: the collar begins to fuse on the dorsal side. Inset 1 shows the proboscis pore arrow. Inset 2 shows the gill pore arrow. H Stage 8. Twenty days after fission: the collar has fused. I Stage 9. One month after fission: the proboscis and collar have begun to become opaque.
Figure 5 Open in figure viewer PowerPoint Internal morphogenesis during regeneration of regenerands in Balanoglossus simodensis.
Anterior is at left and dorsal is towards the top. Arrows indicate wounds.
Arrows indicate closed wounds. A blastema filled with undifferentiated cells has formed. Proboscis organs begin to differentiate. The proboscis pore has formed. The proboscis skeleton has formed on the ventral side of the stomochord.
G—I From stage 7 through stage 9, each organ in the proboscis grows gradually. Figure 6 Open in figure viewer PowerPoint Detail of regeneration of the proboscis. A High magnification of stage 3 blastema filled with undifferentiated cells inset. New type of epithelium differentiated between the blastema ectoderm and gut epithelium asterisk.