Jensen OS 1878 (citation)- describes new species, definition in Latin p 23-24. Lists Aphanostoma griseum as synonym- Plate I- figures 1-3. Graff L v 1882 (citation)- illustration and description. Bohmig L 1895 (citation)- in list p 44. Attems CG 1897 (citation)- noted vacuolation at posterior end- are they osmoregulatory? Iuustration otolith and epithelium. From Helgoland. brief note. Graff L v 1902 (citation)- description of this species - occurs in Puerto Rico, synonym are Aphanostoma elegans and Mecynostomum agile. Occurence in Bergen. Graff L v 1905 (citation)- illustration and long description of Aphanostoma rhomboides. Lohner L 1911 (citation)- on vacuole in this species. Wilhelmi J 1913 (citation)- mentions p 95. Steinbock O 1931 (citation)- from Faroes. Steinbock O 1933 (citation)- lists from Arctic- gives list of synonums- see these. Southern R 1936 (citation)- reports in Ireland. Steinbock O 1938 (citation)- reports from Iceland. Westblad E 1945 (citation)- notes Proporus cyclops is synonym of this. Westblad E 1946 (citation)- brief describption- illustration. "S" shaped copulatory organ. Note it is a littoral species. Marcus E 1948 (citation)- this = Mecynostomum agile p 112, 187- species by Graff is not species by Jensen. says Mecynostomum agile Jensen = Mecynostomum agile Westblad; Aphanostoma rhomboides Graff does not = Aphanostoma rhomboides Jensen; and Aphanostoma rhomboides Jensen = Convoluta. Marcus EDB-R 1948 (citation)- p 12 this = Mecynostomum agile. Westblad E 1948 (citation)- moved to Mecynostomum, p 74. Dorjes J 1968 (citation)- p 85 lists in this genus but on p 157 under Mechynostomum. Antonius A 1968 (citation)- p 370, notes on Westblad's treatment of this species. Tyler S 1976 (citation)- adhesive papillae in. Steinbock O 1931 (citation)- Notes on p 3 that Proporus cyclops O. Schmidt is "probably identical with Aphanostoma rhomboides.
Jensen OS 1878 (citation)- Translation from latin and danish using Google translate: Body about 1 mm long, 0.27 mm wide at both ends, broader in the anterior part, gradually narrower towards the posterior. Color in the middle of the back from yellow to brownish. Otherwise body colorless. Seminal vesicle oval. Penis soft, cylindrical, curved towards the male genital opening. Organs of uncertain function protruding papilliformly around the male genital opening, arranged more or less distinctly in rhomboidal lines. In Orsted's diagnosis of Aphanostoma griseum, which is mentioned above as possibly synonymous with the present species, only the body shape common to several Aphanostomum species and the color, which is different, either grayish or yellowish, are mentioned. It is reasonable that Orsted has confused two separate species in his A. griseum; for the color does not vary so easily in the rhabdocoel. Since I have come across several different species that agree with the yellow form in both body shape and color, it is impossible to decide whether A. rhomboides is identical with it or not. Since, furthermore, Orsted's species name, which only applies to the gray-colored form (or species), does not fit the present species, which is always of a yellow-brown color, I have found it best to give it a new name. When the animal's body is extended to its full length, it becomes almost even. On the surface. In the anterior part of the body, there are spider glands (see page 13). For the otolith, see page 1"). Along the back, there are embedded the peculiar bodies (Fig. 1, b), the histological nature of which is discussed on page 10. In the mouth open fine-grained glandular threads, which converge all around from salivary glands; they are not very numerous. The oval transversely placed spermatic cord ( Fig. 2, b) bears on its posterior side the penis (Fig. 2, c) in the form of a duct or tube, which with its basal part turns backwards and then bends forwards under the seminal vesicle in the direction of the genital opening.*) The walls of the penis are formed by two distinctly separated layers, an inner very thin and an outer thicker, both clear and hyaline. The male genital opening (Fig. 2, d. Fig. 3, a) lies just behind the female (Fig. 2, e, Fig. 3, b); it is a separate opening; of this I have convinced myself by my observations; but often the animal extends the genital openings towards each other, so that they flow together, and the cilia that surround the genital openings form a single long ciliary rim around a common depression where both openings open.In the region behind and on the sides of the male genital opening, there are remarkable papillary bodies protruding above the surface of the body, forming a more or less distinct lattice-shaped network (Fig. 3). The lattices lie in the direction of the genital opening (Fig. 3, a) and extend straight towards it. These papillary bodies are also found in front of and to the sides of the male genital opening; but here only irregularly and sparsely. The papillae* (Fig. 3*) are elongated, tapering towards their free end, which is not quite pointed; their part located in the body also tapers and this more and more, until it disappears from the eye. The bodies thus formed are strongly refractive with a dark field along the middle, certainly the expression of an internal cavity that opens at the ends. They bend easily and serve the senses well, but their essential function is undoubtedly another, which I have not yet discovered. From the female genital opening, which is large, considerably larger than the male, a very short passage leads into a large round sac with powerful walls, formed of fine circular fibres (Fig. 2, f). The inner space of the sac, which is round, corresponding to the shape of a sac, contains a quantity of small and a few larger vacuoles, separated by thin partitions. The sac is probably a bursa copulatrix. I have never seen accessory grain substances in it, nor sperm, which is explained by the presence of a Receptaculum seminis, into which the sperm immediately migrates, and which is also always seen filled with sperm. This Receptaculum seminis (Fig. 2, g) is formed by a double bladder, situated laterally to the side of the bursa copulatrix and connected with it by a passage, which issues from the upper side of the bursa; the passage has at its origin the same width as the inner wall of the bursa; then it gradually tapers as it approaches the receptacle; its walls are thick and show longitudinal ridges. I have found A. rhomboides in numerous specimens in the Alværstrommen (2 miles north of Bergen), some a few feet below the water table on kelp and fucus in June and September. All the individuals found in these months were sexually mature. The foot consists of diatoms and small entomostraces; I have seen shells of these in their interior.
Graff L v 1905 (citation)- Description of Aphanostoma rhomboides translated from german using Google Translate: "Aphanostoma rhomboides (Jens.) Pl. XI, Figs. 11-20. An extremely common form both near Bergen (Puddefjord to Solheimsvik, Follesö on Askö) and near Alexandrovsk (Yekaterinhafen, Pala Guba). Through the examination of numerous specimens, I have come to the conclusion that the minor differences, mostly merely concerning shape and color, which are supposed to separate this species from Jensen's Aphanostoma elegans, are due to greater or lesser amounts of pigment, contraction conditions, and the nature of the diet, while young specimens resemble Mecynostomum agile, established by the same author. Even more than from my preliminary report, the correctness of my interpretation will be demonstrated by comparing the illustrations. My largest 1.5 mm long specimens come from Pala Guba. The body is flat below, slightly curved above, and locomotion is a steady, fairly rapid crawl, occasionally interrupted suddenly to attach itself with the end of the tail (Fig. 14a) and to grope around with the conically protruding front end (b). When crawling freely, the animal has the outline shown in Fig. 11: gently indented in the middle of its length, conically rounded at the front, and with a warty tail posteriorly covered with adhesive cells on the ventrally side. In the fixed specimen (Fig. 12) and in the crush specimen, the end of the tail appears transversely truncated, decorated with protruding adhesive cells, and separated from the body. The shallow constriction at the base of the tail (see also Figs. 16-18) occasionally disappears, whereupon the tail is suddenly thrust forward again and pressed against the substrate. The body is translucent against a black background, especially the two ends, least of all the part behind the frontal gland (sd), due to the more heavily accumulated concretions (lr), which, like the frontal gland, ovaries (ov), seminal bursa (bs), and seminal vesicle (vs), appear white. In striking light, only the color of the parenchyma (cp), which depends on the food, is visible. It is yellowish or reddish yellow where crustaceans and their eggs are eaten (mostly in Bergen and Pala Guba), while the specimens found in ebb pools with diatoms, algae, and plant detritus (immediate vicinity of the Alexandrovsk station) are packed with diatoms and contain many yellow drops or blue-green and olive-green masses (cf. Jensen's fig. 9). The more food objects the body contains, the less the parenchyma appears vacuolated. The skin is always colorless; the parenchyma contains cells with granular yellow pigment, which are particularly abundantly accumulated in the area surrounding the statocyst (Fig. 12 pi) and distributed into the genital region (pi,). However, the number of these pigment cells varies considerably. Similarly distributed are the cell-like calculus clusters (kr), which appear brownish in transmitted light and consist of highly refractive granules with lively molecular movement. These are the corpuscles designated b by Jensen in his Figure 1, whose distribution is usually as shown in Fig. 12: closely packed in a transverse zone behind the statocyst, from which, in more numerous clusters, a stripe extends laterally from the ovaries on each side down to behind the midbody (Fig. 11 kr). They are usually completely absent on the side of the copulatory organs, as well as in front of the statocyst. The spindle-shaped rhabdites, at most 0.008 mm long and sharply pointed on both sides, are distributed over the entire body, usually in 0.012-0.016 mm long clusters of 2-5. They often protrude towards the skin and, especially on the ventral side, show a tendency to be arranged in short rows. These rows, converging towards the mouth and genital opening during contraction, sometimes intersect to form the rhombic stitches considered characteristic by Jensen (fig. 3). The largest rhabdites gave the impression of containing a fine central needle (cf. also Jensen's fig. 3*), but I could not be completely certain of this. Eyes are missing. The frontal glands (sd) open into a sharp- circumscribed field (sdm). The statolith (ot) is bowl-shaped, which is often only confirmed by rolling the statocyst; the rim of the bowl is radially folded, this folding continuing as fine striations up to a hub located in the center of the bowl, which, if observed less closely, could easily be mistaken for the central grain. The mouth (m), usually appearing as a transversely oval opening, lies slightly in front of the center when the body is fully extended. The testicular follicles extend in front of the statocyst on the sides of the frontal glands. The two ovaries (ov,) begin behind the statocyst, and the largest eggs (ov), forming their caudal end, have a diameter of 0.2 mm and are completely colorless. The mature spermatozoa (Fig. 13) possess a fine, granular central filament and narrow, parallel, hyaline margins, which leave a section of the central filament more than twice as long at the back as at the front, a form that was already suspected from the illustrations given by Jensen (Figs. 11 and 24). Of the genital openings, the female one (Fig. 12) is located at the beginning of the last eighth of the body length, the male () very close to the posterior end. The bursa seminalis, when filled, divides into two sections: a spherical, thin-walled seminal reservoir (bs) and a similarly shaped vesicle (bs,), but covered with a thick, light-colored muscularis and lined with glandular epithelium, which appears as the excretory duct of the seminal reservoir and merges almost immediately into the genital opening. The seminal reservoir changes in size and shape depending on its filling level and the pressure of the coverslip. Jensen did not see it at all, but only the spherical excretory duct, which in his Fig. 2 (as I also observed) had propelled its contents laterally in a hernia-like manner (at g) due to excessive compression. Fig. 20 shows the seminal bursa isolated by crushing an animal, where the relationship between the excretory duct (bs,) and the seminal reservoir (bs) is more clearly visible than in Fig. 12. The male copulatory organ consists of a seminal vesicle (vs), usually appearing spherical, and a slender, cylindrical penis (pe) lined with small cells. At rest, it is retracted into its muscular penile sheath (ps), which provides enough space to allow it to move and curve forward with the tip (see also Jensen). If the penis is to be protruded, the tail contracts and separates more sharply from the body than usual (Fig. 18 at *), the genital opening moves to the tip of the tail (Fig. 17), and finally the penis is extended to its full length (Fig. 18). On the other hand, the penis can also be completely retracted or rather invaginated into the seminal vesicle, as shown in Fig. 19. Just as the shape of the seminal reservoir of the bursa seminalis varies, so does that of the seminal vesicle, appearing sometimes spherical, sometimes transversely elongated, sometimes bilobed (see also Figs. 12, 18, 19 rs). I had to examine many specimens to clarify the normal position of the copulatory organs shown in Fig. 12. While in this case the excretory ducts are directed posteriorly, corresponding to the obliquely oriented position in the body from above and anterior to posterior and downward, the excretory parts can be concealed by the seminal receptacles, and the latter can appear laterally displaced. Young specimens (Fig. 15) contain massive amounts of glossy, oily droplets (tr), particularly numerous in the anterior body, while further posteriorly, large vacuoles appear in the parenchyma and the mass of the droplets decreases. Therefore, in striking light, only the anterior end is white, while the rest of the body is glass-like and transparent. With increasing size, the "frontal organ" first becomes visible, followed by the formation of the yellow pigment around the statocyst, and thus the development of the sex glands. Such specimens were described by Jensen as Mecynostomum agile. With further growth, the droplets disappear, vacuolization decreases, and concretions appear. This species prefers to live on the bottom of tide pools and shallow sea areas and hides in the sediment of aquariums. I have not found any Acoel in Sevastopol that I could have related to Nadina pulchella Ulyanin (I. c., p. 5, tab. I, figs. 1-4) or to Aphanostoma, described by Pereyaslawzewa ( I. c., p. 212, tab. I, fig. 2, tab. VIII, fig. 51 a-g, tab. XIV, figs. 101-107) under the same species name. The identity of these two forms is not made probable by anything, and neither genus nor family is even certain. This is less strange in the case of Ulyanin's species, of which only one habitus picture is available, than in the case of Pereyaslawzewa 's species, illustrated by so many illustrations, which, according to Pereyaslawzewa, is sometimes found in the thousands. Neither the characteristics of the genus Aphanostoma nor the specific description of its Aphanostoma pulchella mention anything about the number of genital openings in this form, and regarding the copulatory organs, it states on page 213: "Figure 2, which represents this (i.e., the male) organ, as well as the female sexual organ, has a more defined idea that cannot be described in more detail." However, this figure does not reveal whether there are one or two genital openings, nor whether a chitinous mouthpiece of the seminal bursa is present or not. Only the existence of the latter is certain; everything else is uncertain; indeed, the bulbous pharynx described by Pereyaslawzewa (p. 128, fig. 51 e and f) justifies the suspicion that this species does not belong to the Acoela at all."
Notes from synonyms
Notes for Aphanostoma griseum
Oersted AS 1845 (citation)- Diesing KM 1862 (citation)- describes and references. Jensen OS 1878 (citation)- lists this species as synonym in part of his new species Aphanostoma rhomboides. Marcus E 1948 (citation)- says this one of original species of Aphanostoma but cannot be recognized p 112, 187.
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