With 12 transparent, movable, sword- or blade-shaped lateral appendages. Body short and more or less cylindrical. Common planktonic species. (ref. ID; 1663)
ref. ID; 1850
The precise specific identification of Polyarthra 'species' and 'subspecies' is fraught with pitfalls, and the literature is full of errors. The P. vulgaris, P. luminosa, P. dolychoptera complex is a prime example. They can be distinguished only by the relative body/paddle length ratio that is highly variable, and the length/width ratio of the pectoral fins that are visible only with great difficulty. The pectoral fins can be seen in the living animals as they swim and turn, but only momentarily; or in preserved animals if they are manipulated properly and the fins are spread from the body. (ref. ID; 1850)
ref. ID; 1923
The individuals that hatch from resting eggs do not have paddles; such forms were originally referred to as Anarthra, now apparently an invalid genus. Male present. (ref. ID; 1923)
ref. ID; 2989
The taxonomic characteristics used for identification within the genera are usually: 1. Number of nuclei within the vitellarium, 2. Shape of the body, 3. Situation of the lateral antennae, 4. Presence or absence of ventral fins, 5. Length and width of the body and length and width of the fins. Comparisons of these measurements.
Lake Blankvatn specimens: Length and width of approximately of 100 individuals taken during different seasons and at different depths were measured for identification. A comparison between length and width measurements before and after fixation showed small differences only and most of the measurements were made on fixed individuals. In addition to the individuals whose length and width were measured, several were examined for other taxonomic characteristics. In approximately 50% of the animals, the nuclei could be counted in the vitellarium. Eight nuclei were always found. The body shape of all individuals examined was rectangular with rounded corners. Lateral antennae were situated 1/5-1/7 of body length from the end of the body. Ventral fins were never found. The relations between fin length and body length and between fin width and fin length were no significant differences between the mean values for body length from different depth or seasons. The uniformity of the number of nuclei, body shape, situation of lateral antennae, with and uniformity in total length through the year should indicate that at least the majority of the individuals of the genus Polyarthra from Blankvatn belong to the same species. The variation in body length, however, is greater than usual for one single Polyarthra species (Nipkow 1952; Voigt 1957, pp.392-393). This may be due to other species which have occurred in the material in only small numbers. If the extremes in the body length/fin length diagram are rejected on the grounds that they are other species, the variation becomes more normal. (ref. ID; 2989)
ref. ID; 3050
Synchaetidae without foot or toes but with twelve movable sword or blade-shaped appendages arranged in four groups on dorso-lateral and, ventrolateral surfaces near the anterior end. As stated by Edmondson in Ward and Whipple (1959), species of Polyarthra are distinguished by shape, length and structure of paddles, number of nuclei in vitellaria, location of lateral antennae and presence of an extra pair of cuticular appendages on the ventral side. Considering one of the above characters viz., the number of the nuclei in the vitellarium the species of Polyarthra fall in three groups; (i) P. euryptera having 12 nucei; (ii) P. minor and P. remata having 4 nuclei (P. minor has asymmetrical appendages); (iii) the remaining six species have eight nuclei). Of these six species, P. bicera possesses 2 setiform appendages on the posterior surface. P. proloba has a ventral lobe containing the posterior part of the mastax. In P. dolichoptera (forma typica) and P. longiremis the appendages protrude well beyond the body. In P. major the appendages are very broad and nearly paddle-shaped. The only remaining forms are P. dolichoptera var. brachyptera, P. dissumulans and P. vulgaris. Apart from the difference in the position of the antennae, these three species are characterized by the possession of 12 appendages arranged in four groups which, however, is the general characteristic of the genus and is shown by all the species except P. bicerca. (ref. ID; 3050)
ref. ID; 3086
The diagnostic characters for the identification of the species in the genus Polyarthra have been questioned by many workers (Sudzuki 1964; Ruttner-Kolisko 1959). Nipkow (1952) used the appearance of the resting eggs and the number of nuclei in the vitellarium as taxonomic criteria. However, as Ruttner-Kolisko (1959) pointed out, the resting eggs are seldom available for examination, especially in preserved material. Regarding the number of nuclei in the vitellarium, the constancy of this number is questioned by Sudzuki (1955) in his work on Polyarthra trigla Ehrenberg. In Polyarthra euryptera one of the characters for identification is the number of nuclei in the vitellarium, which is given as 12 (Carlin 1943; Bartos 1950; Nipkow 1952; Sudzuki 1964). However, in a number of specimens we examined, the number of nuclei in the viterallium was found to vary form 10 to 13, the majority of the specimens having 11 or 12 nuclei. This indicates that the number of nuclei in the vitellarium has little value as a taxonomic character in the identification of species in the genus Polyarthra. Ruttner-Kolisko (1959) has observed throat pouches for many of the specimens of Polyarthra dolichoptera that she examined from the Kapruner reservoir, Polyarthra proloba is distinguished by the throat pouch. However, Ruttner-Kolisko see little difference between Polyarthra proloba and Polyarthra dolichoptera which has developed a throat pouch. The throat pouch has also been noticed in Polyarthra vulgaris and Polyarthra remata (Ruttner-Kolisko 1959). In some of the specimens of Polyarthra dolichoptera that we examined during the present study a clear throat pouch has been observed. (ref. ID; 3086)
ref. ID; 4595
With 12 movable, sword-shaped lateral appendages or fins. Body a short, dorso-ventrally flattened cylinder. (ref. ID; 4595)
This species is well distinct from P. vulgaris with a relatively broader body, and rather strongly saw-shaped fins. (ref. ID; 1402)
The body more or less square with appendages narrow and longer than the body. The lateral edges of the appendages are toothed. The median rib of appendages are well developed all along the length. Vitellarium has 8 nuclei. (ref. ID; 2715)
All the specimens encountered had characteristic, relatively long fins in comparison with the length of the body. These fins were narrow and rather strongly serrated. Occasionally fairly distinct lateral nerves were observable in the distal part of the fins, perhaps indicative of transitions to Polyarthra vulgaris Carlin. (ref. ID; 3235)
Fins very extended posteriorly; long and thin, with strong saw-toothed margins. Lateral antennae on the posterior end of the body. Freshwater species, in eastern Baltic and in estuaries. (ref. ID; 4595)
Comments
According to Carlin the P. dolichoptera and P. vulgaris differ by 1) the general shape of body, 2) the position of the lateral antennae, 3) the length of fins with regard to the body and 4) the appearance of the fins. In P. vulgaris the fins are relatively broad with a feebly serrated contour and "lateral nerves" in addition to a "median nerve"; the former can be observed at least distally. In P. dolichoptera the fins are narrower and longer with regard to the body than in P. vulgaris; they are also usually more strongly serrated and without "lateral nerves". In the waters examined by Carlin (particularly in Motalastrom, Ostergotland, Sweden) P. vulgaris behaves as eurythermal and P. dolichoptera as cold-tolerant stenothermal (oligothermal). (ref. ID; 3017)
Measurements
Average total body length 110-120; average fin length 145-155; average fin breadth 4-7 µm. (ref. ID; 1402)
Length of body 102; width 59; length of appendage 112 µm. (ref. ID; 2715)
Body length (contracted) 110; body width 80; length of lateral appendages 100 µm. (ref. ID; 3275)
Length of body 80-145; fins 100-200 µm. (ref. ID; 4595)
It may co-occur with normal specimens carrying paddles, but these are not nearly as abundant. As the cuticle is very thin, all specimens were strongly contracted, to the point of difficulty is recognizing them as Polyarthra. However, the characteristics teeth on the rami, best seen in a caudal view of the trophi, are diagnostic. (ref. ID; 1499)
Polyarthra indica n. sp. belongs to the P. vulgaris-group, as indicated by the presence of accessory paddles. The species-specific dentition on the inner margins of the rami of its trophi and low number of nuclei in the vitellarium (six in P. indica n. sp. versus eight in other taxa of the P. vulgaris-group) distinguish it from its relatives. The denticulate inner margins of the rami are reminiscent of P. remata Skorikov, 1896 and P. leleki Koste, 1989. The new species differs from P. remata by the presence of accessory paddles (absent in P. remata), from P. leleki by the vitellarium having only four or six nuclei (eight in P. leleki). In addition, the shape and number of these rami teeth differs between P. indica n. sp., P. remata and P. leleki. The trophi of P. indica n. sp., appear similar to P. minor Voigt, 1904, but the latter species has no accessory paddles and a characteristic left-dorsal bundle of particularly elongate paddles. (ref. ID; 6645)
Descriptions
Body squarish in dorso-ventral view. Tegument stiff, about 1.5 times as long as wide. Four groups of major, lateral paddles inserted dorsally and ventrally in the neck region. Each group consists of three paddles extending beyond the posterior end of the body by about one third of their length. All paddles equal, length:width about 10:1, with midrib and marginal serration. Accessory pair of ventral paddles inserted medially between ventral pair of bundles, ventral paddles slightly less than half the length of the major paddles, narrow an elongate. Openings of the lateral antennas subdistal. Vitellarium with four or six nuclei. Trophi modified virgate, weakly sclerotized. Fulcrum rod-shaped in ventral, rectangular in lateral view, about 3-4 times as long as high. Posterior margin straight, anterior concave. No basal plate, rami with triangular basal apophysis. Inner margins of both right and left rami with asymmetrical row of alternating teeth; right and left major ramus tooth preceded by four accessory teeth, major tooth on right ramus most developed. Manubria rod-shaped, weakly curved, with well-developed proximal and distal lamellas. Unci vestigial. (ref. ID; 6645)
Comments
The diagnosis and identification of taxa in Polyarthra traditionally relies on dimensions of body and paddles and on paddle morphology. Trophi morphology has been documented in few instances only. Only recently has taxonomic weight been attributed to trophi morphology. In the common and ecologically important P. dolichoptera Idelson, 1925, and P. vulgaris Carlin, 1943, Chengalath & Koste (1988) were the first to report differences in trophi morphology between the two (P. dolichoptera as P. remata. P. vulgaris as P. dolichoptera). Later, it was suggested that the best distinction between P. vulgaris and P. dolichoptera is by trophi characters (Koste & Tobias 1989; Shiel & Koste 1993). Two of the Polyarthra inhabiting Devikulam Lake have trophi resembling those of P. dolichoptera (proximal ridge on the inner margin of the rami and the fulcrum straight) and P. vulgaris (the proximal ridge on right ramus is convex, left concave). However, there appear to be some differences in trophi morphology between the present material and other reports. The fulcrum of Lake Devikulam's P. cf. vulgaris is bent ventrad, a character observed in some (R.J. Shiel, pers. comm.), but not all (W.H. De Smet, pers. comm.) populationns of 'P. vulgaris' and which is possibly connected to the occurrence of a so-called 'proloba' variant in this species. The shape of the major rami teeth of the local P. cf. dolichoptera differs from previous reports on other populations (e.g., Figure 1b in Shiel & Koste, 1993; Figure 19 in Segers & Dumont, 1995). External morphology does not provide a clue either, as some of the characters previously considered to be taxonomically relevant (position of lateral antennas, relative length of paddles versus body length, paddle morphology, number of nuclei in vitellarium), are variable or, at the least, difficult to ascertain (C. Leutbecher, pers. comm., pers. obs.). Evidently, more research on the taxonomy of Polyarthra is required, but available data indicate that current identifications of P. vulgaris and P. dolichoptera may not be reliable. Consequently, reported differences in ecology between the two (P. vulgaris eurythermic, P. dolichoptera a cold-water stenotherm: see Koste, 1978; Shiel & Koste, 1993) require confirmation. In this context, it may be necessary to re-examine Pejler's (1956, 1957) studies reporting introgressive hybridisation between P. vulgaris and dolichoptera, as his reports are based on observations regarding body morphology only. (ref. ID; 6645)
Etymology
The name indica is an adjectival toponym. (ref. ID; 6645)
Type locality
Devikulam Lake, Kerala State, India (77 degrees 05'E - 10 degrees 13'N). Collected on January 14, 1998. (ref. ID; 6645)
Type material
Holotype and three slides containing paratypes in Royal Belgian Institute for Natural Sciences, Brussels, Belgium (K.B.I.N., IG28719, RIR110113), slide with 10 paratypes in the Department Biology, UG, further paratypes in Department Zoology, Christ College; Department of Biology, F.E.P., University of Antwerp, Belgium. (ref. ID; 6645)
Polyarthra major Carlin, 1943 (ref. ID; 1345, 3688); Polyarthra platyptera Ehrenberg, 1900 (ref. ID; 3688); Polyarthra platyptera var. major Burckhardt, 1900 (ref. ID; 1345, 3045, 3264, 3688); Polyarthra trigla (Ehrenberg) Harring, 1913 (ref. ID; 3264); Polyarthra trigla var. major Schreyer, 1921 (ref. ID; 1345, 3264, 3688)
Descriptions
In shape it is closely connected to P. vulgaris, but is considerably larger with usually relatively shorter and distinctly broader fins. (ref. ID; 1402)
Measurements
Average body length 170-175 (range 145-195); fin length 150-160 (125-170); fin breadth around 20 µm. (ref. ID; 1402)
Polyarthra minor Voigt, 1904 (ref. ID; 1345, 1468, 1923, 3264, 3272, 3514, 3688) or 1912 (ref. ID; 3688)
See
Polyarthra remata (ref. ID; 3688)
Synonym
Polyarthra minor Carlin, 1943 (ref. ID; 3688) or Lucks, 1912 (ref. ID; 1345, 3264, 3688); Polyarthra platyptera f. palustris Lie-Pettersen, 1910 (ref. ID; 3688); Polyarthra platyptera var. minor Voigt, 1904 (ref. ID; 1345, 3264, 3688); Polyarthra trigla (Ehrenberg) Harring, 1913 (ref. ID; 3264) or Harring, 1913 (ref. ID; 3688); Polyarthra trigla var. minor Olofsson, 1918 (ref. ID; 3688) or (Voigt) Olofsson, 1918 (ref. ID; 3264)
Descriptions
P. minor differs from P. remata in having the appendages of the right side distinctly shorter than those of the left. (ref. ID; 1923)
The body is more or less rectangular The sword-shaped appendages do not reach the posterior end of the body. The filiform appendages are a bit longer than the body. Five appendages (3 filiform and two sword-shaped) arise from the dorsolateral region on either side of the body while four (3 filiform and 1 sword-shaped) arise from ventrolateral region on either side of the body so that 9 appendages can be observed on either side. The corona is simple and demarcated into two ciliate portions, the anterior and posterior corona. There are present two antennae which are well anterior to the posterior corona. The mouth lies on the elevated ridge and leads into a broad mastax cavity. Opening into the mastax cavity is a pair of salivary glands. This cavity leads into the stomach through the narrow oesophagus. Attached to the stomach is a pair of gastric glands. The stomach passes into a large intestine through a narrow connection between the two. There is a single ovary present attached to a large vitellarium which has eight nuclei. The ovary is round and small as compared to the vitellarium. (ref. ID; 3050)
Comments
The species in my collection resembles P. vulgaris in having the lateral antennae placed well anterior to the posterior corona and in the length of the appendages compared to the length of the body. But there is an important difference viz., that the form in my collection has only six sword-shaped appendages, three on either side and has in addition six filiform appendages on either side. Thus this form differs from all the other known species of Polyarthra in having 18 appendages. I think that the difference in the number of appendages in sufficient to regard of the form in my collection as representing a new species for which I suggest the name P. multiappendiculata, sp. nov. (ref. ID; 3050)
Measurements
Maximum body length 104; maximum body breadth 73; length of sword-shaped appendage 86; length of filiform appendage 125 µm. (ref. ID; 3050)
The old species Polyarthra platyptera Ehrenberg is one of those which have been split up by Carlin (1943). (The abundant seasonal and local morphological variations within this group attracted attention relatively early. In the majority of the forms which have been the subject of more detailed investigation this morphological variation has proved more or less gradual, which has made the delimitation of species difficult task. Polytypical species have also long been known to be of common occurrence in the taxonomy of the Rotatoria. By a detailed morphological examination and the use of statistical methods Carlin (1943) succeeded in splitting some of these old polytypical species into several new ones. Finally it must be mentioned in this connection that the characterization of the different species is usually based exclusively upon the females, since the males are usually considerably reduced and appear only during a short part of the year.) Two of the resulting species are P. vulgaris and P. dolichoptera, of which the latter had been established previously as a variety by Idelson. (ref. ID; 3017)
This species has a large ventral lobe containing the posterior part of mastax. But Pejler (1957) questions the validity of this character. (ref. ID; 1923)
Comments
In certain specimens of Polyarthra, a ventral bulging could be observed resembling that which occurs in P. proloba (see Wulfert 1941, Fig.2 and Nipkow 1952, Pl.1:7). In all other respects most of these specimens were typical representatives of P. dolichoptera Idelson. The posterior part of the mastax projects into the bulge mentioned as it does in the specimens of P. proloba observed by Wulfert and by Nipkow. On account of the fact that this so-called "Kehlsack" (gular pouch) furnishes the most important specific character of P. proloba the observations by the present author might justify a certain measure of doubt concerning the existence of P. proloba as an independent species. The retention of P. proloba might, however, be necessary even after continued investigations, although other specific characters might then have to be given greater weight. The author considers, however, untenable the arguments by the aid of which Nipkow (1952, p.168) tries to prove that P. proloba really is a good species: From resting eggs of individuals of P. proloba Nipkow has obtained aptera individuals with obliquely orientated mastax. According to my opinion this might possibly prove the ventral bulge to be hereditarily fixed, but not that P. proloba is a species by itself as Nipkow wants to assert. The form of P. proloba described by Nipkow exhibits several similarities with P. dolichoptera, particularly with respect to the resting eggs and the aptera generation. The fins are admittedly shorter than the body, but this applies also to certain, otherwise typical, specimens of P. dolichoptera observed by the present author. In the lakes studied by Nipkow P. proloba is a summer-form, P. dolichoptera a winter-form. Carlin (1943, p.113) reported, however, that he has observed in the middle of the summer in eutrophic tarns a form which was morphologically indistinguishable from P. dolichoptera. (ref. ID; 2553)
Measurements
Body length (contracted) 85-125; width of body 50-78; length of appendages 106-120 µm. (ref. ID; 3275)
Fins not very extended posteriorly; rather thin, with a strong midrib, but with thin margins. Lateral antennae near posterior edge of body. Very small species. Freshwater species, also found only in the eastern part of the Gulf of Finland. (ref. ID; 4595)
Measurements
Average body length is around 80-90 (range from 65-100); fin length 105-110 (65-115) µm. (ref. ID; 1402)
Length of body 75-125; width of body 52-60; length of appendages 115-120; width of appendages 4 µm. (ref. ID; 3275)
Length of body 75-105; fins 80-125 µm. (ref. ID; 4595)
Embryonic development of female:
Quote from ref. ID; 3534
The germ nucleus is 8-10 µm in diameter, and in spring and autumn usually larger than that of the vitellarium, both the size relation is inverse in summer. The maturing germ is constricted off form the syncytial ovary, and forms the egg together with the yolk material which has come from the vitellarium through a fine membranous duct -the nutric canal- which is 5 µm in diameter and 15-25 µm in length. Before the settlement of the germ nucleus, a large oil globule is seen within the egg. During the process of the yolk material injection, the egg sojourns for a while near the cloaca, perhaps in an expanded part of the oviduct. In that part Plate (1886, p.18) sees the uterus. The egg is then partly or entirely pushed out from the cloaca making space for the next egg. The egg just deposited adheres to the mother by means of a viscid substance which seems to be secreted by the mass of glandular cells embedded in the epidermis of the mother. The amictic egg just laid is usually of oval form and 45-88x33-63 µm in size. The cleavage is total and spiral and unequal as in other rotifers. Probably after gastrulation, the blastmeres are arranged in a bilateral symmetry. At a glance, the segmentation reminds that of acoelous tuberllarians as stated by Hyman (1951, p.105). At the gastric region of the animal, there is usually a pair of large oil globules, 5-7 µm or more in diameter, which disappear at the moment of formation of each egg. Shortly after their disappearance, a large number of minute oil droplets are found in the vitellarium chiefly around the nuclei; these droplets pass into the egg along with the yolk mass, forming a large oil drop at the vegetal region of egg. Without exception, such an oil drop is found in all stage of the embryo. It is beyond any doubt that it originates from the oil globules lying at the gastric region of the mother. Similar oil drop is found also in the eggs of other planktonic rotifers, but the largeness of size, being 13-20 µm in diameter, is characteristic of this genus. Since its size is almost invariable throughout the development, it seems to serve exclusively for floating the animal as was already mentioned by Wesenberg-Lund (1930, p.88 & p.205), though Lehmensick (1926, p.94) stated that the oil drop is absorbed during the maturing process in Synchaeta. Temporarily as it is, the so-called foot, which is hardly recognizable in the adult, is formed during embryonic development. In such young embryos the bladder, 10 µm in diameter, contracts once per 36-38 sec., in fully developed ones once per 18-22 sec. The flame bulbs and their associating glandular structures are seen at the anal region. There is hardly any difference in size between the egg just deposited and that just before hatching. The young just hatched is mostly triangular in shape. The triangular shape is chiefly due to the oval form of the egg with the pointed end towards the tail region, where the terminal edges of the blades are gathered together. In a few days, the young doubles its size and becomes the adult. (ref. ID; 3534)
Adult female: General characters of the adult female from Urawa are as follows: Lorica is partially stiffened; the outline and the size are variable; the body length is usually 100-150 µm and the body width 70-110 µm. The spines used in producing a skipping motion are three for each of the clusters, which are situated at the shoulders. Each skipping spine or blade consists of about 20 segments with serrated lateral margins, the length of single segment being greatest in the middle part of the blade. The blades are generally 90-170 µm in length, thus barely reaching the body extremity or slightly exceeding it; the ration K2 (percentage of the blade length to the body length) is 80-120, and in this point the present species resembles P. vulgaris (K2 ca. 100), P. major (ca. 96) and P. remata (ca. 106) rather than P. dolichoptera (ca. 144) and P. euryptera (ca. 76). A midrib is distinctly seen, while the lateral ribs are recognizable only at the terminal region of the blade. Two conspicuous articulations as found by Weber (1898, p.399) are seen at the coxal portion of the midrib. The breadth of the blade is variable, too, but never attains the size of P. euryptera, which is 50-60 µm according to Burckhardt (1900, p.414), 40-50 µm after Zacharias (1898), 52-72 µm after Linder (1904, p.236). The small blades or styles are observed attaching to the mastax-region, being 62-76 µm in length. The posterior end of the body is retractile and an expansible orifice is present. Generally, there is no red mark at the anterior part of the body such as found in P. remata but it is present in a few samples collected in summer and autumn. There is a dark red fleck or eye at the cephalic region. At the tip of the head there are two prominences provided each with a brush of styles (12 µm in length). The oral feelers are also present. The lateral antennae, 9 µm in length and consisting of 5-8 setae, are situated between the post-lateral sini; as to their position, therefore, the present species is quite unlike P. minor and P. dolichoptera. The caudo-vesicular ganglia are found in the caudal region. The foot seen in the embryo is obliterated in the adult. The mouth, 6 µm in diameter is situated at the point where the tips of both unci meet. The ciliated esophagus is 15 µm long, around which tiny glandular structure are recognized as observed also in Keratella cochlearis, Asplanchna priodonta and Synchaeta stylata. The mastax is considerably large as compared with the body size. The trophi belong to the modified forcipate type as described by Hudson-Gosse (1886, p.4) and Weber (1898, p.402). The unci and the rami are somewhat complex. The fulcrum, 24 µm in length, reaches the upper region of the stomach. The latter organ is very large, consisting of about 13 lobes when seen from the dorsal side; it is often yellow in color, especially in winter samples, and contains a number of granules in its epithelium. There are certain glands near the trophi, too. They seem to correspond to the salivary glands in Epiphanes. The intestine, the epithelium of which is ciliated, is 17 µm in length and continues to the funnel-like rectum. The anus is 5 µm in diameter. There are two pairs, a pair of large and a pair of small, lobed gastric glands. The large glands are 18x8-12 µm in size and contain 5-6 nuclei, while the smaller one 5-10 µm in diameter. The glands seem to be connected on the ventral side. The nephridic ducts with a simple glandular complex run along the lateral sides of the body and open into the lower region of the bladder, which is globoid in shape and generally measures 15 µm but can reach 20 µm in diameter. This is a protonephridial bladder and contracts rhythmically once per 10-15 sec. (cf. Lehmensick; in Synchaeta, it contracts once per 20-25 sec.). On each side of the body, there are three pairs of flame bulbs, which were often overlooked by the previous authors. The epidermis just beneath the cuticle at the posterior part of the body is glandular in nature. In the vitellarium gland 8-12 nuclei are found, usually 8 even in the tiny specimens of autumn. My species is thus hardly related to P. remata, which has only 4 nuclei. (ref. ID; 3534)
Embryonic development of male:
Quote from ref. ID; 3534
The mictic eggs for males are 32-43x22-32 µm in size, or according to Olofsson (1918, p.578) 30-40x30-33 µm. The cleavage seems to be not unequal. Soon after deposition, ciliary movement is observed at both poles of the egg. This is a characteristic common to various kinds of males. The male embryo breaks the egg-shell mechanically. The male animals do not grow in post-embryonic like and, unlike females, swim about rapidly in water. (ref. ID; 3534)
Adult male: The adult males are very small, 28-42 µm in length, 23-28 µm in width, and 25-27 µm in height. In general features, they resemble the free swimming gametes of Vorticella (Protozoa). Between the auricles rotatory cilia are found. The muscular system consists of two longitudinal muscles for withdrawing the wheel organ and the protrusile penis. The ring muscles are rather obsolete. The sensory cirrus is found at a relatively posterior region of the body. At the hindermost part of the body, there are two prominences provided each with a tuft of cilia. These are the opening of the vas deferens and the tip of the foot respectively. The testis is not so large as described by Plate, Wesenberg-Lund, and is located at the region of mastax which is degenerated. The greater part of the body cavity is occupied by the glands which are regarded as prostate glands by Wesenberg-Lund. The so-called foot is clearly present as was already recognized by Gosse (1856, p.320), though Plate and Wesenberg-Lund did not mention it in this species. The vas deferens or ductus seminalis is ca. 10-20 µm in length and 2 µm in diameter, and its inner epithelium is densely ciliate. Around the duct, a few tiny prostate glands are also found. Within the spermsac of the embryo and the young just hatched, there are usually rod-like spermatozoa chiefly near the duct. The number of these rod-like spermatozoa is, as in other rotifer, usually 5; but that of normal ones is about 38, thus remarkably fewer than in other rotifers (e.g., ca. 300 in Asplanchna after Whitney). The bladder seems to be a cloacal one in its appearance. (ref. ID; 3534)
Resting egg:
Quote from ref. ID; 3534
The resting (or dormant) egg is 55-73x42-51 µm in size. Dieffenbach (1911, p.23) stated that there are two kinds of resting eggs in Polyarthra platyptera. In the present species, the resting eggs seem to be characterized usually by their being provided with a lot of spines on the shell. In just deposited eggs, however, the spines are not so stiff and cling to the egg surface as they did within the body of the mother. Such a fact has been observed also in Gastropus hyptopus, and in this case, the eggs are often perceived erroneously as having no spines. A number of oil drops are found in the resting egg as was already mentioned by Dieffenbach. (ref. ID; 3534)
Comments
Some variation have been found in the present species. In the adult, the size of the body and the blades is fairly variable, even within specimens collected at the same time from the same place. Judging from the figure, the following can be said; first, the body length varies between 65 µm and 208 µm, the body width 48-146 µm, the blade length 60-190 µm; and the blade width 7-19 µm depending on seasons; thus, neither the body width nor the blade length is available for taxonomic purposes. (ref. ID; 3534)
Polyarthra trigla major Burckhardt, 1900 (ref. ID; 3083), var. major Burckhardt (ref. ID; 3063), (Burckhardt) Schreyer, 1920 or Scheryer, 1920 (ref. ID; 3688)
See
Polyarthra major (ref. ID; 1345, 3264, 3688)
Descriptions
Ventral blades wanting. Fertilized dormant egg very close to vulgaris-dolichoptera in general features (Nipkow 1952; Sudzuki 1953). Vitellarium with 8 nuceli. (ref. ID; 3083)
The fins in Polyarthra have their final length and shape at birth, while the body may still "grow" or swell through the rest of the individual's life. The largest animals are usually found under good food conditions, or at the end of a season, when metabolites have been stored in their bodies. (ref. ID; 1402)
Body illoricate, cylindrical. Each side of anterior region with six appendages; appendages about as long as body, spearshaped and with lateral teeth. Lateral antennae situated at the posterior end of body. (ref. ID; 1804)
Two dorso-lateral and two ventrolateral bundles of paddles, each consisting of three paddles, are located at the shoulder region. Each bundle of paddles is attached in a recessed area of integument which is greatly thickened and folded. The paddles are arranged one above the other so that they overlap slightly. Each paddle is lance-shaped and has a central thickening extending nearly its entire length. The paddles arise from the shoulder integument and are attached by short stumps. The gland which secretes the egg thread was observed near the posterior mid-line. The integument in this region is slightly indented and thickened. The gland is composed of two parts: a relatively large, roundish sac in which are numerous mitochondria and a neck region containing two large oval bodies placed side by side with a small channel passing between them. (ref. ID; 1923)
Body with six appendages; appendages long, spear-shaped and with lateral teeth. (ref. ID; 2704)
Body usually larger than in P. dolichoptera. Lateral antenna situated at the posterior lateral end body. Appendages as long as body, spear-shaped with lateral teeth. Vitellarium has 8 nuclei. (ref. ID; 2715)
Body illoricate, transparent and square. Foot absent. Twelve flat cuticular appendages (paddles) in the anterior third of the body, arranged in two dorso-lateral and two ventro-lateral bundles each of three paddles. The broad striated longitudinal muscles which move the fins are visible in the body. On the apical filed two ciliated antennae and numerous sensory bristles. (ref. ID; 2867)
Body oblong, of moderate size. Lateral antennae emerging from the lateral side of the body just in front of the posterior end. Leafy appendages of variable length, but usually as long as the body, spear-shaped, laterally slightly toothed. Median rib well-developed only to about two-thirds of length of appendage. (ref. ID; 3180)
Fins only somewhat longer posteriorly than body; rather wide and with strong saw-toothed margins. Lateral antennae somewhat before the end of body. Freshwater species, in eastern Baltic and in estuaries. (ref. ID; 4595)
Comments
See comments of P. dolichoptera. (ref. ID; 3017)
Measurements
Body length 158; maximum width 65 µm. (ref. ID; 1804)
Length of lorica 100; width 70 µm. (ref. ID; 2282)
Body length 192; maximum width 68 µm. (ref. ID; 2704)
Length of body 160 µm. (ref. ID; 2715)
Total length 170; maximum width 100 µm. (ref. ID; 2867)
Length of body 100-145; fins 85-150 µm. (ref. ID; 4595)
Body length 110; body width 74; fins 104 µm. (ref. ID; 4606)
P. v. vulgaris and P. v. luminosa have to be considered as ecotypes, and not two genetically distinct taxa. (ref. ID; 1850)
Measurements
The length/width ration the ventral fin measured was 18 for P. dolichoptera, 18-25 for P. v. vulgaris and 2.3-4.0 for P. v. luminosa. The same measurements were observed over several years in Lake Ontario as well. The length of the fins varies between 20 and 50 µm, but is normally around 30-35 µm. (ref. ID; 1850)
