Vermiform Embryos Research Articles

ESCAPE PROCESSES IN EMBRYOS OF DICYEMIDS (PHYLUM DICYEMIDA).

Dicyemid mesozoans usually consist of 10 to 40 cells. They are characterized by 2 distinct embryos, vermiform and infusoriform, that develop within the axial cell of the adult. The means of escape of each embryo from the parent body was studied in Dicyema japonicum and Dicyema misakiense, parasites of Octopus sinensis. There were no differences in means of escape between species or embryo type, apparently due to morphological constraints whereby the parents (nematogen or rhombogen) share a similar body organization. Escapes were effected through the gap between adjacent peripheral cells of the adult, rupturing the axial cell membrane and the membrane that envelopes the embryo. After the embryo escaped, the path was closed by the enveloping membrane left behind by the embryo. Vermiform embryos can escape from any region of the body, although more embryos were observed to escape from anterior regions than from posterior regions. Infusoriform embryos escaped from both anterior and posterior regions in the axial cell, with more embryos observed to escape from the posterior regions. The different escape regions for the 2 types of embryo are presumably related to the adult body plan lacking a genital opening, so each different type of embryo has its appropriate site of escape.

Redescription of Dicyemennea eledones (Wagener, 1857) (Phylum Dicyemida) from Eledone cirrhosa (Lamarck, 1798) (Mollusca: Cephalopoda: Octopoda).

Dicyemids are common parasites found in the kidneys of many cephalopods. Species identification previously relied on old species descriptions containing considerable confusions, casting doubt on taxonomy and identification. Detailed morphological description and genotyping of all developmental stages are required for an exact taxonomy. To this end, we undertook the redescription of the dicyemid Dicyemennea eledones (Wagener, 1857), infecting the cephalopod Eledone cirrhosa (Lamarck). Samples were collected off Concarneau in the Bay of Biscay, France, and off La Goulette in the Gulf of Tunis, Tunisia. Dicyemennea eledones is a large species, with adults reaching c.7,000 μm in length. The vermiform stages are characterised by having 23 peripheral cells, a conical calotte and an axial cell that extends to the base of the propolar cells. An anterior abortive axial cell is present in vermiform embryos. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell and the refringent bodies, which were not always seen, are possibly liquid. For the first time, an 18S rDNA sequence is generated for D. eledones, illustrating genetic differences with the other dicyemid 18S rDNA sequences available in databases. This sequence can now be used for D. eledones barcoding, making the identification of the species easier and more reliable.

First descriptions of dicyemid mesozoans (Dicyemida: Dicyemidae) from Australian octopus (Octopodidae) and cuttlefish (Sepiidae), including a new record of Dicyemennea in Australian waters

Three new species of dicyemid mesozoans are described for the first time from Australian octopus and cuttlefish species. Dicyemennea floscephalum sp. n. is described from Octopus berrima Stranks et Norman (southern keeled octopus) collected from Spencer Gulf and Gulf St. Vincent, South Australia, Australia and represents the first description of a species of Dicyemennea Whitman, 1883 from Australian waters. Dicyema papuceum sp. n. and D. furuyi sp. n. are described from Sepia papuensis Hoyle (Papuan cuttlefish) collected from Shark Bay, Western Australia, Australia. Dicyemennea floscephalum sp. n. is a medium to large species that reaches approximately 4.9 mm in length. The vermiform stages are characterised by having 23-28 peripheral cells, and a disc-shaped, flower-like calotte in larger individuals. An anterior abortive axial cell is absent in vermiform embryos and verruciform cells were not observed in nematogens and rhombogens. Infusoriform embryos comprise 37 cells; one nucleus is present in each urn cell. Dicyema papuceum sp. n. is a small species that reaches approximately 1.1 mm in length. The vermiform stages are characterised by having 30-33 peripheral cells and a relatively small, cap-shaped calotte. An anterior abortive axial cell is absent in vermiform embryos and verruciform cells were occasionally observed in nematogens. Infusoriform embryos comprise 37 cells; two nuclei are present in each urn cell. Dicyema furuyi sp. n. is a large species that reaches approximately 5.3 mm in length. The vermiform stages are characterised by having 22-24 peripheral cells and an elongate calotte. An anterior abortive axial cell is absent in vermiform embryos and verruciform cells were not observed in nematogens and rhombogens. Infusoriform embryos comprise 37 cells; one nucleus is present in each urn cell. Three secondary nematogens were also observed in the right renal appendages of two host individuals, confirming the occurrence of this form.

Two New Species of Dicyemid (Dicyemida: Dicyemidae) from Two Australian Cephalopod Species:Sepioteuthis australis(Mollusca: Cephalopoda: Loliginidae) andSepioloidea lineolata(Mollusca: Cephalopoda: Sepiadariidae)

Two new species of dicyemid parasites from Dicyema are described from 2 species of Australian cephalopods, i.e., Dicyema calamaroceum n. sp. from Sepioteuthis australis Quoy and Gaimard, 1832 (southern calamary) collected from Spencer Gulf (SG) and Gulf St Vincent (GSV), South Australia (SA), Australia, and Dicyema pyjamaceum n. sp. from Sepioloidea lineolata Quoy and Gaimard, 1832 (striped pyjama squid), collected from SG, SA, Australia. Dicyema calamaroceum is a medium sized species that reaches approximately 2,400 μm in length. The vermiform stages are characterized by having 31-34 peripheral cells, a conical calotte, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos, and verruciform cells were not observed in nematogens and rhombogens. Infusoriform embryos consist of 39 cells; 2 nuclei are present in each urn cell, and the refringent bodies are solid. Dicyema pyjamaceum is smaller than D. calamaroceum, with a body length that reaches approximately 1,950 μm. The vermiform stages are characterized by having 20-23 peripheral cells, a cap-shaped calotte that forms a cephalic swelling together with the parapolar cells, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos. Verruciform cells and granules in propolar cells were observed in nematogens and rhombogens. Infusoriform embryos consist of 37 cells; 2 nuclei are present in each urn cell, and the refringent bodies are solid. This represents the first description of dicyemid parasites from Australia.

A New Dicyemid from Benthoctopus sibiricus (Mollusca: Cephalopoda: Octopoda)

A new species of dicyemid mesozoan is described from Benthoctopus sibiricus Loyning, 1930, collected in the eastern Chukchi Sea. Dicyemennea chukchiense n. sp. is a medium species that reaches about 2,000 µm in length; it lives in folds of the renal appendages. The vermiform stages are characterized in having 23 peripheral cells, a conical calotte, and an axial cell that extends to the base of the propolar cells. An anterior abortive axial cell is present in vermiform embryos. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell and the refringent bodies are solid. This is the first dicyemid described from the Arctic waters.

A New Dicyemid from Opisthoteuthis depressa (Mollusca: Cephalopoda: Octopoda)

A new species of dicyemid mesozoan is described from Opisthoteuthis depressa Iijima and Ikeda, 1895, collected from Suruga Bay in Japan. Dicyemennea umbraculum n. sp. is a medium species that reaches approximately 3500 microm in length. This species attaches to the surface of the renal appendages. The vermiform stages are characterized as having 22 or 23 peripheral cells, a disc-shaped calotte, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell, and the refringent bodies are solid. This is the first description of a dicyemid from Opisthoteuthis.

Three New Dicyemids from Octopus sasakii (Mollusca: Cephalopoda: Octopoda)

Three new species of dicyemid mesozoan are described from Octopus sasakii Taki, 1942, collected from Tosa Bay and Kii Strait in Japan. Dicyema shimantoense n. sp. is a medium-size species that reaches about 3,000 microm in length, and lives in folds of the renal appendages. The vermiform stages are characterized by having 22 peripheral cells, a conical calotte, and an axial cell that extends to the base of the propolar cells. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell, and the refringent bodies are solid. Dicyema codonocephalum n. sp. is also a medium-size species that reaches about 2,000 microm in length. It too lives in folds of the renal appendages. The vermiform stages are characterized by having 17-22 peripheral cells, an elongated calotte, and an axial cell that extends to the middle of propolar cells. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell, and the refringent bodies are solid. Dicyemennea pileum n. sp. is a medium species that reaches about 2,000 microm in length. It attaches to the surface of the renal appendages. The vermiform stages are characterized by having 23 peripheral cells, a disc-shaped calotte, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos. Infusoriform embryos consist of 38 cells; 2 nuclei are present in each urn cell, and the refringent bodies are liquid. These are the first dicyemids to be described from Octopus sasakii.

Redescription of Dicyemennea nouveli (Phylum: Dicyemida) from Enteroctopus dofleini (Mollusca: Cephalopoda: Octopoda)

A species of dicyemid mesozoan is redescribed from the giant Pacific octopus, Enteroctopus dofleini (Wülker, 1910), collected off Iwase in Toyama Bay, Honshu, Japan. Dicyemennea nouveli McConnaughey, 1959, is a large species that reaches about 12,000 microm in length. This species lives in folds of the renal appendages. The vermiform stages are characterized as having 30-41 peripheral cells, a conical calotte, and an axial cell that extends to the middle of the metapolar cells. An anterior abortive axial cell is present in vermiform embryos. Full-grown vermiform embryos have as many as 4 agametes. Infusoriform embryos consist of 39 cells; 2 nuclei are present in each urn cell and the refringent bodies are solid.

A New Dicyemidfrom Sepiella japonica (Mollusca: Cephalopoda: Decapoda)

A new species of dicyemid mesozoan is described from Sepiella japonica Sasaki, 1929, collected from the eastern area of Inland Sea, Osaka Bay, and Kii Strait in Japan. Dicyema sepiellae n. sp. is a large species that reaches about 4,000 microm in length. This species lives in folds of the renal appendages. The vermiform stages are characterized as having 24-29 peripheral cells, a conical calotte, and an axial cell that extends to the middle of the metapolar cells, but to the base of propolar cells in vermiform embryos. Infusoriform embryos consist of 39 cells; 2 nuclei are present in each urn cell and the refringent bodies are solid. This is the first description of a dicyemid in any species of Sepiella.

REDESCRIPTION OF TWO DICYEMENNEA (PHYLUM: DICYEMIDA) FROM ROSSIA PACIFICA (MOLLUSCA: CEPHALOPODA: DECAPODA)

Two species of dicyemid mesozoan are redescribed from Rossia pacifica Berry, 1911, collected off Iwase in Toyama Bay, Honshu, Japan. Dicyemennea brevicephaloides Bogolepova-Dobrokhotova, 1962, is a large species that reaches about 4,000 microm in length. This species attaches to the surface of the branchial heart appendages. The vermiform stages are characterized as having 23 peripheral cells, a disc-shaped calotte, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos. Infusoriform embryos consist of 35 cells; a single nucleus is present in each urn cell and the refringent bodies are absent. Dicyemennea rossiae Bogolepova-Dobrokhotova, 1962, is a medium species that reaches about 2000 microm in length. This species lives in folds of the renal appendages. The vermiform stages are characterized as having 29-34 peripheral cells, a conical calotte, and an axial cell that extends to the middle of the metapolar cells. An anterior abortive axial cell is present in vermiform embryos. Infusoriform embryos consist of 39 cells; 2 nuclei are present in each urn cell and the refringent bodies are solid.

THE EXPRESSION OF TUBULIN AND TEKTIN GENES IN DICYEMID MESOZOANS (PHYLUM: DICYEMIDA)

Dicyemid mesozoans (Phylum Dicyemida) are endoparasites (or endosymbionts) that typically are found in the renal sac of benthic cephalopod mollusks such as octopuses and cuttlefishes. Adult dicyemids likely adhere to the renal appendage of hosts via cilia of calotte peripheral cells. These cilia seem to be continuously worn away in the interaction between the dicyemids and the epidermal cells of host renal appendages. We cloned 4 cDNAs and genes, alpha-tubulin, beta-tubulin, tektin B, and tektin C, which are thought to play a key role in ciliogenesis, from Dicyema japonicum, and studied expression patterns of these genes by whole-mount in situ hybridization. We detected coexpression of these genes in the calotte peripheral cells, but not in the trunk peripheral cells. This suggests that regeneration and turnover of cilia continuously occur in the calotte. In vermiform and infusoriform embryos, we also detected coexpression patterns of these genes, which might correlate with ciliogenesis during the embryogenesis. We also predicted the secondary structure and the coiled-coil regions of dicyemid tektins.

Serotonin immunoreactivity in a highly enigmatic metazoan phylum, the pre-nervous Dicyemida

Dicyemida are simply organized metazoans with a long axial cell surrounded by a layer of ciliated peripheral cells. Stem cells and propagates develop inside the cytoplasm of the axial cell. Two types of propagates exist, asexually formed vermiform embryos and sexually derived infusoriform larvae, neither of which, however, develop by gastrulation. Thus, Dicyemida lack all traits typical of common metazoa and represent a pre-nervous state of organization. In this study, immunofluorescence and immunoelectron microscopy have been used to investigate the presence of a serotonin-like molecule in adults and larvae of Dicyema typus and Dicyemennea antarcticensis. Generally, in the adults of both species, the main immunoreactive structures are confined either to small vesicles inside the peripheral cells or to prominent vesicles in the axial cell, the latter vesicles apparently playing a role during the differentiation of the stem cells and the development of the propagates. In all stages, faint immunoreactivity can be observed over the surface membrane and the ciliary apparatus and over the heterochromatic blocks in the nuclei. Surprisingly, in the infusoriform larva, striking immunoreactivity occurs in the vesicles of the capsule cells covering the urn cells, which contain germinal cells. These vesicles might represent stores used in a later life phase of the animal. The results suggest that, in the pre-nervous Dicyemida, serotonin in its ancestral form may function as a hormone regulating essential developmental and morphogenetic processes.

Biology of dicyemid mesozoans.

We reviewed recent advances of some aspects on the biology of dicyemid mesozoans. To date 42 species of dicyemids have been found in 19 species of cephalopod molluscs from Japanese waters. The body of dicyemids consists of 10-40 cells and is organized in a very simple fashion. There are three basic types of cell junction, septate junction, adherens junction, and gap junction. The presence of these junctions suggests not only cell-to-cell attachment, but also cell-to-cell communication. In the development of dicyemids, early stages and cell lineages are identical in vermiform embryos of four genera, Conocyema, Dicyema, Microcyema, and Pseudicyema. Species-specific differences appear during later stages of embryogenesis. In the process of postembryonic growth in some species, the shape of the calotte changes from conical to cap-shaped and discoidal. This calotte morphology appears to result from adaptation to the structure of host renal tissues and help to facilitate niche separation of coexisting species. In most dicyemids distinctly small numbers of sperms are produced in a hermaphroditic gonad (infusorigen). The number of eggs and sperms are roughly equal. An inverse proportional relationship exists between the number of infusorigens and that of gametes, suggesting a trade-off between them. Recent phylogenetic studies suggest dicyemids are a member of the Lophotrochozoa.

Reproductive traits in dicyemids

Several characters involved in the life cycle in dicyemids were examined to understand reproductive strategy and adaptations to cephalopod hosts. In most dicyemids distinctly small numbers of sperms are produced in a hermaphroditic gonad (infusorigen). The number of eggs and sperms are roughly equal (means of the number of sperm:egg=1:1.58). An inverse proportional relationship was found between the number of infusorigens and the gametes, suggesting a trade-off between them. Fecundity was positively correlated with the body size of adult stages (nematogens and rhombogens). Fecundity of a single dicyemid is not very high compared with that of the other endoparasite taxa, but a total reproductive capacity per community is high, because a great number of individuals multiply asexually in the renal sac. The size of mature infusoriform embryos (dispersal embryos) that develop from fertilized eggs was not correlated with their adult sizes, but the size of embryos was correlated with the maximum mantle length of the host octopus species. Although at present the process of infecting new hosts is still unknown, the size of the infusoriform embryo is likely determined by host-specific factors in this process. The size of vermiform embryos that are asexually formed from agametes was positively correlated with size of the adults; however, the number of vermiform embryos present in the axial cell of adults was not correlated with size of the adults. A correlation was not found between maximum mantle length of the host cephalopod species and length of the adult dicyemids. In dicyemid species the size of adults appears to be constrained by the renal habitat, including renal-pancreatic complex and branchial hearts of each host cephalopod species. Size thus may be determined by the volume of the renal sac, the diameter of the renal tubules, or the depth of folding in the surface of glandular renal appendages of cephalopods.

New species of Dicyemennea (phylum: Dicyemida) in deep-water Graneledone (Mollusca: Cephalopoda: Octopoda) from the Antarctic.

Two new species of dicyemids are described from 2 species of deep benthic cephalopods, Graneledone antarctica and G. macrotyla, collected in the Southern Ocean south of the Antarctic Convergence. Dicyemennea bathybenthum n. sp. was found in G. antarctica. It is a medium-sized dicyemid whose length does not exceed 1,000 microm. The calotte is bluntly rounded or conical in small individuals, but the shape becomes discoidal in large individuals. Nematogens and vermiform embryos have 23 peripheral cells. An anterior abortive axial cell is present in vermiform embryos. Other stages in the life cycle were not observed. Dicyemennea dorycephalum n. sp. was found in G. macrotyla. It is a medium to large dicyemid that rarely exceeds 4,000 microm. The calotte is distinctly pointed, similar in shape to a spearhead. Vermiform stages typically have either 25 or 27 peripheral cells. An anterior abortive axial cell is present in vermiform embryos. Infusoriform embryos have 37 cells, the refringent bodies are solid in composition, and 2 nuclei are present in each urn cell.

Dicyema shorti n. sp. (phylum Dicyemida) from Octopus burryi (Mollusca: Cephalopoda: Octopodidae) in the Gulf of Mexico.

Nematogens and vermiform embryos of a new species of Dicyema are described from an octopus collected off Veracruz, Mexico. Dicyema shorti n. sp. is a small dicyemid species that rarely exceeds 500 microm in length. It is further characterized by the presence of 18 peripheral cells in the vermiform stages, a conical-shape calotte, and an axial cell that extends to the base of the propolar cells. Other stages in the life cycle of the parasite are not known. This is the first dicyemid to be described from Octopus burryi Voss. 1950, and also from both the southern Gulf of Mexico and the country of Mexico.

Developmental patterns and cell lineages of vermiform embryos in dicyemid mesozoans.

Patterns of cell division and cell lineages of the vermiform embryos of dicyemid mesozoans were studied in four species belonging to four genera: Conocyema polymorpha, Dicyema apalachiensis, Microcyema vespa, and Pseudicyema nakaoi. During early development, the following common features were apparent: (1) the first cell division produces prospective cells that generate the anterior peripheral region of the embryo; (2) the second cell division produces prospective cells that generate the posterior peripheral region plus the internal cells of the embryo; (3) in the lineage of prospective internal cells, several divisions ultimately result in cell death of one of the daughter cells. Early developmental processes are almost identical in the vermiform embryos of all four dicyemid genera. The cell lineages appear to be invariant among embryos and are highly conserved among species. Species-specific differences appear during later stages of embryogenesis. The number of terminal divisions determines variations in peripheral cell numbers among genera and species. Thus, the numbers of peripheral cells are fixed and hence species-specific.

Differential assembly of alpha- and gamma-filagenins into thick filaments in Caenorhabditis elegans.

Muscle thick filaments are highly organized supramolecular assemblies of myosin and associated proteins with lengths, diameters and flexural rigidities characteristic of their source. The cores of body wall muscle thick filaments of the nematode Caenorhabditis elegans are tubular structures of paramyosin sub-filaments coupled by filagenins and have been proposed to serve as templates for the assembly of native thick filaments. We have characterized alpha- and gamma-filagenins, two novel proteins of the cores with calculated molecular masses of 30,043 and 19,601 and isoelectric points of 10.52 and 11.49, respectively. Western blot and immunoelectron microscopy using affinity-purified antibodies confirmed that the two proteins are core components. Immunoelectron microscopy of the cores revealed that they assemble with different periodicities. Immunofluorescence microscopy showed that alpha-filagenin is localized in the medial regions of the A-bands of body wall muscle cells whereas gamma-filagenin is localized in the flanking regions, and that alpha-filagenin is expressed in 1.5-twofold embryos while gamma-filagenin becomes detectable only in late vermiform embryos. The expression of both proteins continues throughout later stages of development. C. elegans body wall muscle thick filaments of these developmental stages have distinct lengths. Our results suggest that the differential assembly of alpha- and gamma-filagenins into thick filaments of distinct lengths may be developmentally regulated.

Dicyemennea discocephala sp. n. (Mesozoa: Dicyemidae) in a Finned Octopod from the Antarctic

Dicyemennea discocephala sp. n. is described from Grimpoteuthis glacialis (Robson, 1930) (Ceph- alopoda). It is the fifth species of dicyemid to be described from Antarctic waters, and the first species to be reported from a finned octopod host. Mature nematogens of D. discocephala were stocky, and could be distinguished from all other species in the genus by very large, disc-shaped calottes. The peripheral cell number of vermiform stages was typically 22 or 23. The largest nematogens measured about 1,450 gm. Vermiform embryos lacked an abortive axial cell and reached lengths of 150 to 195 jtm at eclosion. This paper constitutes the fourth in a series on dicyemid mesozoans from Antarctic waters (for review see Hochberg and Short, 1970). The species description is based on limited material from a single individual of Grimpoteuthis gla- cialis (Robson, 1930). It is significant in that this represents the first record of dicyemids infecting cirrate or finned octopods. Until now dicyemids were thought to occur exclusively in shallow- water benthic, incirrate octopods and in a few species of epibenthic decapods (i.e., cuttlefishes, sepiolids, and loliginids). The octopod suborder Cirrata is currently in need of major systematic revision. In addition, our knowledge of the biology and ecology of most finned octopods is fragmentary and often con- tradictory. Early workers, such as Chun (1914) and Robson (1932) inferred a benthic existence for Grimpoteuthis, and in the original description Robson (1930) mentioned the presence of ben- thic invertebrates (polychaetes) in the stomach of G. glacialis. Voss (1967) on the other hand, considered that morphological features, such as a delicate, gelatinous body, poorly developed musculature, reduced sucker size and reduced eyes indicated the genus was abyssopelagic and fed on plankton. On the basis of deep-sea pho- tographs, Roper and Brundage (1972) used the term benthopelagic to imply that many cirrates probably float above and rarely come in con- tact with the bottom. Of the three species of Grimpoteuthis that oc- cur in the Antarctic, G. glacialis appears to be

Ascaris suum: Oxidative phosphorylation in mitochondria from developing eggs and adult muscle

Respiration and the phosphorylating capability of mitochondria isolated from one-celled fertilized eggs, 10-day vermiform embryos, 21-day infective larvae, and adult body wall muscle from Ascaris suum were compared with that of rat liver mitochondria. Although oligomycin-sensitive ATPase and O 2 consumption/ mitochondrion in the presence of succinate and malate was lower in eggs than in liver, other properties such as respiratory control, ADP:O and P:O ratios at sites I, II, III, and the sensitivity of respiration to cyanide, azide, oligomycin, rotenone, and malonate were similar. In muscle mitochondria, the oligomycin-sensitive ATPase and O 2 consumption/ mitochondrion were sharply reduced, respiratory control was poor, and electron transport at sites II and III in particular was inefficiently coupled with phosphorylation. In addition, about 60% of the respiration was insensitive to cyanide or azide but sensitive to salicylhydroxamic acid. The results support earlier evidence that the free-living eggs of A. suum are aerobes. The adult parasite, while continuing to ferment actively in the presence of oxygen, nevertheless possesses one or more electron transport systems that are inefficiently coupled with aerobic phosphyorylations. The physiological significance of these systems has yet to be elucidated.