Fig 1 - uploaded by Igor A. Kosevich
Content may be subject to copyright.
Scheme of Dynamena pumila colony organization. (A) General scheme of the colony structure (modified after (Kuhn, 1914)); (B) enlarged part of the shoot with lateral branch (from (Cornelius, 1979)). br, branch of a shoot; hy, hydrotheca; nd, nodal constriction between shoot internodes; sh, shoot; sht, shoot stem; sl, stolon of a hydrorhiza. Stolon and shoot growing tips are labelled black.
Source publication
Modular organization of colonial hydroids is based on cyclic morphogenesis during growth of their body. In many thecate hydroids (Hydrozoa: Leptomedusae) the shoots of the colony consist of a few distinct elements and possess complex spatial organization. In most cases, the evolutionary sequence of morphogenetic modifications that led to present-da...
Contexts in source publication
Context 1
... thecate hydroid colony is composed of two main parts- the net of tubular branching stolons of hydrorhiza creeping over the substrate and set of branching shoots on the upper side of stolons ( Figure 1A). Each shoot consists of numerous internodes with hydrothecae-the hydranth (zooid) protec- tive housing. ...
Context 2
... this paper we chose well studied species of thecate colonial hydroid Dynamena pumila (Linnaeus, 1758) (Hydrozoa: Leptomedusae: Sertulariidae). The colony consists of a net of the tube-form stolons and shoots protruding into sur- rounding water ( Figure 1A). The following description is based on works of Cornelius (1979) and Naumov (1969). ...
Context 3
... shoots branch sparsely and irregu- larly in one plane. The stem and branch divided in internodes of the same organization with nodal constrictions between every one, two or three internodes ( Figure 1B). Each internode bears two hydrothecae in opposite to sub-opposite pairs. ...
Context 4
... comparison in several sertulariid species the diaphragms of two successive alternate hydrothecae can be located very close one to another, but still obviously at differ- ent levels ( Figure 5D-G), e.g. Abietinaria filicula, A. articu- lata, Dynamena crisioides, D. nigra, D. disticha, Idiellana 1969)), Idiellana pristis (E) (from (Migotto, 1996)), Abietinaria filicula (F) and Diphasia nigra (G) (from (Cornelius, 1979)). ...
Context 5
... comparison in several sertulariid species the diaphragms of two successive alternate hydrothecae can be located very close one to another, but still obviously at differ- ent levels ( Figure 5D-G), e.g. Abietinaria filicula, A. articu- lata, Dynamena crisioides, D. nigra, D. disticha, Idiellana 1969)), Idiellana pristis (E) (from (Migotto, 1996)), Abietinaria filicula (F) and Diphasia nigra (G) (from (Cornelius, 1979)). ...
Context 6
... comparison in several sertulariid species the diaphragms of two successive alternate hydrothecae can be located very close one to another, but still obviously at differ- ent levels ( Figure 5D-G), e.g. Abietinaria filicula, A. articu- lata, Dynamena crisioides, D. nigra, D. disticha, Idiellana 1969)), Idiellana pristis (E) (from (Migotto, 1996)), Abietinaria filicula (F) and Diphasia nigra (G) (from (Cornelius, 1979)). ...
Similar publications
This annex to the U.S. Southeast chapter in “The State of Deep-Sea Coral and Sponge Ecosystems in the United States” provides a list of deep-sea coral taxa in the Phylum Cnidaria, Classes Anthozoa and Hydrozoa, known to occur in U.S. waters from Cape Hatteras to the Florida Keys. Deep-sea corals are defined as azooxanthellate, heterotrophic coral s...
This annex to the U.S. West Coast chapter in “The State of Deep-Sea Coral and Sponge Ecosystems of the United States” provides a list of deep-sea coral taxa in the Phylum Cnidaria, Classes Anthozoa and Hydrozoa, known to occur in U.S. waters off Washington, Oregon, and California. This list is an update of the peer-reviewed 2017 list by Whitmire et...
A new genus and species of sympagic trachymedusa, Glaciambulata neumayeri, are described based on material from Antarctica. Its generic features are compared to those of its relatives, Ptychogastria Allman, 1878 and Tesserogastria Beyer, 1959, and a review of the family Ptychogastriidae Mayer, 1910, based on literature data, is provided. From this,...
Hydrozoans are recognized as one of the main and most characteristic zoological groups of the Antarctic benthos, despite the fact that there are still large Antarctic areas where the hydrozoan fauna is completely unknown or poorly known (e.g., the Admunsen Sea and Mary Byrd Land, in West Antarctica, and Queen Maud Land and Enderby Land, in East Ant...
Citations
... The perisarc also forms hydrothecae, which serve as protective housing for the hydranths. On the shoot, the hydrothecae are arranged in two practically opposite longitudinal rows, and each shoot internode has a pair of hydrothecae ( Figure 3C) (Kosevich, 2008). The stolons are tubeshaped between the adjacent shoot bases and form a characteristic widening at the shoot base ( Figures 3A, B). ...
Background
As the sister group to all Bilateria, representatives of the phylum Cnidaria (sea anemones, corals, jellyfishes, and hydroids) possess a recognizable and well-developed nervous system and have attracted considerable attention over the years from neurobiologists and evo-devo researchers. Despite a long history of nervous system investigation in Cnidaria, most studies have been performed on unitary organisms. However, the majority of cnidarians are colonial (modular) organisms with unique and specific features of development and function. Nevertheless, data on the nervous system in colonial cnidarians are scarce. Within hydrozoans (Hydrozoa and Cnidaria), a structurally "simple" nervous system has been described for Hydra and zooids of several colonial species. A more complex organization of the nervous system, closely related to the animals' motile mode of life, has been shown for the medusa stage and a few siphonophores. Direct evidence of a colonial nervous system interconnecting zooids of a hydrozoan colony has been obtained only for two species, while it has been stated that in other studied species, the coenosarc lacks nerves.
Methods
In the present study, the presence of a nervous system in the coenosarc of three species of colonial hydroids - the athecate Clava multicornis , and thecate Dynamena pumila and Obelia longissima - was studied based on immunocytochemical and ultrastructural investigations.
Results
Confocal scanning laser microscopy revealed a loose system composed of delicate, mostly bipolar, neurons visualized using a combination of anti-tyrosinated and anti-acetylated a-tubulin antibodies, as well as anti-RF-amide antibodies. Only ganglion nerve cells were observed. The neurites were found in the growing stolon tips close to the tip apex. Ultrastructural data confirmed the presence of neurons in the coenosarc epidermis of all the studied species. In the coenosarc, the neurons and their processes were found to settle on the mesoglea, and the muscle processes were found to overlay the nerve cells. Some of the neurites were found to run within the mesoglea.
Discussion
Based on the findings, the possible role of the colonial nervous system in sessile hydroids is discussed.
... The morphological variability in hydrozoan populations is a common phenomenon that should not go unnoticed (Ralph 1956;Wyttenbach et al. 1973;Kosevich 2008;Cunha et al. 2015Cunha et al. , 2016Cunha et al. , 2020. The lack of knowledge on this issue has resulted in numerous misidentifications of species over history. ...
... Currently, the location of the gonads, the features in the branching patterns and number of radial canals, and the number of marginal tentacles are recognized as the most reliable taxonomic characters to identify the species (Bouillon et al. 2004. However, the studies focused on the morphological variability of C. radiatum are scarce and old or represent populations from Europe, so its taxonomy Introducción La variabilidad morfológica en poblaciones de hidrozoos es un fenómeno común que no debe pasar desapercibido (Ralph 1956;Wyttenbach et al. 1973;Kosevich 2008;Cunha et al. 2015Cunha et al. , 2016Cunha et al. , 2020. La falta de conocimiento sobre este tema ha resultado en numerosas identificaciones erróneas de las especies a través de la historia. ...
On the morphological variations in a population of Cladonema radiatum (Hydrozoa: Cladonematidae): New evidence from the southern Gulf of Mexico Sobre las variaciones morfológicas en una población de Cladonema radiatum (Hydrozoa: Cladonematidae): Nueva evidencia en el sur del golfo de México Abstract. The lack of knowledge on the morphological variability in hydrozoan populations has resulted in numerous misidentifications over history. Cladonema radiatum Dujardin, 1843 is characterized by presenting different morphologies in different localities of the world, which has caused many taxonomic confusions within the group. In this study, the morphological variability in a population of C. radiatum is analyzed. The material came from a coastal lagoon in the southern Gulf of Mexico. The samplings were carried out for 3 months in 2017. Salinity, dissolved oxygen, and temperature were recorded at each sampling site. Cladonema radiatum was more abundant and bigger when the lagoon showed the lowest levels of salinity. Six different morphologies were recognized. The presence of gelatinous papillae on the abaxial surface of marginal bulbs and an abaxial arrangement of nematocysts in the shortest branches of the tentacles are features recorded for the first time in the species. These considerations enrich the taxonomic description of C. radiatum and contribute to the knowledge on the taxonomy of Hydrozoa in Mexico. The taxonomy of Cladonema continues to be confusing, and the present work sets a basis for further integrative studies clarifying the morphological boundaries of the genus. However, only integrative works based on the morphology and molecular analyses of the species would be able to decode its cryptic nature.
... The coenosarc tube and the hydranth stem gradually shrink during this evolution, turning into a fragment of the coenosarc of a more complex shape, and the hydrotheca ceases to be goblet shaped, with one of its sides remaining inseparable from the internode [41]. All of these are signs of heterochrony-one of the main "engines" of the evolutionary process and the biological mechanism of species variability-the generation of diversity based on the same genotype [44]. ...
... turning into a fragment of the coenosarc of a more complex shape, and the hydrotheca ceases to be goblet shaped, with one of its sides remaining inseparable from the internode [41]. All of these are signs of heterochrony-one of the main "engines" of the evolutionary process and the biological mechanism of species variability-the generation of diversity based on the same genotype [44]. The evolutionary transformation of the sympodial structure into a multi-row structure (monopodial with an apical growth zone) highlights a significant complication of shoot morphogenesis. ...
The intraorganismal variability of the shoot modules of three species of hydroids was studied to determine the degree of similarity between them. The strict form of the internodes (modules) of the shoots is repeated many times, which is useful for the study of intraorganismal variability. Against the general background of the high stability of the shape of the internodes, we found significant deviations from the norm. Some resemble the structure of the internodes in other genera of the same family. Their morphogenesis is different from that characteristic of the studied species. Most of the anomalies were characterized by stable forms and low frequencies of occurrence (<0.2%). After the appearance of abnormal internodes, normal ones were found to usually re-form. Thus, it is doubtful that the anomalies were caused by mutations. There is also no reason to believe that the anomalies were caused by environmental factors, since they always formed singly along with normal shoot modules of the same modular organism. In Dynamena pumila, Diphasia fallax, and Abietinaria abietina, the composition of their morphovariations was found to be similar, and their frequencies were comparable, which confirms the assumption that several latent phenotypes can be formed indeterminately based on one genotype. The study was conducted on samples of >20,000 internodes of each of the three species.
... According to Hill & Wells (1967), the modern solitarily living representatives are nude, while chitinous ("horny") exoskeletons exclusively characterize the colonial forms. The surface of the chitinous thecae of modern and fossil (e.g., Ordovician : Miller & Williams 1991) taxa are smooth or irregularly wrinkled and do not show any regular ornaments, except of some tiny gonothecae with collar-like concentric ring-structures (e.g., Cantero et al. 2004;Kosevich 2008;Àngel 2017). There are no similarities with Liapora n.g. ...
Two cone-shaped Early Jurassic (Late Pliensbachian) chitino-phosphatic fossils are described from a clay pit near Buttenheim (northern Bavaria, Germany). The chemical composition and microstructure of their black wall corresponds partially with that of Palaeozoic presumed scyphopolyps like conulariids and the genus Byronia Matthew, 1899 and show similarities with the circular periderm tube of the modern Stephanoscyphus . A possible relationship to other chitino-phosphatic fossils, like inarticulate brachiopods or anaptychi of ammonites, is excluded. The presence of growth-lines on the tube surface further excludes an interpretation as remains of ecdysozoa (e. g., arthropods). Accordingly, the new findings are assigned to scyphozoan polyps representing a new family Liaporidae, with Liapora neubigi n. g. et n. sp. The new Early Jurassic scyphozoan genus Liopora shortens the gap in the fossil record between the so far youngest known conulariids from the Late Triassic and modern thecate scyphopolyps (Coronatae).
... Presumably a signal to develop a lateral bud was connected with bending of the preceding zooid (or permanently immature stolonal main axis) in a way similar to that observed in extant ramose hydroids (Kossevitch 2002;Kossevitch et al. 2001). The arrangement of zooids only on the upper side of lateral branches seems to be a plesiomorphic trait in the erect hydroid colonies (Kosevich 2008). However, a vertical orientation of individuals bearing perioral tentacular apparatus is a prerequisite of Fig. 3 proper filtratory action. ...
A fossil of a colonial organism with pyritized soft tissues of elongated fusiform zooids, found in the middle part of the early Floian Fenxiang Formation in Hubei Province of China, probably represents the oldest reliable record of a hydroid cnidarian. The preservation of the fossil is sufficiently different from that of associated carbonized skeletons of graptolites to exclude affinities with this group. The fossil is unlikely to be a bryozoan because of the mode of budding from proximal, not distal, parts of parent zooids, which is typical rather of hydroids. Although no thecae are preserved, the fossil, named Sinobryon elongatum gen. et sp. nov., is suggested to be a thecate hydroid, possibly related to the Haleciidae. The apparent presence of an advanced member of the thecaphoran Macrocolonia clade in strata 470 Ma old means that much of the hydroid (and cnidarian) diversification preceded the Middle Ordovician.
... The diversity of hydranth cells is formed on the terminal stages of the morphogenetic cycle of the shoot internode after the hydranth bud reaches its final size. As it was shown in investigations, the diversity of cellular types in the hydranth is formed both due to final differentiation of the coenosarc and growing tip cells, which are the part of the hydranth bud, and also due to migration of certain types of cells from coenoss arc (Kosevich, Fedosov, 2008). Thus, terminal differr entiation of cells in colonial hydroids takes place in the location of their final functioning, where they occur as a result of processes of growth and migration, but commitment is realized earlier, most probably, after division. ...
... This feature (morphoo genetic constraint) determined the possibility of hydrothecae polymerization formed on the same internode with an increase in the sizes of the growing tip. By the example of several species, it may be retraced how the laying of hydrothecae verticils with 2, 3, and more hydrothecae on one level occurs with a relative increase in the diameter of the growing tip (Pyataeva, Kosevich, 2008) (Fig. 7). At the same time, hydrothecae alternate in the following verticils: in upstream verticil hydrothecae are located in spaces between hydrothecae in downstream verticils. ...
... In accorr dance with these hypotheses (models), the next hydrothecae are set at a certain minimal distance from the existing hydrothecae. Variants of the spiral organii sation of hydrothecae, which are transitional between the alternate position in the proximal part of the shoot with a relatively small diameter of the axis and the verr ticillate position in the distal part of the shoot with a rell atively large diameter of the axis, can be evidence of the plausibility of a given mechanism of hydrothecae posii tion regulation (Pyataeva, Kosevich, 2008) (Fig. 7d). Thus, in shoot organization of thecate hydroids, the following tendencies of increasing of evolutionary complexity are observed: —increase in sizes of the tip relative to the sizes of maternal structures (on which the emergence of the growing tip occurs) and sizes of hydrothecae formed in a given morphogenetic cycle of the growing tip; —integration of primary modules into complexes of secondary modules; —stabilization of positions and regularity of branching; —polymerization of the number of hydranths in the internode (Fig. 8). ...
The morphogenetic approach is applied to analyze the diversity of spatial organization of shoots in thecate hydroids (Cnidaria, Hydroidomedusa, Leptomedusae). The main tendencies and constraints of increased evolutionary complexity in thecate hydroids colonies are uncovered.
... The significance of new data from morphological and behavioural studies, especially those using living material, should not be underestimated. In Leptomedusae the discovery and description of rare morphotypes leads to an understanding and reconstruction of the morphogenetic evolutionary scenario (Kosevich, 2008). The cytomorphological study of Polypodium, a unique cnidarian parasite of fish eggs, suggests that this species is not aberrant as previously thought but is a relic of a major hydrozoan group (Raikova, 2008). ...
... The cytomorphological study of Polypodium, a unique cnidarian parasite of fish eggs, suggests that this species is not aberrant as previously thought but is a relic of a major hydrozoan group (Raikova, 2008). Study of the organization of soft tissue in hydroids has shown that their structural complexity, comprising something more than two epithelial layers, does not contravene limits to the ground plan of this group of Hydrozoa (Pyataeva & Kosevich, 2008). A revision of the symbiotic relationships of hydrozoans with other phyla demonstrates that together with ecological processes, symbioses are a source of evolutionary diversity (Puce et al., 2008b). ...
Modular organization is a suitable model for evolutionary developmental biology. Homeotic transformations of modular organisms played an important role in their morphological and taxonomic evolution. The study of mechanisms will contribute to further development of integrity issues in biology.
The high diversity of spatial organization of shoots in colonies of thecate hydroids (Cnidaria, Hydroidomedusa, Leptomedusae) is determined by their modular organization, which is characterized by the cyclic morphogenesis in the colony. It is attempted to show that evolutionary and ontogenetic changes in the spatial organization of hydroids of this group are based on the allometric growth of modules of colony shoots. An increase in size of a developing module provides prerequisites for earlier initiation of the growing tips of succeeding moduls (heterochrony). In some cases, heterochronies determined transition from cyclic to acyclic morphogenesis. The earlier emergence of new growing tips allowed integration of several primary modules into secondary modules, resulting among other things in changes in relative positions of primary modules (heterotopy). In complex colonies, these changes are traced in the ontogeny of a single colony.
