Predatory feeding of the hydromedusae Obelia geniculata and Phialla quadrata

1985 ◽  
Vol 87 (1) ◽  
pp. 47-54 ◽  
Author(s):  
R. S. Fulton ◽  
R. G. Wear
Keyword(s):  
Obelia Geniculata

scholarly journals The permeability to calcium of pigeon erythrocyte ‘ghosts’ studied by using the calcium-activated luminescent protein, obelin

1975 ◽  
Vol 152 (2) ◽  
pp. 255-265 ◽  
Author(s):  
Anthony K. Campbell ◽  
Robert L. Dormer
Keyword(s):  
Pyruvate Kinase ◽  
Time Course ◽  
Small Concentration ◽  
Ionophore A23187 ◽  
Erythrocyte Ghosts ◽  
Experimental Conditions ◽  
Bivalent Cation ◽  
Low Concentration ◽  
Triton X ◽  
Obelia Geniculata

1. Obelin, the Ca2+-activated luminescent protein from the hydroid Obelia geniculata, was sealed inside pigeon erythrocyte ‘ghosts’ in order to investigate effects on their permeability of different methods of preparation and of the bivalent cation ionophore A23187. 2. Changes in free Ca2+ within the ‘ghosts’ were studied by following the rate of luminescence of obelin. The possibility that the obelin might have been released from the ‘ghosts’ during an experiment was investigated by studying the release of inulin and pyruvate kinase from the ‘ghosts’. Less than 10% of the inulin or pyruvate kinase sealed within the ‘ghosts’ was released under any of the experimental conditions. 3. Triton X-100 (0.1–10%, v/v) made the ‘ghosts’ highly permeable to Ca2+. In the presence of 1mm-Ca2+ and Triton, 95–100% of the obelin was utilized within 10–20s. 4. A time-course of resealing ‘ghosts’ at 37°C showed that over a period of 90min, the ‘ghosts’ became gradually less permeable to Ca2+. ‘Ghosts’ which remained at 0°C retained only a small concentration of obelin and ATP, and were highly permeable to Ca2+. 5. Erythrocyte ‘ghosts’ resealed for 30min at 20°C rather than 37°C were more permeable to Ca2+, as shown by the fact that 92% of the obelin in the ‘ghosts’ was utilized during the first 60s after the addition of 1mm-Ca2+, as opposed to 44% for ‘ghosts’ resealed at 37°C. 6. Haemolysis at pH6.0 rather than 7.0 resulted in ‘ghosts’ which were highly permeable to Ca2+ after resealing for 60min at 37°C. Of the obelin in the ‘ghosts’, produced by haemolysis at pH6.0, 90% was utilized in the first 60s after the addition of 1mm-Ca2+ compared with 23% for ‘ghosts’ produced at pH7.0. 7. The bivalent cation ionophore A23187 increased the permeability of the ‘ghosts’ to Ca2+. Maximum effects of the ionophore (16μg/ml) were obtained by preincubating the ‘ghosts’ with the ionophore A23187 (16μg/ml) in the presence of a low concentration of Mg2+ and in the absence of Ca2+.

Behavioural Physiology of the Colonial Hydroid Obelia

1971 ◽  
Vol 54 (3) ◽  
pp. 689-706
Author(s):  
JAMES G. MORIN ◽  
IAN M. COOKE
Keyword(s):  
Mouth Opening ◽  
The Other ◽  
Behavioural Responses ◽  
Electrical Potentials ◽  
External Stimuli ◽  
Colonial Hydroid ◽  
Obelia Geniculata

1. Spontaneous electrical potentials from Obelia geniculata hydranths were recorded using fine-tipped suction electrodes. 2.The primary behavioural responses of the hydranths were observed and correlated with specific electrical potentials: the contraction potential (KP) associated with hydranth withdrawal, the mouth-opening potential (MOP) associated with mouth opening, and the tentacle contraction potential (TKP) associated with oral flexion of individual tentacles. 3. KPs occurred in rhythmic bursts while the TKP and MOP responses were infrequent and non-rhythmic. 4. Two other species, O. longissima and Gonothyraea loveni, were shown to produce the same three types of potentials with corresponding behavioural responses. 5. The MOP activity may occasionally drive the KP responses within a hydranth, but the coupling is very loose. None of the other possible interactions within a hydranth was observed. 6. No interaction of any of the potentials between adjacent hydranths was found in the absence of external stimuli. 7. It seems likely that the KPs in Obelia are homologous with the contraction potential (CP) in Hydra and the hydranth potential (HP)) in Tubularia. MOP and TKP activity do not show apparent homologies with potentials of the other hydroids Hydra, Tubularia and Cordylophora.

Memoirs: The Early Prophases of the First Oocyte Division as Seen in Life, in Obelia Geniculata

1929 ◽  
Vol s2-73 (290) ◽  
pp. 225-242
Author(s):  
G. H. FAULKNER
Keyword(s):  
Early Growth ◽  
Growth Phases ◽  
Homologous Chromosomes ◽  
The Individual ◽  
Obelia Geniculata

1. The nueleolus of the resting oocyte represents a condensed chromatic spireme, hence it is identical with the total chromosomal contents of the nucleus. 2. During the early growth phases of the oocytes, the nueleolus elongates and fragments. Each fragment has been identified as a pair of homologous chromosomes indistinguishably united; later each of these bivalent elements divides in half, and the individual chromosomes are thus separated. The two components of the largest bivalent element are unequal in size, and probably represent an XY pair. 3. The chromosomes can be counted either at the bivalent or at the univalent phase, the numbers obtained being seventeen and thirty-four respectively. 4. At a still later stage the chromosomes fragment into numerous small globules, which become evenly distributed over the nucleus. 5. The whole of the account is based on observations made on living oocytes.

scholarly journals Extraction, partial purification and properties of obelin, the calcium-activated luminescent protein from the hydroid Obelia geniculata

1974 ◽  
Vol 143 (2) ◽  
pp. 411-418 ◽  
Author(s):  
Anthony K. Campbell
Keyword(s):  
United Kingdom ◽  
Peak Height ◽  
Partial Purification ◽  
Large Excess ◽  
Lower Affinity ◽  
The United Kingdom ◽  
Final Volume ◽  
Purification And Properties ◽  
The Stability ◽  
Obelia Geniculata

1. The Ca2+-activated luminescent protein obelin was extracted from the hydroid Obelia geniculata. 2. After the addition of a large excess of calcium (greater than 5mm) a peak in the rate of luminescence occurred within 100ms, followed by an exponential decay (k=2.8s−1). The obelin activity (light emitted) was measured by the peak height or by the total number of counts recorded on a scalar in the first 10s after addition of Ca2+. 3. After an overnight extraction in 40mm-EDTA–200mm-Tris–HCl, pH7.0, 7.2×1011 counts were obtained from 186g of wet hydroids. 4. The stability of the crude extracts was dependent on pH, being optimal at pH7.0. 5. Obelin could be purified threefold with a yield of 69% by selecting the protein precipitated between 60%- and 100%-saturated (NH4)2SO4. The precipitate could be stored for at least 6 months as a suspension in 40mm-EDTA+saturated (NH4)2SO4, pH7.0, frozen at −70°C with a recovery of 95–100%. 6. Luminescence was also stimulated by Sr2+. However, obelin appeared to have a lower affinity for Sr2+ than for Ca2+. Mg2+ inhibited Ca2+-activated luminescence. 7. Obelin could be used to assay as little as 50pmol of Ca2+ in a final volume of 1ml. 8. At pH7.0 in Ca2+–EGTA [ethanedioxybis(ethylamine)tetra-acetate] buffers the rate of obelin luminescence was proportional to the square of the free Ca2+ concentration in the presence and absence of 1 and 10mm-Mg2+. Over the range 0.1–10μm-Ca2+ less than 0.03% of the obelin was consumed/s. 9. In order to use obelin to study free ionized Ca2+ concentrations similar to those found inside cells in the presence of 10mm-Mg2+ a minimum of 108 counts were required. A total of 1012 counts can be readily extracted from about 200g of wet hydroids. Thus a sufficient quantity of an aequorin-like calcium-activated luminescent protein should now be available to workers in the United Kingdom in order to carry out physiological experiments.

scholarly journals Comparison of proteomic profiles of the phaeophyte Saccharina japonica thalli proximal to and beneath the front of epiphytic hydrozoan colonies against healthy tissue

2019 ◽  
Vol 62 (4) ◽  
pp. 369-378
Author(s):  
Paulos Getachew ◽  
Bo-Hye Nam ◽  
Yong-Ki Hong
Keyword(s):  
Saccharina Japonica ◽  
Healthy Tissue ◽  
Signaling Proteins ◽  
Hect Domain ◽  
Obelia Geniculata

Abstract The stoloniferous hydrozoan Obelia geniculata commonly colonizes macroalgae such as Saccharina japonica. Each Obelia colony consists of thread-like hydrorhizae attached to the seaweed thallus. The early signaling proteins of epiphytic contamination can be identified using proteomics. To isolate these early signals, parts of the thallus proximal to the hydrozoans were separated from beneath the colony front and from healthy tissue. From the proteomic profiles of S. japonica, we detected 110 protein spots from tissue proximal to hydrozoan colonies (56 increased, 53 decreased, and 1 unchanged in expression relative to healthy tissue) and 133 spots from tissue at the colony front (67 increased, 60 decreased, and 6 unchanged in expression). Of the proteins with increased and decreased expression, SIPA1L1 and actin increased strongly only in the proximal tissues, while NEK2 kinase decreased. CIPK20 and SIPA1L2 increased markedly in both the colony-front and proximal tissues, while CaMK2N2 and GK25369 decreased in both tissues. ATPase β, ADA, kinesin, and HECT domain proteins increased only in the colony-front tissues. Among them, SIPA1L2 increased strongly in both the thallus tissues proximal to the hydrozoans and those beneath the colony front, but was not expressed in response to bryozoan infection.

Behavioural Physiology of the Colonial Hydroid Obelia

1971 ◽  
Vol 54 (3) ◽  
pp. 707-721
Author(s):  
JAMES G. MORIN ◽  
IAN M. COOKE
Keyword(s):  
Rate Constant ◽  
Mechanical Stimulation ◽  
Mouth Opening ◽  
Physiological Mechanisms ◽  
Variable Intensity ◽  
Frequency Coupling ◽  
Constant Shape ◽  
Degree Of Coupling ◽  
Colonial Hydroid ◽  
Obelia Geniculata

1. Electrical, mechanical or chemical (KC1) stimuli produce similar luminescent flashing in Obelia geniculata. Hydranth withdrawal also occurs upon electrical or mechanical stimulation. 2. Luminescent flashes in response to individual stimuli occur in bursts. The first few flashes of the burst facilitate in intensity and then decline. Successive flashes within each burst show a constant shape and duration but a variable intensity. 3. The decay phase of the luminescent flash has a rate constant of 50 s-1 at 20±1 °C and 29 s-1 at 127plusmn; 1 °C. From these figures an energy of activation of about 12 kcal can be calculated. 4. Upon stimulation, an excitation system, the luminescent potential (LP) system, initiates the luminescent effector flashing. The LPs are monophasic, positive, and slow (duration about 120 ms) and are distinguishable from contraction potentials (KPs) mouth-opening potentials (MOPs) and tentacle contraction potentials (TKPs). LPs are all-or-none, non-decremental, through-conducting (at least over short distances) and show non-polar spread. 5. The LP systems can drive the KPs at the LP frequency. Coupling varies from none to very tight, and the degree of coupling is determined at each hydranth. 6. Several other campanulariids and probably most, if not all, luminescent hydroids possess similar physiological mechanisms for controlling stimulus-initiated luminescent responses.

Mitochondrial evolution and phylogeography in the hydrozoan Obelia geniculata (Cnidaria)

2004 ◽  
Vol 146 (2) ◽  
pp. 213-222 ◽  
Author(s):  
A. F. Govindarajan ◽  
K. M. Halanych ◽  
C. W. Cunningham
Keyword(s):  
Mitochondrial Evolution ◽  
Obelia Geniculata

scholarly journals When morphometry meets taxonomy: morphological variation and species boundaries in Proboscoida (Cnidaria: Hydrozoa)

2020 ◽  
Vol 190 (2) ◽  
pp. 417-447
Author(s):  
Amanda F Cunha ◽  
Allen G Collins ◽  
Antonio C Marques
Keyword(s):  
Intraspecific Variation ◽  
Morphological Variation ◽  
Species Delimitation ◽  
Species Boundaries ◽  
Nominal Species ◽  
Genetic Sampling ◽  
Taxonomic Implications ◽  
Obelia Geniculata

Abstract Species delimitation in marine taxa is often problematic given large intraspecific variation. Based on extensive, recently published genetic sampling from specimens of the hydrozoan families Campanulariidae, Clytiidae and Obeliidae, we evaluate morphological variation in this group, correlating morphometric and phylogenetic patterns for species delimitation. Several species of Campanulariidae are confidently delimited based on differences in size (e.g. Bonneviella species, Tulpa tulipifera and Rhizocaulus verticillatus), while others are re-identified and corroborated based on differences in perisarc thickness (e.g. Silicularia rosea, Orthopyxis and Campanularia species). In Clytiidae, the length and diameter of hydrothecae, height of hydrothecal cusps and perisarc thickness delimit the species Clytia linearis, C. elsaeoswaldae and C. noliformis from others. However, few characters reliably differentiate the clades associated with the nominal species C. gracilis and C. hemisphaerica. In Obeliidae, Obelia geniculata is distinctive in its higher perisarc thickness, and corroborated as a widely distributed species. Obelia longissima and clades refered to O. dichotoma are subtly distinguished, showing a few differences in size and branching of colonies. The taxonomic implications of these results are discussed. With a few exceptions, species can be delimited based on morphometric patterns, once morphological variation is compared.

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