Thyroxine in Early Strobilation in Aurelia aurita

Radiochromatographic studies of ¹³¹I-treated Aurelia polypsrevealed synthesis of three compounds tentatively identifiedas monoiodotyrosine (MIT), diiodotyrosine (DIT), and thyroxine(T₄). One compound, MIT, is found within 8 hr after ¹³¹I administration,before the detection of DIT or T₄ which appear within 24 hr.T₄ is not usually detected after 48 hr although MIT and DITwere found up to the segmentation period. None of the compoundswere detected in ephyrae treated with ¹³¹I for 24 hr. Administration of low dosages of the goitrogens, thiourea,,propylthiouracil, and potassium thiocyanate, in conjunctionwith iodide, prevented strobilation induction. Radiochromatographyof jellyfish given the goitrogens and ¹³¹I revealed a reduceduptake of iodide and an impairment of the synthesis of the iodinatedcompounds. Jellyfish use thyroxine directly for strobilatioa inductionas demonstrated by ¹³¹I - labeled T₄ administration. The T₄was detected in the polyps up to the 48-hr period of strobilationduring which time some of the T₄ was excreted into the medium,as was some ¹³¹I. The fact that T₄, synthesis has thus far been found only instrobilating forms of Aurelia suggests that T₄ is involved primarilywith the differentiation of new structures which occurs duringstrobilation.     

D-Methionine and gold chloride alleviate adverse effects of glutamate on motility of ephyrae of Aurelia aurita (Linnaeus, 1758) (Scyphozoa: Semaeostomeae)

Glutamate (MSG) causes low pulse numbers and swimming cessation in Aurelia jellyfish ephyrae. Ephyrae given MSG for 1h and subsequently maintained in artificial sea water (ASW) were observed at 1, 3, 24, and 48 h intervals. Abnormality of motility was found at all post-treatment periods but some ephyrae resumed swimming and normal pulsing within 48 h. Swimming and pulsing were impaired in a significant number of ephyrae within 15 min of MSG treatment. The mechanism of MSG action on ephyrae motility is unknown, but glutamate damage to neurons and hair cells of higher animals is partly attributed to the formation of reactive oxygen species (ROS). Laser confocal fluorescent microscopy of ephyrae following MSG treatment indicated an increase of calcium and free radicals in the ephyrae as early as 5 min following MSG exposure. To determine whether antioxidants could alleviate MSG effects, we exposed ephyrae to gold chloride before, during, and after treatment with MSG. Ephyrae given gold chloride pre-treatment for 1h and then transferred into gold chloride plus MSG for 1h showed statistically significant recovery from MSG impairment of pulsing at the 3, 24, and 48 h post-glutamate time periods and higher numbers of swimmers at 3 h and 24 h. Ephyrae groups given gold plus MSG but without gold pretreatment showed recovery of swimming at 24 h and pulsing at 48 h. d-methionine given simultaneously with MSG significantly improved the pulse numbers and swimming of ephyrae at the 3, 24, and 48h post-glutamate time periods compared to those receiving MSG alone. Both d-methionine and gold chloride accelerated the time of recovery from glutamate-induced motility impairment, possibly through their antioxidant activities.     

Biomass and size structure of the scyphomedusa Aurelia aurita in the northwestern Black Sea during spring and summer

The abundance, biomass and size structure of the scyphomedusa,Aurelia aurita, was measured during two research cruises tothe northwestern Black Sea (July–August 1995 and April–May1997). Average biomass of Aurelia was relatively constant (132–179g wwt m^–2) throughout the investigation period and similarto previous years. Abundance and biomass at individual stationsappeared to be unrelated to temperature and salinity when thelatter exceeded ~13. Biomass was low at coastal stations inthe plume of the Danube where depth was <20 m and salinitydropped to <11. The spring cruise (April–May) coincidedwith, or just followed the peak of strobilation. The summercruise (July–August) took place near the beginning ofplanulae larvae release. The population size structure was dominatedby small individuals in spring, while large medusae prevailedmainly in late summer. Aurelia was, on average, larger at deepwater stations during summer, suggesting that per capita foodsupply was higher further offshore. The individual body massincreased from spring through summer. Accordingly, the volume(wet wt) to length (bell diameter) relation changed significantly.If all medusae measured throughout the seasons were pooled,volume (V, in cm³) was related to length (L, in cm) accordingto V = 0.08 L^2.71, which is similar to measurements conductedin other coastal areas. In contrast to the common conjecture,we did not find inverse relations between biomasses of Aureliaand the combjelly Mnemiopsis leidyi. Preliminary feeding experimentsindicate that Aurelia may feed upon small Mnemiopsis. The significanceof indirect trophic relations and direct feeding interactionsamong the gelatinous zooplankton in the Black Sea has importantconsequences for the energy flow along the food web and, therefore,needs further study.     

Release and growth of Cyanea capillata (L.) ephyrae in the Gullmar Fjord,western Sweden

In an investigation carried out in the Gullmar Fjord, western Sweden, the autecology of the scyphozoans Aurelia aurita (L.) and Cyanea capillata (L.), has been studied. This paper focuses on results concerning C. capillata, but comparisons with Aurelia aurita are made and discussed. The main period of strobilation was in winter and early spring. The extent of ephyrae release was only one tenth of that of A. aurita. The period of rapid growth of ephyrae and medusae during the spring was delayed one month compared to the pattern for Aurelia. The Cyanea scyphistomae are exposed to predation by the nudibranch Coryphella verrucosa and only very limited settling of Cyanea planulae occurred in the area. Immigration from the North Sea is probably a major factor regulating the appearance of Cyanea capillata along the western coast of Sweden.     

The effects of X irradiation on the metamorphosis and budding of Aurelia aurita

With the aid of the Aurelia metamorphosis test system, the acute and subtle developmental and behavioral effects of X irradiation in the presence and absence of thyroxine on the Norfolk Aurelia aurita were described. Radiation doses were 0 (control), 50, 100, 150, 200, and 400 Gy. Morphology of the ephyrae, and statolith and rhopalia numbers were recorded using the light microscope. Developmental abnormalities of the polyps and ephyrae were recorded with the scanning electron microscope and light microscope. Major findings from this investigation were the absence of rhopalia and statoliths in ephyrae at 150 and 200 Gy, a reduction in pulses per minute in the ephyrae at 100, 150, and 200 Gy, a reduction in ephyrae released at 150, 200, and 400 Gy, and the development of polyp monsters. There was a significantly higher frequency of polyp monsters in the group exposed to thyroxine prior to radiation than in the thyroxine-free group prior to radiation.     

Population dynamics of the scyphomedusa Aurelia aurita in Southampton Water

The population dynamics of the scyphomedusa Aurelia aurita inSouthampton Water is characterized. Strobilation, indicatedby the presence of 1 mm ephyrae, occurred from the end of Januaryto the middle of March. Maximum abundances of up to 8.71 m^–3occurred soon after ephyrae release, after which numbers declinedsteadily until the end of June, when the population was absentfrom Southampton Water. The residence time of 3–4 monthsis somewhat less than that reported in many other areas, includingKiel Bight and Gullmarfjord. The carbon biomass of A.auritaaccounted for 92–97% of the predominant gelatinous biomass(A.aurita, Pleurobrachia pileus and Phialidium hemisphericum)in the upper estuary, and this reached a maximum of 30.2 mgC m^–3 in May 1990 and 27.6 mg C m^–3 in June 1991.Coincident with increased water temperature and mesozooplanktonabundance during May, growth rates increased from 0.02–0.30mm day^–1 to a peak of 4.8 mm day^–1, with a maximumbell diameter of 120–140 mm reached in late May/earlyJune. Size to maturity was variable, although the smallest medusaobserved to be ‘ripe’, i.e. containing dividingeggs and planula larvae in the brood sacs on the oral arms,were 64–71 mm. Aurelia aurita is believed to be endemicto Southampton Water, but because of the double high water inthe area, short flushing rates of between 4.5 and 20 days maybe responsible for such short residence times of Aurelia medusae.The effects of strong NE winds were considered as factors governingthe distribution of medusae in years of atypical temporal abundance.     

Acid-Base Regulation and Temperature in Selected Invertebrates as a Function of Temperature

The pH of the hemolymph of selected invertebrates decreasesas their body temperature increases. The magnitude of this change(pH/°C) is very similar to the change of the pH of waterwith temperature (pN/°C) and suggests that these invertebrates,like poikilothermous vertebrates, regulate the pH of their extracellularfluid so that its degree of alkalinity relative to the pH ofwater remains constant. The degree of alkalinity (pH_blood-pN)varies between species, but seems to be fixed for any givenspecies. In Limulus pH-pN was essentially the same for in vivosamples, measured after the whole animal had been acclimatedto different temperatures, as it was for in vitro samples inwhich the hemolymph was cooled or warmed anaerobically, suggestingthat the CO₂ content of the extracellular fluid is constantas the temperature changes. The P_CO2 of the hemolymph is invariablylower in animals breathing water than in those breathing air.In the invertebrates, as in the vertebrates, manipulation ofP_CO2 and HCO₃- is probably the major mechanism in the regulationof the relative alkalinity of the extracellular fluid.     

Coelenterate Neuropeptides: Structure, Action and Biosynthesis

Evolutionary "old" nervous systems such as those of coelenteratesare peptidergic: Using various radioimmunoassays we have nowisolated 13 novel neuropeptides from sea anemones and severalothers from hydrozoan polyps and medusae. These peptides areall structurally related and contain the C-terminal sequenceArg-X-NH₂ or Lys-X-NH₂, where X is Ala, Asn, Ile, Phe, Pro orTrp. Three neuropeptides have a novel N-terminal L-3-phenyllactylresidue, which protects against degradation by nonspecific aminopeptidases.The neuropeptides from sea anemones are produced by differentsets of neurones and have excitatory or inhibitory actions onisolated muscle preparations, suggesting that they are neurotransmittersor neuromodulators. We have also cloned the precursor proteinfor the sea-anemone neuropeptide Antho-RFamide (<Glu-Gly-Arg-Phe-NH₂).In Calliactis parasitica this precursor harbours 19 copies ofimmature Antho-RFamide (Gln-Gly-Arg-Phe-Gly) together with 7other, putative neuropeptide sequences. The precursor of Anthopleuraelegantissima contains 14 copies of Antho-RFamide and 19 other,putative neuropeptides. This shows that the biosynthetic machineryfor neuropeptides in coelenterates, the lowest animal grouphaving a nervous system, is already very efficient and similarto that of higher invertebrates, such as molluscs and insects,and vertebrates.     

Immune recognition of fungal beta-glucans

The recognition of conserved microbial structures is a key aspect of metazoan immunity, and beta-glucans are emerging as a major target for the recognition of fungal pathogens. A number of receptors for these carbohydrates have been identified, which upon recognition, trigger a variety of immune responses. In contrast to many other systems, there is little apparent conservation in these mechanisms between vertebrates and invertebrates. In this review, we will highlight all the known receptors for beta-glucans and will discuss the various immune responses they can initiate, with reference to fungal infection, in both vertebrates and invertebrates.     

Immunological Maturation in the Tunicate Ciona intestinalis

The least explored areas in the phylogenetic development ofimmunity are the primitive chordate subphyla. The limited studieson tunicate internal defense mechanisms are presented and discussed.Primary and secondary immune responses and immunological maturationto vertebrate erythrocytes in Ciona intestinalis suggest thatits internal defense mechanisms may be closely allied to boththe invertebrates and vertebrates.     

Amphioxus and the Utility of Molecular Genetic Data for Hypothesizing Body Part Homologies between Distantly Related Animals

Expression domains of developmental genes can indicate bodypart homologies between distantly related animals and give insightsinto interesting evolutionary questions. Two of the chief criteriafor recognizing homologies are relative position with respectto surrounding body parts and special quality (for instance,a vertebrate testis, regardless of its location, is recognizableby its seminiferous cysts or tubules). When overall body plansof two animals are relatively similar, as for amphioxus versusvertebrates, body part homologies can be supported by developmentalgene expression domains, which have properties of special qualityand relative position. With expression patterns of AmphiNk2-land AmphiPax2/5/8, we reexamine the proposed homology betweenthe amphioxus endostyle and the vertebrate thyroid gland, anda previously good homology is made better. When body plans ofanimals are disparate, body part homologies supported by moleculargenetic data are less convincing, because the criterion of relativeposition of gene expression domains becomes uncertain. Thus,when expression of amphioxus AmphiBMP2/4 is used to comparethe dorsoventral axis between amphioxus and other animals, acomparison between amphioxus and vertebrates is more convincingthan comparison between amphioxus and other invertebrates withdisparate body plans. In spite of this difficulty, the use ofdevelopmental genetic evidence comparing animals with disparatebody plans is currently putting the big picture of evolutioninto new perspective. For example, some molecular geneticistsare now suggesting that the last common ancestor of all bilateriananimals might have been more annelid-like than flatworm-like.     

Genie Control of Axolotl Metamorphosis

SYNOPSIS. Neoteny in the Mexican axolotl, Ambystoma mexicanum,is caused by homozygosity for a single recessive gene. The dominantallele causing physical metamorphosis is found in the closelyrelated species, Ambystoma tigrinum, with which it can hybridize.Despite the failure of axolotls to undergo physical metamorphosis,they do undergo a cryptic metamorphosis. A larval-to-adult hemoglobinform change, serum protein changes and other physiological eventsusually associated with amphibian metamorphosis occur duringearly larval life at ages comparable to the age at which Ambystomatigrinum undergoes both the cryptic and external metamorphicevents. Axolotl cryptic metamorphosis can be induced precociouslyby immersion of the larvae in low concentrations of thyroxine;physical metamorphosis can be induced with higher thyroxineconcentrations. The site of action of the gene responsible foraxolotl neoteny has not been identified. A change in the sensitivityof external metamorphic processes to thyroxine, or reduced hormonalstimulation by the pituitary or hypothalamus may be responsible.A comparison of these functions in Ambystoma tigrinum and theaxolotl may identify the lesion.     

Isolation, characterization and inactivation of the mouse Mgat3 gene: the bisecting N-acetylglucosamine in asparagine-linked oligosaccharides appears dispensable for viability and reproduction

The biosynthesis of complex asparagine (N)-linked oligosaccharidesin vertebrates proceeds with the linkage of N-acetylglucosamine(GlcNAc) to the core mannose residues. UDP-N-acetylglucosamine:ß-D-mannosideß1–4 N-acetylglucosaminyltransferase III (GlcNAc-TIII,EC2.4.1.144) catalyzes the addition of GlcNAc to the mannosethat is itself ß1–4 linked to underlying N-acetylglucosamine.GlcNAc-TIII thereby produces what is known as a ‘bisecting’GlcNAc linkage which is found on various hybrid and complexN-glycans. GlcNAc-TIII can also play a regulatory role in N-glycanbiosynthesis as addition of the bisecting GlcNAc eliminatesthe potential for     

The function and regulation of vasa-like genes in germ-cell development

The vasa gene, essential for germ-cell development, was originally identified in Drosophila, and has since been found in other invertebrates and vertebrates. Analysis of these vasa homologs has revealed a highly conserved role for Vasa protein among different organisms, as well as some important differences in its regulation.     

Constitutive activation of β-catenin in ameloblasts leads to incisor enamel hypomineralization

Enamel is the hardest tissue with the highest degree of mineralization protecting the dental pulp from injury in vertebrates. The ameloblasts differentiated from ectoderm-derived epithelial cells are a single cell layer and are important for the enamel formation and mineralization. Wnt/β-catenin signaling has been proven to exert an important role in the mineralization of bone, dentin and cementum. Little was known about the regulatory mechanism of Wnt/β-catenin signaling pathway in ameloblasts during amelogenesis, especially in the mineralization of enamel. To investigate the role of β-catenin in ameloblasts, we established Amelx-Cre; β-catenin^?ex3fl/fl (CA-β-catenin) mice, which could constitutive activate β-catenin in ameloblasts. It showed the delayed mineralization and eventual hypomineralization in the incisor enamel of CA-β-catenin mice. Meanwhile, the amelogenesis-related proteinases Mmp20 and Klk4 were decreased in the incisors of CA-β-catenin mice. These data indicated that β-catenin plays an essential role in differentiation and function of ameloblasts during amelogenesis.     

CRAC channels in dental enamel cells

Enamel mineralization relies on Ca²⁺ availability provided by Ca²⁺ release activated Ca²⁺ (CRAC) channels. CRAC channels are modulated by the endoplasmic reticulum Ca²⁺ sensor STIM1 which gates the pore subunit of the channel known as ORAI1, found the in plasma membrane, to enable sustained Ca²⁺ influx. Mutations in the STIM1 and ORAI1 genes result in CRAC channelopathy, an ensemble of diseases including immunodeficiency, muscular hypotonia, ectodermal dysplasia with defects in sweat gland function and abnormal enamel mineralization similar to amelogenesis imperfecta (AI). In some reports, the chief medical complain has been the patient’s dental health, highlighting the direct and important link between CRAC channels and enamel. The reported enamel defects are apparent in both the deciduous and in permanent teeth and often require extensive dental treatment to provide the patient with a functional dentition. Among the dental phenotypes observed in the patients, discoloration, increased wear, hypoplasias (thinning of enamel) and chipping has been reported. These findings are not universal in all patients. Here we review the mutations in STIM1 and ORAI1 causing AI-like phenotype, and evaluate the enamel defects in CRAC channel deficient mice. We also provide a brief overview of the role of CRAC channels in other mineralizing systems such as dentine and bone.     

The anatomy, physics, and physiology of gas exchange surfaces: is there a universal function for pulmonary surfactant in animal respiratory structures?

(Orgeig and Daniels) This surfactant symposium reflects theintegrative and multidisciplinary aims of the 1st ICRB, by encompassingin vitro and in vivo research, studies of vertebrates and invertebrates,and research across multiple disciplines. We explore the physicaland structural challenges that face gas exchange surfaces invertebrates and insects, by focusing on the role of the surfactantsystem. Pulmonary surfactant is a complex mixture of lipidsand proteins that lines the air–liquid interface of thelungs of all air-breathing vertebrates, where it functions tovary surface tension with changing lung volume. We begin witha discussion of the extraordinary conservation of the blood–gasbarrier among vertebrate respiratory organs, which has evolvedto be extremely thin, thereby maximizing gas exchange, but simultaneouslystrong enough to withstand significant distension forces. Theprincipal components of pulmonary surfactant are highly conserved,with a mixed phospholipid and neutral lipid interfacial filmthat is established, maintained and dynamically regulated bysurfactant proteins (SP). A wide variation in the concentrationsof individual components exists, however, and highlights lipidomicas well as proteomic adaptations to different physiologicalneeds. As SP-B deficiency in mammals is lethal, oxidative stressto SP-B is detrimental to the biophysical function of pulmonarysurfactant and SP-B is evolutionarily conserved across the vertebrates.It is likely that SP-B was essential for the evolutionary originof pulmonary surfactant. We discuss three specific issues ofthe surfactant system to illustrate the diversity of functionin animal respiratory structures. (1) Temperature: In vitroanalyses of the behavior of different model surfactant filmsunder dynamic conditions of surface tension and temperaturesuggest that, contrary to previous beliefs, the alveolar filmmay not have to be substantially enriched in the disaturatedphospholipid, dipalmitoylphosphatidylcholine (DPPC), but thatsimilar properties of rate of film formation can be achievedwith more fluid films. Using an in vivo model of temperaturechange, a mammal that enters torpor, we show that film structureand function varies between surfactants isolated from torpidand active animals. (2) Spheres versus tubes: Surfactant isessential for lung stabilization in vertebrates, but its functionis not restricted to the spherical alveolus. Instead, surfactantis also important in narrow tubular respiratory structures suchas the terminal airways of mammals and the air capillaries ofbirds. (3). Insect tracheoles: We investigate the structureand function of the insect tracheal system and ask whether pulmonarysurfactant also has a role in stabilizing these minute tubules.Our theoretical analysis suggests that a surfactant system maybe required, in order to cope with surface tension during processes,such as molting, when the tracheae collapse and fill with water.Hence, despite observations by Wigglesworth in the 1930s offluid-filled tracheoles, the challenge persists into the 21stcentury to determine whether this fluid is associated with apulmonary-type surfactant system. Finally, we summarize thecurrent status of the field and provide ideas for future research.