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Kinetics of urate accumulation in C. inflata. Animals were prepared as in the Methods section and the wet weight and urate content determined from field collected adults.
Source publication
Like many other ascidians, Corella inflata sequesters uric acid. We have identified microcrystals of uric acid by X-ray powder diffraction, by the characteristic UV absorption for urates at 292 nm which is abolished by uricase and by methenamine-silver staining in situ. The uric acid is precipitated in birefringent spherulites which are formed intr...
Citations
... In a yet-unexplained quirk of tunicate biology, many tunicate species have localized deposits of uric acid (Goodbody 1965;Saffo and Lowenstam 1978;Lambert et al. 1998). Storage as a form of excretion, nitrogen storage for future release, and structural support are among the proposed functions of tunicate urate deposits (Goodbody 1965;Saffo 1988;Lambert et al. 1998). ...
... In a yet-unexplained quirk of tunicate biology, many tunicate species have localized deposits of uric acid (Goodbody 1965;Saffo and Lowenstam 1978;Lambert et al. 1998). Storage as a form of excretion, nitrogen storage for future release, and structural support are among the proposed functions of tunicate urate deposits (Goodbody 1965;Saffo 1988;Lambert et al. 1998). Tunicates in the Molgulidae family have the largest uric acid deposits, which are localized to a specialized, ductless structure, called a renal sac (Saffo and Lowenstam 1978). ...
The phylum Apicomplexa is a quintessentially parasitic lineage, whose members infect a broad range of animals. One exception to this may be the apicomplexan genus Nephromyces, which has been described as having a mutualistic relationship with its host. Here we analyze transcriptome data from Nephromyces and its parasitic sister taxon, Cardiosporidium, revealing an ancestral purine degradation pathway thought to have been lost early in apicomplexan evolution. The predicted localization of many of the purine degradation enzymes to peroxisomes, and the in silico identification of a full set of peroxisome proteins, indicates that loss of both features in other apicomplexans occurred multiple times. The degradation of purines is thought to play a key role in the unusual relationship between Nephromyces and its host. Transcriptome data confirm previous biochemical results of a functional pathway for the utilization of uric acid as a primary nitrogen source for this unusual apicomplexan.
... However, in Styelidae, about 40 –50% of the soluble nitrogen is excreted as urea (Markus and Lambert, 1983). Ascidians also sequester sizeable amounts of nitrogen end products, uric acid, and other purines, in renal vesicles or specialized blood cells called nephrocytes (Goodbody, 1965; Lambert et al., 1998). In a number of marine animals, ammonium is not always excreted as waste, but is used to achieve buoyancy equilibrium instead. ...
... However, in Styelidae, about 40 –50% of the soluble nitrogen is excreted as urea (Markus and Lambert, 1983). Ascidians also sequester sizeable amounts of nitrogen end products, uric acid, and other purines, in renal vesicles or specialized blood cells called nephrocytes (Goodbody, 1965; Lambert et al., 1998). In a number of marine animals, ammonium is not always excreted as waste, but is used to achieve buoyancy equilibrium instead. ...
... The appearance of these crystals is similar to that of uric acid crystal "spherulites" or "spherically symmetrical, radiating crystal aggregates" that can occur in humans with gout (Fiechtner & Simkin, 1980, 1981. Likewise, the crystals are similar to spherulites of uric acid found in nephrocytes of the ascidian Corella inflata (Lambert et al., 1998). As uric acid crystals are soluble in formalin, several investigators (Dobson et al., 2008; examined wet tissue sections at necropsy prior to preserving kidney in formalin for routine histopathology. ...
... However, in Styelidae, about 40 –50% of the soluble nitrogen is excreted as urea (Markus and Lambert, 1983). Ascidians also sequester sizeable amounts of nitrogen end products, uric acid, and other purines, in renal vesicles or specialized blood cells called nephrocytes (Goodbody, 1965; Lambert et al., 1998). ...
Ammonium uptake into the cell is known to be mediated by ammonium transport (Amt) proteins, which are present in all domains of life. The physiological role of Amt proteins remains elusive; indeed, loss-of-function experiments suggested that Amt proteins do not play an essential role in bacteria, yeast, and plants. Here we show that the reverse holds true in the tunicate Ciona intestinalis. The genome of C. intestinalis contains two AMT genes, Ci-AMT1a and Ci-AMT1b, which we show derive from an ascidian-specific gene duplication. We analyzed Ci-AMT expression during embryo development. Notably, Ci-AMT1a is expressed in the larval brain in a small number of cells defining a previously unseen V-shaped territory; these cells connect the brain cavity to the external environment. We show that the knockdown of Ci-AMT1a impairs the formation of the brain cavity and consequently the function of the otolith, the gravity-sensing organ contained in it. We speculate that the normal mechanical functioning (flotation and free movement) of the otolith may require a close regulation of ammonium salt(s) concentration in the brain cavity, because ammonium is known to affect both fluid density and viscosity; the cells forming the V territory may act as a conduit in achieving such a regulation.
... Accumulation in the nephrocyte vacuole is particularly spectacular, especially after inorganic mercury contamination. Cells of this type are found in various tissues of many invertebrate groups: molluscs, arthropods, echinoderms, ascidians, etc. (Meyhoefer et al. 1985, Welsch & Rehkaemper 1987, Meyhofer & Morse 1996, Lambert et al. 1998. Their role in the storage and/or detoxification of heavy metals has been suggested in various aquatic species (Dillaman 1980, Giamberini & Pihan 1996, Soto et al. 1996, Vandenbulcke et al. 1998. ...
In order to better understand the role of the gills in the accumulation of contaminants, branchial uptake and bioaccumulation of inorganic (HgCl2) and monomethylmercury (CH3HgCl) were quantified in the shore crab Carcinus maenas, using living animals and an in vitro perfused gill preparation exposed to 50 mug l(-1) of either chemical forms in the external medium. In addition, localization of accumulated mercury was studied using the histochemical autometallographic technique by both light and electron microscopy. Gill tissue strongly accumulated either inorganic or methylated mercury at similar levels in vitro and in vivo. For both chemical forms of the metal, only about 1% of the total mercury input was recovered in the effluent fluid from in vitro perfused gills and could thus be considered available to distribute inside the animal via the circulatory system. Inorganic Hg was histochemically found to be accumulated at 2 markedly different locations in the gills: at the cuticular surface in direct contact with the contaminated medium and at high local levels in the central vacuole of gill nephrocytes. Although also present at these 2 locations, methylmercury was distributed more diffusely and more evenly in all cells. These results suggest that the high affinity of gill tissue for both forms of mercury may confer on this organ the role of an external barrier strongly limiting the invasion of the metal toward other compartments of the body.
... Uric acid excretion is usually negligible in fish, with some flexibility in response to ammonia or alkaline challenge (Wood, 1993 ). Although heavy reliance on uricotely is first developed in avian and reptilian lineages (Campbell, 1995), it is clear that the pathways for uric acid synthesis were well in place much earlier in the evolution of the phylum Chordata (e.g., in hmicates; Lambert et al., 1998; Saffo, 1988), not least as a corollary to purine biosynthesis and degradation. Thus, it seems reasonable to caution against totally ignoring uric acid and other nitrogenous compounds as excretory/detoxification products in fish. ...
The evolutionary aspects of nitrogen metabolism and excretion in fishes continue to be an exciting and fruitful area for research, hypothesis generation, and testing. The scenario proposed by Griffith can be evaluated more completely because several significant findings of the past decade: (1) Although larval lampreys (ammocoetes) do not appear to express O-UC activity as predicted by Griffith, the O-UC occurs in embryos of teleosts that are typical ammonoteles as adults; (2) urea transport appears to be governed in fish by very specific transport molecules; (3) CPSase activities with some “I” isozyme characteristics, that is, enzymes with at least equal preference for ammonia as substrate, are found in higher teleostean fish; and (4) it is fully understand the cost of osmoregulation in ureosmotic versus hypoosmotic regulators, and the teleostean strategy may prove to be more economical.
... C. injlata absorptivities peaked between 290 and 300 nm, suggesting that MAAs are not responsible for the UV absorbance we measured. The body of this ascidian contains uric acid crystals that are deposited there as metabolic waste products (Lambert et al., 1998). It is possible that uric acid provides some limited protection from UV damage (a uric acid absorbance peak occurs at 292 nm). ...
The solitary ascidian Corella injutu is a com- mon fouling organism in many areas of Puget Sound and the San Juan Archipelago, Washington, USA. Despite its abun- dance, it is conspicuously absent from areas that receive direct sunlight. Previous work suggests that ascidians in unshaded habitats can be overgrown and killed by algal overgrowth. In this study, we tested the hypothesis that UV irradiation contributes to C. inflatu distribution by killing individuals exposed to direct sunlight. To test this, we exposed C. infuta embryos, larvae, juveniles, and adults to UV irradiation and measured the responses. We also tested for UV-absorbing compounds in larvae, juveniles, and adults. In the laboratory, UV significantly damaged all life stages; the earliest stages were most vulnerable. A 3-week UV exposure significantly shortened adult life span. Juve- niles suffered 100% mortality after only 3 days. Tadpole larvae decreased settlement and metamorphosis after I day of UV exposure, and embryos exhibited developmental abnormalities after only 30 minutes of exposure. None of the life-history stages had apparent UV-absorbing com- pounds. Given the vulnerability of this species to UV, we suggest that its unique life-history traits (i.e., time of spawn- ing, brooding behavior, length of larval life) help it persist in its preferred habitat and avoid dispersal into inappropri- ate, UV-exposed areas.
... The appearance of these crystals is similar to that of uric acid crystal "spherulites" or "spherically symmetrical, radiating crystal aggregates" that can occur in humans with gout (Fiechtner & Simkin, 1980, 1981. Likewise, the crystals are similar to spherulites of uric acid found in nephrocytes of the ascidian Corella inflata (Lambert et al., 1998). As uric acid crystals are soluble in formalin, several investigators (Dobson et al., 2008; examined wet tissue sections at necropsy prior to preserving kidney in formalin for routine histopathology. ...
In firefly light organs, reflector layer is a specialized tissue which is believed to play a key role for increasing the bioluminescence intensity through reflection. However, the nature of this unique tissue remains elusive. In this report, we investigated the role, fine structure and nature of the reflector layer in the light organ of adult Luciola cerata.
Our results indicated that the reflector layer is capable of reflecting bioluminescence, and contains abundant uric acid. Electron microscopy (EM) demonstrated that the cytosol of the reflector layer's cells is filled with densely packed spherical granules, which should be the uric acid granules. These granules are highly regular in size (∼700 nm in diameter), and exhibit a radial internal structure. X-ray diffraction (XRD) analyses revealed that an intense single peak pattern with a d-spacing value of 0.320 nm is specifically detected in the light organ, and is highly similar to the diffraction peak pattern and d-spacing value of needle-formed crystals of monosodium urate monohydrate. However, the molar ratio evaluation of uric acid to various cations (K(+), Na(+), Ca(2+) and Mg(2+)) in the light organ deduced that only a few uric acid molecules were in the form of urate salts. Thus, non-salt uric acid should be the source of the diffraction signal detected in the light organ.
In the light organ, the intense single peak diffraction signal might come from a unique needle-like uric acid form, which is different from other known structures of non-salt uric acid form. The finding of a radial structure in the granules of reflector layer implies that the spherical uric acid granules might be formed by the radial arrangement of needle-formed packing matter.
