Martín Ansaldo

Antioxidant levels from different Antarctic fish caught around south Georgia island and Shag Rocks.

Abstract Antarctic fish have been isolated for over several million years in an environment with a very low and constant temperature and high oxygen concentration. In such conditions the oxidative stress might be an important factor affecting their metabolic adaptive strategies. Activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), vitamin E levels and total antioxidant capacity (TRAP) were measured in liver, gill, heart and muscle homogenates of red-blooded (Nototheniidae) and white-blooded (Channichthyidae) Antarctic fish. SOD activity was also measured in blood samples. Gill SOD activity was threefold higher in channichthyids than in nototheniids while CAT and GPx were significantly higher in the gills of channichthyids. The increased SOD activity of channichthyids probably reflects the large PO2 gradient across their gills. The H2O2 produced seems to be preferentially eliminated by diffusion, according to the low levels of CAT and GPx found in the gills of these species. In contrast, blood SOD was about fivefold higher in the latter group, which possesses erythrocytes and thus a much higher oxygen-carrying capacity. CAT activity was always higher in nototheniids except in muscle. However, vitamin E did not show clear differences between families except for the pattern observed in muscle. The higher content of vitamin E in this tissue shown in channichthyids is related to the higher volume density of mitochondria reported for this group, since vitamin E is responsible for preventing membrane lipid peroxidation. Accordingly, TRAP (representative of hydrosoluble antioxidant capacity) was also higher in muscle of channichthyids. This is probably related to the role of ascorbic (a hydrosoluble compound) acid in regenerating vitamin E.

Acid–Base Balance and Ionic Regulation During Emersion in the Estuarine Intertidal Crab Chasmagnathus granulata Dana (Decapoda Grapsidae)

Abstract Haemolymphatic P O 2 , P CO 2 , and pH, and ionic concentrations of haemolymph and branchial chamber water were measured in submerged and emersed crabs. Hypercapnia and respiratory acidosis were recorded after 15 min of air exposure, then P CO 2 remained constant and pH was compensated. Sodium concentration increased in haemolymph and decreased in branchial water. The difference between haemolymph Na + and Cl − increased dramatically. Acid–base balance is restored by two mechanisms: a) increase of the P CO 2 gradient across the gills and consequently the rate of CO 2 excretion; b) the increase in the strong ion difference, caused by branchial sodium uptake, compensates the hypercapnic acidosis.

Effect of cadmium, lead and arsenic on the oviposition, hatching and embryonic survival of Biomphalaria glabrata.

Biomphalaria glabrata is a widespread freshwater gastropod mollusc. The easy aquaculture of these organisms allow its use as an accessible tool for contamination bioassays. B. glabrata showed marked metabolic responses when exposed to cadmium, lead and arsenic. Those responses could also affect the reproduction of the snails. Taking into account this hypothesis, B. glabrata were exposed for 96 h (acute laboratory bioassays) to different concentrations of cadmium (0.1, 0.05 and 0 mg/L), lead (0.5, 0.1, 0.05 and 0 mg/L) and arsenic (0.5, 0.1, 0.05 and 0 mg/L). Snails were removed from the aquaria while eggs were left in the same contaminant concentrations. The effect of the assayed toxicants on snail reproduction was registered as the alterations of the total number of laid eggs (TNLE), hatching time and embryonic survival. At 0.10 mg/L cadmium significantly decreased the TNLE (p<0.05) and no embryos survived. The lowest assayed level (0.05 mg/L) of cadmium, delayed the hatching time twice when it was compared with the control group (p<0.01). Lead decreased the TNLE at 0.5 mg/L level (p<0.01). The other assayed doses (0.05 and 0.10 mg/L) also decreased embryonic survival significantly (p<0.05 and p<0.01 respectively) and extended twice the time to hatching (p<0.01). The 0.50 mg/L level killed all embryos. Arsenic at all studied concentrations decreased the TNLE (p<0.05) while the hatching time was increased by 50%. Embryo survival only decreased at the highest level (0.5 mg/L) of arsenic assayed. In summary, the acute exposure (96 h) to cadmium lead and arsenic, altered the reproduction of B. glabrata, modifying the TNLE, hatching time and embryonic survival.

Endocrine disruptive potential of endosulfan on the reproductive axis of Cichlasoma dimerus (Perciformes, Cichlidae)

Endosulfan (ES), a persistent organochlorine pesticide, is widely used despite its toxicity to non-target animals. Upon reaching water bodies, ES can cause negative effects on aquatic animals, including disruption of hormonal systems. However, the action of ES on fish reproductive axis has been hardly studied thus far. The aim of the present work was to assess the endocrine disruptive potential of endosulfan on the pituitary gonadotropins levels and on the testes function due to ES in the South American freshwater fish Cichlasoma dimerus, using in vitro and in vivo approaches. In vitro experiments showed that ES inhibited the LH-stimulated steroidogenesis in gonads; no change was observed in gonadotropins release from pituitaries in culture. Laboratory waterborne ES (0.1, 0.3 and 1 μg/L) exposure for two months caused decrease in βFSH pituitary content and γGT activity in the testes (Sertoli cell function marker). Testicular histology revealed pathologies such as scarce intermediate stages of spermatogenesis, release of immature germ cells into the lobular lumen, presence of foam cells and interstitial fibrosis. As FSH and FSH-mediated steroidogenesis regulate spermatogenesis and Sertoli cell function, the effect of ES on FSH could be responsible for the morphological alterations observed in testes. In vitro, ES disrupted steroidogenesis in gonads, therefore similar effects in vivo cannot be ruled out. Based on this evidence, ES exhibits an endocrine disruptive action on the reproductive axis of C. dimerus, causing disruption at the pituitary and/or at the gonad level. These effects could acquire ecological significance under prolonged exposure to the pesticide in nature.

Bimodal breathing in the estuarine crab Chasmagnathus granulatus Dana 1851--physiological and morphological studies.

Chasmagnathus granulatus is an estuarine crab which actively moves from subtidal to supratidal areas. To elucidate the possible existence of extrabranchial sites for aerial gas exchange, we measured respiratory and acid-base variables in animals with and without branchial water (controls and experimental crabs, respectively) during air exposure. An histological study of the branchiostegite was also performed. Throughout 4 h of emergence C. granulatus did not suffer venous hypoxia, even without branchial water. The rate of oxygen uptake (M(O(2))) was similar in both groups. The rate of carbon dioxide excretion (M(CO(2))) and the gas exchange ratio (R) significantly decreased during emergence in both groups, with R significantly lower for experimental crabs. Consequently, CO(2) was accumulated in the hemolymph. This variable stabilized after 90 min in control animals, but experimental crabs continued accumulating CO(2). Histological study of the branchiostegites demonstrated the presence of an attenuated and greatly perfused epithelium facing the branchial chamber lumen, with a shortest diffusion distance of 0.5 microm. Simple folds and lobulated projections increase the respiratory surface area. These results suggest that C. granulatus is a bimodal breathing crab, active both in water and air. When emerged, this species extract oxygen directly from air through branchiostegal lungs, but relies on branchial exchange to eliminate carbon dioxide.

Long-Term Starvation and Posterior Feeding Effects on Biochemical and Physiological Responses of Midgut Gland of Cherax quadricarinatus Juveniles (Parastacidae).

We investigated the effect of long-term starvation and posterior feeding on energetic reserves, oxidative stress, digestive enzymes, and histology of C. quadricarinatus midgut gland. The crayfish (6.27 g) were randomly assigned to one of three feeding protocols: continuous feeding throughout 80 day, continuous starvation until 80 day, and continuous starvation throughout 50 day and then feeding for the following 30 days. Juveniles from each protocol were weighed, and sacrificed at day 15, 30, 50 or 80. The lipids, glycogen, reduced glutathione (GSH), soluble protein, lipid peroxidation (TBARS), protein oxidation (PO), catalase (CAT), lipase and proteinase activities, and histology were measured on midgut gland. Starved crayfish had a lower hepatosomatic index, number of molts, specific growth rate, lipids, glycogen, and GSH levels than fed animals at all assay times. The starvation did not affect the soluble protein, TBARS, PO levels and CAT. In starved juveniles the lipase activity decreased as starvation time increased, whereas proteinase activity decreased only at day 80. The histological analysis of the starved animals showed several signs of structural alterations. After 30 days of feeding, the starved-feeding animals exhibited a striking recovery of hepatosomatic index, number of molts, lipids and glycogen, GSH, lipase activity and midgut gland structure.

Physiological response to emersion in the amphibious crab Chasmagnathus granulata Dana (Decapoda Grapsidae): biochemical and ventilatory adaptations

Abstract The adaptation of Chasmagnathus granulata to air breathing depends on two types of physiological mechanisms: (1) Biochemical adjustments, comprising the achievement of new steady state values for partial pressure of carbon dioxide ( P CO 2 ) and total carbon dioxide concentration ( C CO 2 ). The initial increase in hemolymph bicarbonate is stabilized by dehydration to CO 2 presumably catalyzed by carbonic anhydrase (CA) at the basolateral side of the gill epithelium. Thus, an adequate transbranchial gradient of P CO 2 is restored. Inhibition of CA with acetazolamide (Az) reduces the rate of CO 2 excretion and elevates P CO 2 . The respiratory acidosis caused by increased P CO 2 is compensated by increase in the difference between Na + and Cl − concentrations. Az does not affect hemolymph ionic concentrations. (2) Ventilatory control: untreated animals show a significant decrease in scaphognathite frequency ( F SC ) during emersion, while Az treated crabs show a slight increase of this variable. F SC of Az crabs tends to decrease with hemolymphatic CO 2 , presumably by clearance of the CA inhibitor from hemolymph. These results suggest that C. granulata possess a ventilatory control based on a primary oxygen-dependent stimulus and a secondary one dependent on CO 2 .

Characterization of brain gonadotropin-releasing hormone (GnRH) molecular variants in brain extracts from different perciform fishes from Antarctic waters

Abstract Gonadotropin-releasing hormone (GnRH) is the hypothalamic hormone that regulates the reproductive system by stimulating release of gonadotropins from the anterior pituitary gland. The molecular variants of the reproductive neuropeptide GnRH were characterized from brain tissue of three perciform species from Antarctic waters: Pseudochaenichthys georgianus, Chaenocephalus aceratus, and Notothenia rossi. The study involved reverse phase high-performance liquid chromatography (RP-HPLC) followed by radioimmunoassay (RIA) with two antisera that recognize all GnRH variants already identified: PBL 45 and PBL 49. The results showed that brain extracts of P. georgianus, C. aceratus, and N. rossi contain, like those of other perciform fish, three forms of GnRH likely to be: sbGnRH (seabream GnRH), cGnRH-II (chicken GnRH II) and sGnRH (salmon GnRH). They also showed evidence for the presence of a fourth GnRH variant, chromatographically and immunologically different from the other known forms of the vertebrate hormone. Although final conclusions will require isolation, purification, and sequencing of these molecules, these results offer encouraging possibilities of further advances in the characterization of a multiplicity of GnRH molecular variants.

Elemental composition of Usnea sp lichen from Potter Peninsula, 25 de Mayo (King George) Island, Antarctica.

Several pollutants, which include metals, are present in the Antarctic atmosphere, snow, marine and terrestrial organisms. This work reports the elements incorporated by Usnea sp thalli in Potter Peninsula, 25 de Mayo (King George) Island, South Shetlands, Antarctica. Geological origin was analyzed as possible sources of elements. For this purpose, correlations were done using a geochemical tracer, principal component analysis and enrichment factors were computed. Lithophile elements from particulate matter were present in most of the sampling sites. Bromine, Se and Hg showed the highest enrichment factors suggesting other sources than the particulate matter. Mercury values found in Usnea sp were in the same range as those reported for Deception Island (South Shetlands) and remote areas from the Patagonia Andes.

Gonadal histology and gametogenesis of the Antarctic limpet Nacella concinna (Patellogastropoda, Nacellidae) collected at Potter Cove, 25 de Mayo (King George) Island, during austral summer

The limpet Nacella concinna is one of the most widely distributed gastropods along the Antarctic Peninsula. This species has been a useful tool in ecological and physiological studies for understanding Antarctic trophic interactions. Although the reproduction of limpets has been thoroughly studied, very little is known about gametogenesis in the genus Nacella. The purpose of this study is to describe the gonadal morphology and gametogenesis in N. concinna observed by light microscopy and to determine its chromosome complement. All the limpets were sexually mature at the time of sampling. Oocytes were separated by trabeculae with abundant glycogen reserves. There was a predominance of late vitellogenic oocytes. Many previtellogenic oocytes were pyriform in shape. Oogonia were clustered near the ovary wall or the trabeculae. Only two meiotic stages were found: metaphase I and anaphase I, both of which showed a regular arrangement of chromosomes. The oviduct contained mature oocytes surrounded by sperm. Testicular tubules were filled with spermatozoa. The elongated head of the spermatozoon resembles that of other Nacellidae members. One of the bivalents is heteropycnotic. The haploid complement is n = 4 and the sex determination system is XO/XX. Although N. concinna has been commonly characterized as a broadcast-spawner, its unique spawning behavior, the presence of oocytes at anaphase I and spermatozoa within the oviduct suggests internal fertilization.