Influence of environmental factors on macrofoulant assemblages on moored buoys in the eastern Arabian Sea

Factors governing the distribution of organisms in the pelagic ocean are understudied. In this paper we describe environmental parameters and macrofouling assemblages on 11 buoys deployed in the Arabian Sea for an average duration of 322 days. Macrofoulants on all the mooring components extending from the sea-surface to a depth of 1800–4300 m were documented. Role of temperature, salinity, dissolved oxygen, biological productivity and zooplankton community in governing the macrofoulant distribution are described. Species composition, vertical zonation and wet biomass exhibited significant spatial variations. Lepas anatifera constituted more than 90% of foulant wet biomass on all moorings. Assemblages in the southeastern (SEAS), east-central (ECAS) and northeast (NEAS) regions were distinct. Density of L. anatifera on surface buoys were low in SEAS (0.2±0.09 no./cm²), high in ECAS (0.32±0.11 no./cm²) and moderate in NEAS (0.23±0.04no./cm²). Macrofoulants were observed up to a depth of 75 m in SEAS, 130 m in ECAS and 120 m in NEAS. The depth profile of macrofoulant assemblages on moorings could be related to the prevalent hypoxic condition. Vertical profiles of wet biomass on all moorings exhibited subsurface maxima at depth ranging from 10 to 20 m, consequent to the abundance of L. anatifera in a thermally stable depth of water column, wherein diurnal and semidiurnal temperature variability was minimal. We attribute the observed variation in fouling assemblages to dissolved oxygen levels, salinity and diurnal variability in temperature and salinity.

Caste-Specific Expression of Na+/K+-ATPase in the Asian Weaver Ant, Oecophylla smaragdina (Fabricius, 1775)

Social insect colonies adopt different levels of survival strategies and exhibit well-defined reproductive division of labour. Oecophylla smaragdina (Fabricius, 1775) has physiological and behavioral adaptations that enable them to forage at extreme environmental conditions and are lethal to most other insects. Ion homeostasis is the key process in an organism's survival mechanism. Among ion pumps, the ATP-dependent sodium-potassium ion pump is essential for maintaining the Na⁺ and K⁺ ionic balance and is well known as the primary consumer of energy. Oecophylla smaragdina plays pivotal role as a model among social insects for understanding ion homeostasis at the organization level of the castes. We have evaluated the expression and activity of Na⁺/K⁺-ATPase among various castes of O. smaragdina (worker subcastes, queen and male). Real-time PCR and immunoblotting analyses revealed the differential expression of Na⁺/K⁺-ATPase in the castes. Significantly higher expression of Na⁺/K⁺-ATPase mRNA and protein were observed in the minor workers, queen, major workers and males respectively. These results suggest that in the weaver ant colony, the castes might have variously adapted and evolved with a well-developed ion transport mechanism which allows them to perform allocated tasks within the nest and could be a key to their adaptive benefits towards division of labour.

Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics

This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate-sodium thiosulphite as a redox initiator and in the presence of N,N'-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0-6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as DeltaG(0), DeltaH(0) and DeltaS(0) were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater. Adsorbed U(VI) ions were desorbed effectively (about 96.2+/-3.3%) by 0.1M HCl. The adsorbent was suitable for repeated use (more than four cycles) without any noticeable loss of capacity.

Assembly of ovarian follicles in the caecilians Ichthyophis tricolor and Gegeneophis ramaswamii: light and transmission electron microscopic study

Though much is known about various aspects of reproductive biology of amphibia, there is little information on the cellular and mechanistic basis of assembly of ovarian follicles in this group. This is especially true of the caecilians. Therefore, taking advantage of the abundant distribution of caecilians in the Western Ghats of India, two species of caecilians, Ichthyophis tricolor and Gegeneophis ramaswamii, were subjected to light and transmission electron microscopic analysis to trace the sequential changes during the assembly of ovarian follicles. The paired ovaries of these caecilians are elongated sac-like structures each including numerous vitellogenic follicles. The follicles are connected by a connective tissue stroma. This stroma contains nests of oogonia, primary oocytes and pregranulosa cells as spatially separated nests. During assembly of follicles the oocytes increase in size and enter the meiotic prophase when the number of nucleoli in the nucleus increases. The mitochondrial cloud or Balbiani vitelline body, initially localized at one pole of the nucleus, disperses through out the cytoplasm subsequently. Synaptonemal complexes are prominent in the pachytene stage oocytes. The pregranulosa cells migrate through the connective tissue fibrils of the stroma and arrive at the vicinity of the meiotic prophase oocytes. On contacting the oocyte, the pregranulosa cells become cuboidal in shape, wrap the diplotene stage oocyte as a discontinuous layer and increase the content of cytoplasmic organelles and inclusions. The oocytes increase in size and are arrested in diplotene when the granulosa cells become flat and form a continuous layer. Soon a perivitelline space appears between the oolemma and granulosa cells, completing the process of assembly of follicles. Thus, the events in the establishment of follicles in the caecilian ovary are described.

Triiodothyronine and melatonin influence antioxidant defense mechanism in a teleost Anabas testudineus (Bloch): in vitro study

The effect of the hormones triiodothyronine (T3) and melatonin on antioxidant defense system was studied in 6-propyl thiouracil (6-PTU)-treated or photoperiod-exposed teleost Anabas testudineus. 6-PTU (2 microg/g) treatment or photoperiod exposure (24 h) increased malondialdehyde (MDA) and conjugated dienes (CD) concentrations, indicating increased lipid peroxidation (LPO) in the experimental conditions. T3 or melatonin (10(-6) M) treatment for 15 min in vitro in PTU-treated fish reversed the activity of superoxide dismutase (SOD), catalase and glutathione content. T3-treated group showed no change in glutathione peroxidase (GPx) activity, whereas melatonin treatment decreased its activity. T3 inhibited glutathione reductase (GR) activity. Photoperiod exposure (physiological pinealotomy) induced a stressful situation in this teleost, as evidenced by LPO products and antioxidant enzyme activities. Melatonin and T3 treatment for 15 min in vitro also reversed the effect of photoperiod on peroxidation products and the SOD and catalase activities. GR activity decreased in photoperiod-exposed group and melatonin and T3 treatment reversed the activities. The antioxidant enzymes responded to the stress situation after 6-PTU treatment and photoperiod exposure by altering their activities. The study suggested an independent effect of T3 and melatonin on antioxidant defence mechanism in different physiological situations in fish.

Does melatonin have a time-dependent effect on brain and gill ionic metabolism in a teleost, Anabas testudineus (Bloch)?

Exogenous administration of 0.20, 0.40 and 0.60 microg/g body weight melatonin over a 24 hr cycle caused an inhibition of Na+, K+ ATPase activity in both brain and gills of A. testudineus. However, Ca2+ ATPase activity in the brain was significantly inhibited by the highest dose, and that in the gill at all the doses of melatonin. Evening injection of melatonin had an inhibitory effect on both brain and gill Na+ K+ and Ca2+ ATPase activity. Melatonin treatment in the morning for 12 hrs did not have an effect on brain Na+, K+ ATPase, while Ca2+ ATPase was inhibited. Similar treatment stimulated Na+, K+ and Ca2+ ATPase activity in the gills. Sodium, potassium and calcium ions in the gill were significantly reduced in the evening treated group while no change was observed in the morning melatonin injected group. The results suggest that melatonin elicits a time-dependent effect on the enzymes and ionic content in the brain and gills of A. testudineus.

Tri-iodo thyronine regulates antioxidant enzyme activities in different cell fractions through a mechanism sensitive to actinomycin D in a teleost, Anabas testudineus (Bloch)

The present study evaluated the effects of hyperthyroid state on lipid peroxidation and antioxidant enzymes in the crude (CF), post nuclear (PNF) and mitochondrial fractions (MF) of the fish liver. The in vivo injection of T3 (200ng) did not change the lipid peroxidation products, malondialdehyde (MDA) and conjugated dienes (CD), while actinomycin D (10microg), a potent mRNA inhibitor when administered with T3 increased them. The antioxidant enzymes like superoxide dismutase (SOD) and catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) had an increased activity in CF and MF of hyperthyroid group to compete the increased oxidative stress, but actinomycin D partially inhibited the T3-induced activity. SOD and CAT activities in PNF of hyperthyroid group had no change, the glutathione concentration varied depending on the GPx and GR activity. Hyperthyroidism decreased the protein content, while simultaneous administration of actinomycin D inhibited the T3 action of elevating the protein content. The results suggest that the antioxidant defense status in A. testudineus is modulated by thyroid hormone, through an action sensitive to actinomycin D.

Insulin regulates ionic metabolism in a fresh water teleost, anabas testudineus (bloch)

Short term effects of insulin on total brain and branchial Na+K+ ATPase, Ca2+ ATPase and Na+, K+ and Ca2+ ions were investigated in A. testudineus. The increase in brain Ca2+ ATPase after alloxan treatment may account for an increased amount of intracellular calcium required for biochemical events taking place inside the cells. Branchial Na+K+ATPase was significantly stimulated while Ca2+ ATPase significantly inhibited after alloxan treatment. This suggests that alloxan exerts its inhibitory effect on the ATP-driven Ca2+ transport via; its action on the Ca2+ pump protein rather than the membrane permeability to Ca2+. The increased activity of brain Na+K+ ATPase at 3 and 24 hr by insulin to alloxan pretreated fish may account for the stimulated co-transport of glucose and its utilization for energy requirements and the excitatory action on neurons in the brain. The elevated brain Ca2+ ATPase may be due to the role of calcium as a second messenger in hormone action. At 24 hr, the activity of branchial Na+K+ ATPase and Ca2+ ATPase in alloxan pretreated specimens was significantly stimulated by insulin. This may be due to increased synthesis of these enzyme units. Administration of insulin (lU/fish) in normal fish significantly inhibited the activity of brain and branchial Na+K+ ATPase while brain Ca2+ ATPase showed a stimulatory effect at 3 and 24 hr compared to control. Inhibition of total branchial Ca2+ ATPase activity by insulin may be due to increased Ca2+ concentration. Higher plasma glucose level in alloxan treated groups confirms the diabetic effect of alloxan. Insulin reverses this effect. The possible mechanism by which insulin controls Na+K+ ATPase activity appears to be tissue specific. The results seem to be the first report on the effect of insulin on ATPase activity in a teleost. These data are consistent with the hypothesis that insulin performs a role in hydro mineral regulation in freshwater teleosts.