Y. Prabhakara Rao

Zinc accumulation in fiddler crabs Uca annulipes Latreille and Uca triangularis (Milne Edwards)

The effect of exposure time and concentration on the tissue-specific accumulation of Zn in two fiddler crabs, Uca annulipes and Uca triangularis, obtained from polluted (Visakhapatnam Harbor) and unpolluted (Bhimilipatnam) areas was studied. Hepatopancreas registered major accumulation of Zn when the crabs were exposed to sublethal concentrations (6.38 to 15.39 ppm) for 30 days. However, when the crabs were exposed to different concentrations of Zn (LCO, LC25, LC50, LC75) ranging from 12.93 to 99.38 ppm, higher accumulation was recorded in gills than in hepatopancreas. There was a progressive increase in the percentage body burden of Zn in hepatopancreas, but that in gills showed a decreasing trend. The standardized body burdens for both species of crabs were calculated to evaluate their sensitivity to exposure time as well as to concentration. The fractional retention coefficients for exposure time estimated for exposed crabs indicate that U. triangularis from Bhimilipatnam, having the highest value, is sensitive and U. annulipes from Visakhapatnam Harbor, showing the lowest value, is resistant.

Heavy metal toxicity to fiddler crabs, Uca annulipes Latreille and Uca triangularis (Milne Edwards): Respiration on exposure to copper, mercury, cadmium, and zinc

Respiration of animals is considered to be an indicator of their metabolic index and is used to evaluate the effect of stress or toxic substances in the environment. In an earlier investigation, an attempt was made to study the toxic effects of four heavy metals viz., Cu, Cd, Hg and Zn on fiddler crabs Uca annulipes and Uca triangularis obtained from polluted (Viskhapatnam Harbor) and unpolluted (Bhimilipatnam) environs. The present paper deals with respiratory metabolism of fiddler crabs Uca annulipes and Uca triangularis of Visakhapatnam Harbor by exposing them to different test concentrations of heavy metals i.e. Cu, Cd, Hg and Zn as these are the chief pollutants in their environment. A comparison has also been made with the respiratory metabolism of their counterparts collected from an unpolluted environment i.e. Bhimilipatnam.

Copper toxicity in tropical barnacles, Balanus amphitrite amphitrite and Balanus tintinnabulum tintinnabulum

The effect of Cu on survival time, O2 consumption and accumulation of Cu in barnacles, Balanus amphitrite amphitrite and Balanus tintinnabulum tintinnabulum was studied. B. amphitrite amphitrite were found to survive longer than B. tintinnabulum tintinnabulum at all concentrations of Cu. Copper reduced the O2 consumption of both barnacles, but the reduction was greater with B. tintinnabulum tintinnabulum. Copper accumulation in soft parts of the barnacles increased with increasing Cu concentration and time. The barnacles accumulated Cu up to a particular limit (166.7 ± 8.98 μg g−1 in B. amphitrite amphitrite and 173.6 ± 12.17 μg g−1 in B. tintinnabulum tintinnabulum) at all Cu concentrations beyond which they died.

Influence of temperature on copper accumulation and depuration in a tropical cerithiid Cerithidea (cerithideopsilla) cingulata (Geelin 1790)

The effect of temperature on Cu accumulation and depuration in the tissues of Cerithidea cingulata was studied at 18 °C, 28 °C, and 38 °C. The LC50 value for 5 days was observed to be high at ambient temperature (28 °C) that at the high temperature (38 °C). The LC50 for 10 days at the low temperature (18 °C) was higher than at the ambient (28 °C). When exposed to sublethal concentrations for 48 hr, the tissue accumulation of Cu was found to be more at the high temperature than at the ambient and low temperature. The depuration process was faster at high temperatures, and the animals returned to normal condition after 36 hr. At the ambient and low temperature, Cu accumulation was slow and prolonged, and the animals resumed to normal condition after 48 and 72 hr, respectively. The gonad-digestive gland (GDG) complex was found to show greater changes in accumulation and depuration process when compared to foot and viscera.

Evaluation of Cadmium Toxicity on Survival, Accumulation and Depuration in an Intertidal Gastropod, Turbo Intercostalis

The effect of cadmium on tolerance, accumulation and depurationwas studied in an intertidal gastropod, Turbo intercostalis. Initially, the LC50 value for 96 hr wasdetermined by exposing the snails to different concentrations ofcadmium (2.5 to 12.5 ppm) and it was observed to be 6.18 mg L-1. Further, the accumulation and depuration of cadmium was investigated in different tissues namely GDG (Gonad-digestive gland) complex, mantle and foot of T. intercostalis on exposure to a sublethal concentration (1.24 mgL-1) for a period of 20 days. The accumulation of cadmium was found to be more in mantle and GDG complex and less in footduring this exposure and the tissue accumulation was in the order of GDG complex > mantle > foot. The GDG complex was largely responsible for most of the body burden of the metal. The percent body burden of the cadmium exhibited an increasingtrend with exposure time in GDG complex while in mantle therewas a decreasing trend. The foot tissue was observed to have aless percentage of body burden of cadmium. The fractional retention coefficients were also calculated and they showed a gradual increase with exposure time indicating more retention of metal in the tissues. However, depuration of the metal followed a similar trend of increase in all the tissues. The data suggestthat T. intercostalis have a good capacity ofaccumulation and depuration of heavy metal and it may be considered as a suitable species for biological monitoring of the coastal environment.The effect of cadmium on tolerance, accumulation and depurationwas studied in an intertidal gastropod, Turbo intercostalis. Initially, the LC50 value for 96 hr wasdetermined by exposing the snails to different concentrations ofcadmium (2.5 to 12.5 ppm) and it was observed to be 6.18 mg L-1. Further, the accumulation and depuration of cadmium was investigated in different tissues namely GDG (Gonad-digestive gland) complex, mantle and foot of T. intercostalis on exposure to a sublethal concentration (1.24 mgL-1) for a period of 20 days. The accumulation of cadmium was found to be more in mantle and GDG complex and less in footduring this exposure and the tissue accumulation was in the order of GDG complex > mantle > foot. The GDG complex was largely responsible for most of the body burden of the metal. The percent body burden of the cadmium exhibited an increasingtrend with exposure time in GDG complex while in mantle therewas a decreasing trend. The foot tissue was observed to have aless percentage of body burden of cadmium. The fractional retention coefficients were also calculated and they showed a gradual increase with exposure time indicating more retention of metal in the tissues. However, depuration of the metal followed a similar trend of increase in all the tissues. The data suggestthat T. intercostalis have a good capacity ofaccumulation and depuration of heavy metal and it may be considered as a suitable species for biological monitoring of the coastal environment.

Seasonal changes in the level and content of different biochemical constituents in tropical cerithiidsCerithidea (Cerithideopsilla) cingulata (Gmelin 1790) andCerithium coralium Kiener 1841

The level and content of different biochemical constituents were investigated over a period of one year (January–December 1982) in foot, gonad digestive gland complex and viscera of two tropical cerithiids, inhabiting two different regions of backwaters. Their seasonal indices exhibited bimodal pattern of cycling and this trend was more predominant in gonad digestive gland complex and foot. In all the body components of both species, the biochemical content was found to show considerable changes when compared to their levels. In both the cerithiids, the gonad digestive gland depicted remarkable variations with the season, followed by foot. The viscera did not show much variation when compared to other body components. The carbohydrates and glycogen of both the species showed a primary peak in March and a secondary peak in September indicating maturity of gonads. This was followed by a decline in their constituents which might be due to spawning. Lipid utilisation was also observed in both the animals next to carbohydrates and glycogen. Proteins were least utilised in the process of reproduction. Thus a carbohydrate-oriented metabolism was recorded in both the species. The results were compared with the other molluscs.

Starvation as a stress factor influencing the metabolism of a tropical intertidal gastropodMorula granulata (Duclos)

The snailMorula granulata (Duclos) survived the starvation stress over a period of 30 days but 50% mortality occurred on the 70th day. The changes in the level and content of different biochemical constituents viz carbohydrates, glycogen, free sugars, protein, total ninhydrin positive substances and lipids were investigated in foot, gonad digestive gland complex and viscera of the animal at intervals of 10 days up to 70 days. All these biochemical constituents (both level and content) were found to decrease with the period of starvation showing their utilisation except total ninhydrin positive substances which exhibited an increase. Of all the 3 tissues, the gonad digestive gland complex was affected most during starvation. ‘Lipid-oriented’ metabolism was observed in this animal showing maximum utilisation of lipids during starvation. Respiratory studies revealed a decreased pattern of oxygen consumption with increasing period of starvation when calculated per snail or per tissue weight. The recalculated intercept values (a) also showed a decreasing trend when exposed to starvation.

Influence of temperature and size on the respiration of a tropical intertidal gastropod,Morula granulata (Duclos), in air and water

SummaryThe effect of temperature on the size related metabolism of a tropical intertidal gastropod,Morula granulata (Duclos), was studied both in air and water. An increase was observed in the aerial and aquatic respiration with increasing size at all temperatures studied. Significant differences (P<0.05) were found between the regression values (b) and also the intercept values (a) of aerial and aquatic respiration at different temperatures. The aerial regression values at any given temperature were significantly higher (P<0.05) than the aquatic values. Aerial and aquatic respiration ofM. granulata at different temperatures are compared and discussed in relation to the habitat of the animal.

Aquatic and aerial respiration of an intertidal tropical gastropodMorula granulate (Duclos) in relation to temperature

The rates of aquatic and aerial oxygen consumption of an intertidal tropical gastropodMorula granulate increases with increasing temperature. The temperature at which the breakdown occurred in their oxygen consumption was observed to be different, 45°C for aquatic and 42°C for aerial respiration. However, the aquatic rates of oxygen consumption were higher than the aerial rates at all temperatures studied. The aquatic and aerial Q10 values showed almost the same trend, higher at lower temperatures and vice versa. The results were discussed in relation to the habitat of the animal.

Anaerobic response of a tropical intertidal gastropod Morula granulata (Duclos) to low salinities and fresh water

Post-anaerobic elevation of oxygen consumption was observed in Morula granulata (Duclos) when exposed to low salinities (10 and 5%.) and fresh water. The amount of oxygen debt appears to increase with decreasing salinity. Accumulation of end-products, succinic acid, alanine, glutamic acid, and lactic acid, was noticed in M. granulata when it was subjected to low salinities and fresh water confirming a shift into partial and complete anaerobic conditions, respectively. Succinic acid and alanine were found to be the major end-products, while glutamic acid and lactic acid were more minor. Aspartic acid and, to a greater extent, glycogen were utilized during these conditions. The accumulation of succinic acid, alanine, glutamic acid, and lactic acid, and the utilization of glycogen and aspartic acid increased with decreasing salinity (10%. to fresh water) and increasing duration of exposure. The results are discussed in relation to observations on other molluscs.