Intertidal Bivalves Research Articles

Variable Rhythms of Micro-growth Striation Formation in Bivalve Shells (Review)

Recent progress in study on rhythms of micro-growth striation formation (consisting of alternating growth line and growth increment) in bivalves is reviewed herein. Subtidal bivalves have various average frequency of the striation formation. Periodicities such as daily and 1/2 daily ones are known. Involvement of biological clock in keeping these rhythms are doubtful. Rather, it seems that the periodic fluctuation of environmental factors induces these rhythms. Non-periodic formation seems to be more common. Intertidal bivalves form one growth line at each low tide, provided they are exposed. Growth lines of tidal exposure origin are arranged into specific patterns reflecting the tidal type of bivalve's habitats and their relative height in intertidal zone. These patterns have been successfully used in recognizing intertidal bivalves among fossil material or material from archaeological sites.

Seasonal and tidal changes in the length of the crystalline style intertidally living Macoma balthica (Mollusca, Bivalvia)

Samples of Macoma balthica were collected during 1978 and 1979 from the westernmost part of the Dutch Wadden Sea. The length of the crystalline style in the stomach of this intertidal bivalve was studied through tidal and annual cycles. The length of the style was ca. half the shell length and changed slightly with the season. Maximum lengths were recorded in spring, the season of high food intake, and minimal values in autumn and winter. Changes in the length of the style also exhibited a tidal cycle, but with two maxima and two minima. Tidal fluctuations in style length amounted to ca. 5% only. The influence of enzymes and waste products from the digestive diverticula, the food intake as well as the influence of the pH on the length of the style are discussed.

Quantitative analysis of carbohydrases in the crystalline style of some intertidal bivalve molluscs

Amylase activity in different pH ranging from 3·6 to 8·0 and activity of sucrose, maltose, trehalase, raffinase, lactase, glycogenase, pectinase, chitinase, carboxy methyl cellulase and cellulase at their respective optimum pH were quantitatively estimated in the crystalline style of intertidal bivalves,Crassostrea madrasensis, Meretrix meretrix, Meretrix casta, Katelysia opima andDonax cuneatus. Amylase was the most active among all enzymes tested. A maximum activity of 137·5 μg/mg/h was recorded in the style ofKatelysia opima while the activity was minimal inDonax cuneatus (39·3 μg/mg/h). Two pH optima were recorded for style amylase ofCrassostrea madrasensis (6·0 and 6·8) andKatelysia opima (5·6 and 6·8). But the activity was higher at higher optimum pH. The enzymes hydrolysing oligosaccharides were weak in most cases or absent. The enzymes acting on reserve polysaccharides such as amylase and glycogenase showed maximum activity in the species tested. However the activity of enzymes degrading structural polysaccharides such as cellulase, carboxy methyl cellulase, pectinase and chitinase was either at a low level or absent. The role of the style enzymes in the extracellular digestion of bivalves is discussed.

Metabolic Adaptations To Environmental Anoxia in the Intertidal Bivalve Mollusc Mytilus Edulis L

Many invertebrate species are able to withstand periods with interrupted oxygen supply that may extend over days. These so-called euryoxic organisms show metabolic adaptations different from those found in temporarily anoxic vertebrate tissues. It has been the authors' field of research over more than 15 years to investigate metabolic pathways and their regulation in euryoxic marine and freshwater molluscs, especially of the sea mussel Mytilus edulis L. This paper intends to provide, in a more or less chronological way, a survey of metabolic routes and regulation points through which sufficient metabolic energy is released without exhaustion of the available energy stores. It will be shown that reduction of energy demand and activation of highly efficient fermentation processes are the most important elements for survival. Finally, attention will be paid to the processes involved in the return from anoxic to normoxic conditions.

Effect of tidal submersion on lysozyme activity in Mytilus edulis and Tellina tenuis

Changes in mean style weight and in lysozyme activity of the style, digestive gland, gill and mantle of Mytilus edulis and Tellina tenuis from the Clyde Sea area, Scotland, were investigated over tidal cycles in March and August, 1981. For M. edulis, significant changes occurred in the style weight, style lysozyme activity and digestive gland lysozyme activity during a 22 h period. These appear to be related to a diurnal cycle rather than a tidal cycle. Changes in the weight of the style of M. edulis may be caused by dissolution during feeding, and style lysozyme may be secreted independently of the style matrix. The activity of lysozyme in T. tenuis is unaffected by the tide, suggesting that this intertidal bivalve can feed throughout the tidal cycle.

Effects of Lunatia heros predation on the population dynamics of Mya arenaria and Macoma balthica in Maine, USA

The interaction between the naticid snail predator Lunatia heros and 2 iteroparous, infaunal, intertidal bivalves was investigated in Lubec, Maine, USA. The Mya arenaria population consists primarily of young, small individuals. M. arenaria survivorship is low when young (3.5% yr-1 for the first 5 yr), then increases. M. arenaria can attain a length of 60 mm, but it is susceptible to L. heros attack only until it is 30 mm long. It delays reproduction until it is 20 mm long (3.8 yr) and diverts its resources instead into rapid early growth (4.9 mm yr-1 for the first 5 yr). The Macoma balthica population has a larger proportion of older individuals than does that of M. arenaria. Survivorship is higher for M. balthica than for M. arenaria (76.3% yr-1 for the first 5 yr). Unlike M. arenaria, M. balthica attains a final length of only 25 mm and all sizes are susceptible to L. heros attack. M. balthica grows slowly (2.7 mm yr-1 for the first 5 yr) and diverts its resources into earlier reproduction at a length of 10 mm (2.9 yr). These contrasting life-history patterns and the possible relationship between bivalve resource allocation and refuges from predation are discussed.

Seasonal respiratory responses to temperature and hypoxia in relation to burrowing depth in three intertidal bivalves

Respiratory responses to temperature and hypoxia in relation to burrowing depth were determined for winter- (W-C) and summer-conditioned (S-C) individuals of Tellina tenuis , Macoma balthica , and Carastoderma edula . These bivalves occur sympatrically on sand-flats but display different sediment burrowing depths ( C . edule , <2 cm; M . balthica , 3–8 cm; T . tenuis , 5–20 cm). A range depths over which daily temperature variation and O 2 concentration decline rapidly from surface values. Species thermal tolerance limits were found to decrease and to be more greatly temperature compensated with burrowing depth. Oxygen consumption rate (VO 2 increased with temperature to 25°C in C . edule , but was, thereafter, regulated (Q10 ca 1.0) up to 40°C while VO 2 increased with temperature in M . balthica and T . tenuis until thermally streased at 25° to 30°C. The deposit feeding M . balthica does not acclimate VO 2 to temperature while C . edule and T . tenuis , both suspension feeders, show “reverse” acclimation [VO 2 (W-C) < VO 2 (S-C)] that conserves overwintering energy stores. The shallow burrowing C . edule and deposit feeding M . balthica rarely experience hypoxia and are poor to non-regulators of VO 2 in reduced O 2 concentrations. In contrast, when winter-conditioned, T . tenuis is a moderate regulator of VO 2, the degree of regulation increasing in S-C individuals which are exposed to higher levels of hypoxia.

An endogenous rhythm in shell deposition inCerastoderma edule

The intertidal bivalve,Cerastoderma edule, when grown under constant conditions of temperature, salinity, water flow, light and food supply lays down faint internal shell bands at approximately semi-diurnal intervals, though with wide variations in periodicity from individual to individual. Animals grown continuously immersed under natural light/ dark cycles on a raft or below the tide marks produce similar bands. These bands are very faint compared with those in the shells of animals grown intertidally or under simulated semi-diurnal tidal conditions of emersion and immersion. The bands of intertidal animals also differ in their almost exact coincidence with the number of emersions. Cockles subjected to a diurnal cycle of immersion lay down strong bands coinciding approximately with the number of daily emersions, together with irregular faint bands. Thus the total number of bands exceeds the number of emersions.

The tidal rhythm of feeding and digestion in the pacific oyster, Crassostrea gigas (Thunberg)

A study has been made of the processes of extra- and intracellular digestion in the Pacific oyster, Crassostrea gigas (Thunberg) over two 24-h cycles in winter and summer. The results show that the digestive processes are discontinuous and related to the tidal cycle. Variations in tidal height resulting from a diurnal inequality of the tide affect both the relative dissolution of the crystalline style and the relative lengths of the constituent phases of the intracellular digestive process in the digestive diverticula. On a seasonal basis the style is present for a greater length of time in winter and, conversely, remains dissolved longer in summer. A seasonal variation in the structure of the digestive tubules has also been found. The results confirm conclusions reached earlier that the processes of extracellular digestion in the stomach and intracellular digestion in the digestive diverticula of intertidal bivalves are both discontinuous, alternate, and irrevocably interrelated since breakdown of the digestive cells of the digestive diverticula following intracellular digestion results in the dissolution of the crystalline style. The arrival of food in the stomach has a minimal effect upon the style. Moreover, the cytological structure of the digestive diverticula of C. gigas undergoes a series of synchronized changes related to the tidal cycle.

Pumping activity ofArctica islandica(L) and some other common bivalves

Thermistor flowmeters were used to investigate the pumping activity of Arctica islandica together with five other subtidal and three intertidal bivalves. The subtidal species, with the exception of Chlamys opercularis, show an intermittent pattern of pumping activity of several minutes’ periodicity which is independent of phasic shell adduction. In contrast the intertidal species and the subtidal Chlamys pump more or less continuously. The pumping behaviour of Arctica is modified under conditions of respiratory stress; the time spent pumping increases from 40–60 % to over 95% as the PO2 of the ambient water is reduced from 160 mm Hg to 30–35 mm Hg. Continuous recordings were made of the PO2 of the mantle cavity water of Arctica during normal pumping activity. The possible mechanism controlling pumping behaviour is discussed, together with the problems of determining bivalve respiration rates at defined levels of activity.

The nearshore advection of a toxigenic Pseudo-nitzschia bloom and subsequent domoic acid contamination of intertidal bivalves

Along the coast of Washington State, USA, periods of downwelling-favourable winds increase in frequency in late summer and may advect domoic acid (DA)-producing Pseudo-nitzschia to the coast where they toxify coastal razor clams Siliqua patula. During the late summer and early autumn of 2002, measurements of Pseudo-nitzschia species, particulate DA (pDA) and salinity were made in nearshore waters and at Kalaloch Beach. A shift in the relative abundance of Pseudo-nitzschia species was observed following a storm during 8–10 September. After a second storm during 16–18 September, Pseudo-nitzschia cell numbers and levels of pDA increased in nearshore waters. Salinity measured with moored sensors showed the presence of relatively fresh Columbia River plume water on the inner shelf for several weeks, beginning on 8 September and persisting for approximately eight days after the second storm. During that time, DA in intertidal razor clams accumulated to levels that exceeded the regulatory action limit. This study helps to clarify the complex role of the Columbia River plume in the advection of Pseudo-nitzschia populations to the Washington coast.