A.C. Brown

The effects of temperature on oxygen consumption in Bullia digitalis meuschen (Gastropoda, Nassaridae)

Abstract 1. 1. The oxygen consumption of Bullia digitalis from South Africas west coast, measured at a fixed activity level at 15°C, does not differ significantly between winter and summer. 2. 2. The adult acute rate-temperature curve is flattened over the temperature range likely to be encountered in the field, there being no significant difference in oxygen consumption between 15 and 22.5°C. 3. 3. Below this plateau the Q 10 is normal, giving a value of 2.67 between 5 and 10°C, but at temperatures above 22.5°C the Q 10 is less than 2 and oxygen consumption at 30°C does not approach that of the tropical Bullia melanoides at the same temperature. 4. 4. Both field and laboratory acclimated animals provide evidence that the rate-temperature curve is unaffected by such acclimation, either to high or low temperatures.

The Biology of Oniscid Isopoda of the Genus Tylos

Publisher Summary This chapter discusses the biology of Oniscid isopoda of genus Tyros. Terrestrial Crustacea in general evolved from marine ancestors via the marine intertidal zone. This transition involved extensive adaptations, especially with regard to locomotion, respiration, water balance, ionic regulation, and heat relationships. Various scientists have studied the behavior of the genus Tyros. The findings from their studies are summarized in the chapter. From these studies, it is concluded that the genus Tyros represents a condition intermediate between the truly marine and the fully terrestrial. This is illustrated through a wide gradient of behavior, from populations extremely dependent on the sea to populations that have adopted a virtually terrestrial way of life and display an attenuation of the tidal rhythm typical of the genus. Behavioral adaptations are also dependent on this gradient and are discusses in the chapter.

Sandy-Beach Bivalves and Gastropods: A Comparison Between Donax serra and Bullia digitalis

Publisher Summary The biology of a number of invertebrate animals found on sandy beaches is well known. Macrofaunal species tend to live in permanent or semi-permanent burrows. The modes of life of these species are of necessity very different from the two animals discussed in the present review. Bullia digitalis and Donax serra, although originating from very different molluscan stock, have both adapted successfully to high energy beaches, where extreme instability is the most acute problem to be overcome, permanent burrows being out of the question intertidally. Both animals are capable of powerful and rapid burrowing into the sand, a prerequisite under these unstable conditions. Bullia and Donax show remarkable convergence of form to the requirements of a common habitat. This chapter emphasizes that the great success of both species in a common environment can be attributed not only to their individually unique morphological and physiological adaptations but also to the similar way in which they exploit very different natural resources to maintain a positive scope for growth and reproduction (SFG).

Oxygen consumption of the sandy-beach whelk Bullia digitalis meuschen at different levels of activity

Abstract 1. 1. O 2 consumption of suspended Bullia digitalis is not related to water current speed or degree of turbulence, where these are kept constant. 2. 2. The highest levels of O 2 uptake at 15°C are obtained by producing fluctuating surges of turbulence, the animals responding to changes in the movement of water. 3. 3. In buried animals O 2 consumption decreases with time in the absence of water movements. 4. 4. Burrowing and surface crawling require less energy than transport in the surf.

Clearance and yield of bacterioplankton and particulates for two suspension-feeding infaunal bivalves, Donax serra Röding and Mactra lilacea Lam

Abstract Estimates of clearance rate and retention efficiency of bacterioplankton and natural particulates were used to calculate the yield as C and N to two suspension-feeding infaunal bivalves. Mactra lilacea resides subtidally in a lagoon dominated by saltmarsh detritus whereas Donax serra inhabits the surf zone of sandy beaches where suspended material is mainly phytoplanktonic in origin. Concentrations of POC in the lagoon were 1105μ C · I −1 compared with 1637 μg C ·I −1 at the beach. Bacterioplankton (5−6 × 10 6 · m 1 −1 ) comprised ≈7% of this C in both environments. Maximum clearance of particles (0.771· h −1 g · −1 ) with 100% retention efficiency by Mactra occurred in the range of 10.98–12.01 μm diameter. Smaller particles (1.4–1.7 μm) were only retained with 54.2% efficiency and even smaller bacterioplankton with 6.6% efficiency. Particles between 4.8 and 6.9 μm were cleared (0.921· h −1 · g −1 ) and retained most efficiently (100%) by Donax whilst, like Mactra , retention of bacterioplankton was poor (8.4%). Potential yield relative to resource availability indicated that a 1-g Mactra is capable of exploiting 65% of the POC · h −1 and 62% of the total N available. Donax s capability compares at 82 and 76%, respectively. For both species, the low bacterial C ( Donax was assessed as 311.97 μg C · h −1 · g −1 ; this represents 22% of the total C yield (1439.08 μg C · h −1 ) to the animal from surf-zone particulates. For Mactra , minimum C requirements fell between 145 and 645 μg C · h −1 . Based on routine metabolic rates, this represented 59% of the total potential C yield (769.87 μg · h −1 ). Free-living bacteria are, therefore, not a significant trophic resource for either species. Larger particles, which comprise the bulk of natural resources were best utilised. C requirements based on measured O 2 consumption rates and absorption efficiencies approximate to 50% of estimated C yield · h −1 . There is, therefore, considerable scope for growth and reproduction for both bivalves under favourable conditions. Donax may, however, be food limited during summer while Mactra may be more limited in winter.

Feeding, assimilation, and scope for growth in the scavenging sandy-beach neogastropod Bullia digitalis (Dillwyn)

Abstract Ingestion rates, absorption efficiency, and excretion rates in the scavenging sandy-beach gastropod Bullia digitalis (Dillwyn) were measured in the laboratory using bivalve tissue as food. A clear distinction was made between time spent feeding and the duration of the postfeeding phase. Intake of a meal was completed within l h and the period before the next meal was 7–10 days. All data were fitted to allometric equations to describe the relationship between physiological rates and body sizes ranging from 16 to 1000 mg dry tissue weight. The daily ingestion rate was described by IR (mg dry wt · day−1) = 0.34 W0.64 and excretion rates as U (μgNH4-N · h−1) = 1.03 W0.58. Absorption efficiency was independent of size and meaned at 88 %. Published respiration rates were recalculated as IR (μg O 2 · h −1 ) = 12.31 W 0.60 . All energy data were converted to Joules and used to construct a daily energy budget for a size range of Bullia in which the absorbed ration was balanced against the cost of excretion and respiration. All sizes maintained a highly positive scope for growth. Most of the energetic expenditure is due to aerobic respiration, followed by growth and reproduction and then excretion. Adult Bullia show the highest efficiency in converting ingested energy into tissue and this may be associated with the prevailing reproductive condition of adults. The need to be specific in expressing ingestion rates for marine carnivorous gastropods in publications is emphasized.

The burrowing habit of marine gastropods

Publisher Summary This chapter throws the attention on the burrowing habit of marine gastropods. Gastropods are primitively adapted for locomotion over hard substrata many genera having a wide pedal sole that may act both as a locomotors surface and as a holdfast. The mechanism used in burrowing by gastropods also exhibits convergence with burrowing Bivalvia. Burrowing by gastropods is essentially a continuation of surface locomotion obliquely into soft substrata, as occurs in a number of prosobranch families, for example, Naticidae, Cassidae, Olividae, and Nassariidae. In many gastropods, the repeated small pedal waves passing over the sole of the foot, observed in locomotion over hard surfaces have been replaced by a discontinuous stepping motion, somewhat analogous to loping in the pulmonate Helix, which allows greater force to be brought to bear, provided that the stationary part of the foot is securely anchored. Furthermore, the ability to burrow requires only the development of a stepping mode of locomotion but subsequent modifications to the foot and shell improve performance. It is, perhaps, somewhat surprising that so many burrowing gastropods have the ability to burrow only slowly.

Effects of temperature on oxygen consumption in two closely-related whelks from different temperature regimes

The rate of oxygen consumption of the sandy-beach whelk Bullia rhodostoma Reeve from Muizenberg, on the east coast of the Cape Peninsula, South Africa, has been measured at two levels of activity at temperatures between 5 and 40 °C. This rate is temperature-dependent throughout the range, unlike that of B. digitalis (Dillwyn) from the west coast, although the relationship tends to be linear rather than logarithmic. The rate-temperature curves at all levels of activity are lower in summer than in winter, indicating the presence of temperature acclimation, again unlike B. digitalis. The rate of consumption also increases up to a higher temperature in B. rhodostoma than in B. digitalis. These marked differences between the two species may be correlated with the different temperature regimes of which the animals are characteristic and, in particular, with the extreme and rapid fluctuations in temperature to which the west coast is subject, as compared with the Peninsulas east coast. Differences in food availability and in the behaviour of the animals may, however, be significant additional factors in determining their distribution.

Contact chemoreception by the propodium of the sandy beach whelk Bullia digitalis (Gastropoda: Nassariidae)

1. 1. The leading edge (propodium) of the foot of Bullia is shown to be active in contact chemoreception, food extracts applied directly to the epithelial surface stimulating eversion of the proboscis. 2. 2. A number of amino acids are also effective in evoking this response, while trimethylamine, to which the osphradium is sensitive, is not. Concentrated sugar solutions evoke some response but are probably unimportant under field conditions. 3. 3. None of the above solutions applied to the metapodium, anal cirri or cephalic shield produces a positive response.

ACUTE METABOLIC RATE: TEMPERATURE RELATIONSHIPS OF INTACT AND HOMOGENIZED BULLIA DIGITALIS (GASTROPODA, NASSARIIDAE)

SUMMARY The results of experiments to determine the temperature relationships of the active rate of oxygen uptake in the whelk Bullia digitalis are reported. These are compared with previously published data on the temperature relationships of ‘inactive’ and controlled activity routine rates. At all levels of activity the rate of oxygen consumption of intact animals is markedly temperature independent over the range 10 to 20 °C. This contrasts with results gained on the oxygen uptake of whole body tissue homogenates, the latter being temperature dependent. Possible explanations for this difference are discussed and proposals made for further research on the control of metabolism in this species.