Observations on the biology of the trochid gastropod Austrocochlea constricta (Lamarck) (Prosobranchia). I. Factors affecting shell-banding pattern

The intertidal trochid gastropod Austrocochlea constricta (Lamarck) has a variable pattern of banding, the shell ranging from white with fine black stripes, to completely black. The patterns may be classified into six arbitrarily chosen types. Populations were studied on three shores chosen to represent the range of habitat of the species (from estuarine to open coast localities) to determine the relative importance of environmental factors on shell-banding. The densities and proportions of the population in different stripe-classes were estimated from quadrat samples on the three shores. Analysis of size-frequency distributions indicates recruitment to be continuous. In all months, juveniles were at greater densities at the upper level of the distribution of the species on open coast and estuary-mouth platforms; the estuarine population was uni modal in size-frequency distribution. Growth rates of caged animals were higher on the open coast than in the estuary, and changed in animals transferred between the two localities, but did not differ between animals of different banding pattern. The proportion of the population in each stripe-class was constant on each shore, suggesting large scale selection processes do not cause the observed differences in frequencies of each banding pattern.The concentrations of the major shell pigment, uroporphyrin I, varied between stripe-classes and, within classes, between shores, with a trend for more densely pigmented shells on the open coast, a trend also evident for the proportion of the population in the darker stripe-classes. Caged animals transferred from the open coast to the estuary showed changes in banding pattern which were consistent with the differences in pigmentation of the two populations. Animals transferred from the estuary to the open coast changed pattern at the same frequency as controls from the open coast; a result of severe storms which caused the open coast population to show changes of banding pattern.It is concluded that shell-banding patterns in A. constricta are primarily governed by environmental factors.     

Extrinsic and intrinsic influences on the phylogeography of the Austrocochlea constricta species group

Although extrinsic factors, such as oceanic currents and isolation induced by sea level maxima during Plio-Pleistocene glacial cycles, are often suggested as principal determinants of marine phylogeography, they are not always complete explanations. The counterexamples to predominant phylogeographic patterns in southeastern Australia suggest for example, that intrinsic factors such a habitat preference or reproductive mode can have significant influence.We collected DNA sequences from mitochondrial cytochrome c oxidase I (COI) and two nuclear gene introns from the Austrocochlea constricta species group to determine whether its porcata and constricta phenotypes are genetically distinguishable, to examine the phylogeographic effects of the Bassian Isthmus landbridge formed between Tasmania and Victoria during glacial maxima, and to investigate the importance of intrinsic factors in structuring its genetic variability.No fixed genetic differences between the porcata and constricta phenotypes were identified in any gene so the number of species comprised by the group cannot yet be determined. The two major clades recovered in COI analyses were respectively found principally east or west of the Bassian Isthmus. A. constricta is the first lecithotrophic or estuarine invertebrate known to show this pattern. There were no fixed differences, for any of the three genes, between specimens from estuarine and marine populations within either the eastern or western COI clades. Other intrinsic factors such as breeding period (possibly) and larval type (probably) may play roles in modulating phylogeographic patterns.     

Comparative studies on the biology of nerita atramentosa Reeve, bembicium nanum (Lamarck) and cellana tramoserica (Sowerby) (gastropoda: Prosobranchia) in S.E. Australia

Populations of three coexisting intertidal gastropods, Nerita atramentosa Reeve, Bembicium nanum (Lamarck) and Cellana tramoserica (Sowerby), were sampled from a shore in Botany Bay, New South Wales, from July 1972 to September 1973. The recruitment and growth rates of each species were analysed from size frequency distributions. Mortality of each age cohort, and longevity, were estimated from analyses of the densities of Nerita atramentosa and Bembicium nanum.Nerita atramentosa showed no significant mortality during the first two years on the shore, but high mortality (at an instantaneous rate of 0.084 deaths/individual/month) after reaching the age of reproductive maturity, which was 20 months from settlement and at a mean shell-length of 13.5 mm. No growth could be detected after reproductive maturity was reached. Longevity of N. atramentosa was estimated as 3–5.5 years. Bembicium nanum juveniles showed higher mortality (at an instantaneous rate of 0.233 deaths/individual/month) than reproductively mature animals (0.060 deaths/individual/month). Reproductive maturity was reached at a mean shell-breadth of 11.0mm, i.e., about ten months after settlement on the shore. Longevity was estimated as from 4–8 years. Cellana tramoserica showed different growth patterns depending on the time of settlement.The three species showed different patterns of growth and life history relating to variable recruitment (which was demonstrated in all three species) and different rates of mortality of age cohorts.     

Extinction of the trochid gastropod,Umbonium (Suchium) moniliferum (Lamarck), and associated species on an intertidal sandflat

On an intertidal sandflat in western Kyushu, Japan in 1979, the trochid gastropod,Umbonium (Suchium) moniliferum (Lamarck), and the thalassinidean ghost shrimp,Callianassa japonica Ortmann, densely inhabited the lower and upper zones, respectvely.Callianassa japonica subsequently expanded its distribution range considerably, having occupied almost the entire sandflat by 1983. Concurrently, theU. moniliferum population gradually declined, becoming extinct in 1986. Furthermore, the populations of 9 species associated withU. moniliferum (predators, an ectoparasite, and subsequent inhabitants of emptyU. moniliferum shells) had disappeared by the end of 1992. The extinction processes ofU. moniliferum and the two other most numerically dominant species, the ectoparasitic gastropod,Odostomia sp., and the hermit crab,Diogenes nitidimanus Terao, were described in detail. It is believed that the bioturbation of sediments byC. japonica was responsible for the extinctions, possible mechanisms involved being discussed. This is the first documented record of the extinction of a large part of a macrobenthic assemblage centering on a filter-feedingUmbonium species which is characteristic of the benthic communities on many intertidal sandflats extending from Japanese to Southeast-Asian waters.     

The feeding biology of Hydrobia ventrosa (Montagu). I. The assimilation of different components of the food

The assimilation efficiencies for 7 species of diatoms, two of blue-green algae, and one bacterium have been measured in the deposit-feeding prosobranch Hydrobia ventrosa (Montagu). Two methods have been used, a chemical and a radiotracer one.The results of the first method were difficult to evaluate due to the fact that the time taken to clear the gut is ill-defined. The second method gave more consistent results.All diatoms are assimilated efficiently (60–71 %) as is the bacterium (about 75 %). The blue-green algae are less efficiently utilized; an Oscillatoria sp. was assimilated with an efficiency of about 50 % whereas a Chroococcus sp. was only assimilated with an efficiency of 8 %. It is concluded that resource partitioning based on differential utilization of micro-organisms cannot play an important rôle in the co-existence of Hydrobia ventrosa with other deposit-feeders.     

Catadiscus pomaceae sp. n. (Trematoda, Paramphistomatidae) from Pomacea canaliculata (Lamarck, 1801) (Prosobranchia, Ampullariidae).

Catadiscus pomaceae sp. n. from the intestine of the prosobranch mollusc Pomacea canaliculata (Lamarck, 1801), is described. The host snail was collected from a lenitic biotope belonging to the Riachuelo basin (Corrientes province, Argentina) during 1985-1986. So far the species of the genus Catadiscus Cohn, 1904 have been recorded in amphibians and reptiles. This is the first instance of a species of that genus parasitizing a mollusc.     

Acetylcholinesterase in the brain of the marine gastropod Murex trunculus L. (Prosobranchia). Isolation and properties

• 1.1. Cholinesterase (ChE) of two types—acetylcholinesterase (AChE, acetylcholine hydrolase, EC 3.1.1.7) and propionylcholinesterase (PrChE, acylcholine hydrolase, EC 3.1.1.8)—was found in the brain of the marine gastropod Murex trunculus L. (Prosobranchia).
• 2.2. PrChE is a soluble enzyme which can be easily extracted by salt solution after freezing-thawing of the untreated brain.
• 3.3. AChE is membrane-bound. It was solubilized by a 0.2% solution of Triton X-100.
• 4.4. Some part of AChE (up to 36%) can spontaneously pass into solution.
• 5.5. The specific activity of AChE in Triton X-100 extracts is 100 ± 10 nmol acetylcholine/mg protein/min.
• 6.6. Enzyme hydrolysis of acetylcholine (ACh), acetylthiocholine (ATCh) and propionylthiocholine (PrTCh) is suppressed by excess of substrate. Michaelis constants (K_m) for their hydrolysis by AChE are 0.33, 0.017 and 0.018 mM, respectively.
• 7.7. Bimolecular rate constants with organophosphorus inhibitors of different structure points to a similarity of the gastropod brain AChE to the typical enzyme of vertebrates in the structure of the active surface.

     

The effect of the quality of food patches on larval vertical distribution of the sea urchins Lytechinus variegatus (Lamarck) and Strongylocentrotus droebachiensis (Mueller)

Although most invertebrate larvae are weak swimmers and act as passive particles on horizontal scales, they may be able to regulate their vertical position in response to different factors, including increased food concentration. We examined the effect of the quality of food patches on larval vertical distribution for the sea urchins Lytechinus variegatus and Strongylocentrotus droebachiensis, and determined the effect of dietary conditioning on that response in the laboratory. We reared larvae on a mixed algal diet of Dunaliella tertiolecta and Isochrysis galbana under low (500 cells ml⁻¹) and high (5000 cells ml⁻¹) rations. Food patches were maintained in Plexiglas rectangular columns (30×10×10 cm) using a density gradient, where practical salinity in the bottom layer was 33, in the middle layer 30, and in the top layer 27. We examined the magnitude and mechanism of a behavioural response of larvae of L. variegatus in the four-arm stage, and on two developmental stages of S. droebachiensis (four- and six-arm), by manipulating patch quality. In the absence of a patch, larvae of both species and developmental stages swam through to the surface of the experimental columns. In the presence of algae, fewer larvae were present above the patch and more were at the patch than in control columns. More larvae swam through patches of “unflavoured” algal mimics than algal patches, and aggregated at the surface. Larval distribution relative to patches of algal filtrate without algal cells or of “flavoured” algal mimics in algal filtrate was not consistently different from that in either control or algal patches; thus, the magnitude of larval response to filtrate (with or without particles) was intermediate between that to control and algal patches. For L. variegatus, more larvae crossed the patches when reared on low than high rations, indicating that poorly conditioned larvae may be less responsive to environmental cues. Our results suggest that larvae can actively aggregate and maintain a vertical position in response to a food patch that depends on the quality and quantity of food. The response appears to be based mostly on a chemosensory rather than a mechanosensory mechanism.     

Oxygen consumption and aspects of energetics in a Malaysian population of Natica maculosa Lamarck (Gastropoda) feeding on the trochacean gastropod Umbonium vestiarium (L.)

Oxygen consumption in sea water increased with size and tissue weight of Natica maculosa Lamarck at ambient temperatures (28–29.5 dgC) and salinities (31–32‰) in a fashion comparable with other naticids. When measured in submerged shore sand, oxygen consumption resembled that in sea water among smaller and some larger Natica but was much lower in several larger snails. Even using the higher measurements, respiration accounted for a remarkably low proportion of the energy consumed in Umbonium prey, and this also matches previous findings with Polinices. Limited observations indicate that production of egg collars may account for > 30‰ of the consumption in adult females. Estimation of faeces and mucus were, however, unsuccessful. It is suggested that respiration in nature might be higher than recorded hitherto because of high metabolic costs and very long duration of drilling the shelled prey.     

The selective advantage of avoidance of the predatory whelk Lepsiella vinosa (Lamarck) by Littorina unifasciata (Philippi)

The herbivorous snail Littorina unifasciata (Philippi) is widely distributed, and different species of predatory whelks occur in different parts of its range. At Coobowie, South Australia, L. unifasciata coexists with and avoids Lepsiella vinosa (Lamarck), while at Portobello, New Zealand, Littorina unifasciata similarly coexists with and avoids Lepsiella scobina albomarginata (Deshayes). By transporting Lepsiella vinosa from Coobowie to Portobello it was shown that Littorina unifasciata from the latter population did not avoid this foreign species but were captured, drilled and eaten by it.     

A laboratory study on the short-term zonal oscillations of the trochid Monodonta turbinata (Born) (Mollusca: Gastropoda)

Zonal oscillations of Monodonta turbinata (Born) were monitored with an actographic device which precluded clustering behaviour. Unfed snails maintained their cyclic pattern of behaviour for up to 8 days under a light-dark cycle which simulated the natural one. Under constant conditions of light or dark, however, the snails ceased migration and occupied a zonal position typical of day and night, respectively. Experiments in diffuse light and with light from below the floor of the experimental tank showed that the downward migration of M. turbinata in the daytime depends on positive geotaxis combined with negative phototaxis whilst the upward migration at night depends on a negative geotaxis. This mechanism is similar to that described in other littoral molluscs. There was no evidence of an endogenous control of rhythmic zonal activity.     

Temperature effects on calcification rate and skeletal deposition in the temperate coral, Plesiastrea versipora (Lamarck)

The geographic range of the coral, Plesiastrea versipora (Lamarck, 1816), extends into temperate waters outside the southern limit for hermatypic corals. In the present study, calcification in Plesiastrea collected from Port Phillip Bay, Victoria was examined over the coral's normal annual temperature range (10-21 °C), which is well below the normal optimum for coral calcification in tropical corals (25-28 °C). Calcification rate in Plesiastrea was considerably lower than in reef corals, but showed a similar pattern in temperature responses, with a trend towards higher rates at ∼18 °C. The light/dark calcification ratio was markedly lower than that in tropical corals. Autoradiography showed that calcification occurred primarily by deposition of calcium carbonate at the upper surfaces of the septo-costae. Scanning electron microscopy (SEM) showed that skeletal deposition in Plesiastrea had a temperature-dependent diel pattern. In the light, calcium carbonate was deposited as small spheroidal crystals and, at higher temperatures, small needle-shaped crystals. In the dark, calcium carbonate deposition appeared to be in the form of an amorphous sheet-like cementation. Compared with other scleractinian corals, calcification rate in Plesiastrea was relatively slow and showed different patterns of skeletal deposition.     

The effect of temperature-salinity combinations on the functional well-being of adult Lytechinus variegatus (Lamarck) (Echlnodermata,Echinoldea)

The activity coefficient (1000/righting time in sec) was measured to indicate the functional state of Lytechinus variegatus (Lamarck) after exposure to combinations of temperature (22°, 28°, and 34°C) and salinity (25, 30, 35, and 40 ‰). Environmental levels of these variables were 30–33°C and 34–35 ‰. The results indicate that the species lives closer to the upper than lower lethal limits of temperature and salinity. The maximal activity coefficient (18 ± 8) was at 28°C and 35 ‰. A reduction in salinity was probably responsible for a recent mass mortality of the echinoid reported in the eastern Gulf of Mexico.     

Reproductive patterns within sub-populations of Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea)

The annual reproductive cycle of the sea urchin Lytechinus variegatus (Lamarck) was examined in individuals collected from four habitats in the Anclote estuary near Tarpon Springs, Florida. Two periods of advanced gametogenic activity were apparent, but this bimodal pattern was not necessarily reflected by gonad growth curves. Differences in reproductive events among sub-populations were related primarily to patterns of gonad growth. Reproductive synchrony present during spring became less apparent as spawning and recovery within the sub-populations took place at differential rates during late-spring and summer. The final spawnout in late summer returned the sub-populations into gametogenic synchrony.     

Observations on the biology of Boschniakia hookeri (Orobanchaceae)

Observations on Boschniakia hookeri Walp. (Orobanchaceae), a root parasite, have been carried out at locations on the Kitsap Peninsula, Washington State, U.S.A.; Bamfield, British Columbia, Canada; and Sand Lake, Tillamook County, Oregon State, U.S.A. The hosts of B. hookeri , all Ericaceae, identified by excavation of the host root–parasite connection, were Arbutus menziesii Pursh., Gaultheria shallon Pursh., Arctostaphylos uva–ursi (L.) Spreng., and an introduced South American species, Pernettya mucronata Gaud. Seasonal development above ground and recurrence of blooming were monitored. It was shown that the plants are autogamous. Predation plays an important role in the biology of Boschniakia hookeri , including infestation by nematodes, destruction of entire plants by rodents, and attack on the inflorescences by a fly, Pegomya sp. A life history of Boschniakia hookeri was assembled from the data of this study.     

Observations on the reproductive ecology of Thalassia testudinum (Hydrocharitaceae) II. Leaf width as a secondary sex character

Short-shoots of Thalassia testudinum Banks ex König were collected from 5 sites in Florida. A total of 284, 625-cm² quadrat samples, containing 6182 shhort-shoots was analyzed for leaf width, inflorescence number and sex (the latter if determinable). Although leaf widths and reproductive densities differed at the 5 sites, leaf width was consistently greater when reproductive structures were present, and when the number of inflorescences increased. The mean number of inflorescences per short-shoot was significantly higher for shoots bearing male inflorescences compared to female shoots. Female inflorescences were normally solitary; male short-shoots usually had 2 or 3 inflorescences. Sex ratios were male-biased for 4 of the 5 sites. Comparisons of leaf widths between the sexes indicated that leaf width constituted a secondary sex character for this species. Female short-shoots tend to have narrower leaves than male short-shoots. This relationship should also be considered when evaluating the significance of morphogeographic and stress-related variation in leaf width for this species.     

Observations on the in vitro culture of Cotylurus erraticus (Trematoda: Strigeidae)

Mtitchell J. S., Halton D. W. and Smyth J. D. 1978. Observations on the in vitro culture of Cotylurus erraticus (Trematoda: Strigeidae). International Journal for Parasitology8: 389–397. Cotylurus erraticus metacercariae obtained from around the heart of rainbow trout were excysted and grown in vitro and in vivo to egg-producing adults. For in vitro development, tissue culture media M199 or NCTC 135 was used, together with varying amounts of chicken serum. Worms grown in media containing the highest concentration of serum (80% per volume) showed the fastest rate of development, measured by the time taken for the first eggs to appear in the uterus. The testes, ovaries and vitellaria of these worms were comparable in structure and histochemistry with those of worms reared in gulls. Eggs were produced by worms in all media containing chicken serum, but the eggs had abnormal shells and failed to embryonate.