Relationship between heart rate and oxygen consumption in the intertidal limpets Patella granularis and Siphonaria oculus

• 1.1. Aerial heart rate and _O2 linearly correlated for Patella granularis and Siphonaria oculus when these parameters were varied by changing ambient temperature. This relationship for P. granularis was significantly transposed above that for S. oculus.
• 2.2. While prolonged aerial exposure (+24hr) lowered the curve for heart rate against _O2 for P. granularis below that determined over short-term exposure (< 12 hr), it had no significant effect on this relationship for S. oculus.
• 3.3. The correlations of heart rate and oxygen consumption are discussed in terms of functioning of the circulatory system and the predictability of one parameter from the other.

     

Size at sex change and reproductive cycle of the limpets Patella vulgata and Patella ulyssiponensis (Mollusca: Patellogastropoda) from intertidal rocky shores of the Algarve coast (southern Portugal)

ABSTRACT

This study describes the reproductive cycle of the common limpet (Patella vulgata) and rough limpet (Patella ulyssiponensis) from the Algarve coast (southern Portugal). Individuals of both species were sampled monthly during two consecutive years, and subjected to gonad histology and calculation of the mean gonadal index (GI). Both species had balanced sex ratios (P. vulgata = 1M: 0.98F; P. ulyssiponensis = 1M: 1.03F), similar size-frequency distribution between sexes, and equivalent mean shell lengths (SL) and total weights (TW) between males and females. In these protandrous hermaphrodites, the estimated size at sex change was slightly smaller in P. vulgata (SL₅₀ ≈ 29 mm) than in P. ulyssiponensis (SL₅₀ ≈ 36 mm). The reproductive cycles of both species were characterised by a main spawning season in early spring to early summer, sometimes including subsidiary spawning events. A comparison of the main spawning season throughout the species distributional ranges revealed that populations of P. vulgata and P. ulyssiponensis from southern Portugal have later spawning periods than other populations from the northeastern Atlantic Ocean. The present information is relevant for conservation purposes and for the proposal of management measures for the harvesting activity targeting P. vulgata and P. ulyssiponensis in southern Portugal.     

Hemolymph ferritin and radula structure in the limpets Patelloida alticostata and Patella peronii (Mollusca: Gastropoda)

• 1.1. The mean concentration of total hemolymph iron was 3060μg/100 ml in Patella peronii and 2950μg/100 ml in Patelloida alticostata.
• 2.2. Ferritin was found to act as a major iron-binding protein in the hemolymph of both P. peronii and P. alticostata.
• 3.3. P. alticostata ferritin has a molecular weight of approximately 505,000, while that of P. peronii has a mol wt. of approximately 520,000.
• 4.4. The lateral radula teeth of both species are mineralized by deposits of silica (SiO₂) and iron in the form of goethite (α-FeOOH).
• 5.5. Hemolymph ferritin is suggested to act as a high capacity transport system to supply iron to the mineralizing front of the radula.

     

Field experiments on population regulation in intertidal limpets of the genus Acmaea

Summary The numbers of limpets on pier pilings in the intertidal zone were reduced to almost zero and increased to almost double the numbers on control pilings to determine if densities are regulated. Densities on experimental pilings returned to that of control pilings in 3 and 8 months in two experiments. Mechanisms which could explain this readjustment of densities include density dependent vertical migration, cannibalism of newly settled young and the selection of suitable substrate by larval limpets.     

Desiccation of intertidal limpets: Effects of shell size,fit to substratum,and shape

For undisturbed, field populations of the northeast Pacific, intertidal limpet Collisella pelta (Rathke), water loss was found to be proportional to apertural circumference rather than mantle cavity surface area. This contrasts with previous laboratory measurements for other limpet species and emphasizes the importance of the fit of shell to substratum for non-homing limpets. This close fit maintained a meniscus of water between the edge of the shell and the substratum, thereby reducing evaporative surface area and increasing the advantage of large size for reducing the rate of water loss. Shell-raising behavior eliminated the meniscus, increasing the rate of desiccation, and water loss appeared to become proportional to mantle cavity surface area. Indirect evidence suggests that C. pelta may utilize shell-raising behavior for evaporative cooling under thermally stressful conditions in the field.Both shell size and shape affect the ratio of water stores (proportional to internal shell volume) to evaporative surface area (proportional to apertural circumference) and per cent water loss is, potentially, a function of this ratio. Shape, however, (when defined as volume/circumference) exhibits an average allometric increase with increasing size (volume) for C. pelta, as well as for three other sympatric limpet species: C. Paradigitalis (Fritchman), C. Digitalis (Rathke), and Notoacmea scutum (Rathke). An independent measure of shape is, therefore, required to separate shape effects on desiccation from size effects; this measure was obtained by rearranging the allometry equation. In contrast to significant size effects, no measurable effect of shape on desiccation was detected. Variation in limpet shell shape may be partially or wholly maintained by factors other than an adaptational response to desiccation.     

The grazing effect of limpets on the macroalgal community of a rocky intertidal shore

Abstract Abundance of macro-algae in the mid-littoral zone on a Victorian intertidal rocky shore varied seasonally, algae being rare in Summer and common in Winter and Spring. Field experiments demonstrated that, of two species of grazing limpets (Cellana tramoserica and Siphonana diemenensis), only Siphonaria had a major effect on the abundance of foliose algae (e.g. Scytopsiphon lomeniarid) and neither species had a great effect on the encrusting algae (Ralfsia spp.). There was no evidence of competition for food between the two species of limpets, in contrast with results found for similar species in New South Wales.     

Effects of hyposalinity in Thalassia testudinum (Hydrocharitaceae) from Parque Nacional Morrocoy, Venezuela

The year 1996 had a high pluviosity in Morrocoy National Park (western coastal zone, Venezuela) and low salinity in December 1996 affected the seagrass beds, dominated by Thalassia testudinum. Patches without T. testudinum were observed in localities of the park that used to have very dense populations of this plant. Sampling was done at Las Luisas to determine leaf productivity, turnover rate, short shoot density and relative biomass of plant sections, in order to compare with data obtained in September 1996, previous to the event. Green leaves, roots and rhizomes were the most affected parts. Mean green leaf biomass decreased in January and February 1997 to 5% of the plant's total biomass; mean root biomass decreased in March to 40% and mean rhi zome biomass decreased in February to 30%. The density of the active short shoots decreased to a minimum in February, but in April it reached a value similar to that of September 1996. The density of the inactive short shoots decreased to a minimum in March, and they dissappeared in April, matching the increasing density of the active short shoots between these two months. In February 1997, 56% of the inactive short shoots showed evidence of leaf initiation. In January 1997 the leaf productivity and turnover rate values (2.72 +/- 0.35 g/m2/d and 2.15% leaf DW/d) were similar to the annual mean previously determined from Las Luisas (2.35 +/- 0.72 g/m2/d and 1.96% leaf DW/d). Nevertheless, the values of productivity and turnover rate detected at Las Luisas in April 1997 (4.88 +/- 2.14 g/m2/d and 4.66% leaf DW/d) were higher than those values previously reported for this location. In response to the mortality episode, the leaf productivity and turnover rate of T. testudinum increased and the leaf initiation was activated in the inactive short shoots.     

Effects of experimental manipulations on the life history pattern of Lymnaea stagnalis appressa say (pulmonata: lymnaeidae)

Field sampling of an Iowa population of Lymnaea stagnalis appressa Say indicated an annual generation pattern, with survivorship to maturity of i percent or less. Estimates of adult fecundity ranged from about 300 to 800 eggs.Density and food manipulations were performed to determine whether density dependent limitation of growth rates, maturation, or fecundity occurs in this fresh water pulmonate snail. Addition of a high quality food resource, spinach, accelerated growth rates, but did not drastically accelerate maturity, nor increase fecundity. Density increments lowered growth rates, delayed maturity, and lowered fecundity, and the addition of spinach did not counteract high densities. Adult densities are fairly low in the field population, and adults are randomly dispersed, indicating little density dependent regulation of fecundity in this population. However, the low survivorship to maturity, response in growth rates with food addition, and increasing survivorship with age and size indicate that juvenile mortality may play an important role in structuring life history patterns in this population.     

Ecology of Physaloptera capensis (Nematoda : Spiruroidea) infecting the Springhare Pedetes capensis (Mammalia) in Botswana

Incidence and intensity of the stomach nematode Physaloptera capensis in relation to the age, sex, reproductive status, physical condition, density and habitat of its host, the Springhare, were investigated in the Republic of Botswana (August 1971-August 1973). All data indicate that this nematode is a benign parasite of the Springhare. Infections were not randomly distributed within the Springhare population. Mean number of worms per Springhare was 83 and 34% of all Springhares were parasitized. Adults, females and lactating females showed significantly heavier infections than juveniles, males and non-lactating females, respectively. Infection was directly associated with the amount of grass cover in the Springhares' habitat but independent of the density and physical condition of Springhares. Possible causes of differences in rates of infection among Springhares of different age/reproductive classes and from populations of different density are mentioned. It is suggested that numbers of P. capensis may be regulated mainly by density-independent environmental factors operating upon rates of transmission.     

The ultrastructure of the spermatheca of Biomphalaria glabrata (gastropoda,pulmonata)

A study of the ultrastructure of the spermatheca of virgin freshwater snails Biomphalaria glabrata, kept in isolation since hatching, and in freely mating individuals maintained in colonies, shows that the spermatheca, an accessory organ of the female genital tract of pulmonate snails, is a pear-shaped blind pocket, lined with a single-layered columnar epithelium, surrounded by a thin muscle and pigmented connective. The apex of each epithelial cell may be ciliated, whereas the basis lies on a thick basement membrane. In virgin snails the spermatheca is smaller, its lumen contains a gelatinous, amorphous material; the apex of the epithelial cells contains many mitochondria but few granules. The nucleus appears in the basal third of the cell, topped by the Golgi complex and endoplasmic reticulum elements. In snails which have mated, the spermatheca is swollen, with a somewhat distended lower epithelium; its lumen contains numerous spermatozoa, in various degrees of degradation, which increases with the passage of time after copulation. The apex of the epithelial cells becomes very rich in granules with varied content, including multivesicular bodies. The latter are apparently exocytosed. Pinocytosis occurs at the base of microvilli. Glycogen can be seen accumulating in some cells. Tubular structures, ca. 60 nm in diameter, arranged regularly within the endoplasmic reticulum elements, could occasionally be seen at the basal part of the epithelial cells. It is suggested that the multivesicular bodies may contain enzymes which are secreted to the lumen. The partially digested sperm material would then be absorbed by micropinocytosis, and further digested in the secondary phagosomes at the apical portion of the epithelium.     

Coping with aquatic hypoxia: how the plainfin midshipman (Porichthys notatus) tolerates the intertidal zone

Although plainfin midshipman (Porichthys notatus) are primarily known for their alternative reproductive tactics, and the dimorphic male subtypes, in which Type-I males demonstrate parental investment and mate attraction, and Type-II males ‘sneak’ fertilization and show no investment after fertilization, little is known about the physiology and tolerance to low aquatic oxygen while nesting in the intertidal zone. In May 2007, females and Type-I and Type-II males were collected, and in June 2009, only Type-I males were collected from nest sites on the coast of Vancouver Island, British Columbia. In the 2007 season, an initial assessment of hypoxia tolerance and nest parameters was recorded for the three subtypes of midshipman. Historical evidence indicates that Type-I males remain on the nest for prolonged periods, and our results suggest they can cope with repeated bouts of aquatic hypoxia by elevating their hematocrit and tolerating high lactate levels. The 2009 season was directed at examining the aquatic hypoxia tolerance of only the Type-I male. Hypoxic (~15 % air saturated water) Type-I males had oxygen consumption rates at ~12 % of the normoxic control (~100 % air saturated water) and a P_crit, the critical oxygen tension, when a fish switches from oxyregulator to oxyconformer, could not be determined; an indication that these fish are solely oxyconformers. With prolonged exposure to aquatic hypoxia, Type-I males displayed significant elevations in plasma and tissue lactate (heart), tissue glucose (liver), and a depression in gill Na⁺/K⁺ATPase and catalase activities. Results suggest that male Type-I midshipman survival in the intertidal zone is enhanced by metabolic depression and tolerance to anaerobic byproducts.     

Ultrastructure of the osphradium of Siphonaria grisea (Mollusca, Pulmonata)

By means of scanning and transmissive electron microscopic methods osphradium of Siphonaria grisea has been studied. The osphradium of the animal is presented as a small torulus formed by supporting ciliated cells. Among them bodies of receptory cells are situated; they are of smaller size and decorated with a bundle of microvilli. Central processes of the receptory cells, penetrating through a thick layer of the connective tissue, reach the subepithelial neural trunk. Concentration of the neural cells in the periphery of the trunk is small, and in the central area no chemical synapses are revealed. The data presented demonstrate a primitive structure of the osphradial chemoreceptory organ in Siphonaria.     

Anatomy and affinities of pseudococculinid limpets (Mollusca, Archaeogastropoda)

The anatomy of 12 pseudococculinid species, representing the two subfamilies and 10 (of 11 known) genera, is described in detail. Three new genera are erected, Yaquinabyssia, Copulabyssia and Amphiplica. Subfamilial and generic systematics are reconsidered and additionally based on anatomical characters. Characters defining subfamilies and genera (Pseudoeoeculininae: Pseudococculina, Notocrater, Tentaoculus, Mcsopelex, Bandabyssia, Kurilabyssia; Caymanabyssiinae: Caymanabyssia, Colotrachelus, Yuquinabyssia, Copulabyssia, Amphiplica) are the modifications in shell and radula, the number and arrangement of gill-leaflets, the size of the pedal gland, the degree of eye-reduction and the modifications of the seminal groove and of the copulatory organ. Separation of the Pseudococculinidae Hiekman, 1983 from the Cocculinidae Dall, 1882 at the superfamilial level is confirmed by great differences in their anatomy. Whereas the Cocculinidae are closely related to the Bathysciadiidae (Cocculinoidea). the Lepctcllidae, Pyropeltidae, Pseudococculinidae,? Bathyphytophilidae, Osteopeltidae, Cocculinellidae, Addisoniidae and Choristellidae form a clearly separated supcrfamily (Lepetelloidea). Both superfamilies compose the Cocculiniformia. a primitive but highly specialized arehaeogastropod suborder.     

“Nodules” in the achiasmatic meiosis of Bithynia (mollusca,prosobranchia)

In spermatocytes of Bithynia leachi and B. tentaculata, synaptonemal complexes with nodules in an achiasmatic meiosis were demonstrated for the first time by means of the spreading technique. The number and position of the nodules are different in each species and are independent of the length of the chromosomes. Although no crossing over occurs in Bithynia chiasma-like terminal connections of the chromosomes are preserved in diakinesis by the presence of the nodules. — Enzymatic treatments revealed information regarding their composition of alkaline proteins, RNA and DNA. In all proteolytic digestions the nodules more of less retain their position in the central region, while they disappear immediately if SCs are exposed to DNase. On the basis of the results a model of the composition and the function of nodules can be developed considering the concept of a lampbrush-organization of the chromosomes in early meiotic prophase.