Comparative study of two largely infilled estuaries: The Eden Estuary (Scotland) and the Ria de Foz (Spain)

Two small estuaries, the Eden Estuary of eastern Scotland and the Ria de Foz of north west Spain, are compared. The former was glaciated during the Pleistocene, the latter was not. These water bodies are macrotidal, of similar size, entrance morphology and advanced state of sedimentary infill. There are, however, major differences in their sedimentary dynamics partly as a result of anthropogenic interference. A training wall partially confines the main channel of the Ria de Foz, whereas the Eden Estuary lacks comparable structures. Prior to the extension of the Foz wall, the rate of migration of a spit at the mouth of the ria was up to one order of magnitude greater than that of a similar spit in the Eden Estuary. Following completion of the wall, the rate of spit erosion in the Ria de Foz increased to two orders of magnitude greater than that of natural processes in the Eden. A beach nourishment scheme at Foz, relocating sediment deposited within the Ria, has succeeded in stabilising the spit and substantially reducing erosion. Relative stability of land and sea may have existed over the last 5,000 years at Foz but not at the mouth of the Eden, where isostatic uplift has exceeded sea level rise. The requisite stability for complete sedimentary infill at Foz may not exist owing to the predicted worldwide rise of sea level due to global warming. The rise of sea and land levels around the Eden Estuary are now believed to be counterbalanced, providing the necessary geological conditions for complete sedimentary infill.     

Studies on the reproduction of cirripedes. I. Introduction: Copulation,release of oocytes,and formation of the egg lamellae

A brief outline is given of the sequence of events leading to the production of egg lamellae in operculate and pedunculate cirripedes.Details are given of the copulatory act as regards random and possibly directed movements of the penis; the question of mutual ‘recognition’ is discussed. The time spent by a spermatozoon in the penis is estimated. The release of ripe oocytes is described and the results of some experiments suggesting the presence of an agent suppressing their release in the earlier stage of maturation are given. It is shown that seminal plasma can induce muscle contractions and the possible significance of this is discussed.The behaviour subsequent to copulation is described. Fully motile spermatozoa are found in the mantle cavity and may be expelled in the mantle cavity current. The bulk of the semen sets to a translucent jelly which is eventually lost from the mantle cavity. The formation of this gel is due to general autolysis. The production, properties, and functions of the egg membranes and the oviducal sac are discussed.     

A demonstration of allopatric sibling species within the Gymnophallidae (Digenea)

Meiogymnophallus minutus and Meiogymnophallus fossarum n. comb. both use the oystercatcher Haematopus ostralegus as their final host and Scrobicularia plana as the primary host. M. minutus uses only the estuarine cockle Cerastoderma edule as its second host, where it occurs enclosed in mantle epithelium in a wedge-shaped cavity beneath the umbo and causes no apparent damage to the host. In contrast, the metacercariae of M. fossarum occur in a variety of microhabitats in a wide variety of lagoon lamellibranchs, including Cerastoderma glaucum. In this host it occurs free in the extrapallial fluid usually beneath the periostracum along the edges of the two valves, where it severely inhibits shell growth, and also beneath the umbo. Comparative morphology, experimental cross infections, second host and microhabitat selection, together with ecological and geographical distribution, suggest that Meiogymnophallus minutus and M. fossarum n. comb. are allopatric sibling species. The former occurs in estuaries in northern and western Europe and the latter from lagoons along the French Mediterranean coast.

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Resumé Meiogymnophallus minutus et Meiogymnophallus fossarum n. comb. admettent comme hôte définitif l'Hûitriez-pie, Haematopus ostralegus, et comme premier hôte intermédiarie Scrobicularia plana. Les métacercaries de M. minutus parasitent C. edule; elles sont entourées par des proliférations palléales à l'intérieur d'une cavité en forme de coin fichée sous la charnière du Mollusqui; elles n'ingendrent aucun dommage chez leur hôte. Par contre, les métacercaires de M. fossarum si répartisseut dans plusiers types de microhabitats, chez différents espèces de Lamellibranches euryhalins, en particulier chez C. glaucum. Chez ce dernier, les métacercaires vivent librement dans le liquide extrapalléal, souvent logées à l'intérieur du sillon périostracol bordant les lobes palléaux ce qui entraine des perturbations dans la croissance de la cofuille. On trouve aussi des metacercaries sous la charnière mais elles ni y sont jamais enveloppées. La comparaison des caractères morpho-anatomiques de ces deux espécis, les infestations éxperimentales croisées, la sélection des deuxièmes hôtes ainsi que des microhabitats, la répartition géographique et la distribution écologique suggèrent qu'il n'agit de deux espèces jumelles allopatriques. La première se répartit duos les estuaries du nord et de l'ouest de l'Europe, la seconde le long des côtes méditerraneenes francaises.

     

Morphology and biology of Polysaccus japonicus (Crustacea, Rhizocephala, Akentrogonida, Polysaccidae, fam. n.), a parasite of the ghost-shrimp Callianassa japonica

The morphology and biology of Polysaccus japonicus Høeg & Lützen, 1993 is described. Nearly all infected hosts are adults, the females of which become castrated. Each bears 4–50 (female) externae on the underside of the abdomen. The externae are interconnected via a root system within the host's perineural blood sinus. The externae pass through three moults. Cypris larvae inject spermatogonia into the immature externa's mantle cavity, which is where spermiogenesis occurs later. Multiplication of the male cells is probably supported by secretion from paired mantle cavity glands, presumably homologous to the receptacles of kentrogonid rhizocephalans. Late during the 2nd intermoult the visceral mass ruptures to release the ova into the mantle cavity where they become fertilized. The third moult results in opening of the mantle aperture which initiates a period of vigorous peristalsis of the muscular mantle. Following emission of the cypris larvae the externae perish leaving distinct scars. The root system always contains buds of various sizes and stage of development. When the scarred host moults, the most advanced buds emerge to give rise to a new generation of externae. This is thought to be repeated for the rest of the host's life.
The antennule of the cyprid has a relatively very long and slender 3rd segment, a unique construction among Akentrogonida. Because of this and the presence of special mantle cavity glands, a new family, Polysaccidae, is erected, which in some characters is intermediate between the Kentrogonida and the Akentrogonida.     

The life-cycle,ecology and host specificity of the freshwater leech Alboglossiphonia polypompholyx (Glossiphoniidae) in Egypt

Alboglossiphonia polypompholyx spends most of its life cycle endoparasitic in the mantle cavity of the snail Bulinus truncatus — possibly its only host. Adult A. polypompholyx leaves the snail about one month before the commencement of egg-laying. Hatching occurred after about 15 d and after brooding on the venter of the parent for 7–10 d, the young briefly become free-living before entering the mantle cavity of B. truncatus. Within the mantle cavity, A. polypompholyx feeds and grows for 16–20 weeks before leaving the snail as adults. In the field and in laboratory experiments, adult leeches left the snails in August/September and January with cocoons produced in October/November and February/March, respectively. Free-living adult leeches do not feed and die 1–2 months after the cessation of brooding.     

Modern insights on gastropod development: Reevaluation of the evolution of a novel body plan

More than a century of speculation about the evolutionary originof the contorted gastropod body plan has been inspired by adultanatomy and by long-standing developmental observations. Theresult has been a concept of gastropod torsion that I call the"rotation hypothesis." Under the rotation hypothesis, gastropodsoriginated when all components of the visceropallium (shell,mantle, mantle cavity with contained structures, and viscera)rotated by 180° relative to the head and foot. This evolutionaryrotation is echoed during early development of patellogastropodsand vetigastropods and occurs to some extent during developmentof more derived clades. However, comparative developmental dataon ontogenetic torsion are minimal and I argue that the rotationhypothesis is a tautological argument. More recent studies onrepresentatives from 3 major clades of gastropods suggest thatthe highly conserved aspect of gastropod development is notsynchronous rotation of all components of the visceropalliumrelative to the head and foot but rather a state of anatomicalorganization in which the developing mantle cavity is on theright but the shell coil is posterior (endogastric orientation).This conserved state of developmental anatomy has inspired analternative hypothesis for the evolutionary origin of the gastropodbody plan, the "asymmetry hypothesis." Under the asymmetry hypothesis,the gastropod mantle cavity originated from 1 side only of abilateral set of mantle cavities. The asymmetry hypothesis doesnot require a saltation event to explain the origin of gastropods,nor does it require that the ancient molluscan precursor ofgastropods carried the shell coil over the head (exogastricorientation).     

Deposit feeding in Abra tenuis (Bivalvia: Tellinacea)

Deposit feeding in Abra tenuis is described in terms of the size of particles utilized.
Material is collected by the inhalant siphon performing a circular motion sucking in sediment from beneath and on the surface.
The size distribution of silica admitted into the mantle cavity is described and shown to be controlled by physical parameters. The density of a particle does not affect its uptake by the inhalant siphon. The size distribution of the sediment affects the size distribution of particles admitted to the mantle cavity.
No selection of material for ingestion in terms of size occurs after it has been taken into the mantle cavity. Thus the range of material ingested is ultimately controlled by a physical parameter, the inhalant opening.     

Sites of encystment by the metacercariae of Echinoparyphium recurvatum in Lymnaea peregra.

Experimental infection of Echinoparyphium recurvatum von Linstow (Digenea: Echinostomatidae) cercariae in the snail second intermediate host Lymnaea peregra Müller shows that metacercarial encystment takes place on the lining of the mantle cavity, pericardial cavity and kidney lumen, with the mantle cavity the most preferred site. All three sites are accessible via the body openings. The metacercariae appear to be more susceptible to encapsulation in the visceral mass than in the cavity of the mantle, pericardium and the lumen of the kidney.     

Biology and functional morphology of the pallial organs of the Antarctic bivalve Mysella charcoti (Lamy, 1906) (Galeommatoidea: Lasaeidae)

Mysella charcoti is an Antarctic lasaeid bivalve and the most frequently encountered mollusc in Admiralty Bay, King George Island, South Shetlands. The behaviour of the species in aquaria, combined with analyses of the gross and microscopic morphologies and functioning of the organs in the mantle cavity of living and preserved specimens have allowed an understanding of important aspects of its biology. The role of the foot and its ciliature during the processes of dislodgement and burrowing within the sediment are described. The species is a free-living, shallow-burrower, with a predominantly deposit-feeding habit and derives part of its food from the labile settled organic deposits carried into the mantle cavity by the anterior–posterior current of water. Pedal sweep-feeding was not detected. M. charcoti is the first known lasaeid with ctenidia formed of the descending lamellae of the inner demibranchs only, a feature probably related to its highly specialised brooding habit.     

Larvae of Chironomids (Insecta,Diptera) Encountered in the Mantle Cavity of Zebra Mussels,Dreissena polymorpha (Bivalvia,Dreissenidae)

The paper includes data on species composition of chironomid larvae which were encountered in the mantle cavity of zebra mussels (Dreissena polymorpha) within 7 waterbodies in the Republic of Belarus. All were found to be free‐living species commonly present in periphyton and/or benthos. A long‐term study of the seasonal dynamics of these larvae in Dreissena did not reveal any typical pattern. Our data suppose that chironomids do not have an obligate association with zebra mussels and possibly enter their mantle cavity inadvertently. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The temporal and spatial occurrence of Tetrastemma fozensis (Hoplonemertini) in intertidal bivalves

The bivalve Scrobicularia plana, which iscommonly found on tidal flats in northwestern Europe,has disappeared from many locations during the pasttwo decades. Its local disappearance has beensuspected to be a result of pollution, but otherfactors such as parasites have also been discussed. The occurrence of Tetrastemma fozensis, a smallhoplonemertine inhabiting the mantle cavity of S. plana,was examined in bivalves from six differentestuaries in northern Spain. The bivalves are easilycollected, and the nemertines leave the bivalves whenplaced in a small jar with seawater for 72 h. Regularexaminations at 6–10 wk intervals of S. planafrom the estuary of Plencia revealed that thepercentage of bivalves containing nemertines T. fozensisdecreased during the summer months, but wasabove 70% during the rest of the year. In mostestuaries about 40–60% of the bivalves containednemertines, but in March 1994, 100% of the bivalvesfrom the estuary of Hendaye were hosts for nemertines.Nemertines were not found in S. plana from thehighly polluted estuary of Bilbao in either March orSeptember 1994. The number of nemertines withinindividual bivalves was positively correlated with thesize of the bivalves in locations where the percentageof bivalves containing nemertines was above 75%. Inone estuary where the nemertines disappeared almostcompletely from the bivalves between March 1994 andSeptember 1994, parasitic copepods appeared withinsome bivalves in September 1994. The ecology of thenemertine T. fozensis still remains largelyunknown, but we suspect that the nemertines may bebeneficial for their hosts.     

Acid and alkaline phosphatase activities in the clam Scrobicularia plana: kinetic characteristics and effects of heavy metals

The acid and alkaline phosphatase activities of the clam Scrobicularia plana have been partially characterised in different organs and tissues (digestive gland, gills, foot, siphon and mantle) and the 'in vitro' effect of heavy metals on both types of enzymatic activity have been analysed. The optimal pH ranged between 4.0 and 5.5 for acid phosphatase activity and 8.5 and 9.5 for alkaline phosphatase activity. The apparent optimum temperature was in the 30-60 degrees range for acid phosphatase activity and in the 30-40 degrees C range for alkaline phosphatase activity. The effect of substrate concentration on enzymatic activities in the tissues showed a good fit to the Michaelis-Menten model. For both types of enzymatic activity, the highest values were found in the digestive gland. The effect of heavy metals was dependent on the tissue analysed. Mercury showed the highest inhibition in the organs/tissues and the parameters Km and Vmax were modified when the inhibitor concentration increased, thus indicating a mixed type of inhibition.     

Endoscopy of gastropods: A novel view of the mantle cavities and gills of the keyhole limpet Diodora aspera and the abalone Haliotis rufescens

The gills, or ctenidia, of marine gastropods serve as the sites for respiratory gas exchange. Cilia on the surface provide the pump that moves water through the mantle cavity and enhance diffusion. Because the gills are housed inside the shell, it is difficult to view them while they are functioning. Published images of gills show contracted, fragile structures that are distorted by the processes of dissection and preservation. Members of the families Fissurellidae (keyhole limpets) and Haliotidae (abalone) have openings in their shells through which water enters and/or exits. I inserted an endoscope connected to a video camera into the openings of the shells of living, non‐anaesthetized individuals of the fissurellid Diodora aspera and the haliotid Haliotis rufescens. In both species, the dorsal afferent branchial vessel of the afferent gill axis appeared large and inflated, as did the leaflets that extended from either side of the axis. In D. aspera, the leaflets appeared to fill the mantle cavity and responded to touch, particles, and dye in the water by contracting quickly and slowly re‐extending. In contrast, the gills of H. rufescens did not noticeably respond to disturbance. On the other hand, these gills showed a regular pattern of pleats that had not been described in the extensive anatomical literature of these common and economically significant animals. These results provide a novel view of the gastropod mantle cavity as a dynamic space filled by the gills, which divide the mantle cavity into distinct incurrent and excurrent chambers and produce a laminar flow of water through the cavity. J. Morphol. 276:787–796, 2015. © 2015 Wiley Periodicals, Inc.     

The influence of mantle cavity fluid on the aerial oxygen consumption of some intertidal gastropods

The intertidal gastropods Gibbula cineraria (L.), Nucella lapillus (L.), and Littorina littorea (L.) have been investigated. Animals that had attached to a plastic surface under sea water were exposed to air and rapidly frozen. Fluid was found to be retained within the mantle cavity in contact with the gill. For each species the weight of the mantle cavity fluid retained in air was related to the whole weight of the animal. There was no significant difference between the weight of fluid held by animals in the laboratory and that held by animals on the shore 2 h after aerial exposure. The oxygen consumption of inactive individuals in air was measured by two techniques which did not produce significantly different results. The aerial oxygen consumption of all three species was lowered by the loss of mantle cavity fluid. This also reduced the temperature coefficient. A correlation is suggested between a large weight of mantle cavity fluid, the presence of a gill in the mantle cavity and a large reduction in oxygen consumption upon the loss of fluid.     

Sanitation with sponge and plunger: western Atlantic slit-wormsnails (Mollusca: Caenogastropoda: Siliquariidae)

Siliquariid Tenagodus (synonym: Siliquaria) snails are obligatory sponge commensals, with uncoiling and laterally slitted shells embedded inside Demospongiae hosts, and shell apertures facing the outside allowing for respiratory and gill‐filter‐feeding activities. Live‐collected animals observed in situ within hosts provide the first detailed functional morphological study of the group, and form the basis for systematic revision of the western Atlantic members of type genus Tenagodus (Siliquariidae, synonym: Tenagodidae). Three species are recognized. Overall anatomical features of wide‐ranging Atlantic T. modestus (Dall, 1881) and T. squamatus (de Blainville, 1827) [ = T. anguillae Mörch, 1861] are similar to those previously described for New Zealand Pyxipoma. A third species, Tenagodus barbadensis sp. nov. , is described from Barbados, based on shell characters. The three species live embedded in a few species of halichondriid and thrombid sponges at depths ranging from c. 20 to several hundred metres and show several characters not previously documented for the family. These include a short compressed‐S‐shaped osphradium, an anal opening positioned in the posterior mantle cavity, and cuspidate inner marginal radular teeth. Presence of shell septa sealing earlier parts of the shell, first described in the early 1800s but subsequently disputed, was verified. Observations on living T. squamatus demonstrated the use of the large tight‐fitting operculum in plunger‐like fashion, flushing the mantle cavity and discharging waste material (including faeces from the posteriorly located anus) through the shell slit into the host sponge's aquiferous canal system. Uncoiling shells, shell and mantle slits, and specialized opercular, gill and gut morphology are interpreted as adaptive traits of the sessile mode of life embedded in sponge tissue. Actively maintained linkage between snail and sponge water‐flow systems provides mutual benefits; these include the allowance for rapid defensive withdrawal and return‐to‐feeding position of the snail (by using the sponge canal system as a vent or reservoir for displaced water), sanitation of the mantle cavity (waste material can leave the snail through the shell slit at the posterior end of the mantle cavity, avoiding fouling of the gill‐feeding system), and by providing increased water flow and, potentially, extra nutritional particles for the sponge (food and waste particles stemming from the snail's activity). The lectotypes selected herein are Serpula anguina Linnaeus, 1758, Tenagodus anguillae Mörch, 1861, and Siliquaria modesta Dall, 1881. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140 , 307–333.     

Structure of the brachiopod lophophore

Data on the development, structure, and functional morphology of the brachiopod lophophore are analyzed. The common origin of the tentacle apparatus in Lophophorata from the postoral ciliary band of the larva is shown. The brachiopod lophophore is based on the brachial axis consisting of the brachial fold running along the row of tentacles. The brachial axis may be attached to the brachial (dorsal) mantle lobe (trocholophe, schizolophe, and ptycholophe lophophores) or extend freely into the mantle cavity to form coiling brachia (spirolophe, zygolophe, and plectolophe lophophores). The circulation of water flows through the mantle cavity in the brachiopods with attached and free lophophores is described. A new hypothesis on the sorting of particles suspended in water during filtration is proposed.     

Ultrastructure of the nephrostome in Enchytraeus albidus (Annelida, Clitellata)

 The nephrostome of Enchytraeus albidus exhibits a longitudinal slit-like opening on the dorsal side of a bulbous organ which is mainly composed of three cells, one flame cell situated centrally and endowed with a ciliary flame, and two cells lying superficially, called the mantle cell and the accessory mantle cell. The mantle cell occupies the ventral side of the organ extending on both sides up to the opening to constitute its immediate border on the frontal and lateral sides. Here it forms a kind of crest which is heavily subdivided into many protrusions and infoldings endowed with long cilia which exclusively spread into the coelomic cavity. The accessory mantle cell borders the narrow posterior slit of the opening, forming the roof of the initial canal which is devoid of cilia. From its anterior region a projection arises extending above the opening. The flame cell forms a groove from which the ciliary flame arises which extends into the canal. At its posterior region it replaces the accessory mantle cell displacing it onto the dorsal surface of the organ. It is argued that the mantle cell and the accessory mantle cell have presumbly originated from coelothelial cells. Thus the metanephridium may be a composite organ developing from a nephridioblastic and a coeloblastic source. A discussion of results in other annelid species indicates that metanephridia in the Annelida may have evolved more than once. Accepted: 13 October 1997     

Diet, prey-size selection and intake rates of Black-tailed Godwits Limosa limosa feeding on mudflats

This paper describes aspects of the winter feeding ecology of Black-tailed Godwits Limosa limosa on an intertidal mudflat in the Tagus estuary, Portugal. Their diet consisted mainly of the bivalve mollusc Scrobicularia plana , which represented 88% of the ingested biomass. The remaining 12% was the worm Nereis diversicolor and, occasionally, the snail Hydrobia ulvae . Ingested Scrobicularia varied between 10 and 20 mm in length, and all size classes of Nereis present in the sediment, except those smaller than 20 mm, were preyed upon. A change in dietary composition occurred over the winter, probably in response to changes in the availability of Nereis and small Scrobicularia . Intake rates averaged 74.9 mg dry weight per minute, which corresponded to a net energy intake of 1.21 kJ per min.     

Some factors affecting the location of Arthritica crassiformis (Bivalvia: Leptonacea) commensal upon Anchomasa similis (Bivalvia: Pholadidae).

Arthritica crassiformis Powell is found in New Zealand waters commensally associated with the pholad Anchomasa similis (Gray). Its location on the host is highly specific and is occasioned by the complex needs of the commensal and the facilities and limitations imposed by the tunnelling activity of the host. Other species of pholad because of different morphological adaptations do not serve as hosts. With increasing size of the host, the number of commensals/host increases which is due to (a) retention of young individuals within the parental burrow and (b) by colonization from the external environment.
A. crassiformis typically, however, occurs in pairs and is probably a protandric consecutive hermaphrodite. The young are incubated in the interlamellar spaces of the ctenidia of the parental female. This anatomical adaptation together with others including strong rejectory tracts suit the commensal for a life with an active tunnelling host.
The ciliary currents of the mantle cavity of A. similis are described.