Inhalant Siphon Research Articles

MTOR Plays a Conserved Role in Regulation of Nutritional Metabolism in Bivalve Sinonovacula constricta

The mammalian target of rapamycin (mTOR) has been shown to play a central role in regulating cell growth and metabolism. However, little is known about the function of mTOR in nutrient metabolism in bivalve mollusks. In this study, the role of mTOR in the regulation of nutrient metabolism was investigated in Sinonovacula constricta. First, the activation of mTOR was assayed after starvation and refeeding. Afterwards, the role of mTOR in the regulation of nutrient metabolism was investigated using an activator (MHY1485) or inhibitor (rapamycin) of mTOR. The open reading frame of the S. constricta mTOR is 7416 bp in length and encodes a polypeptide consisting of 2471 amino acids. The mTOR amino acid sequence of S. constricta was highly conserved when compared with other species and had a close evolutionary relationship with the TOR proteins of Crassostrea gigas and Lingula anatine. mTOR was expressed in the intestine, exhalent siphon, labial palppus, muscle, inhalent siphon, gill, mantle, digestive land, and gonad tissue of S. constricta, with the highest expression in muscle. During starvation, the level of phosphorylated mTOR protein was relatively low, and the ratio of LC3II/LC3I protein and the AMPKα mRNA level significantly increased with the increase in starvation time. After feeding, the level of phosphorylated mTOR protein increased from 0.13 to 0.56, and the ratio of LC3II/I protein and AMPKα mRNA level decreased from 1.17 to 0.38. MHY1485 significantly increased the level of phosphorylated 4E-BP1 and significantly decreased the ratio of LC3II/I proteins. Furthermore, MHY1485 significantly increased the mRNA level of the glucose metabolism-related gene glucokinase (GK), significantly decreased the mRNA expression of the G6P gene, and significantly increased the mRNA expression of the lipid synthesis-related genes sterol-regulatory element-binding protein (SREBP) and stearoyl-CoA desaturase (SCD). Rapamycin significantly reduced the level of phosphorylated 4E-BP1 and the mRNA expression of mTOR, and the expression level of phosphorylated 4EBP1 decreased from 0.97 to 0.28. Meanwhile, it also significantly reduced the mRNA expression of glucose metabolism-related genes GK, pyruvate kinase (PK), glucose transporter 1 (GLUT1), and G6P, as well as lipid synthesis-related genes SCD and acetyl-CoA carboxylase (ACC). These results indicate a conserved role of mTOR in regulating nutritional metabolism, including glucose metabolism, lipid synthesis, and autophagy in S. constricta.

Bromleyia magnifica n. igen., n. isp.: a feeding trace of a protobranch bivalve

The new ichnotaxon Bromleyia magnifica n. igen., n. isp., attributed to the feeding activity of bivalves, is proposed. This ichnotaxon consists of clusters of closely spaced curved ridges that form a fan-shaped structure oppositely distributed on both sides of a longitudinal axis or, more rarely, being present only on one side. Intergradation between Protovirgularia, Lockeia, and Bromleyia forms a compound trace fossil that records the activity of a cleft-foot protobranch bivalve while burrowing, moving through the sediment, and stopping to deposit feed. A specimen from the Carboniferous of Arkansas, previously regarded as Lophoctenium isp., is here included in Bromleyia magnifica. The spreite in Lophoctenium reflects complex behavioural patterns of horizontal strip-mining deposit feeders, including bundles of tubes bending to one side in a pectinate way or arranged on both sides in a highly systematic fashion, which contrasts with the coarse, horizontal fan-shaped, curved bundle of ridges from the Arkansas specimen. The trace fossil Hillichnus lobosensis records the activities of tellinacean deposit feeders and displays feather-like spreite structures reminiscent of Bromleyia. However, the spreite in Hillichnus is more organized, recording repetitive probing through the sediment in horizontal, oblique, and vertical directions of the tubular inhalant siphon. The resulting complex feeding structure, recorded in multiple preservational tiers, displays an alternate arrangement of ridges on either side of an axial basal structure. This configuration differs from the mostly horizontal, less-organized, coarse bundle of ridges with broadly opposite distribution to the sides of an axis present in Bromleyia. Moreover, contrary to Hillichnus, Bromleyia is commonly associated with Lockeia, indicating significant differences in burrowing strategy and mode of construction between these two ichnotaxa.

A new genus Turneroconcha (Bivalvia: Vesicomyidae: Pliocardiinae) for the giant hydrothermal vent clam 'Calyptogena' magnifica.

A new monotypic genus, Turneroconcha, is established for T. magnifica (Boss Turner) which was originally assigned to the genus Calyptogena Dall. The distinguishing morphological characters of the new genus are the combination of both conchological and anatomical features including: the presence of only two tooth elements in the right valve; submerged location of the posterior part of the posterior lamellar ligament layer; the absence of a subumbonal pit, lunular incision, escutcheon and pallial sinus; the presence of both pairs of demibranchs; the tubular structure of marginal parts of the interlamellar septa in gills; an inner valve of the inhalant siphon without processes; tentaculate inner mantle fold 3 and a Z-shaped digestive tract. Analysis of morphological data on Recent and fossil pliocardiines shows that Turneroconcha gen. nov. can be presently considered as a monotypic genus. The comparative morphological analysis of the new genus with described pliocardiine genera is consistent with available molecular results. Turneroconcha gen. nov. is endemic to the East-Pacific Rise and Galapagos Rift and occurs at water depths of 2251 to 2791 m. It is the only pliocardiine genus known so far with a mainly epifaunal life habit. No fossils of Turneroconcha gen. nov. are known.

Proteome changes in muscles, ganglia, and gills in Corbicula fluminea clams exposed to crude oil: Relationship with behavioural disturbances

The use of online remote control for 24/7 behavioural monitoring can play a key role in estimating the environmental status of aquatic ecosystems. Recording the valve activity of bivalve molluscs is a relevant approach in this context. However, a clear understanding of the underlying disturbances associated with behaviour is a key step. In this work, we studied freshwater Asian clams after exposure to crude oil (measured concentration, 167 ± 28 μg·L−1) for three days in a semi-natural environment using outdoor artificial streams. Three complementary approaches to assess and explore disturbances were used: behaviour by high frequency non-invasive (HFNI) valvometry, tissue contamination with polycyclic aromatic hydrocarbons (PAH), and proteomic analysis. Two tissues were targeted: the pool adductor muscles – retractor pedal muscle – cerebral and visceral ganglia, which is the effector of any valve movement and the gills, which are on the frontline during contamination. The behavioural response was marked by an increase in valve closure-duration, a decrease in valve opening-amplitude and an increase in valve agitation index during opening periods. There was no significant PAH accumulation in the muscle plus nervous ganglia pool, contrary to the situation in the gills, although the latter remained in the low range of data available in literature. Major proteomic changes included (i) a slowdown in metabolic and/or cellular processes in muscles plus ganglia pool associated with minor toxicological effect and (ii) an increase of metabolic and/or cellular processes in gills associated with a greater toxicological effect. The nature of the proteomic changes is discussed in terms of unequal PAH distribution and allows to propose a set of explanatory mechanisms to associate behaviour to underlying physiological changes following oil exposure. First, the first tissues facing contaminated water are the inhalant siphon, the mantle edge and the gills. The routine nervous activity in the visceral ganglia should be modified by nervous information originating from these tissues. Second, the nervous activity in the visceral ganglia could be modified by its own specific contamination. Third, a decrease in nervous activity of the cerebral ganglia close to the mouth, including some kind of narcosis, could contribute to a decrease in visceral ganglia activity via a decrease or blockage of the downward neuromodulation by the cerebro-visceral connective. This whole set of events can explain the decrease of metabolic activity in the adductor muscles, contribute to initiate the catch mechanism and then deeply modify the valve behaviour.

The anatomy of the miniature predator Trigonulina ornata d’Orbigny, 1853 (Bivalvia: Anomalodesmata: Verticordiidae) from continental shelf waters off Brazil

The anatomy of one of the smallest non-septate carnivorous bivalves is described herein and is the first anatomical study of a member of the genus Trigonulina. This paper shows that similar to other verticordiids, Trigonulina ornata d’Orbigny, 1853 possesses a suite of anatomical features that include a prey-capturing inhalant siphon, a septum, an absence of labial palps and capacious mouth, which characterize it as a carnivorous marine bivalve. A discussion about the origin of the septibranch septum is provided showing that the condition seen in T. ornata could be representative of the transition within the Anomalodesmata between suspension-feeding type E ctenidia and the non-filamentar septibranch condition. Finally, fertilized and encapsulated eggs within the visceral mass, the presence of hypobranchial glands plus larval prodissoconch size collectively suggest self-fertilization and the possible early brooding behaviour by T. ornata.

Predatory marine bivalves: A review.

Most bivalves are suspension feeders. On the deep sea floor, however, some are predators, typically of meiobenthic crustaceans: copepods, cumaceans and ostracods. Propeamusiid scallops are one such group of predators. The largest numbers of predators, however, belong to the bivalve subclass Anomalodesmata and constitute, as currently recognised, some 500 species belonging principally to the Verticordioidea (120), Poromyoidea (75) and Cuspidarioidea (304) with four, two and four constituent families, respectively. A further family, the Parilimyidae, is considered to be derived from the Pholadomyoidea-the anomalodesmatan ancestor. These, generally small (<60mm shell length), nacreous and thin-shelled predators share many anatomical features that formerly allowed them to be collectively classified as the Septibranchia. Although this name is now rarely used, it refers to their possession of a ctenidially-derived septum in the mantle cavity and functioning in prey capture. Generally, there is a trend, possibly evolutionary, from a typical bivalve ctenidium (Parilimyidae and some Verticordioidea) to a complete septum (other Verticordioidea, Poromyoidea and Cuspidarioidea). In addition, the inhalant siphon, foot, labial palps, mouth and its lips play a role in prey capture, and ingestion. Similarly, the stomach is modified to digest such, typically chitinous, ingested prey. Most septibranchs are either consecutive or simultaneous hermaphrodites with self-fertilisation possibly usual and with some evidence in a few of larval brooding. Notwithstanding, the deep sea septibranch species are poorly studied with virtually nothing being known about their wider distributions, ecology, detailed reproductive strategies and life history traits.

Overcoming hydrodynamic challenges in suspension feeding by juvenile Mya arenaria clams.

We present some of the few suspension-feeding measurements and to our knowledge the first velocity-field measurements for early post-settlement juvenile bivalve clams. We verify and extend our experimental results with numerical simulations. For 1.8-2.8 mm shell length Mya arenaria clams, pumping rates ranged 0.03-0.22 μl s-1, inhalant siphon Reynolds numbers (Re) ranged 0.16-0.79 and mean inhalant velocities ranged 0.8-3.2 mm s-1 Owing to the low Re at which they pump and the small diameters of their siphons, juvenile clams are subject to unique hydrodynamic challenges, including high siphon resistance and susceptibility to refiltration. At least three features of juvenile clam siphons differentiate them from those of adults-shorter inhalant siphon length, a more rapid increase in inhalant siphon diameter with shell length, and the presence of a prominent exhalant siphon extension. These features are probably adaptations to the challenges of suspension feeding at low Re.

Efficient filtration of micron and submicron particles by ascidians from oligotrophic waters

AbstractSuspended food particles in oligotrophic waters are scarce and the planktonic community is dominated by minute picoplanktonic (&lt; 2 μm) cells. Consequently, suspension feeders inhabiting such environments are faced with the dual challenge of capturing extremely small particles and efficiently processing large volumes of water. We used direct in situ techniques to characterize the size‐dependent capture efficiency curve of four solitary ascidian species (Chordata, Tunicata) from the ultra‐oligotrophic East‐Mediterranean, and two species from the oligotrophic Gulf of Aqaba (Northern Red‐Sea). To control for confounding factors such as particle surface chemistry, we used a suspension of artificial polystyrene microspheres with a wide range of sizes (from 0.3 μm to 10 μm) but identical surface chemistry. This suspension was introduced into the inhalant siphon while the water inhaled and exhaled by the otherwise undisturbed ascidian was cleanly sampled. All the investigated ascidian species captured ≥ 1 μm microspheres at 95% ± 8% efficiency (mean ± 95% Confidence Interval) with no significant difference between species. Moreover, and in contrast to reports from eutrophic waters, both in situ and laboratory experiments revealed an efficient capture of submicron 0.3 μm microspheres at close to 50% efficiency. For most of the species tested, the capture efficiency of microspheres dropped below optimum between 1 μm and 0.5 μm providing an estimation of their mucus mesh pore size. We suggest that ascidians from oligotrophic waters are adapted for capturing submicron particles picoplankton and other. Such adaptation enables “oligotrophic” ascidians to access a much larger food source and facilitates the transfer of planktonic C, N, and P from the water column to the benthos.

Use of the sea hare (Aplysia fasciata) in marine pollution biomonitoring of harbors and bays

Our study evaluated heavy metal concentrations in soft tissues of sea hare, Aplysia fasciata, from the Lower Laguna Madre, Texas. Heavy metals in tissues followed Se>As>Pb>Cd. Concentrations ranged As (BDL-28.08), Cd (BDL-5.50), Pb (BDL-12.85) and Se (4.25–93.43ppm). Median As, Cd, Pb, and Se tissue levels exceeded exposure levels. Significant relationships occurred in metal-metal (AsCd, AsPb, CdPb, CdSe, and PbSe), metal-tissue (significant Se uptake by inhalant and exhalant siphons and As in the hepatopancreas), and metal-metal within tissue (AsPb in the hepatopancreas and CdPb in the digestive cecum) analyses (p<0.05). Bioaccumulation factors (BAF) suggested the inhalant siphon, hepatopancreas, and digestive cecum function as macroconcentrators of Cd, hepatopancreas and digestive cecum as macroconcentrators of Pb, and all tissues were deconcentrators for As and Se. As a bioaccumulator of heavy metals, Aplysia was evaluated as a bioindicator of marine pollution in harbors and bays.

Model-assisted measurements of suspension-feeding flow velocities.

Benthic marine suspension feeders provide an important link between benthic and pelagic ecosystems. The strength of this link is determined by suspension-feeding rates. Many studies have measured suspension-feeding rates using indirect clearance-rate methods, which are based on the depletion of suspended particles. Direct methods that measure the flow of water itself are less common, but they can be more broadly applied because, unlike indirect methods, direct methods are not affected by properties of the cleared particles. We present pumping rates for three species of suspension feeders, the clams Mya arenaria and Mercenaria mercenaria and the tunicate Ciona intestinalis, measured using a direct method based on particle image velocimetry (PIV). Past uses of PIV in suspension-feeding studies have been limited by strong laser reflections that interfere with velocity measurements proximate to the siphon. We used a new approach based on fitting PIV-based velocity profile measurements to theoretical profiles from computational fluid dynamic (CFD) models, which allowed us to calculate inhalant siphon Reynolds numbers (Re). We used these inhalant Re and measurements of siphon diameters to calculate exhalant Re, pumping rates, and mean inlet and outlet velocities. For the three species studied, inhalant Re ranged from 8 to 520, and exhalant Re ranged from 15 to 1073. Volumetric pumping rates ranged from 1.7 to 7.4 l h-1 for M. arenaria, 0.3 to 3.6 l h-1 for M. mercenaria and 0.07 to 0.97 l h-1 for C. intestinalis We also used CFD models based on measured pumping rates to calculate capture regions, which reveal the spatial extent of pumped water. Combining PIV data with CFD models may be a valuable approach for future suspension-feeding studies.

Rewiring of an ancestral Tbx1/10-Ebf-Mrf network for pharyngeal muscle specification in distinct embryonic lineages.

Skeletal muscles arise from diverse embryonic origins in vertebrates, yet converge on extensively shared regulatory programs that require muscle regulatory factor (MRF)-family genes. Myogenesis in the tail of the simple chordate Ciona exhibits a similar reliance on its single MRF-family gene, and diverse mechanisms activate Ci-Mrf Here, we show that myogenesis in the atrial siphon muscles (ASMs) and oral siphon muscles (OSMs), which control the exhalant and inhalant siphons, respectively, also requires Mrf We characterize the ontogeny of OSM progenitors and compare the molecular basis of Mrf activation in OSM versus ASM. In both muscle types, Ebf and Tbx1/10 are expressed and function upstream of Mrf However, we demonstrate that regulatory relationships between Tbx1/10, Ebf and Mrf differ between the OSM and ASM lineages. We propose that Tbx1, Ebf and Mrf homologs form an ancient conserved regulatory state for pharyngeal muscle specification, whereas their regulatory relationships might be more evolutionarily variable.

The biology and functional morphology of the high-energy beach dwelling Paphies elongata (Bivalvia: Mactroidea: Mesodesmatidae). Convergence with the surf clams (Donax: Tellinoidea: Donacidae)

ABSTRACTThe biology and functional morphology of the Australian endemic Paphies elongata (shell length <20 mm) from wave-exposed beaches are described. On Middleton Bay Beach, Albany, Western Australia, the species co-occurs with the smaller (shell length <13 mm) Donax columbella. Both make tidally regulated migrations up and down the shore in the swash and backwash of waves, respectively. Emergence from and re-burrowing into the beach sand in concordance with the waves is fast in both taxa (5–10 s). Adaptations to such a life on these high-energy beaches include an anteriorly elongate and posteriorly reduced shell and a mesh of tentacles within the inhalant siphon that screens out sand grains from the mantle cavity but allows entry for particles of detritus that P. elongata suspension feeds on when they are raised into the water column with each breaking wave. Internally, relatively large ctenidia, small labial palps, a stomach with many sorting areas and a short intestine equip P. elongata for life in such a dynamic habitat. Strong rejectory currents in the mantle cavity keep it clean of sand. Paphies elongata is dioecious, as are species of Donax, which throughout its Australian range P. elongata is sympatric with. These donacid and mesodesmatid taxa have both evolved to exploit the niche and the food resource of detritus held in suspension by breaking waves of high-energy sandy beaches within their respective ranges. Of interest, however, is that the original and sole occupants of such beaches – the Mesozoic Upper Cretaceous Donacidae – have been joined subsequently by representatives of the Mesodesmatidae, such as P. elongata, the adoption of this habitat taking place in the Eocene of the Cenozoic, some 50 million years later.

The organs of prey capture and digestion in the miniature predatory bivalve Spheniopsis brasiliensis (Anomalodesmata: Cuspidarioidea: Spheniopsidae) expose a novel life-history trait

ABSTRACTSpheniopsis brasiliensis, from depths of 17–148 m off the southern Atlantic coast of Brazil, is a predator of epipsammic micro-crustaceans which it sucks into the infra-septal chamber using a raptorial inhalant siphon and internally generated hydrostatic suction forces. Prey items, which include ostracods, are thought to be pushed into the funnel-shaped mouth using the foot. The stomach is capacious with a short style sac conjoined briefly with the mid gut and possessing a stubby crystalline style. Internal stomach architecture is simplified, with no identifiable sorting areas (unlike other cuspidarioids) and lined virtually completely by a gastric shield. The exoskeletal remains of digested prey are held in the posterior end of the stomach and not in a specialised waste storage pouch as in the con-familial Grippina coronata. The mid gut, hind gut and rectum are all extremely narrow and, thus, only the smallest of faeces can be accommodated and transmitted for anal discharge. Spheniopsis brasiliensis, like G. coronata is a self-fertilising simultaneous hermaphrodite with encapsulated lecithotrophic eggs brooded internally. Both taxa are thus ovovivaporous. It is also believed that both taxa are univoltine so that larvae and the exoskeletal prey remains are all released post mortem. Cuspidariids are generally regarded as dioecious but, recently, Cardiomya costellata has been shown to be a non-brooding simultaneous hermaphrodite. The distinguishing characters between cuspidariids and spheniopsids thus appear to be their differing reproductive strategies and life history traits.

The biology and functional morphology of the predatory septibranch Cardiomya costellata (Deshayes, 1833) (Bivalvia: Anomalodesmata: Cuspidariidae) from the Acores: survival at the edge

This is the first comprehensive anatomical study of a representative of the septibranch Cuspidariidae. Particular interest in Cardiomya costellata is related to the fact that only two species of such predatory septibranchs have been recorded from the remote Açorean Archipelago and, here, individuals of both taxa are half the shell length of conspecifics throughout the species’ North-eastern Atlantic range. The shell of C. costellata is thin, fragile and rostrate. This latter attribute allows the inhalant siphon (as in other cuspidarioids) to be extended towards potential prey to effect their capture. How this extension is effected has been described but, herein, the hydrodynamic forces needed to achieve this are put into a firmer anatomical context. Uniquely amongst the Anomalesmata, cuspidarioids have, previously, been regarded as dioecious. This is not the case for C. costellata, which is a protandric consecutive hermaphrodite. The gonads and reproductive strategy of this species are compared with those of the spheniopsid Grippina coronata that is representative of a second cuspidarioid family of deeper water predators and which is a simultaneous hermaphrodite brooding self-fertilized embryos in the gonadial follicles with their release being post mortem. Some evidence suggests that in the Açores, the possible crustacean prey of C. costellata are also smaller than their mainland conspecifics, which, when viewed in the overall context of the predator's biology and anatomy, might explain its poor success in the oligotrophic waters of these mid-Atlantic islands.

Metal partitioning and availability in estuarine surface sediments: Changes promoted by feeding activity of Scrobicularia plana and Liza ramada

Several works have evidenced in the past the importance and influence of plants and terrestrial invertebrates in metal availability in soils and sediments through changes in metal speciation. In contrast, the impact of estuarine invertebrates and fishes in this process has been poorly explored. The partition of metals in estuarine surface sediments was studied in a controlled environment according to four operationally defined fractions. Sediments were analyzed before and after the passage through the gut of two detritivorous species. Scrobicularia plana feeds on the bottom and suspended sediment particles through the inhalant siphon. Liza ramada is an interface feeder, filtering the superficial layer of the sediment and suspended particles in the water column. Cd, Cu and Ni bound to carbonates increased in the pellets of S. plana, compared with the ingested sediment, as did exchangeable Zn. Similarly, Cd and Zn bound to carbonates have also increased in the pellets of L. ramada; on the contrary, a decrease of Ni was observable in the pellets of this fish. The outcome of the controlled experiments pointed to a potential increase in some metals' availability in the estuarine environment, as a result of the more mobile metal forms in the excreted fecal pellets. This draws the attention to a relevant impact of the trophic activity of both species, alongside with the potential enhancement brought to it by the bioturbation promoted by them, in the role that the estuary itself has as a contaminants' buffer.

Austrogena: a new genus of chemosymbiotic bivalves (Bivalvia; Vesicomyidae; Pliocardiinae) from the oxygen minimum zone off central Chile described through morphological and molecular analyses

A new genus, Austrogena, is established for a new species of vesicomyid bivalve (A. nerudai sp. nov.) described from sediments within the oxygen minimum zone off El Quisco, Chilean margin (∼33°S) from ∼340 m depth. The new genus is distinguished by a unique combination of conchological and anatomical features for vesicomyids, including the presence of an escutcheon, a lunular incision, an elongated 4-b tooth in the left valve, a subumbonal pit, both inner and outer pairs of demibranchs and the absence of pallial sinus and processes on the inner vulva of the inhalant siphon. In comparison with the majority of highly specialized pliocardiins, the alimentary gut of Austrogena is not straight and its middle gut changes direction twice. Molecular analysis, based on COI sequences, confirms that A. nerudai sp. nov. is not related to any other pliocardiin. So far, Austrogena gen. nov. is the only endemic vesicomyid genus in the south-eastern Pacific area and A. nerudai sp. nov. is the fourth species of vesicomyids reported from chemosynthetic communities of the Chilean margin. The description of the new genus further contributes to knowledge of biodiversity of chemosymbiotic assemblages in the south-eastern Pacific.http://zoobank.org/urn:lsid:zoobank.org:pub:476A9734-B510-4954-A623-2C0E1F254F9A.

Boundary‐trapped, inhalant siphon and drain flows: Pipe entry revisited numerically

Lay AbstractMany seafloor exchange processes are controlled or strongly influenced by pumping of water into projecting tubes or burrow openings flush with the seabed. Quantitative descriptions of flow inside tubes and burrow openings rely primarily on a model that assumes uniform flow at the pipe entrance and lacks any description of the upstream geometry or flow field. Quantifications of flows in front of the entrance generally assume omnidirectional, convergent flow into the pipe opening. Numerical models of a tube drawing water from a large volume and of a drain flush with the bottom drawing from the center of a large tank explicitly connect flow inside the pipe to the flow outside. They indicate—for slow, viscous, and small‐diameter (of the pipe) flows—that considerable flow adjustment occurs upstream of the pipe entrance and that uniform velocity at the entrance is a poor assumption. For these cases, flow entering the pipe comes from a relatively small, cylindrical region parallel with the pipe rather than being drawn from all possible directions. Uniform entrance flow never becomes a good approximation because much of the flow entering faster, less viscous, and larger‐diameter pipes enters with appreciable radial velocity that affects flow well into the pipe. These results alter estimates of pumping costs, which can represent appreciable fractions of animal energy budgets. They also determine the regions from which food and chemosensory information can be obtained. The results demonstrate the necessity for most applications to replace textbook models based on uniform entry flow.

The effect of temperature on the inhalant siphon regeneration of Amiantis purpurata (Lamarck, 1818) (Bivalvia; Veneridae)

The purple clam Amiantis purpurata inhabits intertidal and shallow subtidal platforms from San Matías Gulf, Argentina to Santa Catarina, Brazil. This edible bivalve is an important component of the marine trophic webs due to siphon nipping. The present study investigates the influence of temperature on the regeneration of the inhalant siphon tentacle crown of A. purpurata. Under laboratory conditions 140 purple clams were exposed to four different temperatures (12, 15, 20 and 22°C). At each temperature, the distal 0.5 cm of the inhalant siphon was removed from each clam. The length of long tentacles from each group was measured on different days until the tentacles had reached asymptotic growth. Four candidate models were used for each tentacle data set for growth at the four experimental temperatures. The data were fitted to size-increments for the long siphon at different temperatures using maximum likelihood. The von Bertalanffy model was the one that best fitted the data at most experimental temperatures. To evaluate differences in tentacle regeneration in each treatment, the growth parameters were compared using a likelihood ratio test. The two interdependent parameters affecting the regeneration process k (growth constant) and t ip (inflexion point), were clearly influenced by temperature. In the case of k, increasing temperature produces acceleration in the regeneration process while t ip is not dependent on temperature. Regeneration was slower than in any other species previously reported in the literature and decreasing temperature slowed down the process.

Life-history strategy, with ctenidial and pallial larval brooding, of the troglodytic ‘living fossil’Congeria kusceri(Bivalvia: Dreissenidae) from the subterranean Dinaric Alpine karst of Croatia

Among freshwater bivalves, the brooding of embryos and larvae within the maternal ctenidia is well known. Exceptions to this generalization are the non-brooding freshwater and estuarine species of Dreissena and Mytilopsis, respectively. It was reported that the freshwater troglodytic cousin, Congeria kusceri Bole, 1962, of these dreissenids does not brood either. It is herein demonstrated that C. kusceri undergoes one reproductive cycle each year. Sexes are separate, with an early male and later female bias. A small percentage (2.14%) of individuals is hermaphroditic. The gonads mature over summer from May to November. Spawning commences in September, when females release mature oocytes into their ctenidia and inhale sperm from mature males. Here the oocytes are fertilized, and develop within interfilamentary marsupia. Ctenidial tissues glandularize, and may provide a source of maternal nutrition for the embryos. At the late prodissoconch-1 or prodissoconch-2 stage (PR2, ~220 μm), larvae are released into the infrabranchial chamber via a birth channel along the outer edge of the ventral marginal food groove of both inner demibranchs. Here, they are brooded further in mantle pouches located beneath the inhalant siphon. Subsequently, after the PR2 stage (nepioconch/dissoconch), they are released from the inhalant siphon and assume an independent life as crawling juveniles. Such juveniles may be found amongst clusters of adults. Not only is C. kusceri unique amongst the Dreissenidae in possessing the capacity to brood internally fertilized ova, but it is also exceptional amongst the Bivalvia in possessing the described methods of brooding and birth. Explanations for both lie in its troglodytic lifestyle, decadal length longevity and habitat: that of byssal attachment to the hard surfaces of underground freshwater rivers, caves, pits, and sinkholes in the Tethyan arc of the Dinaric karst. Internal fertilization of a few large yolky eggs, lecithotrophic larvae, ctenidial brooding, and secondary pallial parental care represent relatively recent, Late Miocene, evolutionary adaptations from a Tethyan lentic ancestor.

Taxonomy of Indonesian giant clams (Cardiidae, Tridacninae)

Hernawan E. 2012. Taxonomy of Indonesian giant clams (Cardiidae, Tridacninae). Biodiversitas 13: 118-123. A taxonomic study was conducted on the giant clam’s specimens deposited in Museum Zoologicum Bogoriense (MZB), Cibinong Indonesia. Taxonomic overviews of the examined specimens are given with diagnostic characters, remarks, habitat and distribution. Discussion is focused on specific characters distinguishing each species. From seven species known to distribute in Indonesian waters, there are six species,Tridacna squamosa Lamarck, 1819; T. gigas Linnaeus, 1758; T. derasa Roding, 1798; T. crocea Lamarck, 1819; T. maximaRoding,1798; and Hippopus hippopus Linnaeus, 1758. This study suggests the need for collecting specimen of H. porcellanus Rosewater, 1982. Important characters to distinguish species among Tridacninae are interlocking teeth on byssal orifice, life habits, presence of scales and inhalant siphon tentacles.