Mucous Strings Research Articles

Sexual reproduction and early life-history traits of the Mediterranean soft coral Alcyonium acaule

Understanding processes that contribute to a better comprehension of the population dynamics of long-lived species is critical for the maintenance and potential recovery of such species. Despite the abundance of soft corals in Mediterranean rocky reefs, little information exists on their life histories and reproductive patterns. In this study, we assessed the main reproductive characteristics and early life-history traits of the long-lived soft coral Alcyonium acaule. The sex ratio was 1:1; the smallest fertile colonies were one finger in size (2.1 ± 0.6 cm in height), and both colony and polyp fertility increased with colony size. Likewise, the number of eggs and spermary sacs per polyp increased significantly with colony size, whereas the diameter of the female and male sexual products did not. Over 6 years of observations (2007–2012), spawning occurred primarily in July, after the seawater reached 20 °C, in a single spawning episode per year. Approximately 80% of female colonies released eggs, which were retained on the surface of the mother colony by mucous strings for up to a few days. High fertilization rates were observed during spawning in 2008 and 2009 (94.9% and 87.0%, respectively). The timing of development was ~24 h for the blastulae, ~48–72 h for the planulae and 8–22 days for metamorphosis into primary polyps. Survivorship of planulae was relatively high (~50% at 45 days after release), but only 24% of larvae metamorphosed into primary polyps, and their survivorship was moderate after 2 months (65% in 2008 and 74% in 2009). Asexual reproduction was negligible, indicating that sexual reproduction is the main mechanism supporting the maintenance and recovery of populations.

The enigmatic viviparous chiton Calloplax vivipara (Plate, 1899) (Mollusca: Polyplacophora) and a survey of the types of reproduction in chitons

The chiton Calloplax vivipara was previously considered as ovoviviparous [40]. However, six females of C. vivipara found on Chilean coast brooded both ova and juveniles in their pallial grooves. Therefore, the data of Plate [39, 40] about ovoviviparity in C. vivipara are to be considered incorrect. The present study discusses four methods of reproduction in chitons: (1) free spawning of separate eggs into the water; (2) spawning of eggs as a mucous mass or a mucous string on the bottom; (3) spawning of eggs into the pallial groove of a female, where eggs and larvae are brooded; and (4) spawning of eggs with hulls (capsules) on macroalgal thalli. Tables with lists of brooding species of chitons are included in the paper. Four brooding species have been recorded for the first time, thus increasing the number of brooding species of chitons to 41.

AN ULTRASTRUCTURAL STUDY OF THE GLAND OF LEIBLEIN OF MURICID AND NASSARIID NEOGASTROPODS IN RELATION TO FUNCTION, WITH A DISCUSSION ON ITS HOMOLOGIES IN OTHER CAENOGASTROPODS

The gland of Leiblein of the muricid Nucella lapillus and the nassariid Hinia reticulata has been examined by scanning and transmission electron microscopy. The origin and functional significance of its complex organization and its relationship with the rest of the mid-oesophagus in Nucella are discussed. It is absorptive as well as secretory, and a mechanism is proposed by which solute-rich fluids may enter the gland. Its epithelium is composed of occasional mucous cells and two major cell types: ciliated cells engaged in protein metabolism and unciliated cells responsible for uptake and storage of lipids and carbohydrates, both of which show evidence of pinocytotic uptake of solutes and intracellular digestion in lysosomes. Some enzyme activity persists in the residual bodies they shed by apocrine secretion, but they remain intact in a mucous string until they reach the stomach. Preliminary ultrastructural examination indicates that the gland absorbs cadmium not only from the blood but also directly from its lumen and that it may have the capacity to sequester a wide range of toxins. The same types of cell occur in Hinia in which their cyclical activity has been correlated with feeding. Similar cells have been identified in the oesophageal glands of other prosobranchs. The foregut glands of carnivorous caenogastropods are compared with the gland of Leiblein. There is an inverse correlation between the role of the mid-oesophagus in digestion and absorption and the complexity of the stomach.

The effect of food supply on feeding strategy in sessile female gastropods Crepidula fecunda

Sessile females of the gastropod Crepidula fecunda are exclusively suspension-feeders. Our previous work showed that particles removed from suspension are entrained on the gill and continuously accumulate as a mucous string on the distal margin of the lamella, although some are transferred by a ciliary tract to the food pouch, where they form a mucous ball. The mucous string is transferred from the gill margin to the neck canal, where it forms a mucous cord which is transported to the mouth. The mucous ball and the mucous cord are ingested with the aid of the radula. In this study we examined the response of the system to a wide range of cell concentrations of the flagellate Isochrysis galbana. As the particle concentration increased from 5,000 to 200,000 cells ml-1, the volume of the mucous ball almost doubled, as did the number of radular extrusions required to ingest it. The total volume of mucous balls produced and ingested increased very slightly as particle concentration rose from 5,000 to 100,000 cells ml-1, but the volume of mucous cord material ingested increased four to five times over the same range. At higher food concentrations the mucous cord increased in thickness, but not in length, which is constrained by the length of the gill margin. At all particle concentrations the mucous cord accounted for 80–95% of the total material (mucous cords plus mucous balls). Ingestion rate reached a maximum at 140,000 cells ml-1 for mucous balls and mucous cords. At higher concentrations the production of pseudofaeces increased from all sources ("type-I" pseudofaeces from rejected mucous balls; "type-II" pseudofaeces from rejected fragments of mucous cords; and "type-III" pseudofaeces, which come from particles trapped in a coarse mucous net at the mouth of the inhalant mantle cavity and are transferred via the lateral ciliary tract to the mantle margin, by-passing the food pouch). Thus C. fecunda has adopted a feeding strategy in which particle entrainment by the gills is continuous, even at very high ambient particle concentrations (200,000 cells ml-1 for I. galbana), and excess material which cannot be ingested is rejected by one or more of three routes for the elimination of pseudofaeces.

Larva on a string

Abstract Many types of suspension-feeding plankton larvae produce one or more, up to 1 cm long mucous strings. These function as drift anchors by increasing hydrodynamic drag. This effect, together with gravitational forces, allows the larvae to remain almost motionless relative to the undisturbed water column while feeding. Larvae that are essentially tethered in the water column enhance their efficiency of suspension feeding by a factor of 1.5–2 relative to larvae that translate through the water. The reason for this is that the flow fields surrounding the animals are different in the two situations. This effect is demonstrated in two kinds of veliger larvae.

Feeding mechanisms in the gastropod Crepidula fecunda

The gastropod Crepidula fecunda feeds in 2 distinct ways: grazing of the substrate and suspension feeding. The taenioglossan radula plays a role in both processes. In the former, the radula rasps the surface, and the material is immediately ingested. This means of food acquisition is mainly used by motile individuals, i.e. juveniles and adult males. Adult females are sessile, and are only able to rasp the area beneath the head region, severely limiting the amount of food acquired. Females brooding egg capsules are even more restricted, since the area normally grazed is occupied by the capsule mass. The second mode of feeding, suspension feeding, is exhibited by late juveniles and all adults. Suspended particles are captured in mucous nets on the ventral and dorsal surfaces of the single gill lamella. The entrained particles, loosely bound in mucus, are transported by ciliary action to the distal tips of the filaments, which are bulbous. The material accumulates in 2 mucous strings which traverse the ventral surfaces of the filaments at right angles to the filaments along the entire length of the distal margin of the gill. These strings coalesce into a single, thicker string, which is transferred at intervals to a food canal in the neck, where it is twisted into a compact, mucous cord by a spiral action of the neck canal musculature. The cord is moved through the neck canal to the buc- cal region, where it is grasped by the radula and ingested. Some material from the gill does not enter the neck canal but is carried by ciliary tracts to a modified region in the mantle, the food pouch, where it is compacted into a mucous ball, which is picked up by the radula and either ingested or rejected as pseudofaeces. In the case of rejection, the ball is pushed to the shell margin by the radula and lips. In C. fecunda food material is stored on the gill, allowing the radula time to undertake other tasks such as rasping the substrate and handling the mucous ball in the food pouch. This dual feed- ing mechanism diversifies the food and probably increases its nutritional value.

Endostyle-like Features of the Dorsal Epibranchial Ridge of an Enteropneust and the Hypothesis of Dorsal-Ventral Axis Inversion in Chordates

Endostyle-like Features of the Dorsal Epibranchial Ridge of an Enteropneust and the Hypothesis of Dorsal-Ventral Axis Inversion in Chordates

The epibranchial organ, its innervation and its probable functioning in Heterotis niloticus (Pisces, teleostei, osteoglossidae)

The high level of encephalization in Heterotis niloticus is due, in part, to a voluminous lobus vagalis, which has the form of a cauliflower and receives the fibers of a strong branch of the 10th (vagal) nerve. This vagal branch comes from a special branchial apparatus, the epibranchial organ, considered to be an air-breathing organ by some, and a microphagous apparatus by others. This organ has a spiral, snail-like form and its lumen is a blind-alley. Its study in a juvenile fish 10 cm SL shows that it has two canals: a peripheric one for water entrance and a central one for food exit. The epithelium between these two canals contains numerous gustatory buds, the innervation of which constitutes the branch of the vagal nerve. This epithelium is also very rich in mucous cells, which probably correspond to a muco-microphagous feeding apparatus. The exit canal, which receives the mucous string enriched with food particles, enters directly into the oesophagus. Striated muscles, attaching along the spiral tours of the epibranchial organ, probably serve as the motor that pumps water in and out and supplies the classical ciliary apparatus of the mucophagous feeding organs.

Frontal ambulacral and peribuccal areas of the spatangoid echinoid Echinocardium cordatum (Echinodermata): a functional entity in feeding mechanism

Echinocardium cordatum (Pennant, 1777) were collected in Normandy, France, in March and November 1985. The grooved frontal ambulacrum of the burrowing echinoid E. cordatum functions in transferring surface sediment from the apex to the mouth of the echinoid. Particles that fall down the burrow's chimney accumulate between the spines of the apical tuft and are taken over by specialized groove spines. Due to the slope of the groove and the type of floor spines it harbours, four successive regions can be recognized, namely the adapical region, the fasciolar region, the ambital region, and the adoral region. As a general rule aboral floor spines (i.e. club-shaped, golf-club-shaped, and isodiametric spines) function in gathering particles while propelling them mouthwards; they simultaneously embed particles in a mucous string. The oral floor spines (i.e. spatulated spines) function in hauling and guiding the mucous string towards the peribuccal area of the echinoid. Once facing the peribuccal area, particles are picked up by the peribuccal tube feet that either transfer them into the esophagus or scrape them out against the peribuccal spines. Spine-retained particles are either sucked up by the pumping action of the esophagus or fall to the burrow's floor where the tube feet may pick them up again. Together the apical tuft, the frontal groove, and the peribuccal area form an efficient food-collecting system that transfers trapped surface particles from the echinoid apex down to the mouth. Compared to that of most other spatangoids the frontal ambulacrum of E. cordatum is highly specialized. Such specialization is related to colonization of fine sediment, as is the occurrence of a chimney linking the burrow to the sediment surface. Actually the burrow's chimney is the only route for oxygen and food supply; it acts as a real ecological umbilical cord for spatangoids buried in fine sediment.

Ultrastructure of the gill of the hydrothermal vent bivalveCalyptogena magnifica, with a discussion of its nutrition

Calyptogena magnifica Boss and Turner, 1980, a new Vesicomyidae found during the Galapagos expedition in hydrothermal vents of the East Pacific Rise, was collected in the same Rise at 21°N during the “Oasis” expedition (March 1982), and samples of the gill were fixed for ultrastructural observations. The large size and structure of the gill indicate that this is the organ mainly involved in the nutritional processes ofC. magnifica. Despite the classic structural appearance of the external cilia of its gill, and an obvious production of mucus,C. magnifica is not a filter-feeder, as it does not use filtering processes to provide its major source of nutrition. Negligible particulate transfer is evidenced by reduction of the ciliary groove, of the labial palps and of the digestive tube, as well as by the absence of mucous strings. Histological and ultrastructural observations endorse the hypothesis that endocellular chemoautotrophic bacteria play an important role in the nutrition of the clam. Except for a superficial zone of ciliated cells, most of the gill tissue is comprised of cells which appear to be bacteriocytes, and which are perfectly integrated into the gill tissue and contain abundant and normally reproducing bacteria. The differences observed in the structure of the bacteriocytes suggest a cyclic process of their colonization by bacteria, their possible resorption, and their replacement by new bacteria-infected cells. Energetic substrates (sulfides and organic molecules) are probably directly absorbed by the bacteriocytes through the microvilli of the epithelial cells. Abundant fingerprint-like mitochondria in ciliate cells attest to a particularly high metabolic activity, perhaps related to active biosynthesis.

Feeding mechanisms in anuran larvae

Larvae of the neotropical frogs Phyllomedusa are distinctive in that they feed normally in mid‐water on phytoplankton, maintaining neutral buoyancy by means of an independently beating tail filament. The feeding mechanism of larval Phyllomedusa trinitatis was studied morphologically and experimentally. The primary feeding mechanism involves a buccal rasp which may in some circumstances render food into small particles, a pumping mechanism which forces water through the buccal cavity and the gill filters, an entanglement system which traps particles in mucous strings produced in special organs, and the formation of mucous cords which transport particles to the oesophagus. In mid‐water feeding and surface feeding the buccal rasp serves only its other function in preventing backflow of the respiratory stream. The primary feeding mechanism is discussed and compared with schemes proposed for Rana temporaria and R. agilis. Little agreement exists between these schemes and that which is here proposed. It is concluded that the primary feeding mechanism is the same in the three forms but that there are behavioural differences in feeding generally. Some comment is made on the primary feeding mechanism in the Microhylidae.

Studies on the influence of various substances on the colon: I. Phenolphthalein and other laxatives

From the results obtained from numerous examinations of stool specimens from normal individuals and patients, with and without evident gastro-intestinal involvement, and before as well as after the ingestion of various test substances, the following conclusions appear justified at the present time: 1. Abnormal stool constituents (excessive mucus, mucous strings, and protein) appear, at one time or another, in a fair percentage of patients, regardless of whether gastro-intestinal symptoms are or are not present. (Cases definitely diagnosed as “colitis” are not included in this series). 2. Changes in the bulk of the stool and the type of diet seem to influence the occurrence of abnormal stool constituents. Stools of hard, low bulk more often contain abnormal stool constituents. 3. Following the ingestion of various drugs and of bulk producing substances employed as laxatives, no appreciable changes appeared in the constituents of the stools examined; in a few instances where the observation was extended over a more prolonged period, the changes were no less unimpressive. 4. No correlation was found between the degree of laxative effect, presence or absence of subjective symptoms (cramps and flatulence) and the finding of abnormal constituents in the stools. 5. The occasional finding of abnormal constituents in the stool of an individual does not justify the diagnosis of “colitis,” nor does it warrant attributing the findings to any medication previously ingested. 6. Since there is no evidence that the occasional use of laxatives produces colitis, their use should not be summarily prohibited; but the public should be enlightened as to when and how to use them.

On a Ciliary Process of Food‐collecting in the Gastropod Turritella communis Risso

SUMMARY.The mantle‐cavity of Turritella communis has an inhalent aperture on the left side and an exhalent one on the right. The former is guarded by a complex array of tentacles preventing the ingress of large particles. Ciliary currents collect particles falling on these and transport them to the foot (text‐fig. 1).Particles are collected on the gill‐filaments and are transferred to a deep groove bounded by folds which runs along the floor of the mantle‐cavity to the right side of the head, ending in a projection below the mouth. Food‐particles are built into a ropy string with mucus in this groove, and this is slowly passed forwards to the mouth, into which it is raked.Exhalent currents pass from the right side of the cavity to a siphonal process on the foot (text‐fig. 2).The mucous string is passed into the buccal cavity, in which lies a reduced odontophore and into which open minute salivary glands, thence down the oesophagus, which is straight apart from the twisting caused by torsion, to the stomach. Into this projects a crystalline style, its head bearing against a gastric shield, and a complex ciliary sorting and mixing mechanism is described on its walls. Small particles pass to the digestive diverticula for ingestion, larger ones to the intestine, where they will be elaborated into fa;cal pellets (text‐fig. 3).In the light of these facts the peculiarities of the feeding mechanism of Turritella are discussed, and it is concluded that they have been evolved in relation to its habitat.