Regeneration time and morphology of the inhalant siphon of Donax denticulatus Linnaeus, 1758 (Bivalvia, Donacidae) after amputation.ABSTRACT To study the process of regeneration and its effect on the morphology of the inhalant inhalant /in·hal·ant/ (in-hal´ant) 1. something meant to be inhaled; see inhalation (def. 3). 2. a class of psychoactive substances whose volatile vapors are subject to abuse. siphon of a tellineacean bivalve bivalve, aquatic mollusk of the class Pelecypoda ("hatchet-foot") or Bivalvia, with a laterally compressed body and a shell consisting of two valves, or movable pieces, hinged by an elastic ligament. , Donax denticulatus, individuals were artificially amputated and placed in aquaria a·quar·i·a n. A plural of aquarium. under laboratory conditions, in the absence of predators. Alter amputation amputation (ăm'pyətā`shən), removal of all or part of a limb or other body part. Although amputation has been practiced for centuries, the development of sophisticated techniques for treatment and prevention of infection has greatly , two individuals were sacrificed twice a day (9 AM and 5 PM) during a 9- day period, and their siphons were examined in the microscope. Within the first 24 hours after amputation, the process was slow, and only the rudiments of the primary tentacles were visible. However, between the second and the third day a fast transformation of the siphon was observed, with regeneration of secondary and tertiary tentacles. The siphon was fully regenerated on the fifth day after amputation. One month later, the siphon showed the same aspect than at the fifth day. Despite the delay observed in the regeneration of the siphon within the first 24 hours after amputation, probably due to physiologic constrains associated with the lack of well developed tentacles, regeneration showed to be a fast process. Development of primary and secondary tentacles must therefore play an important role in providing basic functionality to the siphon, as well as to the whole organism. KEY WORDS: siphon, regeneration, Donna denticulatus, tellineacean bivalve, fish cropping INTRODUCTION To maintain their basic physiologic functions (i.e., feeding, defecation defecation or bowel movement Elimination of feces from the digestive tract. Peristalsis moves feces through the colon to the rectum, where they stimulate the urge to defecate. , and gas exchange), infaunal organisms must establish contact with the sediment-water interface. Soft bodied species of ten achieve this interaction by exposing parts of their bodies outside the sediment in the form of specialize structures such as ramified tentacles (e.g., polychaetes) or siphons (e.g., bivalves) that maximize the area of contact with the water column, thus optimizing the interaction with environment (McLachlan et al. 1995). However, the exposure of such structures can enhance the risk for predation predation Form of food getting in which one animal, the predator, eats an animal of another species, the prey, immediately after killing it or, in some cases, while it is still alive. Most predators are generalists; they eat a variety of prey species. , making infaunal organisms more vulnerable to tissue browsing by benthic ben·thos n. 1. The collection of organisms living on or in sea or lake bottoms. 2. The bottom of a sea or lake. [Greek. feeders such as, crab and shrimp (Kamermans & Huitema 1994), pelagic pelagic living in the middle or near the surface of large bodies of water such as lakes or oceans. juvenile flatfish flatfish, common name for any member of the unique and widespread order Pleuronectiformes containing over 500 species (including the flounder, halibut, plaice, sole, and turbot), 130 of which are American. (Trevallion et al. 1970), and birds (Zwarts 1986). Siphon cropping has been reported for several bivalve species (Trevaillon 1971, Hodgson 1982, Peterson & Quammen 1982, Zwarts 1986). After amputation, siphons can regenerate providing a renewable source of secondary production that has been shown to maintain higher trophic levels (Penchaszadeh 1983, Pekkarinen 1984, Riera 1995, Luzzatto & Penchaszadeh 2001). However regeneration occurs at the cost of growth and reproduction, thus affecting the fitness of these organisms (Geller 1990, Peterson & Quammen 1982, Kamermans & Huitema 1994, Irlandi & Mehlich 1996). The bivalve Donax denticulatus Linnaeus, 1758, locally known as "chipi-chipi" occurs intertidally on sandy beaches throughout the Caribbean all year long (Wade 1969). In Venezuela, it is commonly found in the intertidal zone of fine and medium grain dissipative sandy beaches in the central west coast, together with the bivalves Donax striatus and Tivela mactroides (De Mahieu & Gamba 1980, Penchaszadeh 1983, Penchaszadeh et al 2000). D. denticulatus is an important species in the food chain as a primary consumer of phytoplankton phytoplankton Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use. and detritus detritus /de·tri·tus/ (de-tri´tus) particulate matter produced by or remaining after the wearing away or disintegration of a substance or tissue. de·tri·tus n. pl. and is also eaten by a wide range of predators including the fishes Menticirrhus littoralis, Conodon nobilis, Trachinotus carolinus. Trachinotus goodei and Umbrina coroides, and the ghost crab Ocypode verreauxi (Penchaszadeh 1983, Riera 1995). The siphons of this species are both flexible and extensible as are those of Donax hanleyanus Philippi 1847 (Luzzatto & Penchaszadeh, 2001) and other tellinacean bivalves. They are comprised of 6 primaries, 6 secondaries, 12 tertiaries, and 24 quaternaries tentacles (Wade 1969). When buried, the siphons of D. denticulatus extend through the sediment into the water column and look like a white crown from above. This highly ramified structure prevent large particules (>250 [micro]m) from entering into the stomach (Wade 1969). In this study, we followed a detailed examination of artificially amputated siphon regeneration of D. denticulatus, to establish time of regeneration and the effects of amputation on the morphology of siphons. MATERIALS AND METHODS Individuals of D. denticulatus were collected at the intertidal zone of Tucacas beach located in the central west coast of Venezuela (10[degrees]45'55"N, 68[degrees]19'24"W). Organisms with a shell length of 1.5-2.0 cm were collected to ensure that all were already sexually developed. They were transported to the laboratory in an icebox with wet sand. In the laboratory, 2 groups consisting of 50 animals each (control and experimental groups) were placed separately in aquaria with aerated aer·ate tr.v. aer·at·ed, aer·at·ing, aer·ates 1. To supply with air or expose to the circulation of air: aerate soil. 2. seawater at 35 [per thousand], 23 [degrees]C and a layer of sand deep enough for burrowing. They were fed with Advanced Invertebrate invertebrate (ĭn'vûr`təbrət, –brāt'), any animal lacking a backbone. The invertebrates include the tunicates and lancelets of phylum Chordata, as well as all animal phyla other than Chordata. Formula (Marine Enterprises, Inc.) once a day. The animals were maintained for acclimation acclimation /ac·cli·ma·tion/ (ak?li-ma´shun) the process of becoming accustomed to a new environment. ac·cli·ma·tion n. 1. under these conditions for 5 days. After this period, the experimental organisms were placed in Petri dishes with seawater. Once the siphons were extended, an anesthetic solution of magnesium chloride 7.5% in seawater was slowly added, and then the petri dish was placed in the refrigerator at 4 [degrees]C for 20 min. After this treatment, the siphons are completely elongated e·lon·gate tr. & intr.v. e·lon·gat·ed, e·lon·gat·ing, e·lon·gates To make or grow longer. adj. or elongated 1. Made longer; extended. 2. Having more length than width; slender. and do not retract TO RETRACT. To withdraw a proposition or offer before it has been accepted. 2. This the party making it has a right to do is long as it has not been accepted; for no principle of law or equity can, under these circumstances, require him to persevere in it. in the shell, so we proceeded to cut the siphon tip with dissecting scissors scissors Cutting instrument or tool consisting of a pair of opposed metal blades that meet and cut when the handles at their ends are brought together. Modern scissors are of two types: the more usual pivoted blades have a rivet or screw connection between the cutting ends . The lips were fixed in a glucamine-acetate buffer containing 6% formalin formalin /for·ma·lin/ (for´mah-lin) formaldehyde solution. for·ma·lin n. An aqueous solution of formaldehyde that is 37 percent by weight. (Miloslavich & Penchaszadeh, 1997) and kept in the refrigerator. The animals were left to recover in their aquaria and then sacrificed in groups of 2 individuals twice a day (9 AM and 5 PM) during a 10-day period and then at day 30, cutting and fixing the tips by the described procedure. Observations of the fixed tips were done with a stereoscopic microscope. Also, we observed the siphons of the recovering animals to corroborate To support or enhance the believability of a fact or assertion by the presentation of additional information that confirms the truthfulness of the item. The testimony of a witness is corroborated if subsequent evidence, such as a coroner's report or the testimony of other activity and functionality. RESULTS The regeneration sequence is shown in Figure 1. In the anesthetized a·nes·the·tize also a·naes·the·tize tr.v. a·nes·the·tized, a·nes·the·tiz·ing, a·nes·the·tiz·es To induce anesthesia in. a·nes individuals, the siphon slowly retracted into the shell after the cut and remained retracted for about 30 minutes. After this time, the siphon extended and started to function creating inhalant currents but unable to select or filter particles: some siphons were active up to 5 hours after the cut, and were able to select particles 72 hours after amputation. The siphon showed full functionality on the 5th day. Regarding the regeneration sequence, the 1st day (24 hours after the cut) the process was slow and only the rudiments of the primary tentacles were visible (see Figs. 1c). Within the 2nd and the 3rd day a fast transformation of the siphon was observed, with the regeneration of secondary tentacles (see Fig. 1d to f). The regeneration process was completed within the 5th day, however the regenerated siphon showed less ramification ramification /ram·i·fi·ca·tion/ (ram?i-fi-ka´shun) 1. distribution in branches. 2. a branching. ram·i·fi·ca·tion n. A branching shape or arrangement. than the unamputared one (see Fig. 1h). A schematic sequence of regeneration is shown in Figure 2, highlighting the regeneration process of primary, secondary, and tertiary tentacles. [FIGURES 1-2 OMITTED] Between the 5th and the 9th day no significant transformations were detected (Fig. 3a to c). One month later, the siphon had the same as the 5th day (see Fig. 3d). At the end of experiments, all regenerated siphons were less ramified than unamputated ones, even 1 month after amputation. [FIGURE 3 OMITTED] DISCUSION As noted earlier, siphons are responsible for important activities such as feeding and defecation, therefore its ablation should have direct impact on these activities. Wade (1969) noted that after amputation, particles as large as 700 [micro]m were found in the mantle cavity of D. denticulatus, forcing the organism to invest effort in extracting these particules out of the mantle, and temporarily suspending feeding activity. Additionally, regeneration itself is an energy consuming process. Artificially amputated individuals of Donax serra showed a decrease in growth rates when compared with nonamputated individuals (Hodgson 1982). Pekkarinen (1984) also registered significant growth rates differences in individuals of Macoma balthica, a tellinacean bivalve, when inhalant siphon was removed. The slow process of regeneration observed within the first 24 hours after amputation in our experiment, are probably due to the malfunctioning of the siphon, in the absence of developed tentacles, therefore limiting the food and oxygen intake of amputated individuals. Additionally, Pekkarinen (1984) observed that just after amputation, siphon muscles contract to close the wound, preventing the loss of hemolymph hemolymph /he·mo·lymph/ (he´mo-limf?) 1. blood and lymph. 2. the bloodlike fluid of those invertebrates having open blood-vascular systems. he·mo·lymph n. , but also preventing the water to flow through the siphons. Luzzatto and Penchaszadeh (2001) studied changes in regeneration rates of inhalant siphon of Donax hanleyanus, and showed that this process had a sigmoidal sig·moid also sig·moi·dal adj. 1. Having the shape of the letter S. 2. Of or relating to the sigmoid colon. [Greek s behavior. Within the first hours. regeneration rate was slow, but then increased exponentially between the 1st and the 3rd day after amputation, until the secondary tentacles were developed. Alter that, regeneration rate slowed until the siphon became fully active in selecting particules (5 days after amputation). Siphons of D. denticulatus also showed fast regeneration rate between 24 and 72 hours after amputation (see Fig. 1d-f), with a full development of primary, secondary, and tertiary tentacles on the 5th day after amputation (see Fig. 1h). Pekkarinen (1984) reported full regeneration after 7 days for M. balthica. Close observation of regenerating siphons allowed us to conclude that the highest regeneration occurred at the beginning of the process, with a short lag-time period of 24 hours, in which functionality was reestablished. The most notorious morphologic transformations were detected within the first 72 hours of regeneration, with fast regeneration of primary and secondary tentacles, whereas the regeneration of tertiary tentacles extended for a longer period of time (5 days). Therefore, primary and secondary tentacles must play an important role in providing basic functionality to the siphon, as well as to the whole organism. ACKNOWLEDGMENTS We are indebted to the students of the Marine Biology course of the Universidad Simon Bolivar who helped collecting the animals at Tucacas beach. This work was partially supported by a Decanato de investigacion y Dc sarrollo (USB USB in full Universal Serial Bus Type of serial bus that allows peripheral devices (disks, modems, printers, digitizers, data gloves, etc.) to be easily connected to a computer. ) grant to the Grupo de Ciencias Marinas (G-003) and by cooperative program Venezuela-Argentina funded by Fundacion Antorchas. LITERATURE CITED De Mahieu. G. & L. Gamba. 1980. Zonacion litoral en algunas comunidades de sustrato arenoso del area de Golfo Triste triste adj. Sad; wistful. [Middle English, from Old French, from Latin tristis.] triste Adjective Old-fashioned sad [French] , Venezuela. In: P. Penchaszadeh, editor. Biology, ecology, and culture of aquatic organisms. Primeras Jornadas Cientificas, Caracas. Venezuela: Universidad Simon Bolivar. Equinoccio. pp. 77-114. Geller, J. B. 1990. Reproductive responses to shell damage by the gastropod gastropod, member of the class Gastropoda, the largest and most successful class of mollusks (phylum Mollusca), containing over 35,000 living species and 15,000 fossil forms. Nucella emarginata (Deshayes). J. Exp. Mar. Biol. Ecol. 136:77-87. Hodgson, A, 1982. Studies on wound healing and regeneration of the siphon of the bivalve Donax serra (Roding). Transactions of the Royal Society of South Africa 44:489-498. Irlandi. E. A. & M. E. Mehlich. 1996. The effect of tissue cropping and disturbance by browsing fishes on the growth of two species of suspension-feeding bivalves. J. Exp. Mar. Biol. Ecol. 197:279-293. Kamermans, P. & H. J. Huitema. 1994. Shrimp (Crangon crangon L.) browsing upon siphon tips inhibits feeding and growth in the bivalve Macoma balthica (L.). J. Exp. Mar. Biol. Ecol. 175:59-75. Luzzatto, D. & P. E. Penchaszadeh. 2001. Regeneration of the inhalant siphon of Donax hanleyanus Philippi 1847 (Bivalvia, Donacidae) from Argentina. J. Shellfish Res. 20(1):149-153. McLachlan, A., E. Jaramillo, O. Defeo, J. Dugan, A. de Ruyck & P. Cohetes. 1995. Adaptations of bivalves to different beach types. J. Exp. Mar. Biol. Ecol. 187:147-160. Miloslavich, P. A. & P. E. Penchaszadeh. 1997. Spawn and development of Fusinus cluster Philippi 1850 (Gastropoda, Prosobranchie) from the Verezuelan Caribbean. The Veliger ve·li·ger n. A larval stage of a mollusk characterized by the presence of a velum. [New Latin v , 40:93-100. Pekkarinen. M. 1984 Regeneration of the inhalant siphon and siphonal sense organs of brackish-water (Baltic Sea) Macoma balthica (Lamellibranchiata, Tellinacea). Ann. Zool. Fennici. 21:29-40. Penchaszadeh, P. E. 1983. Sub-tidal sandy beach trophic trophic /tro·phic/ (tro´fik) (trof´ik) pertaining to nutrition. troph·ic adj. Of, relating to, or characterized by nutrition. structure in the area of Punta Moron, Venezuela. In: McLachlan & Erasmus, editors. Sandy beaches as ecosystems. Junk Publishers, The Hague, The Netherlands, pp 523-528. Penchaszadeh, P., C. A. Leon, H. Alvarez, D. Bone, P. Castellano, M. M. Castillo, Y. Diaz, M. P. Garcia, M. Lemus, F. Losada, A. Martin, P. Miloslavich, C. Paredes, D. Perez, M. Sebastiani, D. Stecconi, V. Roa & A. Villamizar. 2000. The Coastline of Venezuela. In: C. Sheppard, editor. Seas at the millennium. An environmental evaluation. Europe, the Americas and West Africa, Vol. I. UK: University of Warwick In the 1960s and 1970s, Warwick had a reputation as a politically radical institution.[3] More recently, the University has been seen as a favoured institution of the British New Labour government. . pp 643-661. Peterson, C. & M. Quammen. 1982. Siphon nipping nip·ping adj. 1. Sharp and biting, as the cold. 2. Bitingly sarcastic. nip  ping·ly adv.Adj. : its importance to small fishes and its impact on growth of the bivalve Protothaca staminea (Conrad). J. Exp. Mar. Biol. Ecol. 63:249-268. Riera, A, A. 1995. Relaciones troficas interespecificas en una comunidad ictica de una playa arenosa del estado Falcon. Universidad Simon Bolivar. Trabajo Especial de Grado. 63 pp. Trevallion, A. 1971. Studies on Tellina tenuis ten·u·is n. pl. ten·u·es Linguistics 1. A voiceless stop. 2. A voiceless unaspirated stop in ancient Greek. (Da Costa). III. Aspects of general biology. J. Exp. Mar. Biol. Ecol.7:95-122. Trevallion, A., R. Edwards & J. Steel. 1970. Dynamics of a benthic bivalve. In, J. Steele, editor. Marine food chains. Edinburgh, UK: Oliver and Boyd. pp. 285-295. Wade, B. A. 1969. Studies on the biology of the West Indian beach clam, Donax denticulatus, Linne. 3. Functional Morphology. Bull. Mar. Sci. 19:306-322. Zwarts. L. 1986. Burying depth of the benthic bivalve Scrobuluria plana (Da Costa) in relation to siphon-cropping. J. Exp. Mar. Biol. Ecol. 100: 25-39. PATRICIA PATRICIA Practical Algorithm To Retrieve Information Coded In Alphanumeric PATRICIA Proving and Testability for Reliability Improvement of Complex Integrated Architectures PATRICIA PApilloma TRIal Cervical cancer In young Adults MILOSLAVICH, (1) * PABLO E. PENCHASZADEH, (2) * ANA KARINNA CARBONINI (1) AND DIEGO SCHAPIRA (1) (1) Universidad Simon Bolivar, Departamento de Estudios Ambientales, P.O. Box 89000, Caracas, 1080, Venezuela and (2) Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Biologia, Laboratorio de Invertebrados, Ciudad Universitaria, Pab. II. C1428EHA EHA European Hematology Association EHA Economic History Association EHA Emmanuel Hospital Association EHA Education for All Handicapped Children Act of 1975 EHA Empty Homes Agency EHA English Hockey Association EHA Electrohydrostatic Actuator , Buenos Aires, Argentina. * Corresponding author (Venezuela). E-mail: pmilos@usb.ve * Corresponding author (Argentina). E-mail: pablop@mail.retina.ar |
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