The Behaviour Of A Supralittoral Gastropod Biology Essay

The Behaviour Of A Supralittoral Gastropod Biology EssayThe species chosen for this experiment (or rather set of experiments) is Melarhaphe neritoides. This is a truly vernacular (sm solely) species of gather found distri buted along the rocky Maltese shores. It is listed in the Phylum Mollusca (Class Gastropoda) and grows to around just under 1cm. Its sides be flat (unlike the more common rounded shell found amongst molluscs) and has a high pointed spire. An operculum covers an oval aperture and a white periostracum leads to the dark blue/black shell. Its niche is located in a real specific stretch on the shore labelled the supralittoral z hotshot. This is that bea located just above the high tide mark. It is not settle but is frequently splashed by ocean spray when it is windy/stormy (in fact it is also known as the splash or spray z unmatched). It is an depressed environment and organisms living here must be very well adapted to its instability. The Melarhaphe neritoides snail must be able to withstand high temperatures, freshwater system system, flavour and brine water, desiccation and exposure to air and of course any shore line animals which might prey upon the snail. In the summer months, the ocean round the Maltese islands is very calm and the snails environment is rarely steadfastted. Also the snail lives in direct contact with the hard rocky fold which reaches high temperatures up to 50 degrees easily (which for most organisms this would be lethal). On the other hand during the winter months, storms are frequent and wave action is very violent on the supralittoral zone. not nevertheless this but when there are no waves, pools of fresh water may form in these rocky patches which for most creatures adapted to a savory (high water potential) environment provide cause osmotic problems. As opposed to the summer months, the temperature of the rocks in winter falls forcefulally some terms even below freezing point. In fact as the mollusc is very well adapted to this environment, it is the dominant macro-faunal organism found there. To accommodate such(prenominal) drastic changes in its environment, Melarhaphe neritoides has many behavioural adaptations. Such adaptations include becoming in agile, taking refuge in pits/rocky overhangs, aggregating in groups and becoming active hotshot when conditions are suitable. To be able to accurately avoid the harshness of the environment, the mollusc must possess some kind of sense as to when to actually begin estivation layovers or when to come out of them, which spot is suitable (offers passable protection) to take refuge in etc. It is these behavioural adaptations that this experiment investigates. A set of disparate habitats and conditions are prepared and a crook of snails tested to see their reaction and mouthful. Such an experiment must be conducted as accurately as manageable as there are many factors which induce errors. In fact the test subjects where freshly caught and a subject (10) of individuals were tested with each method to go through usable and explainable data. Also the individuals tested where seen to be to the highest degree 0.7mm in height. This is the height of juveniles not too young or too old as it is in this part of its life time in which an animal is most believably going to respond as expected in individuals seen in the crackers (as old or young specimens may be less active or inhabit disparate regions of the environment).ProcedureApparatusPetri dishes Graph paper malleable aquariumsRuler snipr Acrylic dwellings (drilled)Measuring cylinder Black bags Glass Rod Gravel Fine Sand Coarse Sand Circular glaze over troughMaterialsCalcium Chloride Sea Water Dis work oned waterVaseline grease Blu-TackMethodexperiment.1A malleable Petri-dish was partitioned by means of thin plastic into 3 set forth parts. One part filled with fine sand, another with coarse sand and the other with exhaust. Ten slothful snails were s cattered across on these 3 different sabstrates and any assumement made annotatingd every 1,2,6,24,36 hrs.Experiment.2Two identical Petri dishes had their bottom ruled to form a 44 grid at 1 cm intervals. One snail was fixed on each grid line intersection. One dish contained a container full of Calcium chloride, whilst the other ho apply distilled water. two dishes were sealed and observed over a period of 3 twenty-four hour periods.A plastic Petri-dish was floated over a pool of water in a broadside glass trough. Ten inactive snails were placed in the Petri-dish which was left opened, but the glass trough was cover. After one hour, the cover was removed just enough to get the snails out. These were tapped gently with a glass rod a some times and put back in the trough. The progeny of active snails after the give-and-take was noted.Experiment.3Two identical Petri dishes as in exp.2 (with a 44 grid) were prepared with one inactive snail per intersection. One dish is filled u p to some 1mm with sea water, whilst the other one was left run dry. Both dishes were sealed with Vaseline grease and observed over a period of one hour. This procedure was repeated further using fresh water instead of sea water.Snails which had been left in dry air for one hour were tapped sharply on the shell and straightaway placed in 1cm of sea water. The time taken for the first noticeable movement of the snails operculum was noted.Experiment.4Two identical measuring cylinders were filled with sea water one to a depth of 5cm and the other to a depth of 20cm. Individual inactive snails were placed in each cylinder, and the time taken for the snail to move 5 cm up the wall in each container was noted.Experiment.5Two identical measuring cylinders are filled to a depth of 3cm with seawater. Each cylinder was pronounced at 3 cm intervals starting from the water surface. One cylinder was stoppered tightly whilst the other was left open. The movement of each snail up the cylinder was noted with time.Experiment.6Two identical plastic aquaria are filled to a depth of 1.5cm with sea water. Regular plastic plates that were drilled with a material body of regular holes were attached to the walls of one of the aquaria. The aquaria were marked off at 3cm intervals starting from the water surface. Ten inactive snails were placed in each aquarium and covered with a lid. After 3 hours the crook of snails at each level was noted.The procedure above was then repeated but instead of the walls, the drilled plate was placed at the bottom of the aquarium. The number of individuals remaining submerged was counted at intervals of 1,2,6,24,36 hours.Experiment.7The procedure of experiment 5 was repeated only this time both the cylinders were tightly stoppered and with 10 snails in each one. One of the cylinders is placed in an opaque black bag whilst the other one is left in the light. The number of snails at each level for both cylinders at intervals of 1,3,6 and 24 hours wa s recorded.PrecautionsSnails that were used for an experiment were not reused but placed separately in a container to note that they have already undergone some treatment. This was make so as not have active snails from a previous experiment ruin the results of the next experiment.The snails were all freshly caught (not more than 2 days) so as to have an accurate result as possible.In most experiments a good number of individuals were used (like 10) and others were possible were replicated.Enough time was left to elapse for results to be collected as the stimuli that activate the snails may be over a long period of time.Snails used were chosen to be of similar size (0.7cm shell height) and handled very gently.ErrorsHandling of snails from capture site to lab and from tray to the experiment may have emotional the snails prior to the actual experiment taking place.Most experiments could have been done only once to the long waiting time, and with a relatively small number of individu als (ten snails may not yield a representative result).The experiment tried to replicate the conditions that the snail would be in the risky. This cannister never be full achieved and so the experiment its self is not so accurate.Movement of apparatus or activity on the bench could have changed snail position in other experiments or activating them due to the vibration not to the variable tested.The snails themselves may have moved other snails in experiment 2 and 3 giving errored results.ResultsExperiment 1Time / hrFine sandGravelRough sand0334133423346343242533625348154No snails were noted to have accumulated on the smooth plastic surface of the Petri-dish.Experiment 2 furcate 2ATime/hrRH=0%RH=100%00061230125413Part 2BSnails activeBefore tappingAfter tapping02Experiment 3Part 3ATime/hrNumber of snails moved00156122414321548165616Part 3BTime for first discernible movement of operculum after left inDry conditionsDry conditions followed by tappingImmersed in seawater140822148332920 44331640528920619753783862811451921141310121050Part 3CTime/hrNumber of snails moved001060240320480561Experiment 4Replicate5cm water20 cm water12340s4140s(69 mins)22400s86400s (1day)39000s2 day49900s2 day586400s2 day62 day2 day72 day2 day82 day2 day92 day2 day102 day2 dayExperiment 5A total of 2 snails were placed in each measuring cylinder. The numbers in the table show the number of snails recorded at each level marked.ClosedOpenTime/hr12624324856126243248560-3cm222222222110003-6cm000000000101106-9cm000000000011019-12cm0000000000000012-15cm0000000000001115-18cm0000000000000018-21cm0000000000000021-24cm0000000000000024-27cm0000000000000027-30cm (top)00000000000000Experiment 6Part 6AAfter 3 hoursAt the bottom of the tank (smooth)In crevicesOn smooth wallSubmerged in seawater8010-3cm above water0013-6cm above water000Part 6BTime/hr12624324856submergedIn crevices6899999On smooth wall4100001Above seawaterIn crevices0000000Not in crevices0111110Submerged (the only one required others are extra)109999910Experiment 7LightDarkTime/hr12624324856126243248560-3cm1010101010101054444333-6cm000000013100116-9cm000000001222119-12cm0000000200010012-15cm0000000011213315-18cm0000000011000018-21cm0000000000000021-24cm0000000001100024-27cm0000000200111027-30cm (top)00000000000112DiscussionThe results were organized in the form of tables usually with length in movement or number of snails against time. In the first experiment, habitat preference was tested. Rough gravel and fine/coarse sand are the typical supralittoral substrates and snails may have a preference to one and not the other. As observed from the table up to the first few hours, no movement was noted. On the sixth hour a single snail had changed substrate from the fine sand onto the gravel. At the end of the experiment two of the 3 snails placed on the fine sand had moved onto the gravel or coarse sand and one from the coarse sand had moved onto the gravel as well. This indicates that the organisms somewhat dislike a l oose substrate such as the fine sand (only 2 remained) but prefer rough gravel (5 snails remained). The coarse sand was somewhat in between the two with 4 snails remaining. This is the expected result as these organisms are found between small rocks and in crevices. The fact that not all of the travelled to one substrate could have been due to the lack of space as with 5 or 4 snails in one section, the Petri-dish became somewhat crowded. No snails were observed to go onto the smooth Petri-dish surface and this is also explained by the fact that their habitat preference is towards rocky terrain.In the second experiment, the effect of humidness on the inactive snails was observed. In part A which consisted of the two Petri-dishes with the grid, the difference in humidness was created by using calcium chloride (anhydrous). This chemical can absorb the water present in the atmosphere creating dry conditions whilst the other had a tap with water giving the environment 100% relative humi dity. In the dry dish 6% of the snails moved whilst in the wet dish, 18% of the snails moved. Although not so many snails moved the difference from dry to wet is already evident with about 3 times the snails moving in the 100% RH than the 0% RH. This shows that although it is not that strong of a stimulus, the relative humidity plays a part in the activation of the sails.In part B of experiment number two, the snails were once again exposed to an atmosphere of 100% RH, but they were also tapped on the shell after one hour and placed back for a few more minutes. The tapping seems to have some effect on the snails as unlike the 100 % RH in part A where the snails took days to move, 20% of the snails in part B after only one hour were noticed to be active (which is roughly the same tot as in part A at 100% RH). This suggests that probably the wave action on the snails combined with the high humidity (as they are wetted) are effective stimuli to activate the snails.Experiment 3 consist ed of three parts. In the first part, the Petri-dish had a grid on the bottom where 16 snails were placed. In the one which contained the 1mm of sea water by the second day all the snails had moved. The period where most snails became active was between the 6th and 24th hour. This when compared to the previous experiment where only the humidity was at 100% shows that water is a much stronger activator as all the snails moved (the dry control had no noticeable movement). This would make sense as if there was wave action apart from high humidity and the mechanical force its self (both of which have shown positive results) , the snails would most likely become submersed in little pockets of sea water. Interesting to note that when as in part 3C the water used was fresh water, no snails moved up to 24 hours and only one moved just slightly over the 3 days period (probably due to humidity not the water its self). This is interesting to note. It can probably be explained by the fact that if it were to rain over the snails which in August or September (although rare) it might, although the snail would feel the mechanical force, be in an atmosphere of high humidity and covered in water it would not be beneficial to come out of dormancy as the environment would not yet be suitable and so it must be sea water to activate the snail as this would only come ashore from waves (indicating a suitable environment). In part B of experiment 3 the time taken for each snail to become active was noted. Prior to the experiment, they were sharply tapped. This tapping followed by the immersion in sea water instantly brought about a response from the snail which opened its operculum. This was very fast, in fact an average time of 17.5 seconds was recorded between the ten snails tested. This once again replicated wave action only a faster response was obtained due to the fact that actual sea water was used and not high humidity or tapping only (which continues to suggest that the snail becomes active after summer during the winter storms).Up till experiment 3, sea water was known to bring about a response, the question then was (answered by experiment 4) if more water would bring about a faster reaction. Apparently this is not so as the time taken for the snails to travel a distance of 5cm up the wall of the cylinder containing 5cm of water was less than the cylinder containing 20cm of sea water. This can probably be explained by the fact that the snail is not adapted to live in deep water but it is actually semi-terrestrial only venturing into the sea to lay its eggs. Thus a higher hydrostatic pressure of 20cm would indicate an unsuitable environment and the snail will most likely remain dormant. Therefore only frequent wetting and not submerging (in more than 10cm of water) brings about a response (once again pools brought about by waves are usually not as deep as 20cm in small crevices where the snail aggregates).Experiment 5 was somewhat baffling and probably should not be considered as a representative result. Only a few snails were activated and the snails which travelled most up the cylinder were in the one not stoppered An expected result based on the other previous experiments and knowledge of the snails habitat preference would be something as follows. Upon introducing the snails to the 3cm of seawater, they would become active and since they would be submerged find a way out which would be to procession onto the cylinders side. Since their habitat lies a fair distance from the sea, the snail should continue to climb up to a good few centimetres. The snails in the stoppered cylinder should reach the top as the high humidity indicates that they are still very close to the water and travel up as far a possible. In the open cylinder having a dryer atmosphere, the snails would probably not move up to the top as they would be under the impression that they are a fair enough distance from the sea located at the bottom.Experiment 6 was an extension of experiment 5 where the upward movement from a submerged place was tested only this time the variable was not humidity but terrain brought about by the drilled plates stuck to the sides of the tank. Again the data was not as expected so much so that the slightly different magnetic declination experiment part 6B did not have the same results as A but was as expected. The reasons for experiments 5 and 6A being somewhat not accurate could be due to the errors mentioned in the sources of errors section above. If one were to follow the result brought about by experiment 6A it would be concluded that the snails prefer to remain submerged and on smooth surfaces rather than in the crevices. This of course is not the case as the snails prefer crevices in rocks as seen from experiment 1 and also in the wild these are found in crevices not submerged on smooth surfaces. In part B where the drilled plate was placed at the bottom, the snails aggregative in the pits and stayed sub merged. This would indicate that they actually do prefer crevices and pits which offer protection against the elements. The pits were submerged, but the expected result was that despite this the snails should not go out of the water. This is because they were submerged under only 1.5cm and in the wild this would be something common for a snail in a small pit to experience a few mm of sea water. So in the pits and under water the mollusc is actually in its preferred environment.Finally experiment 7 tested if the snail is photosensitive. According to the results obtained, when in light the snails (all 10 of them) became active faster (in the first hour even) and climbed a distance of 3cm, whilst in the covered cylinder half as much became active and over a longer time period. The strange thing was that in the light, the snails did not reach the top and in the dark only 1 did. Considering the high humidity in both, all the snails should have gone up to the top, the only difference (if there is) would be in the time taken.pickings into consideration all the results obtained and considering the concordant data, it is noted that the snails become active via various stimuli. In summer humidity is low and the snail would be in a crevice seeking refuge from the direct sun. When the first storms come along, the crevice the snail would be in becomes wet with sea water and very humid (a sort of micro habitat). The pounding action of the waves also has an effect on the snail. The mollusc is at home under a few centimetres of water and in fact in November to March during high tide the snail travels from its habitat to the Eulittoral zone (which is covered in water during this period of the year) and lays its eggs. The snail is affected by hydrostatic pressure (experiment 4) and so only travels a specific distance into the sea (which would be the optimum place to lay its eggs). It also detects the relative humidity and only ventures up shore a fixed distance (up to the supra littoral zone) from the sea. In this zone lichens also grow in the winter and spring times. These are a prime source of food for the snail and may be another reason why it aestivates as in summer, this food source dries up.ConclusionHaving done the experiments and observed the results, it can be concluded that there are various factors which play a part in activating the snail. Each factor affects the snail to a certain degree and the combination of all of them (humidity, mechanic wave action, sea water etc) brings about a reaction either to be inactive due to their lack or to be activated due to their presence.