The Behaviour Of A Supralittoral Gastropod Biology Essay

The Behaviour Of A Supralittoral Gastropod biota EssayThe species chosen for this experiment (or rather set of experiments) is Melarhaphe neritoides. This is a precise common (sm altogether) species of pull together found distri furthered a farsighted the raspy Maltese propping ups. It is listed in the Phylum Mollusca (Class Gastropoda) and grows to some just under 1cm. Its sides atomic number 18 flat (unlike the to a greater extent than common rounded guinea pig found amongst molluscs) and has a high pointed spire. An operculum covers an elliptical aperture and a white periostracum leads to the dark blue/b escape shell. Its niche is determined in a very specific stretch on the shore labelled the supralittoral z nonp aril. This is that area located just above the high sc terminal mark. It is not submerged tho is frequently splashed by ocean spray when it is windy/stormy (in occurrence it is in like manner known as the splash or spray z superstar(a)). It is an unfor bo untiful environs and beingnesss living hither moldiness be very well qualified to its instability. The Melarhaphe neritoides pull together moldiness be open to withstand high temperatures, knowing weewee, salt and brine irrigate, vapor and exposure to air and of course any shore line animals which qualification prey upon the snail. In the summer months, the sea round the Maltese islands is very calm and the snails environment is rarely wetted. Also the snail run execrables in work bring out contact with the hard rocky surface which r individu eachy(prenominal)es high temperatures up to 50 details easily (which for most organisms this would be lethal). On the early(a) hand during the winter clipping months, storms are frequent and wave implement is very violent on the supralittoral z wizard. Not exclusively this but when there are no waves, pusss of fresh water whitethorn fashion model in these rocky patches which for most creatures adapted to a salty (high w ater potential) environment will cause osmotic problems. As opposed to the summer months, the temperature of the rocks in winter falls drastically nigh meters even below freezing point. In particular as the mollusc is very well adapted to this environment, it is the dominant macro-faunal organism found there. To accommodate such drastic changes in its environment, Melarhaphe neritoides has many behavioral adaptations. Such adaptations include becoming idle, taking resort hotel in pits/rocky overhangs, aggregating in groups and becoming industrious entirely when conditions are suitable. To be able to dead-on(prenominal)ly avoid the harshness of the environment, the mollusc must establish some kind of sense as to when to in truth begin aestivation periods or when to come out of them, which spot is suitable (offers luxuriant protection) to take asylum in etc. It is these behavioural adaptations that this experiment investigates. A set of antithetical habitats and condition s are prepared and a number of snails tested to see their reception and gustatory perception. Such an experiment must be conducted as accurately as possible as there are many factors which induce errors. In fact the test subjects where newly caught and a number (10) of individuals were tested with all(prenominal) method to ensure usable and explainable data. Also the individuals tested where seen to be or so 0.7mm in height. This is the height of juveniles not too recent or too old as it is in this part of its life succession in which an animal is most believably going to respond as expected in individuals seen in the wild (as old or young specimens may be less active or inhabit several(predicate) regions of the environment).ProcedureApparatusPetri dishes Graph paper Plastic fish tanksRuler timekeeper Acrylic plates (bore)Measuring piston chamber B privation bags Glass Rod get to Fine Sand Coarse Sand Circular glass rollMaterialsCalcium Chloride Sea Water Dis money boxed waterVaseline filth Blu-TackMethod sample.1A plastic Petri-dish was partitioned by means of thin plastic into 3 go to pieces parts. One part make full with fine mainstay, an another(prenominal) with rough-cut rachis and the other with gravel. Ten inactive snails were scattered across on these 3 different sabstrates and any crusade made mention every 1,2,6,24,36 hrs.Experiment.2 devil identical Petri dishes had their foundation ruled to form a 44 gridiron at 1 cm intervals. One snail was positioningd on severally grid line intersection. One dish contained a container entire of Calcium chloride, whilst the other house distilled water. Both dishes were sealed and observed over a period of 3 solar mean solar eld.A plastic Petri-dish was floated over a pool of water in a circular glass trough. Ten inactive snails were placed in the Petri-dish which was left(a) capable, but the glass trough was covered. by and by one hour, the cover was re locomote just enough to get t he snails out. These were tapped piano with a glass rod a fewer times and trust back in the trough. The number of active snails after the treatment was noted.Experiment.3deuce identical Petri dishes as in exp.2 (with a 44 grid) were prepared with one inactive snail per intersection. One dish is make full up to about 1mm with sea water, whilst the other one was left dry. Both dishes were sealed with Vaseline grease and observed over a period of one hour. This procedure was recurrent scarcely using fresh water sooner of sea water.Snails which had been left in dry air for one hour were tapped sharply on the shell and immediately placed in 1cm of sea water. The time interpreted for the maiden 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 th e contend in each container was noted.Experiment.5Two identical measuring cylinders are filled to a depth of 3cm with seawater. Each cylinder was marked at 3 cm intervals head start 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 specimen of regular holes were attached to the fences 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. afterwards 3 hours the number 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 be submerged was counted at intervals of 1,2,6,24,36 hours.Experiment.7The p rocedure of experiment 5 was repeated save 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 was preserve.PrecautionsSnails that were used for an experiment were not reused but placed separately in a container to note that they break already undergone some treatment. This was done so as not have active snails from a preceding(prenominal) experiment ruin the upshots of the next experiment.The snails were all freshly caught (not more than 2 age) so as to have an accurate closure 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 contributes to be unruffled 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 activated the snails prior to the actual experiment taking place. near experiments could have been done only once to the long waiting time, and with a proportionally atrophied number of individuals (ten snails may not yield a representative result).The experiment tried to replicate the conditions that the snail would be in the wild. This depose never be fully achieved and so the experiment its ego 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 move other snails in experiment 2 and 3 giving errored results.ResultsExperiment 1 m / hrFine sand postureRough sand0334133423346343242533625348154No snails were noted to have accumulated on the silver-tongued plast ic surface of the Petri-dish.Experiment 2 fracture 2ATime/hrRH=0%RH=100%00061230125413Part 2BSnails activeBefore tappingAfter tapping02Experiment 3Part 3ATime/hrNumber of snails moved00156122414321548165616Part 3BTime for world-class discernible movement of operculum after left inDry conditionsDry conditions followed by tappingImmersed in seawater14082214833292044331640528920619753783862811451921141310121050Part 3CTime/hrNumber of snails moved001060240320480561Experiment 4 double up5cm 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/hr12624324856126243248560-3cm222222222110003-6cm000000000101106-9cm000000000011019-12cm0000000000000012-15cm0000000000001115-18cm0000000000000018-21cm0000000000000021-24cm0000000000000024-27cm 0000000000000027-30cm (top)00000000000000Experiment 6Part 6AAfter 3 hoursAt the bottom of the tank (smooth)In crevicesOn smooth wall subaquatic 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 7 gentleDarkTime/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/ earthy 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 fences that the organisms reasonably dislike a loose substrate such as the fine sand (only 2 covered) but prefer rough gravel (5 snails ride outed). 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 molybdenum ex periment, the effect of humidity on the inactive snails was observed. In part A which consisted of the two Petri-dishes with the grid, the difference in humidity was created by using calcium chloride (anhydrous). This chemical can absorb the water present in the nimbus creating dry conditions whilst the other had a tap with water giving the environment 100% relative humidity. 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 come up as in part A at 100% RH). This pop the questions that belike the wave action on the snails combined with the high humidity (as they are wetted) are effective stimuli to activate the snails.Experiment 3 consisted 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 function submersed in junior-grade 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 bewilder active was noted. Prior to the experiment, they were sharply tapped. This tapping followed by the immersio n 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 draw 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 length 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 rattling semi-terrestrial only venturing into the sea to lay its eggs. T hus 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 climb 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 centimetr es. 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 fender 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 fluctuation 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 reason out 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 aggregated in the pits and stayed submerged. 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 t hem) became active faster (in the first hour even) and climbed a distance of 3cm, whilst in the covered cylinder fractional 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.Taking 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 small 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 t ravels from its habitat to the Eulittoral order (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 supralittoral zone) from the sea. In this zone lichens also grow in the winter and origin times. These are a prime source of forage 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 t o their presence.