GB1600832A - Plant for the production of artemia nauplii - Google Patents

Description

(54) A PLANT FOR PRODUCTION OF ARTEMIA NAUPLII (71) We, PIRELLI FURLANIS-APPLI- CAZIONI IDRAULICHE AGRICOLE GOMMA SpA, an Italian Company, of Via V Pisini 28, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention refers to a plant for the production of Artemia nauplii and in particular to Artemia salina nauplii. In particular, this present invention refers to a plant for the continuous production of Artemia salina nauplii.

There exist 'known' plants for the production of Artemia salina nauplii. By the term "nauplii" is meant the first larval stage of the crustacean Artemia salina. Said plants comprise a hemispherical tank containing seawater with a salinity from 37 to 39% at a temperature of from 21 > to 24"C. In the said tank are placed the Artemia salina eggs which hatch within a period of 38 to 41 hours in totally dark and continually aerated ambient conditions. After hatching, besides the nauplii, there also remain the shells of hatched eggs, unhatched eggs (e.g. owing to the embryo dying) and abnormal eggsow- ing to various reasons; moreover, there will also be present many eggs, that for different reasons (difficult to list here) take longer to hatch. There can also be various deposits of an animal, vegetable or mineral origin, cystic forms of other small shell-fish (hereinafter referred to as 'cysts'), all these being the remains of the preparation process of the Artemia. The eggs in fact are caught with fine-mesh nets, or are sucked out by an aspiration means along the shores of saltwater lakes. The subsequent washing and the separation of the eggs through floatation, or by means of air columns, are not able to guarantee either the purity, or the homogeneous character of the product. The result is that once put into salt-water, the eggs and the debris that accompanies them will float, move on the surface, or sink in an unpredictable and variable manner as time passes.

This prevents the obtaining of sufficiently pure nauplii through simple sedimentation.

In 'known' plants for separating the nauplii from said debris, the positive phototropic reaction of the nauplii is exploitedi.e. their natural attraction to a source of light. Thus, a first concentration of the said nauplii is caused by actuating a source of light placed in a tank, and subsequently-al- ong with certain forms of cyst, unhatched eggs and shells, the nauplii thus concentrated are sucked into a second tank. In the said second tank, the flow of water containing the nauplii, the eggs, the cysts, the shells and the various deposits, are sent into a section of the said tank defined by nets made with a 200cm (micron) mesh.

When trying to pass through the said nets, the nauplii contained in the water flow are held back by the mesh of the nets, while the eggs, the cysts and the shells along with the other deposits are washed away towards an automatic exhaust that maintains the level of the water in the said tank. Once the first washing is effected the flow of water is interrupted and the nauplii are once again concentrated by being attracted by the source of light, and sent into a third tank where the washing phase is repeated.

Said 'known' plants present numerous drawbacks. One of these drawbacks is that the separating of the nauplii is done solely by mechanical means such as by nets which filter the flow of water and leave behind the nauplii. Consequently, since the nauplii are retained by the mesh of the nets and are pressed against these nets by the water flow, some of the said nauplii become damagednotwithstanding the possibility of some of the nauplii managing to escape through the nets owing to the pressure of the flowing water. As a result of this, the global yield of the 'known' plants-i.e. the ratio between the number of the nauplii that reach safety for utilisation purposes and the number of eggs put into the hatching tanks-is not very high.

The aim of the present invention is to furnish a plant for the production of Artemia nauplii, in particular Artemia salina nauplii, to provide a continuous flow of the said nauplii for their utilisation, and which will also allow the recovery of any unhatched eggs (if present), with a resulting very high yield overall.

The object of the present invention is a plant for the production of Artemia nauplii, and in particular Artemia salina nauplii, the plant comprising, (i) at least one hatching-tank (ii) at least one collecting-tank provided with a light source and (iii) at least one separating-tank together with means for allowing communication between the hatching-tank (i) and collectingtank (ii) and between the collecting-tank (ii) and the separating-tank (iii), in which the separating-tank (iii) is provided with a) an outlet b) means to attract the Artemia nauplii towards the outlet c) means to prevent shells, cysts, hatched eggs of the Artemia and debris from reaching the outlet, and the hatching-tank, collecting-tank and separating-tank comprise material which impedes light and is non-toxic to the Artemia nauplii.

A further characteristic of the present invention, is a plant for the production of Artemia nauplii, in particular Artemia salina nauplii, wherein the separating-tank comprises means for the recovery of the unhatched eggs of the Artemia salina.

The present invention will be better illustrated by way of example only with reference to the accompanying drawings, in which: Figure 1-shows in vertical cross-section, a 'complex' formed by a hatching-tank and a collecting-tank, comprised in a plant for producing Artemia salina nauplii according to the present invention.

Figure 2-shows in vertical cross-section, a separating tank of a plant for producing Artemia salina nauplii according to the present invention.

Figure 3-is a cross-sectional view along the broken line Ill-Ill of Figure 2.

In general terms, one embodiment of a plant for the production of Artemia salina nauplii according to the present invention comprises at least one 'complex' formed by at least one hatching-tank and one collectingtank, and besides these, it also comprises means adapted to hold back the shells, the cysts, the unhatched eggs of Artemia salina and the deposits whilst allowing the free passage of the nauplii and means that force the nauplii to move in a pre-determined direction, even independently of the flow of water.

A plant for the production of Artemia salina nauplii, according to the present invention, can comprise more than one 'com pled'each of which is formed by a collecting-tank to the edges of which are connected the hatching-tanks. All the collecting-tanks of the 'complex' thus formed, are then connected to at least one separating-tank.

One embodiment of a 'complex' present in a plant for the production of Artemia salina nauplii is shown in vertical cross-section in Figure 1. In said Figure 1, a 'complex'-l is formed (for the sake of descriptive simplicity) by a collecting-tank 2 and by a single hatching-tank 3. In this particular embodiment there can be more than one hatchingtank associated with each collecting-tank.

Both the collecting and hatching-tanks are constructed of a material that impedes the passage of light, and which is non-toxic with regard to the Artemia salina nauplii. Such a material can be, for example, black plexiglass (thermoplastic sheet of acrylic synthetic resin), fibreglass reinforced plastic, cement reinforced with asbestos, or metal painted with non-toxic varnish, or unvarnished asbestos-reinforced cement treated with hydrofluoric acid.

The collecting-tank 2, is a container formed by an upper part 4open at the top and havjing a parallelepipedal form, and by a lower part 5-having an inverted pyramidal form. To the vertex 6 of the said pyramid there is connected a conduit 7. Said conduit 7 is provided with closing means known per se, for example a ball-valve or a gate-valve 8 and is the conduit that takes the nauplii to the separating-tank (which is not shown in Figure 1 but which will be described later on). Over the upper part of the said tank, there is placed a light source 9. The hatchingtank 3 is also formed of an upper part 10 having a parallelepipedal form and a lower part 11 having an inverted pyramidal form.

The vertex 12 of the lower part 11 is connected to an exhaust conduit 13 provided with shutting means 'known' per se, for example a valve 8 of the type mentioned above. The upper part 10 of the tank 3 is provided with a removable cover 14 which, when it is in its shut position, ensures that light is completely excluded from the inside of the tank. Moreover, there can be used in said hatching-tank 3, 'known' means for aerating the tank-for example a conduit 15 for the passage of air, at the extremity of which is a porous stone 16. The hatchingtank and the collecting-tank are provided with means that allow for putting the said tanks into communication between them, or for separating them one from the other, in this case a hole 17 in the common wall 18 that separates the collecting-tank from the hatching-tank, and a door 19. Said door 19 can be hinged (as shown in Figure 1) or it can be sliding. However it is actuated from the collecting-tank, and it is capable of ensuring the complete exclusion of light which is necessary for the hatching-tank.

Means known per se may be used for the admission of water in both the collectingtank indicated by 2' in Figure 1, and in the hatching-tank (not shown in Figure 1). Also envisaged for the hatching-tank is a means for automatically introducing Artemia salina eggs-for example an 'automatic' doser (not shown in the drawings).

The plant for the production of Artemia salina nauplii also comprises at least one separating-tank made of a material which impedes the passage of light and which is non-toxic for the said nauplii-for example any of the material suggested for the previously described 'complexes'. In Figures 2 and 3,.a separating-tank 20 is shown in vertical cross-section (Figure 2) and in plan view (Figure 3). Said separating-tank 20, has a rectangular plan (as shown in Figure 3) and is divided into three chambers by two transverse walls-the walls 21 (the projection of which is indicated with a broken-line in Figure 3 and numbered 22) and the wall 23.

The chambers of the separating-tank, in the order according to which the water flowing from the collecting-tank encounters them, are the entrance-chamber 24, the selectionchamber 25 and the exit-chamber 26.

The entrance-chamber 24 has an open top and is provided on one lateral wall with an exhaust 27, protected by a net 28 and furnished with a closing means for example the valve 8 already mentioned.

The net 28 must have a mesh size of about 200 ,xt (microns); moreover it can be of any type of material that is non-toxic for the nauplii for example nylon and other synthetic polyamide fibres, silk or any other natural fibres or stainless-steel. On the bottom of the said entrance-chamber 24, there is a small well 24', covered by a net 28 (of the type just described above), and at the bottom of which there is present an opening 29 provided with a shutting means--for example the valve 8 previously mentioned. Said small well 24', in association with the net 28, is a particular form of embodiment of the means for recovering the unhatched eggs of the Artemia salina.

The entrance-chamber is provided with already 'known' means-such as the pipe indicated with the number 7-for the admission of water coming from the collectingtank.

The adjacent selecting-chamber 25 is closed at the top by a horizontal wall 30 and is divided from the entrance-chamber 24 by the wall 21 that extends from the horizontal wall 30 towards the base-without however, reaching it-in such a way as to leave a free opening 31 for the passage of the water. At the bottom of the selection-chamber 25 there are also at least two wells 25' and 25" covered by nets 28 and provided with openings 29 that are quite alike the opening present in the entrance-chamber 24 and are provided with a closing valve 8. The small wells 25' and 25", in association with the net 28 present in the selection-chamber, are also a particular embodiment of a means capable recovering the unhatched Artemia salina eggs.

The exit-chamber 26, that has an open top, is divided from the selection-chamber by the wall 23 which extends from the horizontal wall 30 to the bottom of the tank. In the lower part of the said wall 23 there is a hole 32, for allowing the passage of the water and nauplii. In fact, the said wall 23 and the said hole 32 allow the shells, the cysts and the unhatched eggs of the Artemia salina to be held back whilst allowing the passage of the Artemia salina nauplii towards the exitchamber 26 (as will be described later on).

In the wall 33 which faces wall 23 of the exit-chamber 26, there is inserted a sheet 34 of material that is transparent to light and in correspondence to said sheet 34 but outside the exit-chamber 26, there is placed a casing 35 inside which is situated a light source 36.

The horizontal wall 30 and vertical wall 23 are one embodiment (according to the present invention) of the means to prevent shells, cysts, unhatched eggs of the Artemia and debris from reaching the outlet whilst the hole 32 allows the free movement of the nauplii (attracted by the light source 36 protected by transparent sheet 34) independently of the flow of the water, towards the outlet situated in the exit-chamber 26 of the separating-tank 20. Said exit-chamber 26 is provided with a closing means (such as a valve 8 of the type already mentioned) and is also provided with 'known' means for admitting water (not shown in the drawings).

The steady-state functioning of a plant for the production of Artemia salina nauplii according to the present invention and with reference to the accompanying drawings is as follows: -After having introduced the eggs of the Artemia salina into one of the hatching-tanks 3 having the ambient conditions described previously regarding plants of the 'known' type, the period of time necessary for the eggs to hatch is allowed to pass.

-At this point, the input of air and every other cause of disturbance are suspended.

The door 19 is opened, the light source 9 is turned on and the nauplii (due to the attraction that the light source exercies over them) now swim through the opening 17 and thus transfer themselves to the collectingtank 2.

wince the nauplii are transferred, the door 19 is closed. The water admitted into the collecting-tank 2 flows through the valve 8 situated at the bottom of said collecting-tank and enters the chamber 24 of the separating tank 20, through the conduit 7.

-The nauplii that have been transferred into the collecting tank are accompanied by small quantities of eggs, cysts and shells, since the flow of water present inside the collecting tank 2 and admitted into the said collectingtank 2 from the upper part of the tank itself, provokes small currents that spill the water containing eggs, cysts, shells and various deposits from the hatching-tank 3 into the collecting-tank 2. Through the conduit 7. the flow of water carries the nauplii, together with a small quantity of eggs, cysts, shells and various deposits from the said collectingtank 2, to the entrance-chamber 24 of the separating-tank 20. (Once the transfer of the nauplii from the collecting-tank to the separating-tank has taken place, said collectingtank is ready to attract the hatched nauplii that were put into another hatching-tank). In the separating-tank 20, the flow of water passes through in the order of the entrancechamber 24, the selection-chamber 25, and the exit-chamber 26. It then issues out of the opening in valve 8 which is placed downstream of the outlet 37, transporting with it the Artemia salina nauplii exclusively. The cross-sectional area of the opening 31 being smaller than that of the entrance-chamber, the velocity of the flowing water increases and consequently the nauplii, together with any eggs, cysts and shells, are made to enter the selection-chamber where, owing to the increased cross-sectional area, the velocity of the flowing water is once again reduced. In this chamber, as in the entrance-chamber but to a lesser extent, the separation of the eggs, cysts, shells and various deposits from the nauplii takes place.

In fact, owing to the low flow velocity, the buoyant substances (being lighter than water) rise towards the horizontal wall 30 and as a result remain trapped between the said wall 30 and the wall 23. The heavier substances in the water tend to descend to the bottom and hence they either enter into the well by passing the nets that cover them so as to be expelled through the openings 29, or else they settle on the bottom, or remain held back by the lower part of the wall 23. The nauplii, on the other hand, in finding themselves in a dark chamber owing to the presence of the walls 21, 23 and 30, become attracted by the cone of light that passes through the said chamber and which is emitted by the light source 36. In fact, the light coming from the light source 36 crosses through hole 32 entering into said selectionchamber and acts as an attraction for the nauplii. Consequently, said nauplii, even though they are present in a zone where the water has a zero velocity or tends to carry them towards the bottom rather than in the direction of the light source, begin to swim and move relative to the water in the direction of the come of light. In this way, they' re-enter the flow of water directed towards the exit-chamber and so enter into said chamber through the hole 32. Here again, owing to the luminous attraction of the light source 36 that causes them to approach the outlet 37, the nauplii become concentrated near said opening and are sucked by the flow of water that, in flowing through outlet 37, regains velocity and can consequently pull the nauplii with it to the utilisers.

The recovery of the eggs takes place through the opening 29 in the bottom of the entrance-chamber and the selection-chamber. This happens by opening the valve 8, placed downstream of the openings, in such a manner as to create an aspiration that sucks the eggs and draws them away from the separating-tank, along with the water from which they are subsequently extracted. The nets 28, placed for protecting the said openings 29, have the purpose of impeding any nauplii which are still inside the tank from escaping through the said opening 29.

When, after a certain period of time during which the plant has operated continuously, it is necessary to make provision for cleaning the separation-tank, said cleaning is carried out by means of washing-out the separationtank in the following particular way: -Washing-out the said tank takes place by admitting water into the tank through means present in the exit-chamber (not shown in the drawings), and at the same time by closing the valves 8 that are downstream of the openings 29 and 37, and by opening instead the valve 8 that is downstream of the exhaust 27. In this way, all the foreign matter can be eliminated. The net 28, over the exhaust 27, has the function of preventing any eventual escaping of the nauplii still present in the tank, through this exhaust. The plant for the production of Artemia salina nauplii, according to the present invention, can even operate with a continuous recovery cycle with regard to the eggs. In this case, the water containing the unhatched eggs, said water issuing from opening 29, is sent directly into one or more of the hatching-tanks 3 that are substantially devoid of eggs; and here, the quantity of eggs is statistically restored-by introducing other fresh eggs, (for example, by means of an automatic doser).

With this type of operation, the water flow-instead of beginning when the hatching has taken place, with the admission of water into the collecting-tank-actually begins with the admission of water into the hatching-tank, so that even if some unhatched eggs are dragged away by the flow they are nevertheless recovered in the entrance-chamber 24, or in the selection-chamber 25 of the separating-tank 20.

With the plants for the production of Artemia salina nauplii according to the present invention, the previous pre-established aims can be achieved. In fact, with this type of plant, the flow of nauplii to the utilises can be continuous. This is because the plantdue to its being provided with several 'complexes' of hatching-tanks and collecting-tanks, and at least two separatingtanks, can plan the hatching of the eggs in each tank in such a way as to have a continuous flow of nauplii; said flow being apt to be maintained even during the washing-out of one of the separating-tanks.

In the plant for the production of Artemia salina nauplii according to the present invention, a system is employed for separating the nauplii from the cysts, the shells and the unhatched eggs. Said system is quite different to the previous state of the art. In the plant according to the present invention, the cysts, the shells and the eggs are witheld, while the nauplii are freely conveyed to the utilisers; wheras in the 'known' state of the art the nauplii are witheld forcibly and the cysts, shells and eggs are removed in such a manner that the nauplii consequently tend to be crushed against the nets of the enclosure itself, or are obliged to swim for a long period against the flow itself. It follows from this, that with the type of plant according to the present invention, the nauplii arrive at the utilisation in better physical state and above all in greater numbers, since their mortality rate is reduced to practically zero. What is more, there can be effected a total recovery of the unhatched eggs.

Owing to these two results-i.e. the nauplii arriving at the utilisation in greater quantities and the total recovery of the unhatched eggs; there is, from the plant according to the present invention, a net yield that is superior to that of 'known' plants.

It must also be added, that, owing to said plant having smaller dimensions both as regards the fixed structures, tanks etc., as well as the total volume occupied, it follows that it is quite advantageous also from an economic viewpoint because its initial construction costs are comparatively less.

WHAT WE CLAIM IS: 1. A plant for the production of Artemia nauplii. the plant comprising (i) at least one hatching-tank (ii) at least one collecting-tank provided with a light source and (iii) at least one separating-tank together with means for allowing communication between the hatching-tank (i) and the collecting-tank (ii), and between the collecting-tank (ii) and the separating-tank (iii), in which the separating-tank (iii) is provided with a) an outlet means b) means to attract the Artemia nauplii towards the outlet c) means to prevent shells, cysts, unhatched eggs of the Artemia and debris from reaching the outet, and the hatching-tank, collecting-tank and separating-tank comprise material which impedes light and is non-toxic to the Artemia nauplii.

2. A plant, according to claim 1, in which the separating-tank comprises means for the recovery of the unhatched eggs of Artemia.

3. A plant, according to claim 2, in which the means for the recovery of unhatched eggs comprises at least one well in the bottom of the separating tank, said well being covered by net.

4. A plant, according to claim 1, 2 or 3, in which the means to attract the Artemia nauplii towards the outlet of the separatingtank comprises a light source downstream with respect to the water flow in the tank.

5. A plant according to any preceding claim in which the means to prevent shells, cysts, unhatched eggs of the Artemia and debris from reaching the outlet comprises a wall within the separating-tank, said wall being at an angle to the flow of water within the tank.

6. A plant substantially as hereindescribed and shown with reference to the accompanying drawings.

7. A method for the production of Artemia nauplii comprising introducing into a hatching-tank Artemia eggs, allowing them to hatch, causing them to swim into a collecting-tank which is in communication with said hatching-tank by illuminating the collecting-tank, shutting off the collectingtank from the hatching-tank, allowing the nauplii to pass into a separating-tank where they are induced to swim away from any cells, cysts, unhatched eggs and debris by attracting the nauplii to light, and then allowing the substantially isolated nauplii to leave the plant, the hatching-tank, collectingtank and separating-tank comprising material which impedes light and is non-toxic to the Artemia nauplii.

8. A method according to claim 7 wherein the Artemia nauplii are Artemia salina nauplii.

9. A method according to claim 7 or 8 wherein any unhatched eggs are recovered from at least one well at the bottom of the separating-tank 10. Artemia nauplii when produced by the method according to claim 7, 8 or 9.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. the plantdue to its being provided with several 'complexes' of hatching-tanks and collecting-tanks, and at least two separatingtanks, can plan the hatching of the eggs in each tank in such a way as to have a continuous flow of nauplii; said flow being apt to be maintained even during the washing-out of one of the separating-tanks. In the plant for the production of Artemia salina nauplii according to the present invention, a system is employed for separating the nauplii from the cysts, the shells and the unhatched eggs. Said system is quite different to the previous state of the art. In the plant according to the present invention, the cysts, the shells and the eggs are witheld, while the nauplii are freely conveyed to the utilisers; wheras in the 'known' state of the art the nauplii are witheld forcibly and the cysts, shells and eggs are removed in such a manner that the nauplii consequently tend to be crushed against the nets of the enclosure itself, or are obliged to swim for a long period against the flow itself. It follows from this, that with the type of plant according to the present invention, the nauplii arrive at the utilisation in better physical state and above all in greater numbers, since their mortality rate is reduced to practically zero. What is more, there can be effected a total recovery of the unhatched eggs. Owing to these two results-i.e. the nauplii arriving at the utilisation in greater quantities and the total recovery of the unhatched eggs; there is, from the plant according to the present invention, a net yield that is superior to that of 'known' plants. It must also be added, that, owing to said plant having smaller dimensions both as regards the fixed structures, tanks etc., as well as the total volume occupied, it follows that it is quite advantageous also from an economic viewpoint because its initial construction costs are comparatively less. WHAT WE CLAIM IS:

1. A plant for the production of Artemia nauplii. the plant comprising (i) at least one hatching-tank (ii) at least one collecting-tank provided with a light source and (iii) at least one separating-tank together with means for allowing communication between the hatching-tank (i) and the collecting-tank (ii), and between the collecting-tank (ii) and the separating-tank (iii), in which the separating-tank (iii) is provided with a) an outlet means b) means to attract the Artemia nauplii towards the outlet c) means to prevent shells, cysts, unhatched eggs of the Artemia and debris from reaching the outet, and the hatching-tank, collecting-tank and separating-tank comprise material which impedes light and is non-toxic to the Artemia nauplii.

2. A plant, according to claim 1, in which the separating-tank comprises means for the recovery of the unhatched eggs of Artemia.

3. A plant, according to claim 2, in which the means for the recovery of unhatched eggs comprises at least one well in the bottom of the separating tank, said well being covered by net.

4. A plant, according to claim 1, 2 or 3, in which the means to attract the Artemia nauplii towards the outlet of the separatingtank comprises a light source downstream with respect to the water flow in the tank.

5. A plant according to any preceding claim in which the means to prevent shells, cysts, unhatched eggs of the Artemia and debris from reaching the outlet comprises a wall within the separating-tank, said wall being at an angle to the flow of water within the tank.

6. A plant substantially as hereindescribed and shown with reference to the accompanying drawings.

7. A method for the production of Artemia nauplii comprising introducing into a hatching-tank Artemia eggs, allowing them to hatch, causing them to swim into a collecting-tank which is in communication with said hatching-tank by illuminating the collecting-tank, shutting off the collectingtank from the hatching-tank, allowing the nauplii to pass into a separating-tank where they are induced to swim away from any cells, cysts, unhatched eggs and debris by attracting the nauplii to light, and then allowing the substantially isolated nauplii to leave the plant, the hatching-tank, collectingtank and separating-tank comprising material which impedes light and is non-toxic to the Artemia nauplii.

8. A method according to claim 7 wherein the Artemia nauplii are Artemia salina nauplii.

9. A method according to claim 7 or 8 wherein any unhatched eggs are recovered from at least one well at the bottom of the separating-tank

10. Artemia nauplii when produced by the method according to claim 7, 8 or 9.