Abstract:
An imaging plate includes a plurality of wells individually accommodating little fishes, and the little fishes inside the wells are imaged from bottom portions of the wells. In order to adjust imaging posture or imaging positions of the little fishes inside the wells, an imaging little fish management device includes a water unit which supplies and discharges water into and from each well of the imaging plate. The water inside each well flows through a discharge hole provided laterally at a lowermost portion of each well. The water unit is also used to breed the little fishes of the wells of the imaging plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims benefit under 35 U.S.C. 119 of JP2014-150299 filed on Jul. 24, 2014, the title of IMAGING LITTLE FISH MANAGEMENT DEVICE AND LITTLE FISH IMAGING PLATE USED IN THE SAME the entire content of which is incorporated herein reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to an imaging little fish management device capable of individually observing or imaging a plurality of little fishes and a little fish imaging plate used in the same. 
         [0004]    2. Related Art 
         [0005]    The use of zebrafishes has gained attention in a medical field and a pharmacy field. As an example, after eggs of gene-injected zebrafishes are hatched and bred, the shapes and the like of the adult fishes are visually checked or imaged. As another example, after immature zebrafishes are bred while a specific medical agent is introduced into their living water system, a fish shape or a partial tissue shape is visually checked or imaged. Since the zebrafishes are small and grow fast, the zebrafishes can be highly efficiently used as a plurality of kinds of subjects. Further, an ethical issue on animals is also relieved. 
         [0006]    In order to observe or image the zebrafishes, an imaging device such as a microscope or an electronic imaging device is used. However, since the zebrafishes are very small, there has been a problem in sequential observation or imaging of the plurality of zebrafishes, which burdens a skilled worker with a heavy workload. 
         [0007]    In order to highly efficiently image specific regions of the plurality of zebrafishes, an imaging plate which includes a well array having wells formed in a matrix shape and depressed is used. The zebrafishes are separately disposed in the plurality of wells by using a tool such as a pipette or a pincette. In order to suppress the deterioration of zebrafish living conditions, it is favorable that some water be held in each well. 
         [0008]    In imaging work including observation or imaging, it is preferable that illumination light irradiation be performed from the bottom surface side of the imaging plate and reflected light or fluorescence from the zebrafishes is sent from the bottom surface side of the imaging plate to an imaging system. The imaging plate is shifted by the pitch of one well in a direction perpendicular to an optical axis of the imaging system. Accordingly, the zebrafish inside each well is highly efficiently observed or imaged. 
         [0009]    In order to satisfactorily image a specific region of each zebrafish, it is preferable to lay the zebrafish on a center portion of a bottom surface of each well. Further, in order to simplify image processing, it is preferable to arrange the zebrafishes such that the longitudinal direction from the head to the tail of each zebrafish (hereinafter, referred to as a head-to-tail direction) becomes the same direction. However, there has been a problem in work of correcting a position and posture to lay each zebrafish on the center portion of the bottom surface of the well while each zebrafish is arranged in the same direction, which is very troublesome and easily damages the zebrafishes. 
         [0010]    In order to solve this problem, US 2007/0178012 and JP 2014-169951 A (published on Sep. 8, 2014 by HASHIMOTO ELECTRONIC INDUSTRY CO., LTD and the like) adopt a side viewing optical system capable of imaging zebrafishes from the lateral directions of wells. According to the side viewing optical system, the zebrafishes which are not lying can be satisfactorily viewed from the sides thereof. However, since the side viewing optical system needs a reflection surface for deflecting an optical axis, a structure of an imaging plate becomes complex. Further, it has been found that there is a problem of a degraded image due to dirt or the like on the reflection surface. 
         [0011]    Further, when the zebrafishes as subjects are sequentially put into the wells of the imaging plate by using a manipulation tool such as a pipette or a pincette, there has been a case where the zebrafishes are damaged. Moreover, there has been a case where contamination unfavorable for the zebrafishes happens through the manipulation tool. 
         [0012]    In order to solve this problem, it is desirable to grow the zebrafishes while separately putting the zebrafishes into the wells at the immature stage and thereafter giving a medical agent and the like necessary for each immature fish. However, management of water including treatment of feces becomes essential for breeding of the zebrafishes. Further, it becomes essential to put an anesthetic solution during imaging and to replace breeding water after the imaging. In the related art, an imaging plate capable of managing water in this way is not known. 
       SUMMARY 
       [0013]    An object of the present invention is to provide an imaging little fish management device capable of efficiently performing little fish imaging work of sequentially imaging optical examination little fishes separately accommodated in a plurality of wells of an imaging plate. Another object of the present invention is to provide a little fish imaging plate used in the imaging little fish management device and capable of efficiently performing the little fish imaging work. 
         [0014]    Hereinafter, an example will be described in which zebrafishes are used as optical examination little fishes. The imaging little fish management device of the present invention uses an imaging plate in which a plurality of wells individually accommodating the zebrafishes is arranged in a matrix shape, as in the related art. The imaging plate includes a transparent bottom portion which faces each well and a partition wall portion which defines each well, and an upper end of each well is opened. 
         [0015]    A scanning unit sequentially moves the imaging plate, preferably in the horizontal direction, that is, the direction perpendicular to the thickness direction of the imaging plate, and an imaging unit sequentially images each zebrafish, preferably, lying on the bottom portion. 
         [0016]    Particularly, the imaging little fish management device of the present invention performs a preliminary water discharge operation for, before an imaging operation, discharging water inside each of the wells through a discharge hole which is located in the vicinity of a boundary portion between the partition wall portion and the bottom portion and which does not enable each of the little fishes to pass therethrough. Due to a downward water stream or a decreased water level formed by the preliminary water discharge operation, each zebrafish inside each well is easily guided and settled onto the bottom portion. Therefore, a target region of each zebrafish can be clearly imaged without adjusting a focus of the imaging unit. 
         [0017]    Further, since a position or posture of each zebrafish can be adjusted by the water stream formed by the preliminary water discharge operation, it becomes easy to observe or image the zebrafishes. Since the discharge hole is not formed in the transparent bottom portion, the discharge hole does not become an obstacle to the imaging. Moreover, no zebrafish escapes to the outside from the discharge hole. 
         [0018]    Further, since water can be supplied to the wells by preliminarily discharging the water of the wells, the water of the wells can consequently be replaced. As a result, the little fishes inside the wells can be bred for a long period of time. This means that the little fishes can be imaged in time series for a long period of time. 
         [0019]    In a preferred aspect, an anesthesia operation for adding an anesthetic solution to the water inside the wells is performed before the preliminary discharge operation, and an awakening operation for supplying fresh water to the wells is performed after the imaging operation. Accordingly, the anesthesia operation for improving the imaging resolution can be simply performed. 
         [0020]    In a preferred aspect, after the preliminary water discharge operation, a water supply operation for causing water to reversely flow into the wells through the discharge holes, and thereafter a secondary water discharge operation for discharging the water inside the wells through the discharge holes is performed. Accordingly, the zebrafishes stuck to the partition wall portions of the wells by the preliminary water discharge operation can be settled onto the bottom portions again. Further, since the water is discharged and supplied from the boundary portion between the partition wall portion and the bottom portion through the common discharge hole, there is no need to provide an independent water supply hole, and a structure of the imaging plate can be simplified and downsized. 
         [0021]    In a preferred aspect, a little fish arrangement operation for sequentially executing the preliminary water discharge operation, the water supply operation, and the secondary water discharge operation is performed, and thereafter the little fishes of the wells are imaged. Next, the obtained images are processed and it is determined whether a little fish arrangement state is good or not. Next, the little fish arrangement operation is performed again on at least the little fishes being in a poor arrangement state. Accordingly, the arrangement state of each little fish can be largely improved. 
         [0022]    In a preferred aspect, the partition wall portion includes an inclined surface portion which is inclined in a tapered shape toward the bottom portion. Preferably, the inclined surface portion is provided in a lower portion of each well. Accordingly, the zebrafishes become easily settled onto the bottom portion. 
         [0023]    In a preferred aspect, a long side edge of the substantially rectangular bottom portion is formed so as to be longer than an estimated maximum length of the zebrafish. Further, a short side edge of the bottom portion is formed so as to be shorter than the estimated maximum length of the zebrafish. Further, the bottom portions are arranged in a matrix shape in a direction where the longitudinal directions thereof match one another. Accordingly, the zebrafishes inside the wells become easily settled in the substantially parallel direction to one another. 
         [0024]    In a preferred aspect, the water discharge hole is formed adjacent to the long side edge of the bottom portion. Accordingly, the zebrafishes become easily laid on the bottom portion by the water stream caused by the water discharged or supplied through the discharge hole. Although it is preferable that the discharge hole be provided only along one of the pair of long side edges of the bottom portion, the discharge hole can also be provided along both the pair of long side edges of the bottom portion. Further, an upper surface of the bottom portion being in contact with each well can also be provided in a concave lens shape. Accordingly, the zebrafishes become easily guided to a center portion of the bottom portion. 
         [0025]    In a preferred aspect, a water storage sub-well is provided adjacent to the side of each well, and the sub-well and the well in a pair communicate with each other by the discharge hole. Accordingly, the water can be easily supplied to and discharged from each well while the water in each well is independently maintained. Further, it becomes easy to anesthetize the zebrafishes inside the wells. 
         [0026]    In a preferred aspect, an overflow bottom wall portion is provided between the well and the sub-well which are adjacent to each other. The overflow bottom wall portion is formed so as to be lower than the partition wall portion provided between the wells. Accordingly, it is possible to prevent the water inside the sub-well from overflowing into the adjacent well through the partition wall portion when the water is supplied (caused to reversely flow) from the sub-well to the well through the discharge hole. 
         [0027]    In a preferred aspect, the imaging plate includes a concave portion which is defined by the partition wall portion. Further, a cylindrical auxiliary tube member including the well is inserted into the concave portion. Accordingly, the sub-well is automatically formed between the partition wall portion and a peripheral wall portion of the auxiliary tube member. Preferably, the peripheral wall portion of the auxiliary tube member includes the overflow bottom wall portion. In addition, the well and the sub-well can also be integrally formed with each other. 
         [0028]    In a preferred aspect, the water is supplied to the sub-well and is discharged from the sub-well by a plurality of nozzles individually drooped to the plurality of adjacent sub-wells. Accordingly, the water can be easily supplied to and discharged from each sub-well in an independent manner. Note that, preferably, the plurality of nozzles can be arranged in series in one direction among two directions of a direction parallel to an upper surface of the imaging plate and a direction perpendicular to the upper surface thereof. As a result, the imaging plate is shifted by the pitch of one well in the other direction perpendicular to the one direction, whereby the water can be supplied to and discharged from each well by a simple structure. The water supply nozzle and the water discharge nozzle can be separately configured, and a nozzle for both water suction and discharge can also be adopted. 
         [0029]    In a preferred aspect, the discharge hole has a cross-sectional shape that enables prey for each little fish and feces of each little fish to pass therethrough, and the water inside the wells is periodically replaced or circulated. Accordingly, since the water inside each well can be kept clean, and hence each zebrafish to be imaged can be grown inside each well. The water which is discharged from the wells can be cleaned, for example, by filtration using a filter. As a result, the zebrafishes at respective growth stages can be easily imaged. 
         [0030]    The little fish imaging plate can be preferably used in the imaging little fish management device, but can also be used for other application. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0031]      FIG. 1  is a schematic block diagram illustrating an imaging little fish management device of an embodiment; 
           [0032]      FIG. 2  is a perspective view illustrating an example of a nozzle head and an imaging plate; 
           [0033]      FIG. 3  is an enlarged perspective view illustrating the imaging plate; 
           [0034]      FIG. 4  is schematic plan view illustrating one well  12  and one sub-well  13 ; 
           [0035]      FIG. 5  is a schematic cross-sectional view taken along line A-A of the well  12  illustrated in  FIG. 4 ; 
           [0036]      FIG. 6  is a schematic cross-sectional view illustrating the imaging plate into which a nozzle is inserted; 
           [0037]      FIG. 7  is a flowchart illustrating an imaging capturing control routine; 
           [0038]      FIG. 8  is a flowchart illustrating a breeding control routine; 
           [0039]      FIG. 9  is a perspective view illustrating a modification of an imaging plate; 
           [0040]      FIG. 10  is a plan view illustrating an auxiliary tube member; 
           [0041]      FIG. 11  is a longitudinal sectional view illustrating the auxiliary tube member; 
           [0042]      FIG. 12  is a partial plan view illustrating another modification of an imaging plate; and 
           [0043]      FIG. 13  is a partially longitudinal sectional view illustrating the imaging plate illustrated in  FIG. 12 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0044]    A preferred embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiment. A device illustrated in  FIG. 1  includes an imaging plate  1 , a water unit  2 , a drive unit  3 , a controller  4 , and an imaging unit  5 . 
         [0045]    First, the imaging plate  1  will be generally described. The imaging plate  1  includes a plurality of wells and a plurality of sub-wells which are each opened upward. One zebrafish is accommodated in each well together with water. A lowermost portion of each well communicates with a lowermost portion of each sub-well adjacent thereto through discharge holes. However, the wells, the sub-wells, and the discharge holes are not illustrated in the schematic block diagram shown in  FIG. 1 . Shapes of the wells, the sub-wells, and the discharge holes will be described in detail later. 
         [0046]    The water unit  2  includes a pipe  27  to which a nozzle valves  20 , a discharge valve  21 , suction valves  22  to  24 , a three-way valve  25  and a syringe pump  26  are connected. The discharge valve  21 , the suction valves  22  to  24 , the three-way valve  25 , and the syringe pump  26  correspond to an example of a water supply and discharge mechanism that transfers water to the imaging plate  1  through the nozzle valves  20 , and it is clear that the same function can be configured with other known mechanisms. The valves  20  to  25  which are each configured with an electromagnetic valve are opened and closed based on an instruction given by the controller  4 . The eight nozzle valves  20  individually control the communication between the upstream pipe  27  and eight nozzles  28 . The eight nozzle valves  20  built in a nozzle head  2 A are horizontally arranged in a column direction X so as to be adjacent to one another. 
         [0047]    The eight nozzles  28  drooped from the nozzle head  2 A are also arranged in the column direction X by the pitch of one well. The nozzle head  2 A disposed just above the imaging plate  1  can be moved upward and downward by a nozzle drive unit (not illustrated). When the nozzle head  2 A moves downward, each nozzle  28  is individually inserted into each sub-well of the imaging plate  1 . 
         [0048]    The discharge valve  21  which includes a water discharge pipe  21 A drooped into a water discharge bottle (not illustrated) is opened when water inside the pipe  27  is discharged to the water discharge bottle. The suction valve  22  which includes a suction pipe  22 A drooped into a breeding water bottle (not illustrated) is opened when breeding water having a predetermined component is suctioned from the breeding water bottle to the pipe  27 . The suction valve  23  which includes a suction pipe  23 A drooped into a feeding water bottle (not illustrated) is opened when water containing prey is suctioned from the feeding water bottle to the pipe  27 . 
         [0049]    The suction valve  24  which includes a suction pipe  24 A drooped into an anesthesia water bottle (not illustrated) is opened when anesthesia water that is water containing an anesthetic is suctioned from the anesthesia water bottle to the pipe  27 . The three-way valve  25  causes a syringe of the syringe pump  26  to communicate with any one of the pipe  27  and a pure water pipe  29 A. The syringe pump  26  includes a piston which is driven linearly in an electromagnetic manner. 
         [0050]    Hereinafter, a basic operation for the water unit  2  will be described. First, a pure water supply operation for supplying pure water inside the pure water pipe  29 A to the pipe  27  will be described. The pure water supply operation is performed, for example, when an amount of the pure water existing in an upstream pipe portion or the like of the pipe  27  becomes less than an amount at a predetermined value. After the three-way valve  25  causes the syringe pump  26  and the pure water pipe  29 A to communicate with each other, the syringe pump  26  suctions the pure water inside the pure water pipe  29 A into the syringe. Next, after the three-way valve  25  causes the syringe pump  26  and the pipe  27  to communicate with each other, the syringe pump  26  pushes the pure water inside the syringe into the pipe  27 . Accordingly, a predetermined amount of the pure water is always held in the upstream portion or the like of the pipe  27 . When the pure water supply operation is not performed, the three-way valve  25  causes the syringe pump  26  and the pipe  27  to communicate with each other. 
         [0051]    Next, an external water discharge operation for discharging water inside the wells (also referred to as well water) to the outside will be described. The nozzles  28  are inserted into the sub-wells of the imaging plate  1 , respectively. After the nozzle valves  20  are opened, the syringe pump  26  suctions the well water inside the sub-wells to the pipe  27 . Next, after the nozzle valves  20  are closed and the discharge valve  21  is opened, the syringe pump  26  pushes the water inside the pipe  27  out through the discharge valve  21 . Accordingly, the well water inside the pipe is discharged to the outside. 
         [0052]    Next, a breeding water supply operation for supplying the breeding water to the wells will be described. According to the embodiment, normal water filtered by a filter is used as the breeding water. First, after only the suction valve  22  is opened, the breeding water is suctioned into the pipe  27  by the syringe pump  26 . Next, after the suction valve  22  is closed and the nozzle valves  20  are opened, the breeding water inside the pipe  27  is ejected from each nozzle  28  to each sub-well by the syringe pump  26 . Note that, when the water levels of the sub-wells are high or a breeding water supply amount is large before the ejection, the external water discharge operation can be performed in advance so as to decrease the water levels of the sub-wells. 
         [0053]    Next, a feeding water supply operation for supplying the water containing prey to the wells will be described. The water containing prey mentioned here means water mixed with powdered prey or microorganisms for prey. First, after only the suction valve  23  is opened, the water containing prey is suctioned into the pipe  27  by the syringe pump  26 . Next, after the suction valve  23  is closed and the nozzle valves  20  are opened, the water containing prey inside the pipe  27  is ejected from each nozzle  28  to each sub-well by the syringe pump  26 . Note that, when the water levels of the sub-wells are high or a supply amount of the water containing prey is large before the ejection, the external water discharge operation can be performed in advance so as to decrease the water levels of the sub-wells. 
         [0054]    Next, an anesthesia water supply operation for supplying the anesthesia water to the wells will be described. The anesthesia water mentioned here means water containing an anesthetic. First, after only the suction valve  24  is opened, the anesthesia water is suctioned into the pipe  27  by the syringe pump  26 . Next, after the suction valve  24  is closed and the nozzle valves  20  are opened, the anesthesia water inside the pipe  27  is ejected from each nozzle  28  to each sub-well by the syringe pump  26 . Note that, when the water levels of the sub-wells are high or an anesthesia water supply amount is large before the ejection, the external water discharge operation can be performed in advance so as to decrease the water levels of the sub-wells. The external water discharge operation, the breeding water supply operation, the feeding water supply operation, and the anesthesia water supply operation are controlled by the controller  4 . 
         [0055]    According to the embodiment, the imaging plate  1  is placed on a base  3 A of the drive unit  3 . The drive unit  3  includes a built-in drive device (not illustrated) that horizontally moves the base  3 A by the pitch of one well in a row direction Y perpendicular to the column direction X. The horizontal movement of the imaging plate  1  is executed while the nozzle head  2 A is retracted upward. The drive unit  3  can also be omitted by moving the nozzle head  2 A in the row direction Y instead of the imaging plate  1 . According to the aspect of moving the nozzle head  2 A, it is preferable to also move the imaging unit  5  in the row direction Y. 
         [0056]    The imaging unit  5  includes a UV lamp, an imaging device, and an optical system. The optical system irradiates each well through a transparent bottom portion of each well with a UV ray emitted from the UV lamp. Further, the optical system guides fluorescence emitted from the zebrafishes to the imaging device. According to the embodiment, the imaging unit  5  simultaneously images the eight wells arranged in the column direction X. In addition, the eight wells arranged in the column direction X can also be sequentially imaged, and the wells of a plurality of rows adjacent to one another can also be simultaneously imaged. All the wells can also be simultaneously imaged by using an improved optical system. 
         [0057]    Further, the imaging unit  5  includes a built-in image processor that processes imaged images. According to the embodiment, the image processor has a function of determining whether positions or posture of the zebrafishes extracted from the imaged images are good or not. 
         [0058]    The controller  4  controls the operations of the water unit  2 , the drive unit  3 , and the imaging unit  5  based on a program stored in advance.  FIG. 2  is a perspective view illustrating an example of the nozzle head  2 A and the imaging plate  1 . According to  FIG. 2 , the valves  21  to  24 , the three-way valve  25 , and the syringe pump  26  illustrated in  FIG. 1  are separately provided for each nozzle valve  20 . Accordingly, a zebrafish breeding environment can be easily changed every column. 
         [0059]    A detailed structure of the imaging plate  1  adopted in the embodiment will be described with reference to  FIGS. 3 to 6 .  FIG. 3  is an enlarged perspective view illustrating the imaging plate  1 . The resinous imaging plate  1  includes a thick well array plate  10  and a transparent bottom plate  11  which is bonded to a lower surface of the well array plate  10 . The well array plate  10  includes ninety six wells  12  arranged in a matrix shape. The well array plate  10  includes a partition wall portion  14  which has a lattice shape and defines each well  12  and an overflow bottom wall portion  15  which defines each sub-well  13  together with the partition wall portion  14 . 
         [0060]    The overflow bottom wall portion  15  which is an L-shaped wall and is provided at one corner of each well  12  defines each sub-well  13  inside each well  12 . The wells  12  and the sub-wells  13  which are opened upward reach the transparent bottom plate  11 . The overflow bottom wall portion  15  is formed so as to be lower than the partition wall portion  14 . 
         [0061]    Detailed shapes of each well  12  and each sub-well  13  will be described with reference to  FIGS. 4 and 5 .  FIG. 4  is a schematic plan view illustrating the one well  12  and the one sub-well  13 .  FIG. 5  is a schematic cross-sectional view taken along line A-A of the well  12  illustrated in  FIG. 4 . A lower portion of the partition wall portion  14  formed in a lattice shape is branched into two so as to configure a pair of inclined surface portions  18 . Accordingly, the width of the well  12  in the row direction is gradually decreased toward the transparent bottom plate  11  by the pair of inclined surface portions  18  interposing the well  12  therebetween. In other words, an upper portion of the well  12  has a square cylindrical shape, and a lower portion of the well  12  has a substantially inverse roof shape. 
         [0062]    A bottom portion  17  of the well  12  faces the transparent bottom plate  11 , and is interposed between the pair of inclined surface portions  18  to have a rectangular shape. A long side edge of the bottom portion  17  is formed so as to be longer than the maximum length of the zebrafish, and a short side edge thereof is formed so as to be shorter than the maximum length of the zebrafish. Further, a water storage portion  180  having a triangular prism shape is defined by the transparent bottom plate  11  and the pair of inclined surface portions  18  which are branched from the one partition wall portion  14 . 
         [0063]    One of the inclined surface portions  18  is adjacent to the overflow bottom wall portion  15  as the L-shaped wall, and is integrally formed with the overflow bottom wall portion  15 . Since a lower opening of the sub-well  13  communicates with the water storage portion  180 , the water storage portion  180  is considered as a portion of the sub-well  13 . 
         [0064]    Among the two inclined surface portions  18  interposing the one well  12  therebetween, a lower end of the one inclined surface portion  18  integrally formed with the overflow bottom wall portion  15  faces the transparent bottom plate  11  through a plurality of discharge holes  16 . In other words, the plurality of discharge holes  16  is provided between the transparent bottom plate  11  and the one inclined surface portion  18  integrally formed with the overflow bottom wall portion  15 . The plurality of discharge holes  16  is formed below the one inclined surface portion  18  integrally formed with the overflow bottom wall portion  15 , and is arranged at a predetermined pitch in the column direction X. The discharge holes  16  each have a cross-sectional shape that does not enable the zebrafish to pass therethrough and that enables feces or prey of the zebrafish to pass therethrough. Consequently, the discharge holes  16  cause a lower end of the well  12  to communicate with a lower end of the water storage portion  180 . 
         [0065]      FIG. 6  is a schematic cross-sectional view illustrating a state where the eight nozzles  28  which are drooped from the nozzle head  2 A are individually inserted into the eight sub-wells  13  of the imaging plate  1 . However, since each inclined surface portion  18  illustrated in  FIG. 6  is formed so as to be thicker downward, the water storage portion  180  illustrated in  FIG. 6  has a smaller volume than that of the water storage portion  180  illustrated in  FIG. 5 . 
         [0066]    An imaging capturing control routine which is performed by the controller  4  will be described with reference to a flowchart illustrated in  FIG. 7 . First, an anesthesia operation for simultaneously putting the zebrafishes accommodated in the wells  12  to sleep is performed (step S 100 ). According to the anesthesia operation, after the nozzles  28  are respectively inserted into the sub-wells  13  of the first row, the anesthesia water is injected into the sub-wells  13  of the first row by an anesthesia water supply operation. Note that, when the water levels of the sub-wells  13  are high, an external water discharge operation is executed before the anesthesia water supply operation. 
         [0067]    Accordingly, the zebrafishes inside the wells  12  of the first row becomes in a sleep state. Subsequently, all the zebrafishes are anaesthetized by performing the anesthesia water supply operation while the imaging plate  1  is relatively moved by the pitch of one well with respect to the nozzles  28 . 
         [0068]    Next, a row imaging sub-routine of imagining the eight zebrafishes accommodated in the wells  12  of one row will be described below. The row imaging sub-routine includes a preliminary water discharge operation (step S 102 ), a water supply operation (step S 104 ), a secondary water discharge operation (step S 106 ), and an imaging operation (step S 108 ). 
         [0069]    First, the preliminary water discharge operation will be described. The nozzles  28  are individually inserted into the sub-wells  13 , and thereafter the external water discharge operation is executed, whereby the water of the wells  12  of this row is discharged through the sub-wells  13 . Accordingly, downward water streams are formed inside the wells  12 , and the water levels of the wells  12  decrease. Due to the preliminary water discharge operation, the zebrafishes move downward to a nearly settling position. The inclined surface portions  18  guide the zebrafishes to the bottom portions  17  of the wells  12 . 
         [0070]    Next, the water supply operation will be described. The breeding water is supplied to the sub-wells  13  of this row by executing the breeding water supply operation. Since the breeding water is jetted out of the sub-wells  13  through the discharge holes  16  to the lower portions of the wells  12  in the lateral direction, whirling water streams are formed in the longitudinal sections of the wells  12 . Since the zebrafishes which exist in the vicinities of the bottom portions  17  of the wells  12  are biased in a direction where fluid resistance to the water streams decreases, the zebrafishes lie on the bottom portions  17 . 
         [0071]    However, since the discharge holes  16  are narrow, the water levels of the sub-wells  13  abruptly increase when the nozzles  28  eject the breeding water into the sub-wells  13 . As a result, the water of the sub-wells  13  overflows the overflow bottom wall portions  15  and enters the wells  12  communicating with the sub-wells through the discharge holes  16 . However, since the overflow bottom wall portions are formed so as to be lower than the partition wall portions  14  between the wells  12 , the water of the sub-wells  13  does not overflow into the other wells  12 . 
         [0072]    Next, the secondary water discharge operation will be described. The external water discharge operation is executed again, and the water level of each well  12  decreases. Accordingly, the zebrafishes of this row are completely settled on the bottom portions  17 . 
         [0073]    Next, the imaging operation in which the imaging unit  5  images the zebrafishes of this row is performed, and the imaged images are processed (step S 108 ). Next, it is determined whether a lying posture and a lying position of each zebrafish obtained by the image processing are good or not (step S 110 ). When it is determined that the lying posture and the lying positions of the zebrafishes are poor, step S 102  to step S 108  are performed again only on the zebrafishes determined to be in a poor posture and position. That is, the nozzle valves  20  corresponding to the wells in which the zebrafishes are determined to be in a good posture and position are always kept closed. Accordingly, the poor lying posture and lying positions of the zebrafishes are noticeably improved. If a lying success ratio of the zebrafishes of one row is 80% when the row imaging sub-routine is executed once, a lying success ratio of the zebrafishes of one row becomes 96% when the row imaging sub-routine is executed again on the zebrafishes determined to be in the poor posture and position. 
         [0074]    When the image determination result reaches a predetermined level or more, the process proceeds to step S 112 . In step S 112 , it is determined whether the wells  12  of all rows are imaged. When the determination result is No, the imaging plate  1  is shifted by the pitch of one well (step S 114 ), and the row imaging sub-routine is performed on the zebrafishes of the next row. When it is determined that the wells of the last row are imaged, an awakening operation is executed (step S 116 ). According to the awakening operation, each of the external water discharge operation and the breeding water supply operation is performed once or more, and the water of all the wells  12  and all the sub-wells  13  is replaced with the breeding water. Accordingly, all the zebrafishes are awakened again. 
         [0075]    Note that, according to the flowchart illustrated in  FIG. 7 , the zebrafishes are imaged every row, but of course, the imaging capturing control routine is not limited thereto. For example, the preliminary water discharge operation may be performed on all the sub-wells  13 , and thereafter the water supply operation may be performed on all the sub-wells  13 . Subsequently, the secondary water discharge operation may be performed on all the sub-wells  13 . 
         [0076]    A breeding control routine which is performed by the controller  4  will be described with reference to a flowchart illustrated in  FIG. 8 . The breeding control routine is periodically performed. However,  FIG. 8  illustrates only feeding the zebrafishes accommodated in the wells  12  of one row and replacing the water thereof. It is clear that the breeding control routine can be performed on the zebrafishes of each row by moving the imaging plate  1  by the pitch of one well while moving the nozzle head  2 A upward and downward. 
         [0077]    First, it is determined whether the zebrafishes are to be fed (step S 200 ). When it is determined that the zebrafishes are to be fed, the external water discharge operation is performed (step S 202 ), and subsequently the feeding water supply operation is executed (step S 204 ). When it is determined that the zebrafishes are not to be fed, the process proceeds to step S 206 . Accordingly, the zebrafishes are fed. Note that, when the water levels of the wells  12  are low, the external water discharge operation can be omitted. 
         [0078]    Next, it is determined whether the water inside the wells  12  is to be replaced (step S 206 ). When it is determined that the water is to be replaced, the external water discharge operation is performed (step S 208 ), and subsequently the breeding water supply operation is executed (step S 210 ). When it is determined that the water is not to be replaced, the process returns to step S 200 . Accordingly, the water inside the wells  12  and the sub-wells  13  is replaced as necessary. Consequently, since the water supply and discharge at the time of imaging illustrated in  FIG. 7  and the feeding and water replacement illustrated in  FIG. 8  are performed by using the common water unit  2 , it is understood that the configuration of the device becomes largely simplified. 
         [0079]    A modification of an imaging plate  1  will be described with reference to  FIGS. 9 to 11 .  FIG. 9  is a perspective view illustrating the imaging plate  1 . A well array plate  10  of the imaging plate  1  includes a partition wall portion  14  formed in a lattice shape, and the partition wall portion  14  forms a plurality of rectangular penetration holes arranged in a matrix shape. A lower end side opening of each rectangular penetration hole is shielded by a transparent bottom plate  11 . An auxiliary tube member  19  which includes a well  12  inside thereof and has a substantially cylindrical shape is inserted into each penetration hole. As a result, a sub-well  13  is formed between the auxiliary tube member  19  and a partition wall portion  14 . However, the sub-well  13  is not illustrated in  FIG. 9 . 
         [0080]      FIG. 10  is a plan view illustrating the auxiliary tube member  19 , and  FIG. 11  is a longitudinal sectional view of the auxiliary tube member  19 . The auxiliary tube member  19  includes the well  12  which is surrounded by a peripheral wall portion  191  having a substantially cylindrical shape. A lower portion of the peripheral wall portion  191  includes a pair of inclined surface portions  192  and  193  which are inclined so as to narrow the horizontal width of the well  12 . 
         [0081]    The well  12  includes a rectangular opening  194  interposed between the inclined surface portion  192  and the inclined surface portion  193 . Therefore, the transparent bottom plate  11  which faces the opening  194  configures a bottom portion of the well  12 . A lower end of the inclined surface portion  193  is formed so as to be slightly higher than a lower end of the inclined surface portion  192 . Accordingly, a discharge hole  195  is formed between the lower end of the inclined surface portion  193  and the transparent bottom plate  11 . 
         [0082]    The peripheral wall portion  191  of the auxiliary tube member  19  is formed so as to be lower than the partition wall portion  14 . Accordingly, the peripheral wall portion  191  configures an overflow bottom wall portion of the present invention. Further, a portion  191 A of the peripheral wall portion  191  is depressed as illustrated in  FIG. 10 . Accordingly, it becomes easy to insert a nozzle  28  into the sub-well  13  between the partition wall portion  14  and the portion  191 A of the peripheral wall portion  191 . 
         [0083]    Another modification of an imaging plate  1  will be described with reference to  FIGS. 12 and 13 .  FIG. 12  is a partial plan view illustrating a portion of the imaging plate  1 .  FIG. 13  is a partially longitudinal sectional view of the imaging plate  1 . In the imaging plate  1 , four auxiliary tube members  19  arranged in series are connected by connection portions  190 . The connection portion  190  extending from an upper end of a peripheral wall portion  191  of the one auxiliary tube member  19  climes over a partition wall portion  14 , and reaches the upper end of the peripheral wall portion  191  of the next auxiliary tube member  19 . Accordingly, it becomes easy to assemble the imaging plate  1 . 
         [0084]    The peripheral wall portion  191  of the auxiliary tube member  19  illustrated in  FIGS. 9 to 13  is substantially cylindrical, but is not limited to this shape. The peripheral wall portion may have a square shape having a size substantially equal to the space surrounded by the partition wall portion  14  of the imaging plate  1  illustrated in  FIG. 9 . A shape of the auxiliary tube member in that case is similar to those of the well  12  and the sub-well  13  illustrated in  FIGS. 5 and 6 . 
         [0085]    The modified example will be described below. First, it is desirable to introduce the zebrafish into the well  12  along with the anesthetic solution. At this time, the anesthetic solution inside the well  12  tends to flow to the sub-well  13  through the discharge holes  16  communicating the bottom portion of the well  12  with the bottom portion of the sub-well  13 . However, since the diameter of the discharge hole  16  is very small and the surface tension of the anesthetic solution disturbs the flow, there is a case where the anesthetic solution inside the well  12  does not smoothly flow to the sub-well  13 . 
         [0086]    One answer for this problem is to use a centrifugal force. The imaging plate  1  is fixed to a horizontal rotation base having a rotation shaft extending in the vertical direction. The sub-well  13  which communicates with the well  12  by the discharge holes  16  are disposed at the outside of the well  12  in the radial direction. In other words, the sub-well  13  is disposed at a position far from the rotation shaft in relation to the well  12 . 
         [0087]    Accordingly, the anesthetic solution may flow to the sub-well  13  through the discharge holes  16  by the centrifugal force applied to the anesthetic solution of the well  12 . As a result, the anesthetic solution is charged in the discharge holes  16  and flows to the sub-well  13 . Further, when the rotation time is extended, most of water inside the well  12  moves to the sub-well  13 . For this reason, the zebrafish inside the well  12  is satisfactorily laid on the bottom surface of the well  12 . 
         [0088]    Another answer for the problem is to use a pressure difference. The anesthetic solution and the zebrafish are introduced into the well  12 , and the anesthetic solution is introduced into the sub-well  13 . Next, a thin tube is inserted into the sub-well  13 . It is desirable that the tip of the thin tube reach the vicinity of the bottom portion of the sub-well  13 . When the anesthetic solution is rapidly suctioned from the thin tube, the pressure at the outlet of the discharge hole  16  decreases, and hence the discharge hole  16  may be opened. When the suctioning operation is continued, the anesthetic solution inside the well  12  is suctioned into the thin tube through the discharge hole  16 . As a result, the water level inside the well  12  decreases, and hence the zebrafish may be laid on the bottom surface of the well  12 .