Breeding method, shellfishes, immunostimulator, and growth promoter

Abstract

To provide a breeding method for accelerating the growth of shellfishes, and to provide a breeding method in which resistance against pathogen is imparted to shellfishes.SOLUTION: Provided are a breeding method of shellfishes in which shellfishes are bred in a water tank, where the shellfishes are bred in the presence of insects belongs to Lepidoptera, and a breeding method of shellfishes in which shellfishes are bred in a water tank, where the shellfishes are bred in the presence of one or more selected from the group consisting of pathogen to the shellfishes, pathogen-derived protein and pathogen-derived nucleic acid.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a breeding method for breeding shellfish in an aquarium, the bred shellfish, and an immunity activator and a growth promoter for shellfish containing insects as an active ingredient.

Background Art

[0002] In the breeding of shellfish, techniques for efficiently growing shellfish are known. For example, a growth promoter for shellfish characterized by making fine powder of crushed stone soil of rock mainly composed of soft porous marine humus soil, mixing calcium carbonate, and accommodating it in a water-permeable net-like container (see Patent Document 1), a shellfish growth promoting material composed of calcium silicate-containing granular matter (see Patent Document 2), a shellfish adhesion growth promoting material in which at least a part of a carbon material and an iron material are in contact (see Patent Document 3), a bivalve breeding agent having a molecular weight of 540 or less and containing a storage sugar or a sugar constituting the storage sugar, or cellobiose as an active ingredient (see Patent Document 4), etc. are mentioned.

[0003] Techniques for enhancing resistance to pathogens by utilizing the biological defense mechanism of aquatic animals including shellfish are described in the following documents. Patent Document 5 describes a method for administering double-stranded RNA targeting the expression of the outer shell protein VP28 of White Spot Syndrome Virus and other selected genes, and mollusks such as shellfish are cited as specific examples of marine invertebrates that induce an immune response by administration. Patent Document 6 describes a composition containing a dried product obtained by dispersing charcoal powder in wood vinegar or an aqueous solution thereof and drying it, and specific examples of organisms targeted by this composition include seawater fish, freshwater fish, crustaceans, shellfish, and seaweed.

[0004] It is known that some insect larvae and pupae contain polysaccharides that have an immunity activating effect on vertebrates they ingest (see Patent Document 7). Beetle powder (see Patent Document 8) used for the treatment of vibriosis in bivalves and decapod crustaceans is also known.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent No. 7349613 Patent Document 2 Japanese Unexamined Patent Application Publication No. 2019-062775 Patent Document 3 Japanese Unexamined Patent Application Publication No. 2017-046593 Patent Document 4 Japanese Unexamined Patent Application Publication No. 2011-010637 Patent Document 5 WO 2005 / 0056134 Patent Document 6 Japanese Unexamined Patent Application Publication No. 2016-117694 Patent Document 7 WO 2014 / 017451 Patent Document 8 WO 2018 / 134524 Summary of the Invention Problems to be Solved by the Invention

[0006] In the breeding of shellfish, there is a need for a technique to efficiently grow shellfish by an inexpensive and simple method.

[0007] In recent years, many deaths of shellfish have occurred, and infections caused by pathogens such as viruses, bacteria, and parasites have been reported as one of the causes. On the other hand, since shellfish, which are invertebrates, have a different biological defense mechanism from vertebrates, there is no vaccine that has been put into practical use. In addition, among shellfish, bivalves, barnacles, and sea cucumbers, etc., feed on detritus and plankton, so it is extremely difficult to orally administer drugs such as antibiotics to these animals.

[0008] In Patent Document 8, although specific examples of mollusks targeted for the treatment of vibriosis include gastropods, bivalves, and cephalopods, only the breeding test of shrimp is described as an example in this document. Similarly, Patent Document 5 only describes the infection test of shrimp, and Patent Document 6 only describes the infection test of yellowtail (fish) as an example, respectively. Therefore, these patent documents do not contain any technical suggestions regarding whether the active ingredient such as insect powder can act on the biological defense mechanisms of shellfish other than fish and shrimp, and how to administer the active ingredient such as insect powder to animals that feed on detritus and plankton.

[0009] On the other hand, the immune system of invertebrates including shellfish is different from that of vertebrates such as fish. It is known that invertebrates do not have an immune system corresponding to the acquired immunity in vertebrates (see Non-Patent Document 1). Therefore, it has not been easy to confer resistance to pathogens on invertebrates.

[0010] [Non-Patent Document 1] Perazzolo LM, Li C and Somboonwiwat K (2021) Editorial: Aquatic Invertebrate Immunity Against Infectious Diseases. Front. Immunol. 12:762082. doi: 10.3389 / fimmu.2021.762082

[0011] The first problem to be solved by the present invention is to provide a breeding method for enhancing the growth of shellfish. The second problem is to provide a breeding method for conferring resistance to pathogens on shellfish.

Means for Solving the Problems

[0012] That is, the present invention is a method for breeding shellfish in an aquarium, wherein the shellfish are bred in the presence of insects belonging to the order Lepidoptera.

[0013] In another aspect of the present invention, the insect may be a water-soluble and alcohol-insoluble fraction of an insect belonging to the order Lepidoptera. Further, there may be provided a breeding method in which the shellfish are bred in the presence of 0.0001% to 1% by weight of the fraction obtained from the insect in the breeding water of the shellfish.

[0014] Another aspect of the present invention is a method for breeding shellfish in an aquarium, the method comprising breeding the shellfish in the presence of one or more selected from the group consisting of a pathogen for the shellfish, a protein derived from the pathogen, and a nucleic acid derived from the pathogen. The pathogen may be one or more selected from the group consisting of a virus, a bacterium, a fungus, a parasite, and inactivated forms of these pathogens.

[0015] In the present invention, the shellfish may be shellfish other than shrimp, and the shellfish may be mollusks. Further, the present invention may be shellfish bred by these breeding methods.

[0016] Another aspect of the present invention is an immunostimulant for shellfish containing an insect belonging to the order Lepidoptera as an active ingredient, and is also an immunostimulant for shellfish containing a water-soluble and alcohol-insoluble fraction of an insect belonging to the order Lepidoptera as an active ingredient. Yet another aspect of the present invention is a growth promoter for shellfish containing an insect belonging to the order Lepidoptera as an active ingredient, and is also a growth promoter for shellfish containing a water-soluble and alcohol-insoluble fraction of an insect belonging to the order Lepidoptera as an active ingredient. Here, in the present invention, the shellfish may be mollusks.

[0017] Yet another aspect of the present invention is the use of a water-soluble and alcohol-insoluble fraction of an insect belonging to the order Lepidoptera in the breeding of shellfish. The use may be for promoting the growth of shellfish and / or for activating the immunity of shellfish. Here, in the present invention, the shellfish may be mollusks.

Advantages of the Invention

[0018] The present invention can promote the growth of cultivated shellfish in an inexpensive and simple manner. In particular, many shellfish are released into the sea after being cultivated in an aquarium, but the shellfish cultivated by the cultivation method of the present invention can have significantly promoted growth after release. Further, even when the released sea area is contaminated by pathogens, the shellfish cultivated by the cultivation method of the present invention can maintain a high survival rate.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments.

[0021] Shellfish refers to the general term for aquatic animals excluding fish, including shellfish (bivalves, gastropods, etc.), crustaceans, cephalopods, echinoderms, and protochordates. The breeding method of the present invention is applicable to animals having a planktonic larval stage in their life cycle. Specifically, examples of bivalves include pearl oysters (Pinctada fucata, Pinctada martensii, Pinctada maxima, etc.), ark clams, hard clams, scallops, oysters, razor clams, surf clams, littleneck clams, soft-shell clams, geoducks, and mussels. Examples of gastropods include abalones, turban snails, turban shells, and topshells. Examples of crustaceans include shrimp, crabs, mantis shrimp, and barnacles. More specifically, examples include banana shrimp, kuruma shrimp, tiger shrimp, rock crabs, snow crabs, red king crabs, taraba crabs, flower crabs, hairy crabs, horseshoe crabs, and barnacles. The shellfish in the present invention can be shellfish excluding crustaceans or shellfish excluding shrimp.

[0022] Examples of cephalopods include the Japanese common squid, the Japanese flying squid, the longfin inshore squid, the common octopus, and the bigfin reef squid. Examples of echinoderms include sea urchins such as the Ezo sea urchin, the northern sea urchin, the green sea urchin, the purple sea urchin, the red sea urchin, and the white-spined sea urchin, and sea cucumbers such as the Japanese sea cucumber (the black sea cucumber, the red sea cucumber, the blue sea cucumber, etc.). Examples of protochordates include ascidians such as the solitary ascidian and the red ascidian.

[0023] Planktonic larvae refer to larvae that live a planktonic life from hatching until they settle to the bottom. The present invention is a breeding method for breeding shellfish in an aquarium. The shellfish to be bred may be planktonic larvae, or juveniles and / or adults after settlement. Juveniles after settlement are also called fry. When the shellfish are bivalves, juveniles after settlement are also called spat. One embodiment is a breeding method for the production of shellfish seedlings for the purpose of release and / or aquaculture. In such a case, it may be a breeding method for breeding planktonic larvae in an aquarium, or it may also be a breeding method for breeding juveniles in an aquarium during the period from settlement until release and / or migration to the open sea.

[0024] The insects in the present invention are insects belonging to the order Lepidoptera. More specifically, the insects in the present invention can be insects belonging to the superfamily Bombycoidea. The insects can be Bombyx mori, Bombyx mandarina, Oberthuria falcigera, Pseudandraca gracilis, Prismosticta hyalinata, Actias artemis aliena, Samia Cynthia ricini, Samia Cynthia pryeri, Antheraea pernyi, Antheraea yamamai (also known as Antheraea yamamai or Antheraea yamamai), Rhodinia fugax fugax, Rhodinia jankowskii hattoriae, Aglia tau microtau, Dictyoploca japonica japonica, Caligula boisduvalii jonasii, Attacus atlas ryukyuensis, Gonimbrasia belina, Cricula trifenestrata, etc.

[0025] The insects can be eggs, larvae, pupae, and / or adults, but are preferably pupae. It is known that the pupae of insects contain functional substances having an immunostimulating ability against ingested fish and the like.

[0026] One embodiment of the breeding method of the present invention is a breeding method for breeding larvae in the presence of a water-soluble and alcohol-insoluble fraction of insects. The water-soluble and alcohol-insoluble fraction is a fraction derived from insects that is water-soluble and insoluble in alcohol. Specifically, it can be a precipitate obtained by extracting water-soluble components from insects, adding alcohol such as ethanol to the extracted aqueous solution, and centrifuging this.

[0027] In another embodiment of the present invention, the insects may not contain their moisture. That is, this embodiment may be a breeding method of breeding larvae in the presence of the water-soluble and alcohol-insoluble fraction of dried insects. The drying of insects can be carried out using sun drying, hot air drying, microwave drying, vacuum drying, etc.

[0028] In another embodiment of the present invention, the insects may not contain their fat-soluble fraction. That is, this embodiment may be a breeding method of breeding larvae in the presence of the water-soluble and alcohol-insoluble fraction of defatted insects. The defatting of insects can be carried out by physical methods such as pressing and centrifugation, or by methods using organic solvents such as hexane, ether, ligroin, and acetone.

[0029] In another embodiment of the present invention, insects with low contents of moisture and fat-soluble fraction can be used. That is, this embodiment may be a breeding method of breeding larvae in the presence of the water-soluble and alcohol-insoluble fraction of dried and defatted insects.

[0030] The present invention further provides a water-soluble and alcohol-insoluble fraction of insects used in the breeding of shellfish. One embodiment of the invention is a water-soluble and alcohol-insoluble fraction of insects used for growth promotion and / or immunostimulation in the breeding of shellfish.

[0031] The concentration of the insect fraction present in the breeding water is not limited, but the insect fraction may be obtained from 0.0001 wt% to 1 wt% of insects with respect to the breeding water of the larvae, may be obtained from 0.001 wt% to 0.1 wt% of insects with respect to the breeding water of the larvae, or may be obtained from 0.01 wt% to 0.1 wt% of insects.

[0032] Another aspect of the present invention is a breeding method for breeding shellfish in the presence of a pathogen and / or a pathogen-derived protein for shellfish. The pathogen is one or more selected from the group consisting of a virus, a bacterium, a fungus, a parasite, and inactivated forms of these pathogens. Here, when the shellfish is a mollusk, the pathogen can be a birnavirus, a herpes virus, an oyster herpes virus, a spirochaeta, a francisella, a vibrio, etc., but can also include a pathogen that causes an unknown infectious disease.

[0033] The present invention also includes a shellfish breeding step of breeding shellfish in the presence of an individual infected with a pathogen and / or suspected of being infected with a pathogen, or a tissue collected from the individual. When breeding shellfish in the presence of an individual infected with a pathogen and / or suspected of being infected with a pathogen, the individual may be housed in the same water tank as the shellfish to be bred. The individual is not limited as long as it is infected with a pathogen and / or suspected of being infected with a pathogen, and may be of the same species or a different species from the shellfish to be bred.

[0034] The present invention also includes a shellfish breeding step of collecting all or part of an individual infected with a pathogen and / or suspected of being infected with a pathogen, obtaining a body fluid with a high probability of containing the pathogen, and breeding shellfish in the presence of the body fluid. The body fluid may be obtained by collecting all or part of the individual and recovering the liquid component from the collected individual, or by crushing all or part of the collected individual. After recovery or crushing, the supernatant fraction obtained by centrifugation or the liquid fraction obtained by filtration can also be used in this embodiment.

[0035] When the pathogen is a known pathogen, a shellfish breeding step of breeding shellfish in the presence of the isolated and / or cultured pathogen is also included in the present invention. In these shellfish breeding steps, the body fluid and the pathogen may be inactivated by chemical substances such as formalin and ethanol, or by ultraviolet irradiation, ozone treatment, heat treatment, etc.

[0036] As the protein derived from a pathogen, a recombinant protein obtained using Escherichia coli, yeast, cells, etc. can be used. The nucleic acid derived from a pathogen is DNA and / or RNA encoding the full length or a part of the protein of the pathogen, and for delivery to the shellfish to be reared, those encapsulated in a lipid membrane, incorporated into a plasmid, incorporated into a viral vector, etc. can be used.

[0037] The above-described pathogen, body fluid, and protein or nucleic acid derived from a pathogen may be dispersed in the rearing water of the water tank housing the shellfish to be reared, may be dispersed in the water injection into the water tank, or may be provided in a state of being mixed with the feed for the shellfish to be reared (for example, phytoplankton, zooplankton, etc.).

[0038] One embodiment of the present invention is a method for rearing shellfish by rearing the shellfish in a water tank, including: (A) a rearing step of rearing the shellfish in the presence of an insect belonging to the order Lepidoptera; and (B) a rearing step of rearing the shellfish in the presence of one or more selected from the group consisting of a pathogen, a protein derived from a pathogen, and a nucleic acid derived from a pathogen for the shellfish. The rearing step (A) may be a step subsequent to the rearing step (B), and the rearing step (B) may be a step subsequent to the rearing step (A).

[0039] One embodiment of the present invention is a method for rearing shellfish by rearing the shellfish in a water tank, including a rearing step of rearing the shellfish in the presence of an insect belonging to the order Lepidoptera and in the presence of one or more selected from the group consisting of a pathogen, a protein derived from a pathogen, and a nucleic acid derived from a pathogen for the shellfish.

[0040] Another aspect of the present invention is an immunostimulant for shellfish containing an insect belonging to the order Lepidoptera as an active ingredient. The present inventors have found that an insect belonging to the order Lepidoptera has a remarkable immunostimulatory effect on shellfish. Shellfish include mollusks (bivalves, gastropods, etc.), crustaceans, cephalopods, echinoderms, and protochordates. Further, another aspect of the present invention can be an immunostimulant for shellfish (excluding crustaceans) or an immunostimulant for shellfish (excluding shrimp).

[0041] Another invention of the present invention is a growth promoter for shellfish containing insects belonging to Lepidoptera as an active ingredient. The inventors have found that insects belonging to Lepidoptera have a remarkable growth promoting effect on shellfish. Shellfish include mollusks (bivalves, gastropods, etc.), crustaceans, cephalopods, echinoderms, and protochordates. Further, another invention of the present invention can be a growth promoter for shellfish (excluding crustaceans) or a growth promoter for shellfish (excluding shrimp).

[0042] The immunostimulant and / or growth promoter for shellfish of the present invention can exhibit a remarkable immunostimulating effect and / or growth promoting effect by being provided to shellfish housed in an aquarium. The immunostimulant and / or growth promoter for shellfish of the present invention can be a water-soluble and alcohol-insoluble fraction of insects. The immunostimulant and / or growth promoter for shellfish of the present invention can be provided to shellfish such that a fraction obtained from insects, which is 0.0001% to 1% by weight with respect to the breeding water of shellfish, is present in the breeding water of shellfish.

[0043] The present invention provides a method for producing an immunostimulant and / or growth promoter for shellfish. One embodiment of the production method of the present invention includes a step of obtaining a water-soluble and alcohol-insoluble fraction of insects belonging to Lepidoptera. As an example of this step, a first mixing step of mixing insects and water to obtain a first mixture, a first obtaining step of obtaining a water fraction from the first mixture, a second mixing step of mixing the water fraction and alcohol to obtain a second mixture, and a second obtaining step of obtaining an alcohol-insoluble fraction from the second mixture can be mentioned. Tap water, distilled water, etc. are used as water, and ethanol, methanol, propanol, etc. are used as alcohol. The first obtaining step and the second obtaining step can be performed by centrifugation.

Examples

[0044] The present invention will be described in more detail with reference to the examples, but the present invention is not limited to the following examples.

[0045] Using the powder of silkworm (B. mori) pupae defatted with petroleum ether, the water-soluble and alcohol-insoluble fraction of insects was produced. The insect powder was mixed with 10 times the weight of the powder of distilled water and shaken at 25 °C for 6 hours or more. The supernatant and precipitate were obtained by centrifugation. To the precipitate, 10 times the weight of the powder of distilled water was mixed, shaken at 25 °C for 6 hours or more, and the supernatant was obtained by centrifugation.

[0046] The supernatants obtained by two centrifugations were combined and filtered, and concentrated under reduced pressure at 50 °C using an evaporator until the volume became about one-third. To the concentrated supernatant, about 2.5 times the volume of ethanol was added, allowed to stand at 4 °C, and the precipitate was obtained by centrifugation. The obtained precipitate was washed with 70% ethanol by volume, and the water-soluble and alcohol-insoluble fraction of insects was obtained.

[0047] Pearl oysters were collected from the area contaminated with the Billnavirus. It was confirmed that the mantle of the pearl oyster was in an atrophied state and was highly likely to be infected with the Billnavirus. The extracorporeal fluid of the mantle extracted by opening the pearl oyster was filtered through a 100 μm diameter and a 50 μm diameter mesh filter in sequence, and the supernatant was obtained by centrifugation.

[0048] The following Examples 1 to 5 were set using an aquarium (made of polycarbonate, 30 L of breeding water) containing pearl oyster larvae (about 20,000 individuals) with a left shell surface area of 1.05 ± 0.11 mm 2 (average value ± standard error). Example 1: 3 mL of the supernatant obtained from the Billnavirus-infected pearl oyster was added to the breeding water. Example 2: 3 mL of the supernatant obtained from the Billnavirus-infected pearl oyster and the water-soluble and alcohol-insoluble fraction obtained from 3 g of insect powder (about 0.01% by weight with respect to the breeding water) were added.

[0049] Example 3: 3 mL of the supernatant obtained from virus-infected pearl oysters and the water-soluble and alcohol-insoluble fraction obtained from 30 g of insect powder (about 0.1% by weight with respect to the breeding water) were added. Example 4: The water-soluble and alcohol-insoluble fraction obtained from 3 g of insect powder (about 0.01% by weight with respect to the breeding water) was added. Example 5: The water-soluble and alcohol-insoluble fraction obtained from 30 g of insect powder (about 0.1% by weight with respect to the breeding water) was added.

[0050] In each aquarium, the breeding water was changed at two-day intervals, and the supernatant and / or fraction were readded when the water change was completed, and the oysters were bred for a total of 6 days. Also, in each aquarium, in addition to the supernatant and / or insect powder, juvenile pearl oysters were bred in the presence of 8 - 10 million cells / ml of the phytoplankton Pavlova lutheri as food.

[0051] After breeding for 6 days, juvenile pearl oysters were released into two locations (X sea area and Y sea area) in the virus-contaminated sea area, and the growth and survival numbers were measured regularly.

[0052] About 1 month after the release, the pearl oysters of each example and comparative example were observed to confirm whether the shellfish had died or whether mantle atrophy had occurred in the surviving shellfish. The results are shown in Table 1. In this sea area, almost all the pearl oysters bred by the normal method died, while Examples 1 to 5 showed a survival rate of 90% or more in many plots. The pearl oysters of Example 1 had a high atrophy rate of the mantle and signs of virus infection were observed, but in Examples 2 to 5, almost no individuals with mantle atrophy were confirmed.

[0053]

Table 1

[0054] In addition, Fig. 1 shows the left shell surface area of the pearl oysters in the examples or comparative examples about one month after the dredging. Fig. 1(A) shows the surface areas of Examples 1 to 3 dredged in Sea Area X. As shown in Fig. 1, the pearl oysters (Examples 2 and 3) reared in the presence of the water-soluble and alcohol-insoluble fraction of the insect showed significantly promoted growth compared with Example 1. Fig. 1(B) shows the surface areas of Examples 4 and 5 dredged in Sea Area Y and the comparative example. Examples 4 and 5 showed significantly promoted growth compared with the comparative example.

[0055] Furthermore, the pearl oysters produced under the conditions of Example 4 (Example 4) and the pearl oysters produced by the ordinary method (comparative example) were dredged in two places (Sea Area A and Sea Area B) in the area contaminated with the Birnavirus, and the number of survivors was regularly observed. The survival rate in Sea Area A is shown in Fig. 2(A), and the survival rate in Sea Area B is shown in Fig. 2(B), respectively. In Example 4, no deaths were observed during the period in any sea area, and the survival rate of Example 4 was significantly higher than the survival rate of the comparative example.

[0056] After breeding the soft bodies of the pearl oysters for 6 days in each of the above-described examples, 3 individuals of each group were collected, and as a comparative example, 3 individuals of the soft bodies of the pearl oysters before dredging were collected for each group, and differential expression gene (DEG) analysis was performed. In the examples, from the base sequences in which significant variations were observed for the examples or comparative examples, highly homologous known genes were annotated to clarify what gene expression variations had occurred. Representative genes with fluctuating expression are shown in Tables 1 to 3 below.

[0057]

Table 2

[0058] In the pearl oysters of Example 1, the expression of genes related to immunity (1, 3 - 7 in Table 2) and genes involved in shell formation (2 in Table 2) was significantly increased compared with the comparative example. It was also supported by the gene analysis results that the pearl oysters of Example 1 had a higher survival rate and higher growth than the comparative example.

[0059]

Table 3

[0060] In the pearl oyster of Example 5, the expressions of genes related to immunity (8, 9, 14, 15 in Table 3), genes involved in pearl formation (10 - 12 in Table 3), and Heat shock protein that responds to heat stress (13 in Table 3) were significantly increased compared with the comparative example. It was also supported by the gene analysis results that the pearl oyster of Example 5 had a higher survival rate and faster growth than the comparative example.

[0061]

Table 4

[0062] In the pearl oyster of Example 2, the expressions of genes related to immunity (16 - 98, 23, 27, 28 in Table 4) and genes related to the insulin and mTOR (mechanistic target of rapamycin) pathways (20 - 22, 24 - 26, 29 in Table 4) were significantly increased compared with Example 1. In particular, the mTOR pathway is known to play a role in regulating autophagy. It was also supported by the gene analysis results that the pearl oyster of Example 2 had a higher survival rate and faster growth than Example 1.

Claims

1. A method for raising shellfish in an aquarium, comprising the steps of: A method for rearing said shellfish in the presence of insects belonging to the order Lepidoptera.

2. 2. The method according to claim 1, wherein the insects are a water-soluble and alcohol-insoluble fraction of insects belonging to the order Lepidoptera.

3. 3. The method according to claim 2, wherein the shellfish are raised in the presence of the fraction obtained from the insect in an amount of 0.0001% by weight to 1% by weight of the water in which the shellfish are raised.

4. 2. The method according to claim 1, wherein the shellfish are raised in the presence of one or more selected from the group consisting of pathogens for the shellfish, proteins derived from pathogens, and nucleic acids derived from pathogens.

5. The method according to claim 4, wherein the pathogen is one or more selected from the group consisting of a virus, a bacterium, a fungus, a parasite, and an inactivated version of these pathogens.

6. The method according to any one of claims 1 to 5, wherein the shellfish is other than shrimp.

7. The method according to any one of claims 1 to 5, wherein the shellfish is a mollusk.

8. A shellfish bred by the breeding method according to any one of claims 1 to 5.

9. An immunostimulant for shellfish, containing an insect belonging to the order Lepidoptera as an active ingredient.

10. An immunostimulant for shellfish, the active ingredient of which is a water-soluble, alcohol-insoluble fraction of an insect belonging to the order Lepidoptera.

11. The immunostimulant according to claim 9 or 10, wherein the shellfish is a mollusk.

12. A shellfish growth promoter that contains an insect belonging to the order Lepidoptera as an active ingredient.

13. A shellfish growth promoter containing as an active ingredient a water-soluble, alcohol-insoluble fraction of an insect belonging to the order Lepidoptera.

14. The growth promoter according to claim 12 or 13, wherein the shellfish is a mollusk.

15. Use of a water-soluble and alcohol-insoluble fraction of Lepidoptera insects in shellfish farming.

16. The use according to claim 15, wherein the shellfish is a mollusk.

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