A method for improving survival of horse hoof seedlings

Abstract

The application discloses a method for improving survival of Trochus conus seedlings. A plastic film or corrugated plate is placed in a water pool, an algal nutrient solution is added, water flow is suspended, and aeration culture is carried out for 15-30 days. A black sunshade net is installed above the water pool, so that the light intensity is lower than 5000 Lux. The temperature of the culture water body is 20-30 DEG C, and the salinity is 30-32 ppt. After the benthic diatoms grow fully, the water in the water pool is completely discharged, the sunshade net is lifted, the benthic diatoms are exposed to sunlight, and the exposure is continued until part of the benthic diatoms die. Then, water is added to the water pool for aeration, the sunshade net is laid again, and the Trochus conus fertilized eggs are moved into the diatom pool. Water flow is suspended, and aeration culture is carried out. The sunlight exposure method is used to kill about 30%-70% of the benthic diatoms, and part of the fresh benthic diatoms are reserved, so that the attachment metamorphosis and survival of the Trochus conus larvae are obviously improved, and technical support is provided for large-scale production of the Trochus conus.

Description

Technical Field

[0001] This invention belongs to the field of marine animal culture technology, specifically relating to a method for improving the survival rate of horseshoe snail seedlings. Background Technology

[0002] Horseshoe snails belong to the phylum Mollusca, class Gastropoda, subclass Prosobranchia, order Primitive Gastropoda, family Horseshoeidae, genus Horseshoe snails. They typically inhabit the middle, upper, and subtidal zones of the intertidal zone, primarily feeding on algae attached to rocks using their radula. As a major marine economic shellfish in the South China Sea, they possess unique ornamental and medicinal value. They are also important herbivorous gastropods in the South China Sea coral reef ecosystem and key species in many island and reef ecosystems. Their feeding on macrobenthic algae effectively controls algal biomass in coral reef ecosystems, ensuring corals maintain a dominant position in niche competition and thus maintaining the balance of interspecific relationships within the coral reef ecosystem (Li et al., 2014; Villanueva et al., 2013). However, due to climate warming and increased human activity, their survival, metabolism, reproduction, and development have been affected to varying degrees, leading to a significant reduction in their wild populations (Zhang et al., 2020). Therefore, developing artificial breeding technology for horseshoe snails is of great significance for meeting market demand and maintaining the stability of the South China Sea coral reef ecosystem.

[0003] Currently, my country's research focuses on a series of techniques, including artificial spawning induction, artificial seedling cultivation, artificial aquaculture, and marine intermediate cultivation of giant horseshoe snails and pyramidal horseshoe snails. Among these, the settling metamorphosis of horseshoe snail larvae is crucial for successful artificial seedling cultivation and a vital step in determining whether large-scale cultivation is feasible. However, the reported seedling cultivation methods all exhibit low rates of attachment metamorphosis in larvae, which to some extent limits their industrial production. Therefore, exploring a method to improve the attachment metamorphosis of horseshoe snail larvae is essential for their large-scale application. Based on this need, through multiple trials, we have developed a method that can significantly improve the attachment metamorphosis of horseshoe snail larvae, providing technical support for the industrial development of horseshoe snails. Summary of the Invention

[0004] The purpose of this invention is to provide a method that can significantly improve the survival rate of horseshoe snail seedlings and solve the problem of low seedling rate in artificial seedling cultivation.

[0005] The present invention provides a method for improving the survival rate of horseshoe snail seedlings, comprising the cultivation of benthic diatoms, exposure of benthic diatoms to sunlight, and methods for larval attachment and metamorphosis. The method is characterized by: placing a plastic film or corrugated sheet in a water tank, adding algal nutrient solution, suspending water flow, and aerating the tank for 15-30 days. A black shade net is installed above the tank to ensure light intensity is below 5000 Lux, the temperature of the culture water is 20-30℃, and the salinity is 30-32 ppt. After the benthic diatoms have fully colonized the tank, all the water is drained, the shade net is removed, and the benthic diatoms are exposed to sunlight until some die. Water is then added back to the tank for aeration, the shade net is replaced, and then the fertilized horseshoe snail eggs are transferred to the sun-exposed diatom tank. Water flow is suspended, and aeration continues. After all the planktonic larvae in the water have settled, the aeration is increased, and the tank is then kept in a running water culture. If the amount of benthic diatoms is insufficient, fresh benthic diatoms are promptly added.

[0006] Preferably, the algae nutrient solution is prepared by adding 0.3g sodium nitrate, 0.3g urea, 0.05g potassium dihydrogen phosphate, 0.005g ferric citrate, and 0.05g sodium silicate to every 10L of seawater. The ferric citrate needs to be dissolved by heating. All reagents are mixed and dissolved before being added to the water tank.

[0007] Preferably, the partial mortality of benthic diatoms is 30%-70%, more preferably 40%-60%.

[0008] Preferably, the fertilized eggs of the horseshoe snail are those of the large horseshoe snail (Trochus niloticus) or the tower-shaped horseshoe snail (Trochus pyramis Born);

[0009] Preferably, the aerated culture period is about 15 days.

[0010] This invention utilizes sunlight exposure to kill approximately 30%-70% of benthic diatoms while preserving some fresh benthic diatoms. This significantly improves the attachment metamorphosis and survival of horseshoe snail larvae, providing technical support for the large-scale production of horseshoe snails. Detailed implementation method:

[0011] The present invention will be described in detail below with reference to specific embodiments, but this is not intended to limit the present invention.

[0012] Example 1: Attachment metamorphosis and survival of the giant horseshoe snail

[0013] In May 2023, two clean, transparent plastic films measuring 0.5m x 0.5m were placed in two circular plastic buckets, each with a diameter of 0.8m and a height of 0.8m. To ensure the plastic films sank, weights (stones, discarded tiles, bricks, etc.) were placed in the middle. Filtered seawater was then added to a depth of 0.5m. Algae nutrient solution (0.3g sodium nitrate, 0.3g urea, 0.05g potassium dihydrogen phosphate, 0.005g ferric citrate, and 0.05g sodium silicate per 10L of seawater; the ferric citrate needed to be dissolved by heating; all reagents were mixed and dissolved before being added to the water tank) was added. The solution was stirred thoroughly and aerated (10L / min). A black shade net was installed above the water tank to ensure that the light intensity was below 4500 Lux. The seawater temperature was 28±0.5℃, and the salinity was 30ppt. After 15 days, benthic diatoms were found to have grown on the plastic films. The following morning at noon, all the water in one of the plastic buckets was drained, the shade net was removed, and the buckets were exposed to sunlight for a period of time. It was found that approximately 40% of the benthic diatoms had died. Fresh filtered seawater (0.5m depth) was then added, and the shade net was replaced, creating the experimental group. The other plastic bucket served as the control group and was left untreated. Pre-fertilized giant horseshoe snail larvae were transferred to both buckets at a density of 0.1 larvae / ml, and cultured with aeration. After 3 days, a significant decrease in the number of giant horseshoe snail larvae in the water was observed. After 15 days, green seedlings were found attached to the plastic film and the bottom of the buckets. On the 16th day, the number of larvae attached to both buckets was counted. The experimental group had approximately 2500 metamorphosed larvae, while the control group had approximately 250. After the count, an equal volume of filtered seawater was added, the aeration rate was increased (15L / min), and the buckets were cultured in flowing water. If 80% of the benthic diatoms are consumed during the cultivation process, fresh benthic diatoms should be added promptly.

[0014] Example 2: Attachment metamorphosis and survival of the tower-shaped horseshoe snail

[0015] In June 2023, two clean, transparent plastic films measuring 0.5m x 0.5m were placed in two circular plastic buckets, each with a diameter of 0.8m and a height of 0.8m. Weights (stones, discarded tiles, bricks, etc.) were placed in the middle to completely submerge the plastic films in seawater. Filtered seawater was then added to a depth of 0.5m. Algae nutrient solution (0.3g sodium nitrate, 0.3g urea, 0.05g potassium dihydrogen phosphate, 0.005g ferric citrate, and 0.05g sodium silicate per 10L of seawater; the ferric citrate needed to be dissolved by heating; all reagents were mixed and dissolved before being added to the water tank) was added. The solution was stirred thoroughly and aerated (10L / min). A black shade net was installed above the water tank to ensure the light intensity was below 4300 Lux. The seawater temperature was 28±0.5℃, and the salinity was 30ppt. After 16 days, benthic diatoms were found to have grown on the plastic films. The following morning at 12:00 PM, all the water in one of the plastic buckets was drained, the shade net was removed, and the buckets were exposed to sunlight for a period of time. It was found that approximately 60% of the benthic diatoms had died. Fresh filtered seawater (0.5m depth) was then added, and the shade net was replaced, creating the experimental group. The other plastic bucket served as the control group and was left untreated. Pre-prepared fertilized eggs of *Heliotropium indicum* were transferred to both buckets, with a larval density of 0.1 larvae / ml, and cultured with aeration. After 3 days, a significant decrease in *Heliotropium indicum* larvae was observed in the water. On day 15, white seedlings were found attached to the plastic film and the bottom of the buckets. On day 16, the number of larvae attached to both buckets was counted. The experimental group had approximately 2250 metamorphosed larvae, while the control group had approximately 225. After the count, an equal volume of filtered seawater was added, the aeration rate was increased (15L / min), and the buckets were cultured in flowing water. If 80% of the benthic diatoms are consumed during the cultivation process, fresh benthic diatoms should be added promptly.

Claims

1. A method for improving the survival rate of horseshoe snail seedlings, characterized in that: Place a plastic film or corrugated sheet in the pool, add algae nutrient solution, stop the water flow, and aerate for 15-30 days. Install a black shade net above the pool to ensure that the light intensity is below 5000 Lux. The temperature of the culture water should be 20-30℃, and the salinity should be 30-32 ppt. After the benthic diatoms have fully grown, drain all the water from the pool, remove the shade net, and expose the benthic diatoms to sunlight. When some of the benthic diatoms die, add water to the pool and aerate. Replace the shade net and then transfer the fertilized eggs of the horseshoe snails into the sun-exposed diatom pool. Stop the water flow and aerate for further cultivation. The aforementioned partial mortality of benthic diatoms refers to a mortality rate of 30%-70% of benthic diatoms.

2. The method according to claim 1, characterized in that, The algae nutrient solution is prepared as follows: for every 10L of seawater, add 0.3g of sodium nitrate, 0.3g of urea, 0.05g of potassium dihydrogen phosphate, 0.005g of ferric citrate, and 0.05g of sodium silicate. The ferric citrate needs to be dissolved by heating. After all the reagents are mixed and dissolved, add them to the water tank.

3. The method according to claim 1, characterized in that, The aforementioned partial mortality of benthic diatoms refers to the mortality of 40-60% of benthic diatoms.

4. The method according to claim 1, characterized in that, The fertilized eggs of the horseshoe snail mentioned above are those of the giant horseshoe snail ( ). Trochus niloticus ) or tower-shaped horseshoe snail ( Trochus pyramis Born ) fertilized egg.

5. The method according to claim 1, characterized in that, The aeration culture period is 15 days.