Original Li Zhaocheng Southern Fisheries Science2022-11-29 11:00 Published in GuangdongThe sound of being everywhere underwaterMany animals in the ocean make sounds, such as invertebrates, fish, and mammals, but invertebrates make the most vocalizations, while crustaceans make the most sounds. These animals usually use pincers and antennae to make a variety of sounds through impact and friction. Its vocalizations can be broadly divided into two categories: active vocalizations and passive vocalizations. Active vocalization is similar to the human active use of vocal cord vibrations to produce sound during verbal communication. Similarly, crustaceans will also take the initiative to speak out because of their behavior such as reproduction and competition for territory. For example, the drum shrimp, also known as the pistol shrimp, when it hunts, will quickly close its strong and powerful claws, and spray a column of water to form a bubble impact, so as to stun the prey. It is said that this bubble blast can emit a sound of up to 218 decibels, which is far better than the sound of a gunshot (about 150 decibels) and even louder than the roar of a lion. Passive vocalizations are analogous to the sound of human footsteps walking on the ground. The passive vocalizations of crustaceans mostly occur when they swim, avoid predators and feed, and most of them are eating vocalizations. Speaking of the "bar chirp" that eats with special energy, in addition to Zhu Bajie in "Journey to the West", there is also our protagonist today - litopenaeus vannamei.
"Sigh your mouth" actually has a big revelation?As one of the world's important aquaculture products, Penaeus vannamei shrimp, also known as vannamei shrimp, vannamei shrimp and white-footed shrimp, has received continuous attention from farmers and scholars in the past many years, because it directly affects the feed management and breeding efficiency of shrimp. However, the feeding behavior of shrimp is complex and difficult to catch. In the past, the feeding behavior of shrimp was mostly studied by shooting**, followed by the naked eye, and then analyzed by image analysis software. Due to the instability of the light source, the image is prone to blurry, which makes it difficult to accurately obtain some parameters of shrimp feeding. Later, the researchers found that shrimp make sounds when they eat pellet bait, and revealed that the reason for the sound is that their large jaws rub against each other when chewing bait, so they proposed that the total amount of feed eaten can be determined by the sound made by shrimp when they eat food, so as to evaluate the factors affecting shrimp's feeding behavior. This is because the sound signal is generated by the shrimp's jaw movement and is closely related to the amount of feed consumed by the shrimp. Deciphering the "bar chirp" of prawnsAs far as passive vocalizations are concerned, for example, the sound produced by a person walking on a lawn is different from that produced by walking on a wooden floor, so does the sound of Penaeus vannamei shrimp also change depending on the environment?In addition, the sound we make when we eat apples is different from that of bananas, so will Penaeus vannamei also make different sounds because of the different feeds we eat?With these questions in mind, Cao Zhengliang's research team from the School of Marine Sciences of Shanghai Ocean University conducted relevant experiments. The experimental samples were selected from the large pond (diameter 34 m, height 12 m) of Litopenaeus vannamei (body length 9 10 cm), the temperature, salinity, dissolved oxygen and inorganic salts of the aquaculture water were kept within the appropriate range of shrimp (24 h continuous oxygenation, temperature was kept at 28, salinity was 30). Before the experiment, Litopenaeus vannamei was fasted for about 20 h in a temporary water tank (44 cm 28 cm 30 cm) with aeration equipment to ensure the feeding desire of the shrimp during the experiment. The food selected as pellet feed (particle size is. 8 and 12 mm) as well as sand silkworms. A group of shrimp (3 shrimps) were randomly placed into a transparent acoustic experimental glass water tank (44 cm, 28 cm, 30 cm), and under the same conditions as before, one type of feed was fed, and the shrimp were changed to the next type of feed after the experiment. The experimental tank was surrounded by a black membrane cloth and covered with a foam board on the top of the tank to isolate environmental noise, and the hydrophone was suspended about 2 3 near the bottom of the glass tank as the shrimp were mostly active at the bottom during feeding (Figure 1). 
Fig.1 Schematic diagram of experimental layout The experimental results showed that the waveform of shrimp ingesting three different particle size feeds was similar, and the signal time width was about 8 10 ms. The frequency of the shrimp feeding vocal signal is between 5 45 kHz, of which 04 and 0The peak center frequency of the vocalization signal spectrum of 8 mm particle size feed was about 17 kHz, and the feeding was 1The peak center frequency of the 2 mm particle size acoustic signal is approximately 10 kHz (Figure 2);The sub-main peak of the high-frequency region is found in the sound signal spectrum of the three different particle size pellet feeds (if you are interested in the signal spectrum, click "Read Original" at the bottom left). The frequency of the vocal signal of shrimp feeding sand silkworm in the laboratory is between 5 20 kHz, and the center frequency of the spectral peak is around 7 kHz, so it can be distinguished from the signal of pellet feeding, and the specific acoustic parameters are compared in Table 1. 
a.Waveform and spectrogram of the feeding vocalization signal;b.Spectral comparison and mean of the signal. Fig.2 Ingestion 1Acoustic signal diagram of a 2 mm pellet feed
In addition, the research team also collected the feeding vocalization signals of shrimp in the farmed shrimp pond in August 2020 (Fig. 3), and the body length and growth state of the shrimp in the shrimp pond during this period were similar to those used in the laboratory. 
Fig.3 Feeding vocal signal diagram of shrimp in farmed shrimp ponds It can be seen that shrimp do produce different sounds when eating different foods, and these sounds are distinguishable from each other. And when the shrimp is hungry, it makes a louder sound when it eats the feed, just like humans, once we are full, we will not "chirp". It is also worth noting that humans make different sounds when eating different foods, for example, we make a "rattling" sound when we eat an apple, but we can hear a wet sound when we eat a banana. Therefore, we can also judge whether the shrimp is full and whether they like to eat a certain food by the sound of shrimp feeding underwater, which provides a theoretical basis for the development of intelligent feeding monitoring system in the future. Wonderfully interesting underwater soundsIn addition to crustaceans like Penaeus vannamei shrimp making sounds, fish can also make a variety of sounds in the water. As we all know, fish do not have specialized vocal organs, and their vocalization is carried out by their special tissues, such as skeletal tissue, muscles and swim bladder. Many fish make very interesting sounds, such as the box pufferfish, which makes a sound like a dog barkingThe sound of the red lady fish is like the clatter of an old man's smoking bag;Sardines can make a sound similar to the "clatter" of waves crashing on the shore. So, do you know what the words to describe a fish call are?That's the sound of 唼 (shà) 喋 (zhá), don't answer "gurgling" in the future!
Related Articles:
Cao Zhengliang, Shen Mengting, Li Zhaocheng, Wang Hao, Wang Xiuxiu. Vocal signal characteristics of Penaeus vannamei shrimp ingested with different particle size pellet feeds[J].South China Fisheries Science, 2022, 18(6): 26-34
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Written by |Li Zhaocheng.
Edit |Zhang Liping.
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