What to do when a giant salamander has difficulty laying eggs? These handling measures need to be mastered

Observation of egg-laying in giant salamanders

After injecting exogenous hormones into sexually mature female giant salamanders, the mature yolk granules detach from the ovary (i.e. are laid), fall into the abdominal cavity, and then need to be moved upward by the movement of the abdominal wall muscles to the fimbriae of the oviduct near the forelimbs at the thoracic membrane, then enter the oviduct where a series of physiological processes wrap the yolk granules and form them into a gelatinous band, finally being laid outside the body. In cases of "internal laying", the process from the oviduct to expulsion from the body has an optimal time window; egg bands laid during this stage are of better quality and have better fertilization capacity. Through years of induced spawning trials, we have worked out a set of artificial spawning-promotion methods for giant salamanders, solving the technical difficulty of delayed egg-laying in giant salamanders under fully artificial induced-spawning conditions due to insufficient stimulation from the external ecological environment, and significantly improving their fertilization rate. After induced spawning, female giant salamanders with better gonadal development will show abdominal swelling after about three days; this is a sign before imminent laying. After artificial spawning promotion, most female giant salamanders like to crawl along the edge of the pond, then stop and remain motionless in a corner near the pond wall, with the head slightly extended above the water surface, breathing rapidly and frequently; just before the gelatinous band is about to be laid, the cloaca becomes relaxed and open, and some will even show violent side-to-side swaying of the body, finally laying the yolk-containing gelatinous band outside the body.

Handling techniques for difficult egg-laying in female giant salamanders

During artificial induced spawning, some female giant salamanders show difficult egg-laying, with only abdominal swelling and prolonged failure to lay eggs; or even if an egg band is laid, it easily breaks automatically. These all belong to cases of difficult egg-laying. Such cases must be discovered in time, and artificial spawning-promotion methods should be adopted. The specific operational techniques are: the technician carefully enters the brood salamander pond, gently presses the abdomen with the hand to expel accumulated urine from the bladder, then gently strokes the back, ventral surface, lateral folds and around the cloaca with the hand. The female giant salamander may also be gently lifted out of the water, then gently stroked along the head, trunk and abdomen. This achieves the purpose of overcoming tension and relaxing the female giant salamander about to lay, facilitating smooth laying. Do this once every 1 hour, generally for more than 3 consecutive times; if handled properly, it can prompt the female giant salamander to lay eggs. But note that during spawning promotion, the technician should first trim the fingernails, then disinfect with 0.05% potassium permanganate, so as not to scratch the giant salamander. In addition, increasing water flow stimulation can also play a certain role. III. Post-spawning management After the brood salamanders finish laying eggs, the female and male brood salamanders should be promptly moved separately into brood salamander ponds with the same water temperature as the original pond for careful rearing, because during the egg-laying process brood salamanders often chase each other, causing injuries to the body surface such as mucous membrane and skin; and brood salamanders that have just finished laying are also relatively weak. When moving them out of the spawning pond or when changing water later, ensure the giant salamanders are not harmed. If injured brood salamanders are found, promptly apply anti-inflammatory drugs to the wounds. When feeding, also be careful and cautious, and observe their activity and appetite. Start with less feeding, and feed some bait with good palatability; after the physique returns to normal, then feed according to the standard and carry out normal management. Especially after brood salamanders reproduce, due to improper technical handling, or excessive hormone dosage, sudden water quality changes and other reasons, mass death of brood salamanders often occurs. This is a very distressing problem, and the author believes prevention should be carried out from the following 4 aspects.

1. Water temperature problem: after brood salamanders lay eggs, their physique is relatively weak, and they cannot be arbitrarily scooped from the rearing pond into the spawning pond. As a result, often because the water temperature difference is too large, the giant salamanders catch cold and become ill, and in severe cases this causes death of brood salamanders. For this reason, after laying, the female and male brood salamanders should as far as possible be put back into the original pond to rest quietly.

2. Feeding problem: after intense reproduction, giant salamanders have a weak physique, their digestive function is also affected, and their appetite is poor. Under such circumstances, reduce feeding and feed easily digestible bait, until the brood salamanders' activity and appetite return to normal, only then may normal feeding be resumed.

3. Injury problem: during the reproduction process of giant salamanders, skin abrasions and peeling are caused by manual handling, and at this time the temperature is relatively high, which is the season for pathogen reproduction. Bacteria and parasites can take advantage of the wounds on the body surface to enter, making brood salamanders very easily infected with disease and die. For this reason, usually a small amount of gentamicin (concentration of 1 gram/cubic meter) is placed in the brood salamander pond for soaking, each soaking for 1 hour, used 5 times consecutively.

4. Water quality problem: because giant salamanders have difficult egg-laying, or their gonads are not yet mature enough, but after reproduction ends, the reproductive glands of female and male giant salamanders gradually mature. Whenever stimulated by new water and while foraging, some female giant salamanders will still lay eggs, and male giant salamanders also secrete male hormones and even release sperm. Thus, although this is not formal egg-laying, these secretions or sperm dissolve in the water, making the water whitish; if the water is not changed in time, it will become fishy and foul. Therefore, promptly observe the post-spawning reactions of brood salamanders, and promptly scoop out egg bands or egg granules. Where there are no conditions for flowing-water rearing, adopt the method of changing water 3 times a day; where there are conditions for flowing-water rearing, keep the water flow unobstructed to ensure good water quality.