No. 24 “Additional information on past articles XNUMX”

A female half-orange vampire crab that protects a large egg in its abdomen. It's hard to see, but this individual's eggs seem to have just been laid, and development hasn't progressed very far.

Although I have previously introduced this in this column, there is still much information that was unknown at that time. This time, I would like to introduce the newly obtained information along with photos.

First,No. 7 “Crabs that live in the air”Regarding. Geosesarma krathing However, the commercial name Half Orange Vampire Crab has recently become very popular, so I would like to use that name.
At the time of the first article, it was thought that this species lived only in Chanthaburi in eastern Thailand, but it has since been discovered that it is widely distributed as far east as Talat. It probably changes depending on the food and environment, but the Talat population seems to have a slightly stronger red color than the Chanthaburi population.

The habitat of Tallat's half-orange vampire crab is dominated by Saraka palms, which prefer wetlands. Some individuals hide among the clusters of fruit like this.

Like Chanthaburi, Talat's habitat is somewhat wetland in the mountains, and it is often found in areas where Saraka palms, a popular fruit in Thailand, grow thick. The fruit of this Saraka palm has a slightly peculiar odor, but it has sweet and sour flesh, making it a very popular fruit among Thai people. My friends from Japan don't really like the smell of stuffy socks, but I love it. When I find a ripe fruit while taking photos, I often pick it up to quench my thirst.
Since it prefers to grow in wetlands, it is often found wild near streams in jungles, so it is not a fruit thief. However, this Sarakayashi is not only delicious, but also quite a melody. Because it is full of thorns, the habitat of this half-orange vampire crab is extremely dangerous for those who are not used to it.

The thorny Saraca palm is an excellent habitat for the half-orange vampire crab.

If you place yourself between these thorns, you will be less likely to be attacked by external enemies.

Old fallen branches are also full of thorns, so if you accidentally step on one, it will easily pierce the rubber of your shoe. I myself have had a sharp thorn stuck in the sole of my foot several times, and had it removed by a Thai friend I went out with. At that time, I was laughed at and told how soft the soles of Japanese feet are. It is nonsense to compare them with Thai people who have been playing around barefoot since childhood. The danger is not only under your feet, but also over your head and under your arms.If you don't walk carefully, you will be exposed to thorns. However, for the Half Orange Vampire Club, this environment has great advantages. It is convenient for protecting oneself from foreign enemies and is a good hiding place.

A female half-orange vampire crab with a large egg in her belly. The breeding season is during the dry season in Thailand, and the habitat tends to be dry. Is there any advantage to breeding at this time?

When the eggs are close to hatching, the black eyes of the baby crabs can be clearly seen inside the eggs.

In a previous article, I wrote that the breeding season for this half-orange vampire crab is from January to April. This information has been described in papers on this species, but I wanted to see it for myself, so I visited several times during this period over two years to observe this species. At that time, he noticed something very interesting. As the breeding season approaches, the sex ratio of this species becomes unbalanced. This phenomenon can be seen from around November, and the large individuals found on leaves are almost exclusively females. This is the same from January, when spawning begins, to around April, when breeding ends. Where do the males go during this period? From several observations, I felt that the males were often close to the ground during this period. It is unknown what it is for. There is also a theory that the female eats the male before laying eggs, like the praying mantis, but this theory cannot explain this because once the breeding season ends, the sex ratio returns to about 50/50.

A female with eggs in her abdomen will have what is called a crab fundoshi wide open, so it can be seen from above that she is carrying eggs.

In the Talat habitat, females with large eggs in their abdomens become conspicuous in February. This species is landlocked and lays large eggs, and when the eggs hatch, the babies are already crab-shaped. This large egg-shaped, landlocked species is unique among the Crassulaceae family. It seems that it takes about a month for the eggs to hatch. Around March, many females carry small baby crabs in their abdomens. Some species of the Geothesarma genus are known to have hatched baby crabs that are protected by riding on the backs of their female parents, but this half-orange vampire crab does not seem to have such a lifestyle.

They spend some time protected in their abdomens, but eventually the baby crabs become independent.

A female parent holding hatched baby crabs.

When young crabs become independent from their parents, they initially hide under fallen leaves on moist ground. As they grow larger, they move away from water and begin to live on trees or grass. Observations in the field show that there are three different sizes of crabs: large, medium, and small, so it seems that this species takes three years to grow to a large size. I can guess. Currently, my main interest is in the mystery of why the sex ratio is biased during the breeding season. There are some speculations, but there aren't enough observations to prove this. It may take several more years of observation to clarify this. During that time, how many times will we be baptized with the thorns of the Saraca palm?

Recent Posts

Popular