Commonly known as Black Marsh Turtle, Siebenrockiella crassicollis is a freshwater turtle endemic to Southeast Asia. The specific epithet “crassicollis” comes from Latin crassus (“thick”) and collum (“neck”). The generic name was coined in honor of the Austrian zoologist Friedrich Siebenrock.
First described by the British zoologist John Edward Gray from three specimens from the collections of Thomas Bell. Siebenrockiella crassicollis are distinguished by a variety of vernacular names among hobbyists.
Along with Black Marsh Turtle, these reptiles are also known as black terrapin, black mud turtle, Malaysian black mud turtle, Siamese temple turtle, fat-headed turtle, thick-necked turtle, and Borneo black leaf turtle.
Black Marsh Turtles are culturally important to Buddhism. In Thailand and Japan, large numbers of Black Marsh Turtles, along with the yellow-headed temple turtles (Heosemys annandalii) are released into temple and castle ponds and cared for by Buddhist monks. They are treated as sacred by the public, is believed to contain the souls of people who died while trying to rescue other people from drowning. One of their common names, Siamese temple turtle, originated from this practice.
Formerly under the genus Emys, Black Marsh Turtles are now classified under, is only species in the Siebenrockiella. and can be found in the family Geoemydidae.
Black Marsh Turtles used to be monotypic within the genus Siebenrockiella until Diesmos showed based on genetic studies and morphology. In 2005, he revealed that the recently rediscovered and critically endangered Philippine forest turtles, until that time known as Heosemys leytensis, were very closely related. Philippine forest turtles were subsequently reassigned to Siebenrockiella under the subgenus Panyaenemys.
Black Marsh Turtles can be found in southern Vietnam, Cambodia, southern Myanmar (Tenasserim), central and peninsular Thailand, eastern and western Malaysia, Singapore, and the Indonesian islands of Java, Kalimantan, and Sumatra.
Black Marsh Turtles live in slow-moving or stagnant warm waters with abundant vegetation such as marshes, swamps, and ponds. As their common name implies, Black Marsh Turtles are primarily aquatic and prefer to stay buried in soft mud when not feeding.
Adult Black Marsh Turtles are usually small to medium-sized, averaging at around 7 inches in length and rarely exceeding 8 inches. Some individuals, however, are known to grow to twice this size.
The ovoid carapace (the dorsal shell) is widest just behind the middle portion, with a strongly serrated posterior margin. A prominent central ridge (known as keels) also runs through the middle of the carapace. Two lateral keels are present as well, though they are not always visible.
The carapace is almost entirely black or dark brown with black radiating patterns. The plastron (the ventral shell) is not hinged and has a shallow U-shaped notch in the pair of anal scutes.
The bridge (the parts connecting the abdominal and pectoral scutes of the plastron to the carapace) is approximately the same length as the rear part of the plastron (consisting of the femoral and anal scutes). Both the bridge and the plastron can be entirely black, dark brown, or yellowish with splotches or patterns of darker colors.
The forelimbs are covered with large transverse scales. Both the forelimbs and the hind limbs are webbed, reflecting their largely aquatic habits. The necks of black marsh turtles are characteristically thick, forming a collar around the head when it is retracted into the shell.
All of the limbs, the tail, and the neck are dark gray to black. The head is broad with a short upwardly pointed snout.
It is mostly black on top with cream to yellow markings around the eyes and at the throat. It also has a pair of pale white to yellow spots just behind the tympanum, usually hidden behind the folds of the neck.
Black Marsh Turtles are sexually dimorphic. Males have concave plastra in contrast to the flat plastron of females.
The markings around the eyes and throat, present in all juveniles, disappear among males upon reaching adulthood while they are retained in females. The tails are also longer and thicker for males than for females.
These remarkable reptiles have a diploid karyotype of 52 chromosomes. They are also notable for being the first turtle shown to exhibit an XX/XY system of chromosomal sex determination, specifically with macrochromosomes. Very rare in turtles where the gender of developing embryos are usually determined by environmental temperatures.
Black Marsh Turtles are predominantly carnivorous and prefer to feed underwater.
They prey on insects, worms, mollusks, amphibians, crustaceans, and small fish, though they will occasionally scavenge rotting plants, fruits, or carcasses of larger animals that fall into the water. Juveniles are typically more carnivorous than adults. Repcal aquatic turtle diet is ideally formulated to meet the needs. However, we believe in a varied diet.
Shy creatures, these animals are mostly aquatic and nocturnal. However, they will sometimes come out to land at night to forage or mate, and occasionally during the day to bask. In fact, the majority of the time they prefer to stay underwater, partially buried in mud in shallow water or swimming near the bottom in deeper still waters.
The powerful jaws are pale yellow to pale brown in color and curves upwards, earning it the charming name of ‘smiling terrapin’. Their powerful jaws are also capable of inflicting wounds if handled roughly.
Black Marsh Turtles reach sexual maturity at five years. In the wild breeding season starts in February or March. Eggs will be laid from April till June. But in captivity males will be interested in mating almost all year long. Females will be most accepting after temperatures are raised. In courtship, males will bob their heads up and down while chasing a female. It may bite the legs of the females several times before mating.
Females will lay three or four clutches. Each clutch consisting of one or two relatively large eggs, around 2.4 by 1.2 inches and weighing 30 g (0.066 lb). The eggs are incubated for 68 to 84 days before hatching. The hatchlings are tiny, measuring around 2 inches.
The maximum known lifespan of black marsh turtles observed in captivity is 16.7 years.
Black Marsh Turtles are now being captive bred both for conservation and for the pet trade. In 2004, a black marsh turtle hatched at the Bristol Zoo Gardens. It was the first of its species to successfully hatch in a European zoo. Captive-bred Black Marsh Turtles are preferable as pets, being healthier and more acclimated to handling than individuals captured from the wild and illegally exported.
Black Marsh Turtles are classified as Vulnerable by the International Union for Conservation of Nature. They are also listed on CITES Appendix II. Aside from signatories to CITES, Black marsh turtles are also specifically protected in Thailand under the Wild Animals Reservation Protection Act (WARPA). General laws against the trade and/or capture of freshwater turtles or wildlife that also extend to black marsh turtles are also in place in Myanmar, Singapore, and Vietnam.
Despite these sanctions, the greatest threat to Black Marsh Turtles, along with other Southeast Asian freshwater turtles, is the rising demand for turtles for the international meat trade, particularly for the Chinese food markets.
Black Marsh Turtle populations in Cambodia and Vietnam are already considered Endangered for this reason. The plastra of Black Marsh Turtles are also among those sought after for traditional Chinese medicine, particularly for a traditional preparation known as Kuei-Lu-Erh-Hsien-Chiao (KLEHC). Thousands of individuals are often confiscated regularly in shipments.
Each representing just a small fraction of the actual number of wild turtles being caught and sold in the Asian markets. Official records in 1999 show that around 135,000 individuals were exported within the span of 10 months in Malaysia alone. In addition to this, black marsh turtles are increasingly being threatened in its native range by habitat loss.
In a study in 2010, Black Marsh Turtles were among the turtles found to contain high levels of mercury in their tissues. Their consumption as food is discouraged as they have the potential to cause mercury poisoning. When threatened, black marsh turtles excrete a foul-smelling secretion from their cloaca to ward off would-be predators.