''Geosesarma dennerle'' is a species of small land-living

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s found on

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

. It is popular in the aquarium trade, where ''G. dennerle'', in particular, is often simply called the vampire crab. The species is named after the aquarium supply company Dennerle, which supported one of the describing authors' study in Java. The coloration of ''G. dennerle'' can be very similar to '' G. bicolor''. The describing paper mentions

cheliped A chela ()also called a claw, nipper, or pinceris a pincer-shaped organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through Neo-Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds ...

s, male abdominal and G1 structures as distinguishing features.

Description

''Geosesarma'' ''dennerle'' is a member of the phylum

Arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

a, and subphylum

Crustacea Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

. This species resides in the genus ''Geosesarma de Man'', which comprises 67 recognized species, commonly found in Southeast Asia. These crabs are generally from in size. The crab features a two-colored

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

, being predominantly purple with a patch of cream/yellow on its back. ''Dennerle'' also possesses bright yellow eyes and vibrant violet claws. As a member of the order

Decapoda The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfish, shrimp, a ...

, this crab has 5 pairs of segmented limbs. Unlike some species of crab that have specialized claws, d''ennerle'' does not have swollen chellae. The carapace is described as square-esque in shape, with well defined regions of the shell, and the abdomen being broad. The ambulatory legs of this crab are generally long and thin, with broad segments. Dennerle often have tubercles along its dorsal carapace, providing some texture to the otherwise smooth shell. ''G. dennerle'' are similar to other species of crabs with the occurrence of

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. The sex of ''Geosesarma'' species can be identified by observation of abdominal flaps. The males have narrow and pointed abdominal flaps, while the females possess wider flaps which are ovular in shape. Males are also noted to be slightly larger than females.

Ecology

''G. dennerle'' is endemic to Central Java. As the prefix "geo-" suggests, ''G. dennerle'' is a

terrestrial crab A number of lineages of crabs have evolved to live predominantly on land. Examples of terrestrial crabs are found in the families Gecarcinidae and Gecarcinucidae, as well as in selected genera from other families, such as '' Sesarma'', althou ...

. It is common to find ''dennerle'' hiding in burrows in areas composed of muddy creek valleys, with rocks and dense vegetation. The diet of ''dennerle'' is greatly composed of insects and plant matter. The high endemism of species within the ''Geosesarma'' genus, means there is not a great amount of geographic distribution.

Reproduction

Sexual reproduction in ''Geosesarma dennerle'' is similar to that of the majority of other species of crabs. Little has been observed towards specific variations in this species reproduction method in comparison to other species in the ''Geosesarma'' genus. Members of the ''Geosesarma'' genus commonly produce large eggs, averaging between 1.2 and 1.8 mm in diameter. Members of ''Geosesarma'' become sexually mature around 6 months of age, with breeding consisting of the male mounting the female to fertilize eggs. This species has

direct development Direct development is a concept in biology. It refers to forms of growth to adulthood that do not involve metamorphosis. An animal undergoes direct development if the immature organism resembles a small adult rather than having a distinct larval ...

offspring: fully formed miniature versions of the adults hatch from the eggs. The female will carry around 20–80 fertilized eggs for about a month before hatching occurs. These newly hatched offspring are often independent, and will disperse from the point where they hatch.

References

{{Taxonbar, from=Q19345966 Grapsoidea Freshwater crustaceans of Asia Crustaceans described in 2015 Taxa named by Peter Kee Lin Ng