Macrophthalmus
A genus of Indo-Pacific crabs known as sentinel crabs.
Macrophthalmus, a genus of crabs commonly called sentinel crabs, is found throughout the Indo-Pacific region.
Subgenus Chaenostoma: *Macrophthalmus boscii*, *Macrophthalmus dentatus*, *Macrophthalmus punctulatus*.
Subgenus Euplax: *Macrophthalmus leptophthalmus*, *Macrophthalmus dagohoyi*.
Subgenus Hemiplax: *Macrophthalmus hirtipes*.
Subgenus Macrophthalmus: *Macrophthalmus abbreviatus*, *Macrophthalmus atambua*, *Macrophthalmus banzai*, *Macrophthalmus brevis*, *Macrophthalmus ceratophorus*, *Macrophthalmus consobrinus*, *Macrophthalmus convexus*, *Macrophthalmus crassipes*, *Macrophthalmus darwinensis*, *Macrophthalmus gallardoi*, *Macrophthalmus graeffei*, *Macrophthalmus grandidieri*, *Macrophthalmus hilgendorfi*, *Macrophthalmus laevimanus*, *Macrophthalmus latipes*, *Macrophthalmus malaccensis*, *Macrophthalmus microfylacas*, *Macrophthalmus milloti*, *Macrophthalmus parvimanus*, *Macrophthalmus philippinensis*, *Macrophthalmus sandakani*, *Macrophthalmus serenei*, *Macrophthalmus sulcatus*, *Macrophthalmus telescopicus*, *Macrophthalmus tomentosus*, *Macrophthalmus transversus*.
Subgenus Mareotis: *Macrophthalmus abercrombiei*, *Macrophthalmus crinitus*, *Macrophthalmus definitus*, *Macrophthalmus depressus*, *Macrophthalmus frequens*, *Macrophthalmus japonicus*, *Macrophthalmus laevis*, *Macrophthalmus pacificus*, *Macrophthalmus teschi*, *Macrophthalmus tjiljapensis*, *Macrophthalmus tomentosus*, *Macrophthalmus setosus*.
Subgenus Paramareotis: *Macrophthalmus boteltobagoe*, *Macrophthalmus erato*, *Macrophthalmus holthuisi*, *Macrophthalmus quadratus*.
Subgenus Tasmanoplax: *Macrophthalmus latifrons*.
Subgenus Venitus: *Macrophthalmus barnesi*, *Macrophthalmus dentipes*, *Macrophthalmus gastrodes*, *Macrophthalmus latreillei*, *Macrophthalmus leptophthalmus*, *Macrophthalmus serratus*, *Macrophthalmus vietnamensis*.
Quick Facts
- Taxon
- Macrophthalmus
- Type Species
- Goneplax transversus
- Type Species Authority
- Latreille, 1817
Facts from the source article.
Lore & Background
The genus Macrophthalmus contains numerous species arranged into several subgenera, including Chaenostoma, Euplax, Hemiplax, Macrophthalmus, Mareotis, Paramareotis, Tasmanoplax, and Venitus. These crabs are widespread across the Indo-Pacific region. The species within the genus are often referred to as sentinel crabs, a common name that reflects their ecological role or appearance. The subgenus Macrophthalmus includes a large number of species, such as Macrophthalmus abbreviatus, Macrophthalmus banzai, Macrophthalmus brevis, and Macrophthalmus telescopicus, among many others. Other subgenera contain fewer species; for example, Hemiplax includes only Macrophthalmus hirtipes, and Tasmanoplax includes only Macrophthalmus latifrons. The subgenus Venitus includes species such as Macrophthalmus barnesi, Macrophthalmus dentipes, and Macrophthalmus latreillei, the latter being known from a Pleistocene fossil in northern Australia.
Reader's Guide
The genus Macrophthalmus holds significance as a diverse and widespread group of crabs across the Indo-Pacific, with species distributed from the western Indian Ocean to the Pacific islands. Its classification into multiple subgenera reflects morphological and possibly ecological diversity, with some subgenera containing many species and others only one. The common name 'sentinel crabs' suggests a distinctive behavior or appearance that has drawn attention. The fossil record includes Macrophthalmus latreillei from the Pleistocene of northern Australia, indicating the genus's long presence in the region. The genus has been studied by numerous carcinologists, including H. Milne-Edwards, Stimpson, Barnes, and Serène, who have described many of its species. The subgeneric structure, with groups like Mareotis and Venitus, provides a framework for understanding evolutionary relationships within the genus. The inclusion of species described as recently as 2026 (Macrophthalmus atambua) shows ongoing taxonomic work. Overall, Macrophthalmus represents a key component of intertidal and estuarine crab faunas in the Indo-Pacific, with its sentinel crab species contributing to local biodiversity and ecological studies.
Did You Know?
- The genus contains at least eight subgenera, including Chaenostoma, Euplax, and Venitus.
- Species in this genus are often called sentinel crabs.
- Macrophthalmus atambua was described in 2026.
More in Decapod Crustacean Genera 1-24
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