Post by Infinity Blade on Jul 4, 2020 19:26:26 GMT 5
Maclear’s Rat: Rattus macleari
1887 illustration of Rattus macleari by Joseph Smit.![]()
Temporal range: Holocene (extinct by 1908 CE)[1]
Scientific classification:
Life
Clade: Neomura
Domain: Eukarya
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Cephalochordata
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Clade: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Clade: Therapsida
Clade: Neotherapsida
Clade: Theriodontia
Clade: Eutheriodontia
Clade: Cynodontia
Clade: Epicyonodontia
Clade: Eucynodontia
Clade: Probainognathia
Clade: Chiniquodontoidea
Clade: Prozostrodontia
Clade: Mammaliformes
Class: Mammalia
Subclass: Theria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Magnorder: Boreoeutheria
Superorder: Euarchontoglires
(unranked): Glires
Order: Rodentia
Suborder: Myomorpha
Superfamily: Muroidea
Family: Muridae
Subfamily: Murinae
Genus: Rattus
Species: †R. macleari
Maclear’s rat is an extinct species of rat endemic to Christmas Island, Australia.
Description:
This rat species was described as being about the size of a “roof rat” (referring to an invalid subspecies of black rat), with a head and body 235-240 mm long, and a tail 246-267 mm long. The fur on the dorsal surface was described as grizzled rufous brown. The belly had slightly lighter, pale rufous fur. Its feet were dark like its body. There were these longer, black hairs, and they were especially prominent on the lower back. Maclear’s rat had a tail that was dark in the proximal half, but white on the distal half. The skull was described as being large and strongly built, possessing beaded supraorbital edges and an anterior edge of the zygomatic plate projecting forward noticeably.[1]
Behavior and ecology:
It has been proposed that these rats kept the numbers of red land crabs on Christmas Island in check.[2] It was semi-arboreal.[3]
Extinction:
Maclear’s rat was extremely abundant when Christmas Island was settled on in the 1890s.[4] Although Christmas Island was discovered and named two centuries before, the (uninhabited) island wasn’t actually occupied until the 1890s.[5]
In 1899, the black rat (Rattus rattus) was introduced to Christmas Island. Three hypotheses emerged as to how this would have affected Maclear’s rat. The traditional explanation was that introduced black rats introduced diseases that native Maclear’s rats had no immunity to. Alternative ideas were competitive exclusion/predation or hybridization with black rats leading to extinction.[2][5] The presence of black rats on islands has not invariably led to the extinction of the indigenous fauna, so there is no reason to think that this is what happened on Christmas Island.[5]
Some Christmas Island rat specimens thought to be R. rattus x R. macleari hybrids have been collected in the past, and have had their DNA analyzed. These specimens have simply turned out to be morphological variations of the black rat, thus there is no direct evidence of hybridization between the two species. From a theoretical perspective, if intensive hybridization actually occurred, it would have had to take place within a relatively short time span, for Christmas Island’s indigenous rats went extinct, at most, 9 years after the introduction of the black rat.[5]
Samples from bulldog rats (R. nativitatis, another extinct rat species endemic to Christmas Island) collected pre-black rat introduction have yielded no evidence of infection from trypanosomes. By contrast, R. macleari, as well as R. rattus samples from the island, collected after the introduction of black rats did show evidence of infection, particularly from Trypanosoma lewisi. It would appear that the murines of Christmas Island were immunologically naïve to the diseases of black rats from being isolated for so long.[5] This is consistent with contemporary reports[5]; by 1902-03 the company doctor of Christmas Island reported seeing dead and dying (diseased) R. macleari everywhere.[2][3] They were never seen again after 1903[2], and are thought to have become completely extinct by 1908.[5]
T. lewisi surrounded by blood cells. Image source->
Parasite coextinction:
Maclear’s rats were hosts to two species of parasites: the Christmas Island flea (Xenopsylla nesiotes), which too was endemic to Christmas Island[6], and a tick species known as Ixodes nitens[7]. Neither the rat nor the flea have been seen since the time of the former’s extinction. This suggests that when Maclear’s rat went extinct, so too did the flea, which specifically depended on it.[6] Likewise, other endemic rat species did not harbor I. nitens, which suggests that this tick was also specifically dependent on Maclear’s rat as a host. It too appears to be extinct.[7]
References:
[1] Harper, F. (1945). Extinct and vanishing mammals of the Old World. Extinct and Vanishing Mammals of the Old World.
[2] Flannery, T. F., & Schouten, P. (2001). A gap in nature: discovering the world's extinct animals. Atlantic Monthly Press.
[3] Breed, B., & Ford, F. (2007). Native mice and rats. CSIRO PUBLISHING.
[4] Zichy-Woinarski, J. C., Burbidge, A., & Harrison, P. (2014). The action plan for Australian mammals 2012. CSIRO publishing.
[5] Wyatt, K. B., Campos, P. F., Gilbert, M. T. P., Kolokotronis, S. O., Hynes, W. H., DeSalle, R., ... & Greenwood, A. D. (2008). Historical mammal extinction on Christmas Island (Indian Ocean) correlates with introduced infectious disease. PloS one, 3(11), e3602.
[6] Kwak, M. L. (2018). Australia’s vanishing fleas (Insecta: Siphonaptera): a case study in methods for the assessment and conservation of threatened flea species. Journal of Insect Conservation, 22(3-4), 545-550.
[7] Mihalca, A. D., Gherman, C. M., & Cozma, V. (2011). Coendangered hard-ticks: threatened or threatening?. Parasites & Vectors, 4(1), 71.
1887 illustration of Rattus macleari by Joseph Smit.
Temporal range: Holocene (extinct by 1908 CE)[1]
Scientific classification:
Life
Clade: Neomura
Domain: Eukarya
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Cephalochordata
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Clade: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Clade: Therapsida
Clade: Neotherapsida
Clade: Theriodontia
Clade: Eutheriodontia
Clade: Cynodontia
Clade: Epicyonodontia
Clade: Eucynodontia
Clade: Probainognathia
Clade: Chiniquodontoidea
Clade: Prozostrodontia
Clade: Mammaliformes
Class: Mammalia
Subclass: Theria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Magnorder: Boreoeutheria
Superorder: Euarchontoglires
(unranked): Glires
Order: Rodentia
Suborder: Myomorpha
Superfamily: Muroidea
Family: Muridae
Subfamily: Murinae
Genus: Rattus
Species: †R. macleari
Maclear’s rat is an extinct species of rat endemic to Christmas Island, Australia.
Description:
This rat species was described as being about the size of a “roof rat” (referring to an invalid subspecies of black rat), with a head and body 235-240 mm long, and a tail 246-267 mm long. The fur on the dorsal surface was described as grizzled rufous brown. The belly had slightly lighter, pale rufous fur. Its feet were dark like its body. There were these longer, black hairs, and they were especially prominent on the lower back. Maclear’s rat had a tail that was dark in the proximal half, but white on the distal half. The skull was described as being large and strongly built, possessing beaded supraorbital edges and an anterior edge of the zygomatic plate projecting forward noticeably.[1]
Behavior and ecology:
It has been proposed that these rats kept the numbers of red land crabs on Christmas Island in check.[2] It was semi-arboreal.[3]
Extinction:
Maclear’s rat was extremely abundant when Christmas Island was settled on in the 1890s.[4] Although Christmas Island was discovered and named two centuries before, the (uninhabited) island wasn’t actually occupied until the 1890s.[5]
In 1899, the black rat (Rattus rattus) was introduced to Christmas Island. Three hypotheses emerged as to how this would have affected Maclear’s rat. The traditional explanation was that introduced black rats introduced diseases that native Maclear’s rats had no immunity to. Alternative ideas were competitive exclusion/predation or hybridization with black rats leading to extinction.[2][5] The presence of black rats on islands has not invariably led to the extinction of the indigenous fauna, so there is no reason to think that this is what happened on Christmas Island.[5]
Some Christmas Island rat specimens thought to be R. rattus x R. macleari hybrids have been collected in the past, and have had their DNA analyzed. These specimens have simply turned out to be morphological variations of the black rat, thus there is no direct evidence of hybridization between the two species. From a theoretical perspective, if intensive hybridization actually occurred, it would have had to take place within a relatively short time span, for Christmas Island’s indigenous rats went extinct, at most, 9 years after the introduction of the black rat.[5]
Samples from bulldog rats (R. nativitatis, another extinct rat species endemic to Christmas Island) collected pre-black rat introduction have yielded no evidence of infection from trypanosomes. By contrast, R. macleari, as well as R. rattus samples from the island, collected after the introduction of black rats did show evidence of infection, particularly from Trypanosoma lewisi. It would appear that the murines of Christmas Island were immunologically naïve to the diseases of black rats from being isolated for so long.[5] This is consistent with contemporary reports[5]; by 1902-03 the company doctor of Christmas Island reported seeing dead and dying (diseased) R. macleari everywhere.[2][3] They were never seen again after 1903[2], and are thought to have become completely extinct by 1908.[5]
T. lewisi surrounded by blood cells. Image source->
Parasite coextinction:
Maclear’s rats were hosts to two species of parasites: the Christmas Island flea (Xenopsylla nesiotes), which too was endemic to Christmas Island[6], and a tick species known as Ixodes nitens[7]. Neither the rat nor the flea have been seen since the time of the former’s extinction. This suggests that when Maclear’s rat went extinct, so too did the flea, which specifically depended on it.[6] Likewise, other endemic rat species did not harbor I. nitens, which suggests that this tick was also specifically dependent on Maclear’s rat as a host. It too appears to be extinct.[7]
References:
[1] Harper, F. (1945). Extinct and vanishing mammals of the Old World. Extinct and Vanishing Mammals of the Old World.
[2] Flannery, T. F., & Schouten, P. (2001). A gap in nature: discovering the world's extinct animals. Atlantic Monthly Press.
[3] Breed, B., & Ford, F. (2007). Native mice and rats. CSIRO PUBLISHING.
[4] Zichy-Woinarski, J. C., Burbidge, A., & Harrison, P. (2014). The action plan for Australian mammals 2012. CSIRO publishing.
[5] Wyatt, K. B., Campos, P. F., Gilbert, M. T. P., Kolokotronis, S. O., Hynes, W. H., DeSalle, R., ... & Greenwood, A. D. (2008). Historical mammal extinction on Christmas Island (Indian Ocean) correlates with introduced infectious disease. PloS one, 3(11), e3602.
[6] Kwak, M. L. (2018). Australia’s vanishing fleas (Insecta: Siphonaptera): a case study in methods for the assessment and conservation of threatened flea species. Journal of Insect Conservation, 22(3-4), 545-550.
[7] Mihalca, A. D., Gherman, C. M., & Cozma, V. (2011). Coendangered hard-ticks: threatened or threatening?. Parasites & Vectors, 4(1), 71.
