Transandinomys talamancae

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Transandinomys talamancae
Skull
Skull of a male from Gatun, Panama, seen from above[1]

Least Concern  (IUCN 3.1)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Sigmodontinae
Genus: Transandinomys
Species:
T. talamancae
Binomial name
Transandinomys talamancae
(J.A. Allen, 1891)
Map
Distribution of Transandinomys talamancae in southern Central America and northwestern South America[3]
Synonyms[13]
  • Oryzomys talamancae J.A. Allen, 1891[4]
  • Oryzomys mollipilosus J.A. Allen, 1899[5]
  • Oryzomys magdalenae J.A. Allen, 1899[6]
  • Oryzomys villosus J.A. Allen, 1899[7]
  • Oryzomys sylvaticus Thomas, 1900[8]
  • Oryzomys panamensis Thomas, 1901[9]
  • Oryzomys medius Robinson and Lyon, 1901[10]
  • Oryzomys carrikeri J.A. Allen, 1908[11]
  • Transandinomys talamancae: Weksler, Percequillo, and Voss, 2006[12]

Transandinomys talamancae is a

braincase is low. The number of chromosomes
varies from 34 to 54.

The species was first described in 1891 by

morphologically
similar.

Active during the night, Transandinomys talamancae lives on the ground and eats plants and insects. Males move more and have larger

parasites
occur on this species. Widespread and common, it is of no conservation concern.

Taxonomy

In 1891, Joel Asaph Allen was the first to scientifically describe Transandinomys talamancae, when he named Oryzomys talamancae from a specimen from Talamanca, Costa Rica. He placed it in the genus Oryzomys, then more broadly defined than it is now, and compared it to both the marsh rice rat (O. palustris) and to O. laticeps.[14] Several other names that are now recognized as synonyms of Transandinomys talamancae were introduced in the following years. In 1899, Allen described Oryzomys mollipilosus, O. magdalenae, and O. villosus from Magdalena Department, Colombia.[15] Oldfield Thomas added O. sylvaticus from Santa Rosa, Ecuador in 1900[16] and O. panamensis from Panama City, Panama, in 1901.[17] In the same year, Wirt Robinson and Markus Lyon named Oryzomys medius from near La Guaira, Venezuela.[18] Allen added O. carrikeri from Talamanca, Costa Rica, in 1908.[19]

Alfred Gardner again listed it as a valid species, an action more fully documented by Guy Musser and Marina Williams in 1985.[22] Musser and Williams also found that the holotype of Oryzomys villosus, the affinities of which had been disputed, in fact consisted of a skin of O. talamancae and a skull of the Oryzomys albigularis group (equivalent to the current genus Nephelomys). They restricted the name to the skin, making villosus a synonym of O. talamancae.[23] They also examined the holotypes of panamensis, carrikeri, mollipilosus, medius, and magdalenae and identified them as examples of Oryzomys talamancae. Additionally, they included sylvaticus and Oryzomys castaneus J.A. Allen, 1901, from Ecuador as synonyms, but without examining the holotypes.[24] Musser and colleagues reviewed the group again in 1998 and confirmed that sylvaticus represents Oryzomys talamancae; however, they found that castaneus was in fact an example of Oryzomys bolivaris (the current Transandinomys bolivaris).[25]

In 2006, Marcelo Weksler published a

vibrissae, or whiskers, above the eyes).[28] Transandinomys is one of about 30 genera in Oryzomyini, a diverse assemblage of American rodents of over a hundred species,[29] and on higher taxonomic levels in the subfamily Sigmodontinae of family Cricetidae, along with hundreds of other species of mainly small rodents.[30]

Several common names have been proposed for Transandinomys talamancae, including "Talamanca Rice Rat",[31] "Transandean Oryzomys",[32] and "Talamancan Rice Rat".[2]

Description

Transandinomys talamancae is a medium-sized, brightly colored rice rat.[33] It is similar to T. bolivaris and the two are often confused.[34] They are about as large, but in T. talamancae the tail is longer and the hindfeet shorter.[35] Both species share uniquely long vibrissae, with both the mystacial (above the mouth) and superciliary vibrissae extending to or beyond the back margin of the ears when laid back against the head, but those in T. bolivaris are substantially longer.[12] H. alfaroi, a widespread species ranging from Mexico to Ecuador, is also similar.[36] It is smaller and darker, but young adult T. talamancae are similar in color to adult H. alfaroi and often misidentified.[37] Hylaeamys megacephalus,[Note 1] with which T. talamancae was synonymized for some decades, is similar in body size, but is not known to overlap with T. talamancae in range.[39]

The fur is short, dense and soft in Transandinomys talamancae;

molted into the dark brown subadult fur when the animal is about 35 to 40 days old. This fur is replaced by the bright adult fur at age 49 to 56 days.[44] Juveniles are never blackish as in T. bolivaris.[42] The ears are dark brown,[40] large, and densely covered with very small hairs.[45]

Measurements of Transandinomys talamancae[46]
Country n[Note 2] Head and body Tail Hindfoot Ear
Panama 22 124.4 (101–136) 124.7 (110–143) 29.2 (27–32) 21.1 (16–25)
Colombia 13 135.2 (120–151) 125.2 (114–140) 29.5 (27–32) 19.0 (18–22)
Ecuador 20[Note 3] 124 (118–136) 128.5 (118–137) 29.1 (28–31) –
Measurements are in millimeters and in the form "average (minimum–maximum)".

The sparsely haired tail is approximately as long as the head and body.[45] It is dark brown above and lighter below.[40] In contrast, the tail of H. megacephalus has little to no difference in color between the upper and lower surface.[43] In 2006, Weksler and colleagues noted tail coloration as a difference between the two species of Transandinomys (bicolored in T. talamancae and unicolored in T. bolivaris),[12] but in their 1998 study, Musser and colleagues could not find differences in tail coloration between their Panamanian samples of the two species.[47]

The hindfeet are long and have the three central digits longer than the two outer ones.

ungual tufts of silvery hair that are longer than the claws themselves.[49] The claws are short and sharp.[50] Parts of the sole are covered by indistinct scales (squamae), which are usually entirely absent in T. bolivaris.[51] The pads are moderately large.[47]

The length of the head and body is 105 to 151 mm (4.1 to 5.9 in), tail length 105 to 152 mm (4.1 to 6.0 in), hindfoot length 26 to 32 mm (1.0 to 1.3 in), ear length 17 to 24 mm (0.67 to 0.94 in), and body mass 38 to 74 g (1.3 to 2.6 oz).

caudals; a pair of supernumerary (additional) ribs is occasionally present.[54]

Skull and teeth

Skull
Skull from Gatun, Panama, seen from below[1]

The skull has a long rostrum (front part), a broad

premaxillary bones extend about as far backward.[31] The interorbital region is narrowest toward the front and shows weak beading at its margins;[57] T. bolivaris is similar, but has stronger beading[58] and H. megacephalus entirely lacks the beading.[59] The parietal bone is usually limited to the roof of the braincase and does not extend to its side, as it does in most T. bolivaris.[58] The interparietal bone, part of the roof of the braincase, is large.[31]

The

auditory bullae.[40] As in most oryzomyines, the subsquamosal fenestra, an opening at the back of the skull, is present.[62] The pattern of grooves and foramina (openings) in the skull indicates that the circulation of the arteries of the head in T. talamancae follows the primitive pattern, as in most similar species but unlike in Hylaeamys.[59]

The

diastema between the lower incisor and the first molar, opens towards the side, as usual in oryzomyines.[64] The upper and lower masseteric ridges, which anchor some of the chewing muscles, do not join into a single crest and extend forward to below the first molar.[65]

The upper incisor is

hypoflexid on the second lower molar, the main valley between the cusps, is very long, extending more than halfway across the tooth; in this trait, the species is again similar to T. bolivaris but unlike H. alfaroi.[68] Each of the upper molars has three roots (two at the labial, or outer, side and one at the lingual, or inner, side) and each of the lower molars has two (one at the front and one at the back); T. talamancae lacks the additional small roots that are present in various other oryzomyines, including species of Euryoryzomys, Nephelomys, and Handleyomys.[69]

Male reproductive anatomy

Mandible
Mandible (lower jaw) from Gatun, Panama, seen from the labial (outer) side[70]

As is characteristic of Sigmodontinae, Transandinomys talamancae has a complex penis, with the distal (far) end of the baculum (penis bone) ending in a structure consisting of three digits.[71] As in most oryzomyines, the central digit is larger than the two at the sides.[72] The outer surface of the penis is mostly covered by small spines, but there is a broad band of nonspinous tissue.[73]

Some features of the accessory glands in the male genital region vary among oryzomyines. In Transandinomys talamancae,

vesicular gland is irregularly folded, not smooth as in most oryzomyines.[75]

Karyotype

Three molars on both the left and right, decreasing in size from above to below
Upper molars (left) and lower molars (right) of a specimen from Cana, Panama[76]

The

pericentric inversions (reversals of part of a chromosome that includes the centromere) are needed to explain the difference between the two groups. Musser and colleagues, in discussing these karyotypes, assumed that the 2n = 40–42 sample was from within a hybrid zone between two karyotypic morphs.[80]

The karyotype of an Ecuadorean sample from north of the Gulf of Guayaquil is similar to that of Venezuelan animals at 2n = 36, FN = 60; it includes four acrocentric and two subtelocentric pairs and no submetacentrics. In contrast, a sample from south of the Gulf had 2n = 54, FN = 60, including 23 pairs of acrocentrics and four pairs of metacentrics (with two equally long arms). Musser and colleagues termed the difference between the two Ecuadorian forms "impressive"[80] and noted that further research was needed to understand the karyotypic differentiation within the species more fully.[81] Both T. bolivaris and H. alfaroi have more chromosomes and arms, at 2n = 58, FN = 80 and 2n = 60–62, FN = 100–104 respectively.[82] Hylaeamys megacephalus has 2n = 54, FN = 58–62 and the similar Hylaeamys perenensis has 2n = 52, FN = 62; these karyotypes resemble that of southern Ecuadorean T. talamancae.[83]

Distribution and habitat

The distribution of Transandinomys talamancae extends from northwestern Costa Rica south and east to northern Venezuela and southwestern Ecuador, up to 1,500 m (5,000 ft) above sea level.

deciduous forest.[84] Although its distribution broadly overlaps that of T. bolivaris, it is more widely distributed in South America because of its greater tolerance of dry forest habitats.[85]

Transandinomys talamancae reaches the northern limit of its range in Costa Rica, but except for one record from the far northwest (in Guanacaste Province near the southern margin of Lake Nicaragua), it is known only from the southeastern third of the country. In contrast, T. bolivaris and H. alfaroi occur further north, into Honduras and Mexico respectively. It occurs throughout Panama at low elevations. Along the Pacific coast in Colombia and Ecuador, it is found on the coastal plain and the adjacent foothills of the Andes.[85] The southernmost known record is in far southwestern Ecuador, but the species may range into nearby Peru.[84]

It also occurs throughout northern Colombia at low elevations and into western Venezuela west of Lake Maracaibo and at the foot of the western part of the Venezuelan Coastal Range east to Guatopo National Park.[85] Hylaeamys megacephalus occurs further to the east in the eastern portion of the coastal range, separated by the coastal Eastern Caribbean Dry Zone.[43] There is a record from the Orinoco Delta of northeastern Venezuela, well within the range of Hylaeamys megacephalus, but Musser and colleagues suggest that this is based on mislabeled specimens.[86] The species has also been found on the narrow strip between the Llanos and the Andes (Cordillera Oriental and Cordillera de Mérida) in eastern Colombia and northwestern Venezuela.[85] The unforested Llanos separate these areas from Hylaeamys populations. Hylaeamys perenensis[Note 6] does, however, occur further south along the eastern foothills of the Cordillera Oriental in Colombia and it is possible that the two overlap in this area.[43]

Ecology and behavior

Transandinomys talamancae is a common, even abundant, species.

omnivorous: including both plant material such as seeds and fruits; and adult and larval insects.[44]

Males tend to travel longer distances than females. The average home range size in Fleming's study was 1.33 hectares (3.3 acres); males had larger home ranges on average.[92] Specimens that were once captured tended to be captured more frequently than those that had never been captured.[93] Fleming estimated that population densities reached peaks of up to 4.3 per ha (1.7 per acre) late in the rainy season (October–November), but dropped to near zero around June; however, these figures may well be underestimates.[94] In central Venezuela, population densities vary from 5.5 to 9.6 per ha (2.2 to 3.8 per acre).[95]

In Panama, this species breeds year-round without apparent seasonal variability.

gestation period is 28 days;[97] Linares reports 20 to 30 days in the wild.[95] Females produce an average of six litters per year and there are two to five (average 3.92) young per litter, so that a single female may produce about 24 young per year;[98] this is likely an overestimate because most females would not live for a full year. Larger females may have larger litters.[99] Animals become sexually mature when less than two months old; in Fleming's study, some females in juvenile fur, probably less than 50 days old, were already pregnant.[100] The oldest specimen Fleming observed was nine months old;[101] he estimated that animals were unlikely to live for more than a year in the wild[102] and that the mean age at death was 2.9 months.[103]

Ten species of mites (

Haemolaelaps glasgowi, Laelaps dearmasi, Laelaps pilifer, Laelaps thori, Mysolaelaps parvispinosus,[110] and Paraspeleognathopsis cricetidarum),[111] thirteen chiggers (Aitkenius cunctatus,[112] Ascoschoengastia dyscrita, Eutrombicula alfreddugesi, Eutrombicula goeldii, Intercutestrix tryssa, Leptotrombidium panamensis, Myxacarus oscillatus, Pseudoschoengastia abditiva, Pseudoschoengastia bulbifera, Trombicula dunni, and Trombicula keenani),[113] and four fleas (Jellisonia sp., Polygenis roberti, Polygenis klagesi, and Polygenis dunni) have been found on T. talamancae in Panama.[114] G. aitkeni has also been found on this species in Colombia.[105] In addition, the sucking lice Hoplopleura nesoryzomydis and Hoplopleura oryzomydis occur on T. talamancae.[115]

Conservation status

A widespread and common species, Transandinomys talamancae is listed as "

Least Concern" by the IUCN Red List. It occurs in numerous protected areas, tolerates disturbed habitats well, and no important threats are known.[2]

Notes

  1. ^ Oryzomys megacephalus, as used by Musser et al. (1998), was more broadly defined than the current Hylaeamys megacephalus (it was transferred to the new genus Hylaeamys by Weksler and colleagues in the same 2006 paper that introduced Transandinomys); in their definition, it occurred throughout Amazonia and north to Trinidad and south to Paraguay.[37] However, western Amazonian populations of the species have since been separated into a different species, Hylaeamys perenensis. In the following comparisons, based on Musser et al. (1998) who did not separate the two, only H. megacephalus is mentioned, but both species are morphologically virtually identical and are known to differ only in size, karyotype, and mitochondrial DNA sequences.[38]
  2. ^ Number of specimens measured.
  3. ^ 19 for tail length.
  4. ^ The male accessory glands of T. talamancae, and of a number of other sigmodontines, were described by Voss and Linzey (1981). Their sample of "Oryzomys capito" included specimens from Panama and Trinidad, representing Transandinomys talamancae and Hylaeamys megacephalus, respectively, but their description can be applied to both.[74]
  5. ^ In one specimen, it could not be determined whether FN was 66 or 67; the other three had 66.[78]
  6. ^ Reported as Oryzomys megacephalus by Musser et al. (1998), but only perenensis is currently recorded from Colombia.[87]
  7. ^ This species was described among others from specimens of "Oryzomys laticeps" from Rio Cobaría, Arauca Department[105] (actually in Boyacá Department);[106] San Juan Nepomuceno, Bolívar Department;[105] Socorre, upper Rio Sinu, Bolívar, Colombia;[107] and Cerro Azul, Panama.[104] "Oryzomys laticeps", as defined in the 1960s, included Transandinomys talamancae and no other species that occur in this region;[108] furthermore, Musser et al. (1998) listed Oryzomys talamancae for all these localities.[109]

References

  1. ^ a b Goldman, 1918, plate IV
  2. ^
    doi:10.2305/IUCN.UK.2017-2.RLTS.T15615A22332803.en
    . Retrieved 15 November 2021.
  3. ^ Musser et al., 1998, fig. 66; Linares, 1998, map 134
  4. ^ Allen, 1891, p. 193
  5. ^ Allen, 1899, p. 208
  6. ^ Allen, 1899, p. 209
  7. ^ Allen, 1899, p. 210
  8. ^ Thomas, 1900, p. 272
  9. ^ Thomas, 1901, p. 252
  10. ^ Robinson and Lyon, 1901, p. 142
  11. ^ Allen, 1908, p. 656
  12. ^ a b c d Weksler et al., 2006, p. 25
  13. ^ Musser et al., 1998, pp. 273–274
  14. ^ Allen, 1891, pp. 193–194
  15. ^ Allen, 1899, pp. 208–210; Musser et al., 1998, pp. 273–274
  16. ^ Thomas, 1900, pp. 272–273
  17. ^ Thomas, 1901, pp. 252–253
  18. ^ Robinson and Lyon, 1901, pp. 142–143
  19. ^ Allen, 1908, pp. 656–657
  20. ^ Goldman, 1918, pp. 71–74
  21. ^ Hershkovitz, 1960, p. 544; Musser et al., 1998, p. 179
  22. ^ Musser and Williams, 1985, p. 9
  23. ^ Musser and Williams, 1985, p. 7
  24. ^ Musser and Williams, 1985, pp. 13–14
  25. ^ Musser et al., 1998, pp. 275–276
  26. ^ Weksler, 2006, pp. 75–77
  27. ^ Weksler, 2006, figs. 34–39
  28. ^ Weksler et al., 2006, p. 26
  29. ^ Weksler, 2006, p. 3
  30. ^ Musser and Carleton, 2005
  31. ^ a b c d e f g Goldman, 1918, p. 73
  32. ^ a b Musser and Carleton, 2005, p. 1155
  33. ^ Musser and Williams, 1985, p. 14; Musser et al., 1998, p. 173
  34. ^ Musser et al., 1998, p. 125
  35. ^ Musser et al., 1998, p. 127
  36. ^ Musser et al., 1998, pp. 167, 169
  37. ^ a b c Musser et al., 1998, p. 169
  38. ^ Patton et al., 2000, p. 140
  39. ^ Musser and Williams, 1985, p. 18; Musser et al., 1998, p. 169
  40. ^ a b c d e f Musser and Williams, 1985, p. 14
  41. ^ Musser et al., 1998, pp. 127–128
  42. ^ a b Musser et al., 1998, pp. 128–129
  43. ^ a b c d e Musser et al., 1998, p. 173
  44. ^ a b Fleming, 1970, p. 479
  45. ^ a b Goldman, 1918, p. 71
  46. ^ Musser and Williams, 1985, table 2
  47. ^ a b c Musser et al., 1998, p. 129
  48. ^ a b Musser et al., 1998, p. 131
  49. ^ Goldman, 1918, pp. 71–72
  50. ^ Goldman, 1918, p. 72
  51. ^ Weksler et al., 2006, p. 25; Musser et al., 1998, p. 124
  52. ^ Linares, 1998, p. 287; Tirira, 2007, p. 200; Reid, 2009, p. 208
  53. ^ Weksler, 2006, pp. 17, 19
  54. ^ Steppan, 1995, table 5
  55. ^ Goldman, 1918, p. 73; Musser and Williams, 1985, p. 14
  56. ^ Weksler, 2006, pp. 31–32
  57. ^ Weksler, 2006, p. 29, table 5
  58. ^ a b Musser et al., 1998, p. 135
  59. ^ a b Musser et al., 1998, p. 174
  60. ^ Musser and Williams, 1985, p. 14; Weksler, 2006, pp. 34–35
  61. ^ Goldman, 1918, p. 73; Weksler, 2006, p. 35; Musser and Williams, 1985, p. 14
  62. ^ Weksler, 2006, pp. 38–39
  63. ^ a b Musser et al., 1998, p. 140
  64. ^ Weksler, 2006, p. 41
  65. ^ Weksler, 2006, p. 42
  66. ^ Weksler, 2006, p. 43
  67. ^ Weksler, 2006, pp. 43–44
  68. ^ Musser et al., 1998, pp. 140–141
  69. ^ Weksler, 2006, pp. 42–43
  70. ^ Goldman, 1918, plate V
  71. ^ Weksler, 2006, p. 55
  72. ^ Weksler, 2006, pp. 55–56
  73. ^ Weksler, 2006, pp. 56–57
  74. ^ Weksler, 2006, p. 58, footnote 10
  75. ^ Weksler, 2006, pp. 57–58; Voss and Linzey, 1981, p. 13
  76. ^ Goldman, 1918, plate VI
  77. ^ Musser et al., 1998, p. 163
  78. ^ Musser et al., 1998, pp. 163–164
  79. ^ Musser et al., 1998, pp. 164–165
  80. ^ a b Musser et al., 1998, p. 165
  81. ^ Musser et al., 1998, pp. 165–166
  82. ^ Musser et al., 1998, pp. 125, 169, table 13
  83. ^ Musser et al., 1998, p. 174; Patton et al., 2000, p. 140
  84. ^ a b Musser et al., 1998, p. 158
  85. ^ a b c d Musser et al., 1998, p. 157
  86. ^ Musser et al., 1998, pp. 157–158, footnote 9
  87. ^ Musser and Carleton, 2005, pp. 1151, 1153
  88. ^ Reid, 2009, p. 208; Tirira, 2007, p. 200
  89. ^ Fleming, 1970; 1971
  90. ^ Fleming, 1971, p. 5
  91. ^ Fleming, 1971, p. 60
  92. ^ Fleming, 1971, p. 50
  93. ^ Fleming, 1971, p. 22
  94. ^ Fleming, 1971, p. 23, fig. 6
  95. ^ a b c Linares, 1998, p. 288
  96. ^ Fleming, 1971, p. 40
  97. ^ Fleming, 1971, p. 65
  98. ^ Fleming, 1971, table 11
  99. ^ Fleming, 1971, p. 41
  100. ^ Fleming, 1971, p. 43
  101. ^ Fleming, 1971, p. 29
  102. ^ Fleming, 1971, p. 32
  103. ^ Fleming, 1971, p. 48
  104. ^ a b Lee and Strandtmann, 1967, p. 30
  105. ^ a b c Lee and Strandtmann, 1967, p. 28
  106. ^ Musser et al., 1998, p. 259
  107. ^ Lee and Strandtmann, 1967, p. 29
  108. ^ Hershkovitz, 1960, p. 544; see Musser et al. (1998) for review.
  109. ^ Musser et al., 1998, pp. 150 (locality 16), 151 (localities 52, 53), 153 (locality 68)
  110. ^ Tipton et al., 1966, p. 42
  111. ^ Clark, 1967
  112. ^ Brennan and Reed, 1979, p. 535
  113. ^ Brennan and Yunker, 1966, p. 262
  114. ^ Tipton and Méndez, 1966, p. 330
  115. ^ Durden and Musser, 1994, p. 30

Literature cited

External links

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