Drymoreomys

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Drymoreomys

Near Threatened  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Sigmodontinae
Genus: Drymoreomys
Percequillo, Weksler, & Costa, 2011
Species:
D. albimaculatus
Binomial name
Drymoreomys albimaculatus
Percequillo, Weksler, & Costa, 2011
Collection localities of Drymoreomys albimaculatus

Drymoreomys is a

Near Threatened" on the IUCN Red List. Within Oryzomyini, Drymoreomys appears to be most closely related to Eremoryzomys from the Andes of Peru, a biogeographically
unusual relationship, in that the two populations are widely separated and each is adapted to an arid or a moist environment.

With a body mass of 44–64 g (1.6–2.3 oz), Drymoreomys is a medium-sized rodent with long fur that is orange to reddish-

braincase are weak. The palate is short, with its back margin between the third molars
. Several traits of the genitals are not seen in any other oryzomyine rodent.

Taxonomy

Drymoreomys was first recorded in 1992 by Meika Mustrangi in the state of

generic name, Drymoreomys, combines the Greek δρυμός (drymos), meaning "forest", ὄρειος (oreios), meaning "mountain-dwelling", and μῦς (mys), meaning "mouse". The name refers to the animal's occurrence in mountain forest.[4] The specific name, albimaculatus, derives from the Latin albus, meaning "white", and maculatus, meaning "spotted", a reference to the spots of white in the animal's fur.[2] Percequillo and colleagues found little geographic variation among samples of Drymoreomys, although a few traits differ in frequency between populations from the states of São Paulo and Santa Catarina.[5]

According to a

saturation of the phylogenetic signal in mitochondrial data.[8] Oryzomyini includes well over a hundred species distributed mainly in South America, including nearby islands such as the Galápagos Islands and some of the Antilles. It is one of several tribes recognized within the subfamily Sigmodontinae, which encompasses hundreds of species found across South America and into southern North America. Sigmodontinae is the largest subfamily of the family Cricetidae, other members of which include voles, lemmings, hamsters, and deermice, all mainly from Eurasia and North America.[9]

Description

External morphology

Drymoreomys albimaculatus is a medium-sized, long-tailed, short-eared, short-footed rodent.[4] It is quite distinct from other oryzomyines and has a number of unique traits.[10] In 11 adults from Parque Natural Municipal Nascentes do Garcia in Santa Catarina, head and body length was 122 to 139 mm (4.8 to 5.5 in), tail length was 140 to 175 mm (5.5 to 6.9 in), hindfoot length was 25.8 to 30.5 mm (1.02 to 1.20 in), ear length was 16 to 22 mm (0.63 to 0.87 in), and body mass was 44 to 64 g (1.6 to 2.3 oz).[11] The fur is long and dense and consists of thin, short, woolly underfur and long, thick overfur. Overall, the fur of the upperparts is orange to reddish-buff.[12] In the closely related Eremoryzomys, the upperparts are grayish.[10] The hairs of the underfur, which are 12 to 14 mm (0.47 to 0.55 in) long, are grayish for most of their length and orange or brown at the tip. In the overfur, the cover hairs (which form the main body of the fur), are 14 to 17 mm (0.55 to 0.67 in) long and brown at the tip, with an orange band below the tip, and the longer, sparse guard hairs are red to dark brown in the half closest to the tip and are 17 to 21 mm (0.67 to 0.83 in) long. The sides are reddish brown. On the underparts, the hairs are grayish at the base and white at the tip, except on the throat, chest, and (in some specimens) groin, where the hairs are entirely white[13]—a trait unique among the oryzomyines.[10] In overall appearance, the underparts are grayish, with white spots where the hairs are completely white.[13]

The small, rounded ears are covered with dense golden hairs on the outer and with reddish brown hairs on the inner surface. The mystacial vibrissae (whiskers on the upper lip) are long, usually extending a little beyond the ears when laid back against the head, but the superciliary vibrissae (whiskers above the eyes) are short and do not extend beyond the ears. The upper surface on the forefeet is covered with brown fur, and there is white or silvery fur on the digits. Ungual tufts (fur around the bases of the claws) are present on the second through fourth digits.[13] On the short, fairly broad hindfeet, the upper side is covered densely with silvery to white hairs near the tips of the feet and toes, and with brown fur otherwise.[14] No other oryzomyine has such brown fur on its hindfeet.[10] The second through fourth digits have long silvery-white ungual tufts, but those on the first digit are short. On the sole, the pads are very large.[13] Among oryzomyines, only Oecomys and the extinct Megalomys have similarly large pads between their digits.[10] There is a dense cover of short brown hairs on both the upper and lower sides of the tail.[14] Unlike in Eremoryzomys, the tail is the same color above and below.[10] The tail ends in a tuft, an unusual feature among oryzomyines.[15]

Skull

In the skull, the rostrum (front part) is relatively long. The

braincase and interorbital region are weakly developed.[14] Eremoryzomys has larger crests on its interorbital region.[10]

The

foramina (openings), is present in all Drymoreomys specimens examined, except in one juvenile specimen.[14]

The

angular process, below the condyloid, is fairly short and does not extend further backwards than the condyloid.[16] There is no noticeable capsular process (a raising at the back of the jaw that houses the root of the lower incisor).[17]

Dentition

The upper incisors are

mesolophid, a crest corresponding to the mesoloph but located on the lingual side.[18] Each of the lower molars has two roots.[10]

Other anatomy

There are 12 ribs and 19

lobule, is present. The preputial glands (glands in front of the genitals) are large. The lack of lateral bacular mounds, presence of a lateral lobule, and size of the preputial glands are all unique traits among the oryzomyines.[10]

Karyotype

The

submetacentric (with one arm noticeably longer than the other), and X is larger than Y. Blocks of heterochromatin are present on all autosomes and the long arm of Y. Telomeric sequences are found near the centromeres of the sex chromosomes.[19] Aspects of this karyotype—with a high number of mostly acrocentric chromosomes and the presence of heterochromatin on the Y chromosome—are consistent with the pattern seen in other oryzomyines. However, no other oryzomyine has exactly the same karyotype as D. albimaculatus.[20] Other species in clade D have fewer chromosomes, down to 16 in Nectomys palmipes, although the karyotype of Eremoryzomys polius is unknown. This suggests an evolutionary trend of decreasing chromosome number within the clade.[21]

Distribution and ecology

Some morphological traits in Drymoreomys suggest it is arboreal.

Drymoreomys albimaculatus occurs in the Atlantic Forest on the eastern slopes of the Serra do Mar in the Brazilian states of São Paulo and Santa Catarina, at 650 to 1,200 m (2,130 to 3,940 ft) above sea level.[4] It has not been found in the intervening state of Paraná, but is likely to occur there.[2] The biogeographical pattern indicated by the relationship between Drymoreomys and the Andean Eremoryzomys is unusual. While there are some similar cases of relationships between Andean and Atlantic Forest animals, these involve inhabitants of humid forests in the Andes; Eremoryzomys, by contrast, lives in an arid area.[22]

Drymoreomys albimaculatus appears to be a specialist of dense, moist,

arboreal (tree-dwelling) habits, most specimens were collected in pitfall traps on the ground.[3]

Conservation status

The range of Drymoreomys albimaculatus is relatively large and the species occurs in several

Near Threatened" under the IUCN Red List criteria.[23]

References

  1. ^ Engelbrektsson 2019.
  2. ^ a b c Percequillo, Weksler & Costa 2011, p. 368.
  3. ^ a b Percequillo, Weksler & Costa 2011, p. 357.
  4. ^ a b c Percequillo, Weksler & Costa 2011, p. 360.
  5. ^ Percequillo, Weksler & Costa 2011, pp. 369, 371.
  6. ^ Percequillo, Weksler & Costa 2011, p. 378, figs. 7, 8.
  7. ^ Percequillo, Weksler & Costa 2011, p. 373.
  8. ^ Pine, Timm & Weksler 2012, p. 856; Turvey, Brace & Weksler 2012, p. 409.
  9. ^ Musser & Carleton 2005.
  10. ^ a b c d e f g h i j k l m Percequillo, Weksler & Costa 2011, p. 367.
  11. ^ Percequillo, Weksler & Costa 2011, table 2.
  12. ^ Percequillo, Weksler & Costa 2011, pp. 360–361.
  13. ^ a b c d Percequillo, Weksler & Costa 2011, p. 361.
  14. ^ a b c d e f g Percequillo, Weksler & Costa 2011, p. 362.
  15. ^ Weksler & Percequillo 2011, p. 283.
  16. ^ Percequillo, Weksler & Costa 2011, p. 363.
  17. ^ a b Percequillo, Weksler & Costa 2011, p. 364.
  18. ^ Percequillo, Weksler & Costa 2011, p. 365.
  19. ^ Suárez-Villota et al. 2013, p. 68.
  20. ^ Suárez-Villota et al. 2013, p. 70.
  21. ^ Suárez-Villota et al. 2013, pp. 70–72.
  22. ^ Percequillo, Weksler & Costa 2011, p. 379.
  23. ^ a b Percequillo, Weksler & Costa 2011, p. 377.

Literature cited

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