Proechimys quadruplicatus, Hershkovitz, 1948

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Echimyidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 552-604 : 572-573

38.

Napo Spiny-rat

Proechimys quadruplicatus

French: Rat-épineux du Napo / German: Napo-Kurzstachelratte / Spanish: Rata espinosa de Napo

Other common names: Venezuelan Spiny-rat

Taxonomy. Proechimys quadruplicatus Hershkovitz, 1948 ,

“Llunchi, an island in the Rio Napo, about 18 kilometers below the mouth of the Rio Coca, [Orellano,] eastern Ecuador.”

Proechimys quadruplicatus is a member of the goeldirspecies group. It includes amphichoricus as a synonym. Monotypic.

Distribution. W Amazon Basin in S & E Colombia, S Venezuela, NW Brazil, E Ecuador, and N Peru, largely N of the Amazon River and E to the left bank of the Rio Negro at Manaus.

Descriptive notes. Head-body 211-295 mm, tail 125-202 mm; weight 300-700 g. The Napo Spiny-rat is similar in all external and cranial characteristics to Steere’s Spiny-rat (P. steerer), but its karyotype and mtDNA sequences differ. These two species are so alike that, at least until adequate analyses of morphological characteristics are made, identification may rest solely on either chromosomes or molecules, or on general distributions. The Napo Spiny-rat is large-bodied and has proportionately short tail (¢.70% of head-body length). Overall color is ocherous orange, although it darkens considerably along midline from head to rump. Venter may be pure white or lightly washed pale buff; pale thigh stripe is usually confluent with dorsal surface of hindfoot, which itself is characteristically bicolored, with an external dark longitudinal band encompassing digits four and five and contrasted with a pale internal band encompassing at least digits one and two, and usually three. Tail is bicolored but not as sharply so as in sympatric Simons’s Spiny-rat ( P. simonsi ). Tail appears nearly naked from a distance because scales are large and conspicuous, averaging 8 annuli/cm at mid-length. Dorsal pelage is stiff to the touch, with well-developed aristiform spines ¢.20 mm long and c.1 mm wide and terminating in weakly developed whip-like tip. Distal one-third of spines are black, which gives an overall darkened tone to midline of back and rump. Spines are most well developed over mid-back, less so in shoulder region or over rump. Skull of the Napo Spiny-rat is large and elongated, with long rostrum and heavy supraorbital ridges that extend posteriorly onto parietals as distinct ridges, especially in older individuals. Incisive foramina vary from weakly lyre-shaped to oval, with lateral margins either tapering slightly posteriorly or parallelsided; premaxilla part of septum is short, usually one-half or less the length of foramen; maxillary part varies greatly, most commonly weak and attenuate, often not in contact with premaxillary part, but sometimes broadly spatulate and filling much of foramen; maxillary part may be slightly ridged butis never keeled, and only rarely does this ridge extend onto anterior palate; and posterolateral margins of foramen are only moderately flanged so that only moderately developed grooves are present on the anterior palate. Moderately developed groove is present in the floor of infraorbital foramen, although its development varies among individuals. Mesopterygoid fossa of the Napo Spiny-rat is narrower than either that of Goeldi’s Spiny-rat (FP. goeldii ) or Steere’s Spiny-rat, with angle averaging 61° and extending anteriorly to middle of M”. Counterfold pattern of cheekteeth varies slightly, 4(3)—4(3)-4(3)—4(3) /4-3(4)-3(4)-3, but characteristic four folds upon which Hershkovitz based his name quadruplicatus is the most common condition present in all samples. Counterfold pattern of holotype of amphichoricus, however,is 3-3-3-3/3-3-3-3, which characterizes ¢.50% ofall specimens examined from southern Venezuela and adjacent Brazil. Baculum is comparatively short (length 7-1-8-:3 mm) and stout (proximal width 2-5-2-9 mm; distal width 2-5-3-1 mm), with nearly straight sides and only slightly flared apical wings and expanded base, similar to those of Goeldi’s Spiny-rat and Steere’s Spiny-rat. Rather short baculum of the Napo Spiny-rat defines a notably small phallus for such a large-bodied rat and particularly contrasts with actually larger phalli in nearly all other species of Proechimys , except for Steere’s Spiny-rat. Significance of these differences in phallic size is unknown. Chromosomal complement is 2n = 26 and FN = 42 in southern Venezuela and 2n = 28 and FN = 42-44 in eastern Ecuador, northern Peru, and north-western Brazil.

Habitat. Seasonally flooded forest (varzea and igapo) during dry season and margins of upland forest during the wet season.

Food and Feeding. There is no information available for this species.

Breeding. Pregnant Napo Spiny-rats were trapped in northern Peru (Rio Santiago) in July-August, with modal embryo counts of one (range 1-2).

Activity patterns. The Napo Spiny-rat is nocturnal and terrestrial.

Movements, Home range and Social organization. The Napo Spiny-rat shifts its use of microhabitats during the flood season, moving into terra firma forests otherwise occupied by the Guyenne Spiny-rat (FP. guyannensis ) in southern Venezuela and northcentral Brazil or the Short-tailed Spiny-rat ( P. brevicauda ), Cuvier’s Spiny-rat ( P. cuvieri ), and Simons’s Spiny-rat in northern Peru.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Napo Spiny-rat is widespread and present in several forest types and protected parks in north-western Amazonia that is sparsely populated by humans. As a result, it is unlikely to be declining. Additional studies on distribution, habitat, abundance, ecology, and conservation threats to Napo Spiny-rat are needed.

Bibliography. Eisenberg (1989), Eisenberg & Redford (1999), Emmons (1990, 1997a), Hershkovitz (1948), Moojen (1948), Patton (1987), Patton & Gardner (1972), Patton & Leite (2015), Patton & Reig (1989), Woods (1993), Woods & Kilpatrick (2005).

Figures

12. Broad-headed Spiny-rat (Clyomys laticeps), 13. Guiara (Euryzygomatomys spinosus), 14. White-spined Spiny-rat (Irinomys albispinus), 15. Elias’s Spiny-rat (Trinomys eliasi), 16. Rigid-spined Atlantic Spiny-rat (Trinomys paratus), 17. Yonenaga’s Spiny-rat (Trinomys yonenagae), 18. Elegant-spined Atlantic Spiny-rat (Trinomys setosus), 19. Moojen’s Spiny-rat (Trinomys moojeni), 20. Pau Brasil Spiny-rat (Trinomys mirapitanga), 21. Rio de Janeiro Spiny-rat (Trinomys dimidiatus), 22. Sao Paulo Spiny-rat (Trinomys thering), 23. Gracile Atlantic Spiny-rat (Trinomys gratiosus), 24. Sao Lourenco Punare (Thrichomys laurentius), 25. Jacobina Punare (Thrichomys inermis), 26. Lagoa Santa Punare (Thrichomys apereoides), 27. Pantanal Punare (Thrichomys pachyurus), 28. Foster’s Punare (Thrichomys fosteri), 29. Painted Tree-rat (Callistomys pictus), 30. Coypu (Myocastor coypus), 31. Armored Rat (Hoplomys gymnurus)

Distribution. W Amazon Basin in S & E Colombia, S Venezuela, NW Brazil, E Ecuador, and N Peru, largely N of the Amazon River and E to the left bank of the Rio Negro at Manaus.