New record of Stolzmann's crab-eating rat Ichthyomys stolzmanni (Rodentia: Cricetidae) in Ecuador

Abstract

Stolzmann's crab-eating rat Ichthyomys stolzmanni is known from six locaties, two of those in the eastern slopes of Ecuador and four in southeastern Peru. We recorded a male specimen in the Jurumbuno River, on the eastern slopes of Ecuador at the province of Morona Santiago. We described the body and cranial characteristics, which are within the range known for the species, except that the tail is bicolored to the medial portion and the rear half is uniformly dark. The digestive tract contained traces of insects (Corydalus sp.), shrimps (Macrobrachium sp.), and isopods (Artystone trisibia); the latter parasitizes fish, and this is the first report of this parasite in the diet of I. stolzmanni. Our record in the Jurumbuno River is the third locality in Ecuador for the species studied, 40 years after its previous capture.

Occipital condyle width (OCW) is a highly accurate predictor of body mass in therian mammals

“…Additional file 12: Table S1. Database of average OCW and body mass in all specimens measured, as well as skull length (measured as condylobasal or condyloincisive length when available), HBL, and brain mass for each species compiled from the previously published literature (.csv) [12,136,180,[209][210][211].…”

A new species of crab-eating rat of the genus Ichthyomys, from Ecuador (Rodentia, Cricetidae, Sigmodontinae)

“…Although Pacheco and Ugarte-Núñez (2011) synonymized these names, they mentioned an undetermined specimen (AMNH 10109/11817, skull and skin, respectively) from northeastern Peru, which could refer to I. stolzmanni or represent an undescribed species (see Anthony 1923:8;Supplementary Figure S4). Thus, the record attributed to I. stolzmanni from an eastern Ecuadorean locality by Brito et al (2016) acquired a new significance. As they noted, this specimen from the Río Jurumbuno has about half of its tail bicolored proximally, with its distal half dark all around.…”

“…Our description of Ichthyomys pinei demonstrates how difficult it is to obtain specimens of these poorly known aquatic rodents. Considerable changes in skull morphology, both quantitative and qualitative, occur in members of the genus Ichthyomys during ontogeny (Voss 1988, Pacheco and Ugarte-Núñez 2011, Brito et al 2016. In order to partially remediate this situation, in taxonomic work, comparison among specimens at the same stage of development is advisable.…”

“…Ichthyomys pinei is distinguishable by the combination of generally smaller size (Table 1, Figure 7) and a broader and heavily fringed hindfoot. Ichthyomys pinei shares, with the apparently widespread Ichthyomys stolzmanni (see Brito et al 2016), the bicolored tail, but their conspecificity can be ruled out owing to trenchantly different sizes. In addition, the rugged cornified stomach epithelium is more restricted in I. stolzmanni than in I. pinei ( Figure 5).…”

“…Recent literature on ichthyomyines includes a number of new locality records, in several cases providing noteworthy range extensions (e.g. Santillán and Segovia 2013, Rodríguez-Posada 2014, Medina et al 2015, Brito et al 2016, Caviedes-Solís et al 2017, Marín-C et al 2018. Also, new species have been described (Hanson et al 2015) or are awaiting description (N. Reid, pers.…”