Regional skin histomorphology in adult greater cane rats (Thryonomys swinderianus): A pilot study

Neocortex neurogenesis and maturation in the African greater cane rat

BACKGROUND

Neocortex development has been extensively studied in altricial rodents such as mouse and rat. Identification of alternative animal models along the "altricial-precocial" spectrum in order to better model and understand neocortex development is warranted. The Greater cane rat (GCR, Thyronomys swinderianus) is an indigenous precocial African rodent. Although basic aspects of brain development in the GCR have been documented, detailed information on neocortex development including the occurrence and abundance of the distinct types of neural progenitor cells (NPCs) in the GCR are lacking.

METHODS

GCR embryos and fetuses were obtained from timed pregnant dams between gestation days 50-140 and their neocortex was analyzed by immunofluorescence staining using characteristic marker proteins for NPCs, neurons and glia cells. Data were compared with existing data on closely related precocial and altricial species, i.e. guinea pig and dwarf rabbit.

RESULTS

The primary sequence of neuro- and gliogenesis, and neuronal maturation is preserved in the prenatal GCR neocortex. We show that the GCR exhibits a relatively long period of cortical neurogenesis of 70 days. The subventricular zone becomes the major NPC pool during mid-end stages of neurogenesis with Pax6 + NPCs constituting the major basal progenitor subtype in the GCR neocortex. Whereas dendrite formation in the GCR cortical plate appears to initiate immediately after the onset of neurogenesis, major aspects of axon formation and maturation, and astrogenesis do not begin until mid-neurogenesis. Similar to the guinea pig, the GCR neocortex exhibits a high maturation status, containing neurons with well-developed dendrites and myelinated axons and astrocytes at birth, thus providing further evidence for the notion that a great proportion of neocortex growth and maturation in precocial mammals occurs before birth.

CONCLUSIONS

Together, this work has deepened our understanding of neocortex development of the GCR, of the timing and the cellular differences that regulate brain growth and development within the altricial-precocial spectrum and its suitability as a research model for neurodevelopmental studies. The timelines of brain development provided by this study may serve as empirical reference data and foundation in future studies in order to model and better understand neurodevelopment and associated alterations.

A study of scientific publications on the greater cane rat (Thryonomys swinderianus, Temminck 1827)

BACKGROUND

The greater cane rat (GCR), reputed to be African's second largest rodent, is a precocial hystricomorph with an uncommon phenotype and life history. Scientific and socio-economic interests in the GCR have led to heightened research efforts targeted towards a better understanding of its biology and exploration of its economic and translational usefulness.

METHODS

Records of all online scientific publications on the GCR from Google, Google Scholar, PubMed, science.gov, Ebscohost and Worldwide science, with the exception of research theses, proceedings, unpublished projects and abstracts, were collated and analyzed using descriptive statistics.

RESULTS

A total of 146 published scholarly articles spanning about six decades were retrieved, with 98% of the GCR publications originating from African countries. Nigeria boasts the highest number of publications (58.22%) followed by Ghana (21.23%) and South Africa (5.48%) while Senegal contributed the least (0.69%). Publications were sorted into ten field categories. The field with the highest number of articles (41.78%) was animal breeding and management recording, closely followed by anatomy (37.67%). Lesser contributions were made by parasitology (5.48%), biochemistry/hematology (4.8%), pharmacology/toxicology (4.11%), pathology (2.06%), and surgery/anesthesia and physiology (1.37% apiece). The fields with fewest contributions were microbiology and developmental biology (0.69% each).

CONCLUSION

This study chronicles the spectrum of knowledge available on the GCR, highlighting the knowledge gap that still exists in various fields in order to provide advocacy for new frontiers in research efforts on this rodent. We suggest the need for a clearly defined and well integrated national/regional policy aimed at establishing Africa's foremost micro-livestock rodent, the greater cane rat, on the world's scientific radar.

Developmental horizons in the pre-natal development of the Greater cane rat (Thryonomys swinderianus)

The Greater cane rat (GCR, Thyronomys swinderianus) is a precocial rodent predominantly found within Africa. Economic and scientific interests have led to several research efforts towards the domestication and better understanding of the biology and development of this rodent. Despite these efforts, information on the pre-natal development of this rodent is currently lacking. This study characterises distinct developmental milestones including skin pigmentation, emergence and distributions of hairs, calvarium consistency, teeth eruption, development of appendages, sensory organs and external genitalia in the pre-natal GCR and assesses quantitative body parameters, that is body weight, body and crown-rump lengths across its entire gestation length (gestation days [GDs] 10-140). Using these external features, we provide baseline reference ontogenetic scales for GCR embryos and fetuses, employable for stage, age and sex estimation of the pre-natal GCR in future studies. We observed that the first evidence of an embryo was not seen before the end of the first trimester (GD50) and that the late second trimester (GD80-GD100) marks the transition from embryogenesis to fetogenesis in the GCR. As both events occur at a much later developmental time point when compared to precocial non-rodents including human, sheep and pig and slightly later when compared to other precocial rodents such as guinea pig, our data provide first indication that the pre-natal GCR development might be associated with a reproductive delay. Together, this study expands our knowledge of the development and biology of the GCR, which will improve reproductive and breeding management, and native species conservation of this hystricomorph mammal.