Blind mole rat (Spalax leucodon) masseter muscle: structure, homology, diversification and nomenclature.

BACKGROUND: It is well known that rodents are defined by a unique masticatory apparatus. The present study describes the design and structure of the masseter muscle of the blind mole rat (Spalax leucodon). The blind mole rat, which emer- ged 5.3-3.4 million years ago during the Late Pliocene period, is a subterranean, hypoxia-tolerant and cancer-resistant rodent. Yet, despite these impressive cha- racteristics, no information exists on their masticatory musculature. MATERIALS AND METHODS: Fifteen adult blind mole rats were used in this study. Dissections were performed to investigate the anatomical characteristics of the masseter muscle. RESULTS: The muscle was comprised of three different parts: the superficial mas- seter, the deep masseter and the zygomaticomandibularis muscle. The superficial masseter originated from the facial fossa at the ventral side of the infraorbital foramen. The deep masseter was separated into anterior and posterior parts. The anterior part of the zygomaticomandibularis muscle arose from the snout and passed through the infraorbital foramen to connect on the mandible. CONCLUSIONS: The construction of the deep masseter and zygomaticomandibularis muscles were of the Myomorpha type. Further studies are needed to reveal features such as muscle biomechanics, muscle types.

Comparative morphometric study of the filiform lingual papilla in the middle east blind mole rat (Spalax ehrenbergi, Nehring, 1898) and Wistar albino rat / Estudio morfométrico comparativo de la papila lingual filiforme en la rata topo ciega del medio oriente (Spalax ehrenbergi, Nehring, 1898) y la rata albino Wistar

This study aimed to reveal the morphometric differences between blind mole rats which live under ground and rats which live under laboratory conditions with regard to the length, base width, keratinization thickness and microscopic papilla depth. For this purpose, 7 adult blind mole rats and 7 adult Wistar albino rats were used in the study. All tongues were removed and fixed in 10 % neutral formalin. 4-5 micrometer of sections were obtained from paraffine sections which were obtained with routine histological follow ups and Crossman's modified triple staining was applied. While papilla length was found as 184.73±26.68 µm, base width 65.46±16.51 µm, keratinization thickness 11.60±1.37 µm, microscopic papilla depth 49.89±8.19 µm in blind rats; these values were found as 177.49±31.44 µm, 50.08±7.57 µm, 13.08±5.32 µm and 89.12±19.31 µm, respectively in rats. While a statistically significant difference was not detected between lengths (p>0.05), the difference between papilla width was found significant (p<0.05). While keratinization was found to be thicker on posterior side compared to anterior side in both species, a difference was not detected between keratinization thickness measurements (p>0.05). The difference between two species with regard to papilla depth was detected to be significant (p<0.001). The finding that papilla depth decreases as base width increases and the difference's being statistically significant suggested that living in different environments with different humidity could be effective on morphologic structures of the tongue in blind mole rats and rats.

Este estudio tuvo como objetivo revelar las diferencias morfométricas de las papilas linguales filiformes entre ratas topo ciegas que viven bajo tierra y ratas que viven en condiciones de laboratorio, con respecto a la longitud, ancho de la base, espesor de la queratinización y profundidad microscópica de las papilas. Para este propósito, se utilizaron 7 ratas topo ciegas adultas y 7 ratas albinas Wistar adultas. Se retiraron las lenguas y se fijaron en formalina neutra al 10 %. Se obtuvieron secciones de 4 a 5 µm a partir de técnicas histológicas de rutina, aplicándose la tinción triple modificada de Crossman. En las ratas topo ciegas se obtuvieron los siguientes datos morfométricos en relación a las papilas linguales filiformes: longitud 184,73 ± 26,68µm, ancho de la base 65,46 ± 16,51 µm, espesor de queratinización 11,60 ± 1,37 µm, profundidad microscópica de la papila 49,89 ± 8,19 µm, mientras que en las ratas control, los valores que se encontraron fueron 177,49 ± 31,44 µm, 50,08 ± 7,57 µm, 13,08 ± 5,32 µm y 89,12 ± 19,31 µm, respectivamente. Si bien no se detectó diferencia estadísticamente significativa entre las longitudes (p> 0,05), la diferencia del ancho de la papila fue significativa (p <0,05). Mientras que la queratinización fue más gruesa en la parte dorsal comparado con la parte ventral en ambas especies, no se detectó diferencia entre las mediciones de espesor de la queratinización (p> 0,05). Se detectó que la diferencia entre las dos especies con respecto a la profundidad de la papila era significativa (p <0,001). Se determinó que la profundidad de la papila disminuye a medida que aumenta el ancho de la base y la diferencia es estadísticamente significativa, lo que sugiere que vivir en diferentes ambientes con diferente humedad podría ser eficaz en las estructuras morfológicas de la lengua de ratas topo ciegas y de ratas de laboratorio.

Macroscopic anatomy of the lower respiratory system in mole rats (Spalax leucodon).

The morphologic and morphometric features of the lower respiratory system in mole rats were examined. It was seen that the low respiratory system of this species leading a special life under highly hypoxic/hypercapnic conditions underground is structurally similar to other mammals living on land in terms of the parts examined; trachea was formed by 29.5 ± 4 oval-formed cartilaginous tracheals arranged backwards and became gradually more stenotic diameter from cranial to the caudal of the neck. The trachea was separated in two principal bronchus at the fourth thoracal intercostal spatium level. The angle between the two main principal bronchi was 60.5 ± 2.35°. The lung constituted 1.29 ± 0.03% of the body weight and the right lung was heavier than the left lung. Fissura inter-lobaris was deep and separated the lung lobes wholly, and the right lung was separated in four lobes, whereas the left lung was not separated into the lobes. Also, the medial lobe of the left lung was the lightest lobe.

Macro-anatomical and karyological features of two blind mole rat subspecies (Rodentia: Spalacidae) from Turkey.

The morphometric and karyological analyses of 52 specimens belonging to the two subspecies of Nannospalax leucodon were examined from 14 localities in Turkey. Five karyotypic forms were recorded (2n = 60, the total numbers of chromosomal arms (NF) = 74, the numbers of autosomal arms (NFa) = 70; 2n = 60, NF = 76, NFa = 72; 2n = 60, NF = 82, NFa = 78; 2n = 56, NF = 72, NFa = 68; 2n = 38, NF = 74, NFa = 70). The morphological features of two subspecies were studied using both numerical taxonomy and traditional methods. Thirty skull measurements and four baculum measurements were subjected to discriminant function analysis to find morphometric criteria allowing subspecies identification. Two subspecies were clearly separated from each other by macroanatomical characterictics and numeric characteristics. The first upper molar has four alveoli cubicles in young specimens of Nannospalax leucodon anatolicus, while M(1) has 1 cubicle in Nannospalax leucodon cilicicus. In the western subspecies (N. l. anatolicus, 2n = 38), urethra openness is surrounded by three lobes. However, in the eastern subspecies (N. l. cilicicus, 2n = 60), there are two lateral lobes.