Ingo W. Stuermer

Mobile larynx in Mongolian gazelle: Retraction of the larynx during rutting barks in male Mongolian gazelle (Procapra gutturosa Pallas, 1777).

This study provides the first evidence of pronounced temporary laryngeal descent in a bovid species. An elaborate acoustic display is prominent in male courtship behavior of polygynous Mongolian gazelle. During rut, rounding up of females is accompanied by continuous head‐up barking by dominant males. Throughout the rut their evolutionarily enlarged larynx descends to a low mid‐neck resting position. In the course of each bark the larynx is additionally retracted toward the sternum by 30% of the resting vocal tract length. A geometric model of active larynx movements was constructed by combining results of video documentation, dissection, skeletonization, and behavioral observation. The considerable distance between resting position and maximal laryngeal descent suggests a backward tilting of the hyoid apparatus and an extension of the thyrohyoid connection during the retraction phase. Return to the resting position is effected by strap muscles and by the elastic recoil of the pharynx and the thyrohyoid connection. An intrapharyngeal inflation of the peculiar palatinal pharyngeal pouch of adult males is inferred from a short‐time expansion of the ventral neck region rostral to the laryngeal prominence. The neck of adult dominant males is accentuated by long gray guard hairs during the rut. The passive swinging of the heavy larynx of adult males during locomotion gives the impression of a handicap imposed on rutting males. Apparently, this disadvantage becomes outweighed by the profits for reproductive success. J. Morphol., 2008.

Intraspecific Allometric comparison of Laboratory gerbils with Mongolian Gerbils Trapped in the Wild Indicates Domestication in Meriones unguiculatus (Milne-Edwards, 1867) (Rodentia: Gerbillinae)

A survey of adult male Mongolian gerbils, Meriones unguiculatus (Milne-Edwards, 1867), either trapped during an expedition in Mongolia near 47 °N and 105,5 °E in June 1995 (WILD) or obtained from a laboratory strain bred in captivity since 1935 (LAB), revealed significant morphological and behavioural differences, which are likely a result of domestication in the laboratory strain. Mean body length (125.4 mm), tail length (95.5 mm) and body weight (53.6 g) was lower in WILD, although no other external characteristics were obviously different. Related allometrically to net carcass weight, organ weights were significantly lower (p < 0.01) in LAB (brain – 17.6%, eyes – 26.0%, heart – 22.3%, lungs – 43.3%). Seizures frequently seen in LAB were absent in WILD trapped (n = 167) or subsequently housed in Germany (n = 81), and rare in their offspring. Mean litter size was greater in LAB (n = 5.5) than in WILD bred in the laboratory (n = 4.4). The WILD breeding strain was named Ugoe:MU95. A genetic bottleneck (n = 9) that occurred in 1954 and remarkably smaller brains in LAB indicate that the laboratory strain has become domesticated and should be designated as “Laboratory gerbils” (M. unguiculatus forma domestica) to signify this new case of domestication among rodents.

High-resolution mapping of neuronal activity using the lipophilic thallium chelate complex TlDDC: Protocol and validation of the method

In neurons the rate of K(+)-uptake increases with increasing activity. K(+)-analogues like the heavy metal ion thallium (Tl(+)) can be used, therefore, as tracers for imaging neuronal activity. However, when water-soluble Tl(+)-salts are injected systemically only minute amounts of the tracer enter the brain and the Tl(+)-uptake patterns are influenced by regional differences in blood-brain barrier (BBB) K(+)-permeability. We here show that the BBB-related limitations in using Tl(+) for imaging neuronal activity are no longer present when the lipophilic Tl(+) chelate complex thallium diethyldithiocarbamate (TlDDC) is applied. We systemically injected rodents with TlDDC and mapped the Tl(+)-distribution in the brain using an autometallographic (AMG) technique, a histochemical method for detecting heavy metals. We find that Tl(+)-doses for optimum AMG staining could be substantially reduced, and regional differences attributable to differences in BBB K(+)-permeability were no longer detectable, indicating that TlDDC crosses the BBB. At the cellular level, however, the Tl(+)-distribution was essentially the same as after injection of water-soluble Tl(+)-salts, indicating Tl(+)-release from TlDDC prior to neuronal or glial uptake. Upon sensory stimulation or intracortical microstimulation neuronal Tl(+)-uptake increased after TlDDC injection, upon muscimol treatment neuronal Tl(+)-uptake decreased. We present a protocol for mapping neuronal activity with cellular resolution, which is based on intravenous TlDDC injections during ongoing activity in unrestrained behaving animals and short stimulation times of 5 min.

Early experience and domestication affect auditory discrimination learning, open field behaviour and brain size in wild Mongolian gerbils and domesticated Laboratory gerbils (Meriones unguiculatus forma domestica)

The influence of early experience and strain differences on auditory discrimination learning, open field behaviour and brain size was investigated in wild-type Mongolian gerbils (strain Ugoe:MU95) raised in the wild (wild F-0) or in the laboratory (wild F-1) and in domesticated Laboratory Gerbils (LAB). Adult males were conditioned for 10 days in a shuttle box go/no-go paradigm to discriminate two frequency-modulated tones. Significant learning was established within 5 days in wild F-0 and within 3 days in wild F-1 and LAB. Spontaneous jumps in the shuttle box (inter-trial crossings) were frequently seen in wild F-0 and F-1, but rarely in LAB. All groups exhibited nearly the same ability to remember after 2 weeks without training. In the open field test applied on 5 consecutive days, no differences in locomotion patterns and inner field preferences were found. Rearing frequency decreased over 5 days in wild gerbils. Running distances (4-6m/min) were similar in wild F-0 and LAB, but higher in wild F-1. The ratio of brain size to body weight did not differ between wild F-0 and F-1, but was 17.1% lower in LAB. Correspondingly high brain weights in wild F-1 and F-0 support our domestication hypothesis and negate any serious effect of early experience or captivity on brain size in Mongolian gerbils. In contrast, wild F-1 raised in the laboratory show a rapid improvement in learning performance, indicating that early experience rather that genetic differences between strains affect shuttle box discrimination learning in gerbils.

Domestication differentially affects cochlear nucleus subdivisions in the gerbil.

We analyzed the effects of domestication on the subdivisions of the cochlear nucleus in the gerbil (Meriones unguiculatus) by comparing their volumes and rostrocaudal extents in laboratory gerbils and in age‐matched F1 offspring of gerbils caught in the wild. In addition, soma size was systematically analyzed in the anteroventral cochlear nucleus of both groups. Total cochlear nucleus volume and rostrocaudal extent were not significantly different between groups either for young (postnatal day 9) animals before the onset of hearing or for young 4‐month‐old animals. However, the dorsal cochlear nucleus was significantly larger and the anteroventral cochlear nucleus was significantly smaller in young adults of the wild strain. Thus the relative proportions of the cochlear nucleus subdivisions differed between the groups. In addition, soma size was significantly larger in the low‐frequency portion of the anterovental cochlear nucleus in domesticated gerbils compared to wild gerbils. To our knowledge, this is the first reported instance of a well‐defined brain structure (e.g., the antreovental cochlear nucleus) being larger in the domesticated than in the wild form. J. Comp. Neurol. 428:609–615, 2000.

Head Anatomy of Male and Female Mongolian Gazelle — A Striking Example of Sexual Dimorphism

The first scientific description of the Mongolian gazelle by Pallas (1777) already depicted a sexual dimorphism of the larynx and the thyrohyoid connection (Fig 1.1). Open image in new window

Strain-dependence of age-related cochlear hearing loss in wild and domesticated Mongolian gerbils

The Mongolian gerbil (Meriones unguiculatus) is one of the animal models in auditory research that has been used in several studies on age-related hearing loss. The standard laboratory strain is domesticated as it was bred in captivity for more than 70 years. We compared properties of distortion product otoacoustic emissions (DPOAEs) in domesticated gerbils with wild-type gerbils from F6-F7 generations of a strain originating from animals trapped in Central Asia in 1995. Up to an age of 9months, DPOAE thresholds were comparable between both strains and were below 10dB SPL for f2 frequencies between 4 and 44kHz. In older domesticated animals, the thresholds were increased by up to 12dB. Significant increases were found at stimulus frequencies of 2kHz, 12-20kHz, and 56-60kHz. The best frequency ratio f2/f1 to evoke maximum DPOAE amplitude was larger in domesticated animals at the age of 9 months or older. While these data show that there is a deterioration of cochlear sensitivity due to domestication, the magnitude of the described changes is small. Thus, the general suitability of domesticated gerbils for auditory research seems not to be affected.

A review on herring, Clupea harengus (Actinopterygii: Clupeiformes: Clupeidae) recruitment and early life stage ecology in the western Baltic Sea

Herring, Clupea harengus L., is an important commercial fish species in the Baltic Sea region since medieval times. The western Baltic spring spawning herring (WBSS) is one of three major Baltic Sea herring stocks, supporting a significant over-regional fishery in the western Baltic Sea as well as in the Kattegat and Skagerrak area. One major component spawns in the vicinity of the German island of Rugen and the associated major spawning ground, the Greifswalder Bodden (GWB), a shallow, semi-enclosed sub-system of estuarine character. Research of herring biology and ecology has an extensive history in the area probably due to the long fishery tradition and the importance of this particular herring stock for the local Baltic coast economy. In this review most of the scientific findings about WBSS in its spawning areas, mainly the GWB, is summarized. This study is based on critical review of over 120 publications and scientific sources from the past 100 years containing relevant information on possible consequences of multiple environmental and anthropogenic induced stressors of herring recruitment and productivity. Besides current peer reviewed literature a significant amount of grey literature was included, consisting primarily of papers and reports written in German language and representing the only historical data sources and published documentation of regional western Baltic herring ecology.