A Novel Understanding of Phocidae Hearing Adaptations Through a Study of Northern Elephant Seal (Mirounga angustirostris) Ear Anatomy and Histology.

The most conspicuous aural adaptation in northern elephant seals (NES) is complete absence of an auricle and a tortuous collapsed external acoustic meatus. The NES epitympanic recess contains massive ossicles immersed in the middle ear cavernous sinuses. Engorgement of the cavernous sinuses would make ossicles fully buoyant during deep diving. NES have a comparatively larger cochlear nerve, which carries a significantly larger number of axons than in terrestrial mammals, which would give them auditory ability similar to the obligate marine mammals such as cetaceans. Our calculations show that the traditional "air-dependent" impedance matching mechanism in NES functions to just half of the capacity compared with the one described in terrestrial mammals. Impedance matching would be further hindered in NES while diving due to fully collapsed external acoustic meatus. Thanks to similarities of acoustic impedance between the sea water, soft tissues, and blood sinuses, very little sound energy would be reflected and lost. When sound is generated underwater, the large ossicles, buoyant in the cavernous sinus, would not move due to oscillation of tympanic membrane. Rather, they would be oscillating due to their inertia and process of acoustic streaming. Our mathematical simulation shows that an increase in sound frequency would cause increased displacement of the stapedial footplate and thus transmit the sound energy to the inner ear. We contend that during diving, impedance matching and sound signal amplification in the middle ear courses through the cavernous sinuses and oscillates the enlarged ossicles, thus enabling a high-frequency ultrasonic hearing range in Phocidae. Anat Rec, 302:1605-1614, 2019. © 2018 American Association for Anatomy.

Eye Histology and Ganglion Cell Topography of Northern Elephant Seals (Mirounga angustirostris).

Northern elephant seals are one of the deepest diving marine mammals. As northern elephant seals often reach the bathypelagic zone, it is usually assumed that their eyes possess evolutionary adaptations that provide better ability to see in dim or scotopic environments. The purpose of this study was to carefully describe anatomical and histological traits of the eye that may improve light sensitivity. Northern elephant seals have large, somewhat elliptical eyes, with equatorial and anteroposterior diameters of 5.03 and 4.4 cm, respectively. The cornea is large in diameter and the lens is completely spherical. The iris has pronounced constrictor and dilator muscles, whereas the ciliary muscle is notably less developed. The tapetum lucidum is more prominent than in other pinnipeds, making up about 63% of retinal thickness in the posterior aspect of the globe. Within the retina, the pigmented epithelium lacks pigment except for the region close to the ora serrata. Parts of the photoreceptor and outer nuclear layers are folded. Although the photoreceptor layer is composed predominantly of rods, cone photoreceptors were also observed. Cells within the retinal ganglion cell layer are arranged in a single level. Ganglion cells reach their maximum density (∼1,300 cells per mm(2) ) dorsal to the optic disc, whereas the periphery of the retina is sparsely populated (<100 cells per mm(2) ). All above mentioned features are consistent with the predicted evolutionary adaptations to the photic environment of the bathypelagic zone. Anat Rec, 299:798-805, 2016. © 2016 Wiley Periodicals, Inc.

Seasonal anatomical changes in the testis of the one-humped camel: a review

The male camel shows sexual activity during specific days of the year (breeding or rutting period). This is influenced by testicular morphology which varies with the season of the year. These anatomical changes in the camel testis are well established, but some morphometric variations in the seminiferous tubules are still dubious. This article reviews the basic concepts of male camel reproduction with special reference to the seasonal anatomical changes in the testis (AU)

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Skin histology and its role in heat dissipation in three pinniped species.

BACKGROUND: Pinnipeds have a thick blubber layer and may have difficulty maintaining their body temperature during hot weather when on land. The skin is the main thermoregulatory conduit which emits excessive body heat. METHODS: Thorough evaluation of the skin histology in three pinniped species; the California sea lion-Zalophus californianus, the Pacific harbor seal-Phoca vitulina richardsi, and the Northern elephant seal-Mirounga angustirostris, was conducted to identify the presence, location and distribution of skin structures which contribute to thermoregulation. These structures included hair, adipose tissue, sweat glands, vasculature, and arteriovenous anastomoses (AVA). Thermal imaging was performed on live animals of the same species to correlate histological findings with thermal emission of the skin. RESULTS: The presence and distribution of skin structures directly relates to emissivity of the skin in all three species. Emissivity of skin in phocids (Pacific harbor and Northern elephant seals) follows a different pattern than skin in otariids (California sea lions). The flipper skin in phocids tends to be the most emissive region during hot weather and least emissive during cold weather. On the contrary in otariids, skin of the entire body has a tendency to be emissive during both hot and cold weather. CONCLUSION: Heat dissipation of the skin directly relates to the presence and distribution of skin structures in all three species. Different skin thermal dissipation patterns were observed in phocid versus otariid seals. Observed thermal patterns can be used for proper understanding of optimum thermal needs of seals housed in research facilities, rescue centers and zoo exhibits.

Veterinary medical education in Iraq.

Iraq is an agricultural country with a large population of animals: sheep, goats, cattle, water buffaloes, horses, donkeys, mules, and camels. In the 1980s, the successful poultry industry managed to produce enough table eggs and meat to satisfy the needs of the entire population; at one time, the thriving fish industry produced different types of fish for Iraqis' yearly fish consumption. There are four veterinary colleges in Iraq, which have been destroyed along with the veterinary services infrastructure. Understandably, improvements to the quality of veterinary education and services in Iraq will be reflected in a healthy and productive animal industry, better food quality and quantity, fewer zoonotic diseases, and more income-generating activities in rural areas. Thus, if undergraduate, graduate, and continuing education programs are improved, the veterinary medical profession will attract more competent students. This will satisfy the country's increased demand for competent veterinarians in both public and private sectors. Although Iraq has an estimated 5,000-7,000 veterinarians, there is a need for quality veterinary services and for more veterinarians. In addition, there is a need for the improvement of veterinary diagnostic facilities, as zoonotic diseases are always highly probable in this region. This article provides insight into the status of veterinary medical education and veterinary services in Iraq before and after the 1991 Gulf War and gives suggestions for improvement and implementation of new programs. Suggestions are also offered for improving veterinary diagnostic facilities and the quality of veterinary services. Improving diagnostic facilities and the quality of veterinary services will enhance animal health and production in Iraq and will also decrease the likelihood of disease transmission to and from Iraq. Threats of disease transmission and introduction into the country have been observed and reported by several international organizations.