General Body Size and Shape
The Rihannsu are generally a tall, thin people, falling in the upper average height range for Humanoid/Vulcanoid species. Adult males average between 5'9" and 6'7" (1.75 - 2.0 m) in height, adult females 5'2" - 6' (1.57 - 1.83 m). Weight is commensurate with height and build, although Rihannsu weigh slightly more than expected due to tissue density. Muscle density and strong attachment to the skeletal structure make Vulcanoids much stronger for their size than most Humanoids. Rihannsu display a natural ability in many athletic events and martial arts. Their tall, thin body structure also aids in the dispersion of heat.
Rihannsu Biochemical Makeup
The biochemical makeup in Rihannsu is very similar to that in many Humanoid and especially Vulcanoid species of known space. At the cell nucleus level can be found DNA and chromosomal structures similar to most Humanoid/Vulcanoid races.
The blood of most Vulcanoids, including Rihannsu, is made up of hemoglobin based on copper. This copper-based blood is most obvious from its green color, which also tints the tissues of Rihannsu greenish, much like the iron-rich red blood of many other races tints their tissues a pinkish or reddish color. Having copper-based blood aids in the utilization of oxygen under low atmospheric pressure and low oxygen conditions. The Vulcanoid blood cells have a double-convex form, which in addition to helping to maximize oxygenation, also aids in cooling each blood cell, the blood stream, and ultimately the entire body. A lot of the waste heat conducted by blood cells is transferred into the lungs during respiration, thus making the exhaled breath of Vulcanoids fairly hot under most conditions, especially during exertion.
Rihannsu have a forward-facing, stereoscopic pair of eyes. Each eye is protected by a clear inner eyelid or nictating membrane that helps filter out harmful radiation, heat and dust. Rihannsu vision is less acute in bright light, while their night vision is more acute. Because of their eyes, Rihannsu living accommodations or vessels are much more dimly lit than those of most other species.
Rihannsu have a pair of ears on each side of their heads. The ears of most Vulcanoids are very distinctive in that the top of the external ear structure tapers into a clearly defined point. Rihannsu eartips are more blunt than their Vulcan ancestors. There appears to be a clear sexual dimorphism in ear shape, with males tending to have bigger ears with more prominent points. Rihannsu hearing is very acute under most conditions. While the Rihannsu low frequency hearing range is nearly identical to that of Terrans, their high frequency hearing range is significantly higher.
The size and shape of the Rihannsu nose conforms to the normal range of most Humanoid/Vulcanoid species. Because of their evolution in a hot, arid environment, though, the Vulcanoid nose has become highly adapted to filtering dust and sand from the air during inhalation, and minimizing moisture loss during exhalation. Because the sinus spaces of the Rihannsu contain moisture-reclaiming cells in place of what would be a large number of olfactory cells in other beings, the sense of smell of Rihannsu is not nearly as acute as that of most other Humanoid species.
The size and shape of the Rihannsu tongue conforms to the normal range of most Humanoid/Vulcanoid species. Due to the fact that taste is related to the sense of smell, Rihannsu have a lack of taste sensation. Vulcanoids are especially weak in tasting sweet things, although their sense of taste for salty and bitter things is relatively good. In order to enjoy the taste of things, Vulcanoids have historically tended to highly spice or season their foods. Some traditional Rihannsu dishes are nearly impossible to eat by other Humanoids.
Rihannsu have a very acute sense of touch in all its forms, especially heat, pressure and texture. Rihannsu are tactile beings by nature.
Body Organs and Systems
The epidermis of Vulcanoids, unlike that of many other Humanoids, is a twin-featured moisture-proof barrier to prevent dehydration. Rihannsu lack sweat glands as an evolutionary development to conserve moisture in an extremely hot, arid climate. Excess heat is drawn away by the blood to be exhaled or stored and radiated from the skin when external temperatures are lower. This is why Rihannsu have a very warm breath and their skin is almost hot to the touch under most conditions. Another difference in the Rihannsu skin is the fact that, even though the skin does not give off moisture, it can directly absorb moisture from the surroundings if there is any. In prehistoric times, Vulcans would stand in rare fog or rainfalls nude to maximize absorption of precious water that the body then stored. This technique is taught to the present day as a survival tool. Due to the structure of the skin, Rihannsu have little or no body hair other than that on the scalp, eyelashes and eyebrows.
Externally, it is difficult to tell the Vulcanoid brain from that of most sentient Humanoid/Vulcanoid species. Of course, if a Terran and Rihannsu brain were set side by side, it would be possible even for a layman to tell which was which simply by color - the Terran brain is greyish with a pink tinge, whereas the Rihannsu brain is greyish with a green tinge. A normal Rihannsu brain is about 1600 cc in size, practically identical to that of Terrans. The olfactory center of the Vulcanoid brain is smaller due to function (see the "Nose" section above), while the Rihannsu mid-brain is somewhat larger and slightly more convoluted than that of a Terran, but smaller and less convulted than that of Vulcans. This explains why there are almost no Rihannsu telepaths.
The Rihannsu heart is located approximately where one would expect to find the liver in Terrans. It is believed that the Vulcanoid heart was displaced to allow additional space for the lungs which are somewhat larger in order to extract sufficient oxygen from a thin atmosphere. In order to protect the heart region, cartilaginous ribs extend lower on the Rihannsu torso. Another consequence of the position of the heart and lower ribs is that the fetus is carried quite low in Rihannsu women, often causing discomfort for most of the pregnancy. The adult Rihannsu heart rate is approximately 240 beats per minute and normal blood pressure is 80/40, both far from the norm of most Humanoids.
The Rihannsu liver is much smaller than that of most Humanoids because many of the functions it has in other Humanoids is done elsewhere in the Vulcanoid body. For example, the kidneys not only filter fluids, they filter out and store certain substances. Other parts of the digestive and circulatory systems also have additional functions.
Kidneys and Bladder
In some ways the Rihannsu kidneys are more important than any other organ, since they manage the body's water retention system. The Rihannsu urinary system passes slightly less than half of all water taken into the body, while the rest is recycled. This is an adaptation to life on a very dry, arid planet where water is rarely found in its natural state. The urine of Vulcanoids is relatively thick and viscous, actually more like an oil than a watery liquid. The Vulcanoid bladder can hold urine for a number of days. The lining of the bladder also plays a small part in retrieving some water before the urine is finally eliminated.
Stomach and Digestion
Digestion begins in the mouth with the chewing of food and its mixture with saliva. As part of their evolutionary development to conserve moisture, Vulcanoids do not salivate from emotional or external sensual cues. Food has to actually be in the mouth being chewed before saliva will be released. After swallowing, the food bolus travels down the esophagus to the stomach with peristaltic contractions. The esophagus is separated from the stomach by the esophageal valve. The Rihannsu "stomach" is actually two joined chambers - the first section is a spherical muscular object and the second section is a flattened oval object. The two sections are separated by the first pyloric valve. In the first stomach, the undigested food is mixed with acids and enzymes, then subjected to vigorous muscular contraction until it is broken down into a mash. After formation of this mash, the first pyloric valve opens and the contents enter the second stomach. The first valve closes, as well as a second pyloric valve at the posterior end, if not already closed. The second stomach is where the mash from the first stomach is subjected to more intense acids, bile and enzymes, quickly reducing the contents to their basic components. After digestion is complete, the second pyloric valve opens and the soupy mixture enters the intestine where absorption of nutrients and water takes place.
Intestine and Excretion
The Rihannsu intestine is very simple compared to those of most Humanoid species. Instead of a complicated system of duodenum, jujunum, ileum, and large intestine, the Rihannsu only have a continuous coil of intestine that is a blend of features from the small and large intestines of other Humanoids. Rihannsu do not possess an appendix. As with all Rihannsu body systems, the intestine is very efficient, and the feces that is eliminated is a fairly dry, compact mass. Diarrhea, although very rare, will kill a Rihannsu relatively quickly, unless copious amounts of water are ingested immediately.
Rihannsu females are always fertile and the males can mate at any time. Rihannsu do not undergo pon farr.
The Rihannsu penis is an erectile structure without external sheath or foreskin. As part of the evolutionary process of Vulcan life, the male organ is almost fully retracted into the body when not in use as a protective measure. Vulcanoids also have two testes in a scrotal structure that is close to the body, not pendulous, and a prostatic body that produces and stores seminal fluid. Once ejaculated, the Rihannsu sperm is viable for a maximum of about 30 hours before losing mobility. Rihannsu males remain fertile during their entire adult life.
Rihannsu female reproductive organs are comprised of a vagina, uterus and ovaries. The ovaries are directly connected to the uterine body by short ducts. As part of the evolutionary process to conserve body water, Vulcanoid women do not menstruate. Ovulation occurs each month from alternate ovaries. The ovum enters the uterus usually in less than a day, where it remains awaiting fertilization. If no fertilization takes place within 10-14 days, the ovum deteriorates and its substance is absorbed into the uterine lining. Should fertilization occur, the blastocyst will implant itself in the uterine wall and hormones will activate formation of a placenta. Growth and development of a fetus will occur within the uterus with delivery being made through the vagina. The need for Caesarian types of deliveries, although rare, is not unknown to Rihannsu. Twinning is very rare. Fraternal twins are exceedingly rare, whereas identical twins are the norm. Multiple births beyond three are unheard of. Rihannsu female are fertile well into their second century.