SAMPLINGS 



Hidden World in the Desert 



Although the word "oasis" might conjure im- 

 ages of gently swaying palm trees and pools 

 of sparkling water, those rare watery refuges 

 in the desert offer more than just respite for 

 parched travelers. They're also complex eco- 

 systems. According to a recent study, a par- 

 ticularly complex patch called the Cuatro 

 Cienegas Basin (CCB) lies in the midst of 

 Mexico's windswept Chihuahuan Desert. It 

 covers 325 square miles and includes a di- 

 verse array of aquatic habitats, including 

 lakes, marshes, ponds, springs, and streams. 

 Besides hosting more than seventy endemic 

 species of aquatic vertebrates, the CCB shel- 

 ters a unique community of microorganisms, 

 relics of the oasis's ancient past. 



Led by Valeria Souza, an evolutionary 

 ecologist at the National Autonomous Uni- 

 versity of Mexico in Mexico City, a team of 

 investigators sequenced microbial DNA and 

 discovered thirty-eight previously unknown 

 microbial lineages in the CCB's waters. Sur- 



No Laughing 

 Matter 



To be top dog in a society of spotted 

 hyenas, you've got to be a real bitch. Fierce- 

 ly competitive scavengers, hyenas have no 

 truck with the usual mammalian rules of 

 dominance: females control the social hier- 

 archy with an aggressiveness normally ex- 

 erted only by males. Whether in females or 

 males, aggression means androgens — male 

 sex hormones, such as testosterone — and 

 plenty of them. Biologists have known that 

 prenatal exposure to androgens (indepen- 

 dent of an individual's genetic endowment) 

 fosters lifelong reproductive success in 

 birds. Now, Stephanie M. Dloniak and Kay 



Spotted hyena mothers pass down social rank, 

 along with hormones, to their cubs. 



prisingly, the closest rela- 

 tives of half the lineages 

 are marine species, even 

 though the CCB has been 

 separated from the ocean 

 for tens of millions of years 

 Souza and her team also 

 discovered closely related 



microorganisms in valleys 



^ ■ i ,i ,~^r> ■ i Cuatro Cieneqas 



outside the CCB — evidence 



of hydrological connections 



between the oasis and its surroundings. 



In recent years the CCB, a federally des- 

 ignated "area for the protection of flora 

 and fauna," has come under increasing 

 pressure, particularly from the irrigation of 

 nearby alfalfa fields for cattle, which may 

 drain the aquifers that supply the oasis. 

 Souza and her group hope their findings 

 help promote more stringent measures to 

 conserve the region's water. (PNAS 1 03: 

 6565-70, 2006) — Nick W. Atkinson 



E. Holekamp, wildlife biologists with Michi- 

 gan State University in East Lansing, and 

 one of their colleagues have shown that 

 prenatal androgen exposure in at least one 

 mammal — the hyena — may translate into 

 access to food and mates. 



Androgens, like other hormones, pass 

 from the blood of a pregnant female hyena 

 through the placenta to her developing fe- 

 tuses. By studying fluctuations in androgen 

 levels during pregnancy, the biologists dis- 

 covered that during the late stages, domi- 

 nant females have higher androgen levels 

 than do females further down the pecking 

 order. That extra androgen boost in the 

 womb leads to increased aggressiveness 

 and mounting behavior in cubs of high-sta- 

 tus females, traits that should give the 

 cubs a competitive edge later in life. 



Practice at mounting is particularly 

 important for male hyenas, say the 

 biologists. The female mates and 

 gives birth through her uniquely 

 masculinized genitalia — an elongated 

 clitoris that resembles a penis. Mating 

 (not to mention birthing) is thus ex- 

 tremely difficult. So, the more mount- 

 ing males do as cubs, the more suc- 

 cessful at mating they're likely to be 

 as adults. {Nature 440:1 190-3) 



—N.W.A, 



Basin is an oasis for microorganisms. 



Oh, the Trials 

 of Motherhood 



When it comes to mothering, some caecil- 

 ians willingly give the skin off their backs. 

 Caecilians are tropical, soil-dwelling, legless 

 amphibians that range in length from four 

 inches to more than four feet. They look like 

 giant earthworms. Alexander Kupfer, a 

 biologist at the Natural History Museum in 

 London, captured and then videotaped 

 twenty-one females of the Kenyan species 

 Boulengerula taitanus, along with broods of 

 between two and nine young. Kupfer and his 

 colleagues were amazed to see the young 

 literally munching 

 on Mom. 



A newly 

 hatched B. tai- 

 tanus has teeth 

 specially suited 

 for peeling off its 

 mother's outer 

 layer of skin — her 

 epidermis. Mom 

 doesn't mind; in 

 fact, she's a will- 

 ing participant. 

 While nursing, her epidermis grows to twice 

 its normal thickness and develops modified 

 cells full of nutritious fats and proteins. 



This newly recognized form of parental 

 care joins a long list of ways parents give 

 of their own bodies to feed their young. 

 Female mammals, of course, secrete milk. 

 Some female frogs and fishes produce unfer- 

 tilized eggs for their hungry young to eat. 

 But males, too, can be generous: flamingos, 

 emperor penguins, and pigeons of both gen- 

 ders produce "bird milk" — cells that slough 

 off the internal lining of the crop or esopha- 

 gus — and certain cichlid fishes, male as well 

 as female, secrete nutritious mucus through 

 their skin. (Nature 440:926-9, 2006) 



— Stephan Reebs 



Worms? Think again: 

 Boulengerula taitanus is 

 an amphibian with 

 strange nursing habits. 



NATURAL HISTORY July/August 2006 



