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patterns—electric blue in the westernCaribbean, lemon yellow in the Northern Why Gobies Are Like Hobbits
Bahamas, and stark white in the eastern Stephen R. Palumbi and Robert R. Warner Caribbean—might be local signals to preda-tors that these gobies are the valet service As Bilbo Baggins famously warned, trav- genetic breaks between island groups that rather than the entrée. If this is true, then the el is an uncertain business: "You step live relatively close together. These breaks wrong color pattern of an "immigrant" goby into the Road, and … there is no know- coincide with well-established color-pattern may not be recognized, and so would be ing where you might be swept off to" (1). For differences among goby fish—for example, strongly selected against.
the better part of a century, marine biologists the white and blue forms in the Caribbean But within two of the three color areas, have assumed the roads of ocean currents are waters around Puerto Rico are genetically goby populations remain remarkably distinct just as uncertain, and distinct populations even though they reside from island to island, so this explanation can- that the drifting eggs within 23 km of each other (see the figure). Enhanced online at not suffice. The other possibility is that the www.sciencemag.org/cgi/ and larvae and rafting goby larvae manage somehow to content/full/299/5603/51 propagules of many avoid dispersing on ocean currents— marine species end up that is, they have a hidden level of drift far from their homes, on distant shores.
control not predicted by most larval Now, on page 107 of this issue, Taylor and biologists. Gobies may be particularly Hellberg (2) help to overturn this notion. They adept at this because their larvae are provide further evidence that at least some often found nearer to shore than are marine species whose larvae have the potential the larvae of other reef fishes. But this to disperse over long distances, instead show genetic pattern is by no means restrict- a remarkable fondness for home.
ed to gobies. In fact, gobies join an During the past 2 years, evidence for increasing number of island species this new way of thinking has come that have fine-scale genetic structures from two very different sources: and low dispersal. Mantis shrimp in Indonesia advanced genetic monitoring of show genetic differences similar in spatial widely scattered populations, as scale and genetic depth to the gobies studied demonstrated by Taylor and Hellberg by Taylor and Hellberg in their new work; and elemental (4). Fish within closed analysis of the chemical signatures Polynesian lagoons are contained in larval structures (3).
genetically different from By comparing the genes of indi- those outside the lagoons In living color. The white
viduals collected from different (5). And crabs, fish, (top) and blue (middle)
places, genetic analysis can help to oysters, and mussels, a forms of the cleaner goby underscore the way in which marine veritable genetic paella, fish, Elacatinus (Gobiosoma) populations move around. Because show gene-frequency evelynae. In the Caribbean every adult or larva or egg that moves waters around Puerto Rico, the differences across bio- carries with it the genes it inherited white and blue forms of the geographic boundaries from its parents, genetic variation can goby live within 23 km of each between the Gulf of serve as a natural tag. Moreover, pop- other, yet remain genetically separate. Even though their Mexico and the west Atlantic (6), or between ulation genetic theory shows that pelagic larvae could be dispersed over large distances by the Mediterranean and the east Atlantic (7).
even a small amount of migration ocean currents, the larvae prefer to remain close to home.
These genetic results are paralleled by new between populations can wipe out (Bottom) A cleaner goby (also called a sharknose goby) cleans
information gleaned from the chemical signa- most genetic differences. So, when the parasites from a red hind (Epinephelus guttatus).
ture of fish otoliths (calcareous components of differences emerge from marine the inner ear) or mollusk statoliths (calcareous OM) STEPHEN FRINK/CORBIS genetic data, the implications are strong that The gobies studied by Taylor and Hellberg components in the balance organs). These very little population exchange has taken place.
have high dispersal potential—their larvae hard structures of calcium carbonate grow like Just such a conclusion emerges from the remain adrift in ocean currents for about 3 tiny pearls within the animal, depositing a Taylor and Hellberg study (2). They show weeks, a period long enough for drifting layer for each day of life—including the days that there are remarkably strong patterns of buoys to travel hundreds of kilometers (2).
spent as pelagic larvae. As larvae pass through genetic structure in the mitochondrial genes Two types of explanations are possible for different trace-metal environments, the hard WILK/ REEFNET INC of a small Caribbean reef goby fish (see the sharp genetic distinctions in the face of such parts act as a sort of flight recorder that can be figure). Such patterns demonstrate not only dispersal potential. First, there might be read after the larvae settle in their final loca- that distant islands harbor genetically distinct strong selection against the wrong genotypes.
tion. The information thus gleaned differs in populations, but also that there are sharp These gobies are cleaners—that is, they make significant ways from that obtained through their living picking the parasites off larger genetic analysis. It reflects an individual's his- S. R. Palumbi is in the Department of Biological fish, often the same fish that any rational tory since birth, including the pelagic pathway Sciences, Stanford University, Pacific Grove, CA 93950, goby would consider a dangerous predator.
taken as a larva, and potentially provides much USA. E-mail: [email protected] R. R. Warner is in Yet the large fish hold their appetites at bay more fine-scale spatial data. But the results are the Department of Ecology, Evolution, and Marine while the tiny gobies dart about them, picking Biology, University of California, Santa Barbara, CA similar to those obtained by genetic analysis.
93106, USA E-mail: [email protected] their skin clean of parasites. The variable color For example, populations of fish on tropical islands are capable of seeding themselves uncharacteristic in that they are almost all 3. S. E. Swearer et al., Bull. Mar. Sci. 70, 251 (2002).
despite having larvae that survive for weeks from island populations (9). Yet these exam- 4. P. H. Barber, S. R. Palumbi, M. V. Erdmann, M. K. Moosa, with the potential for long-distance dispersal ples of fine-scale patterns in genetic or chem- Nature 406, 692 (2000).
5. S. Planes, P. Romans, R. Lecomte-Finiger, Coral Reefs (3). Whelk populations along the California ical signatures tell us that the conventional 17, 9 (1998).
coast also appear to be colonized by locally wisdom of marine biology—that the ocean 6. J. C. Avise, Phylogeography (Harvard Univ. Press, produced larvae (8).
road is a long one for larvae—may prove to be Cambridge, MA, 2000).
7. H. Quessada, C. Zapata, G. Alvarez, Mar. Ecol. Progr.
These emerging empirical data obtained a coarse generalization (10). It turns out that Ser. 116, 99 (1995).
using two very different approaches are telling most hobbits do not take the long road 8. D. Zacherl, thesis, University of California, Santa us the same thing: that in some times and either—Bilbo was an exception—and in the Barbara (2002).
9. C. Mora, P. F. Sale, Trends Ecol. Evol. 17, 422 (2002).
places, marine larvae are capable of maintain- end gobies and hobbits like to stay at home.
10. The extent of marine larval dispersal will be one of ing close links to home despite their proximity the subjects of a symposium at the upcoming AAAS to the ocean highways of the sea. Of course, References and Notes
meeting in Denver, CO: "Opening the Black Box: 1. J. R. R. Tolkien, The Lord of the Rings: The Fellowship Understanding Ecosystem Dynamics in the Coastal many other marine species seem to disperse of the Ring (Houghton Mifflin, Boston, 1994), p. 72.
Ocean" (B. Menge, R. Warner, and J. Lubchenco, co- broadly, and the examples cataloged here are 2. M. S. Taylor, M. E. Hellberg, Science 299, 107 (2003).
form. Thus, there are 3 C22H28 tetraman-tanes, 6 isomeric C26H32 pentamantanes,and as many as 17 possible C mantane isomers.
As the number of isomers increases, dif- Delving into Nature's Bounty
ferences between their relative thermody-namic stabilities decrease, and the com- plexity of the potential-energy surface con- necting these isomers increases.
The molecular lattice of diamond, first Thus, it becomes increasingly elucidated in 1913 (1), consists of difficult to promote a smooth repeating units of 10 carbon atoms forming a tetracyclic cage system. Shortly to obtain a single isomer. As the thereafter it was recognized that a series of limitations of rearrangement saturated hydrocarbons can be superim- synthesis became clear, interest posed on this diamond lattice. The simplest in diamondoid hydrocarbons of these "diamondoids," with the common waned once again.
name adamantane (from αδαµας, the In a report by Dahl et al. (5) Greek word for diamond), is a tricyclic on page 96, they present results C10H16 isomer. The series of saturated that may reawaken interest in hydrocarbons can then be regarded as this important class of com- higher "adamantologs" of adamantane (see pounds. There are compelling the figure).
reasons to do so. Substituents Adamantane and the larger diamon- can be introduced easily at doids long remained hypothetical mole- bridgehead positions of diamon- cules. They could neither be isolated from doids (6, 7). Such functionalized a natural repository, nor made through diamondoid molecules have Diamond in miniature. The structures of adamantane
rational organic synthesis. As a result, important pharmaceutical appli- (left), diamantane (center), and triamantane (right) are seg-
interest in these molecules and their chem- cations. Perhaps the most widely ments of the diamond lattice.
istry remained dormant until 1957, when known is 1-aminoadamantane Schleyer reported that endo-trimethyle- tane (C14H20) (see the figure). This com- (also known as amantadine or Symmetrel), nenorbornane (which can be prepared read- pound—unknown in the literature at the which is used extensively as an antidyski- ily) rearranges to adamantane when time—was chosen as the official emblem netic to treat parkinsonism and related refluxed overnight with aluminum bromide of a 1963 IUPAC conference. In response extrapyramidal syndromes and as a chemi- or aluminum chloride (2).
to the implied challenge, Schleyer again cal antiviral agent to treat Type A influenza This Lewis acid–catalyzed thermody- used his "rearrangement synthesis" in humans (6). Polyalkyladamantanes have namic rearrangement of hydrocarbons approach successfully to prepare diaman- been studied as high–energy-density afforded a method to prepare adamantane tane (3). The third member of the dia- materials, particularly as components of simply and inexpensively. It led to mondoid series, C18H24, nicknamed tria- jet fuel blends (8–10). There is also renewed interest in the synthesis and mantane, was isolated and characterized renewed interest in nanotechnological chemistry of adamantane and related dia- shortly thereafter (4).
applications of diamondoid molecules, mondoid molecules with the chemical for- As higher diamondoids were sought, particularly in the area of microelectron- mula C(4n+6)H(4n+12), where n = 0, 1, 2, 3, … however, it rapidly became apparent that ics (11).
The next diamondoid molecule to the rearrangement synthesis approach has Dahl et al. (5) have isolated and charac- become a focus of attention was diaman- severe limitations. Whereas each of the terized several previously unknown higher first three members of the series (adaman- diamondoid hydrocarbons from crude oil.
tane, diamantane, and triamantane) exists In addition, they have developed improved The author is in the Department of Chemistry, as a single isomer, higher members of the methods for isolating higher diamondoids University of North Texas, Denton, TX 76203, USA.
E-mail: [email protected] series can exist in more than one isomeric that hold considerable promise for the

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