PZ Myers is one of those truly inspired scientists…Joyce Hays, Target Health Inc.


The Greatest Science Paper Ever Published in the History of Humankind


PZ Myers is a biologist and associate professor at the University of Minnesota



by PZ Myers, June/July 2011

That’s not hyperbole. I really mean it. How else could I react when I open up the latest issue of Bioessays, and see this: Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules. Just from the title alone, I’m immediately launched into my happy place: sitting on a rocky beach on the Pacific Northwest coast, enjoying the sea breeze while the my wife serves me a big platter of bacon, and the cannula in my hypothalamus slowly drips a potent cocktail of cocain and ecstasy direct into my pleasure centers…and there’s pie for dessert. It’s like the authors know me and sat down to concoct a title where every word would push my buttons.

The content is pretty good, too. It’s not perfect; the development part is a little thin, consisting mainly of basic comparative embryology of body plans, with nothing at all really about deployment of and interactions between significant developmental genes. But that’s OK. It’s in the nature of the Greatest Science Papers Ever Written that stuff will have to be revised and some will be shown wrong next month, and next year there will be more Greatest Science Papers Ever Written — it’s part of the dynamic. But I’ll let it be known, now that apparently the scientific community is aware of my obsessions and is pandering to them, that the next instantiation needs more developmental epistasis and some in situs.

This paper, though, is a nice summary of the emerging picture of cephalopod evolution, as determined by the disciplines of paleontology, comparative embryology, and molecular phylogenetics, and that summary is internally consistent and is generating a good rough outline of the story. And here is that story, as determined by a combination of fossils, molecular evidence, and comparative anatomy and embryology.

Cephalopods evolved from monoplacophoran-like ancestors in the Cambrian, about 530 million years ago. Monoplacophorans are simple, limpet-like molluscs; they crawl about on the bottom of the ocean under a cap-like shell, foraging snail-like on a muscular foot. The early cephalopods modified this body plan to rise up off the bottom and become more active: the flattened shell elongated to become a cone-like structure, housing chambers for bouyancy. Movement was no longer by creeping, but used muscular contractions through a siphon to propel the animal horizontally. Freed from its locomotor function, the foot expanded into manipulating tentacles.





These early cephalopods, which have shells common in the fossil record, would have spent their lives bobbing vertically in the water column, bouyed by their shells, and with their tentacles dangling downward to capture prey. They wouldn’t have been particularly mobile — that form of a cone hanging vertically in the water isn’t particularly well-streamlined for horizontal motion — so the next big innovation was a rotation of the body axis, swiveling the body axis 90° to turn a cone into a torpedo. There is evidence that many species did this independently.





The tilting of the body axes of extant cephalopods. This was a result of a polyphyletic and repeated trend towards enhanced manoeuverability. The morphological body axes (anterior-posterior, dorso-ventral) are tilted perpendicularly against functional axes in the transition towards extant cephalopods.

We can still see vestiges of this rotation in cephalopod embryology. If you look at early embryos of cephalopods (at the bottom of the diagram below), you see the same pattern: they are roughly disc-shaped, with a shell gland on top and a ring of tentacle buds on the bottom. They subsequently extend and elongage along the embryonic dorsal-ventral axis, which becomes the anterior-posterior axis in the adult.





In extant cephalopods the body axes of the adult stages are tilted perpendicularly versus embryonic stages. As a con- sequence, the morphological anterior-posterior body axis between mouth and anus and the dorso-ventral axis, which is marked by a dorsal shell field, is tilted 908 in the vertical direction in the adult cephalopod. Median section of A: Nautilus, B: Sepia showing the relative position of major organs (Drawings by Brian Roach). C: shared embryonic features in embryos of Nautilus (Nautiloidea) and Idiosepius (Coleoidea) (simplified from Shigeno et al. 2008 [23] Fig. 8). Orientation of the morphological body axes is marked with a compass icon (a, anterior; d, dorsal; p, posterior; v, ventral; dgl, digestive gland; gon, gonad; ngl, nidamental gland).

The next division of the cephalopods occurred in the Silurian/Devonian, about 416 million years ago, and it involved those shells. Shells are great armor, and in the cephalopods were also an organ of bouyancy, but they also greatly limit mobility. At that early Devonian boundary, we see the split into the two groups of extant cephalopods. Some retained the armored shells; those are the nautiloids. Others reduced the shell, internalizing it or even getting rid of it altogether; those are the coleoids, the most successful modern group, which includes the squids, cuttlefish, and octopuses. Presumably, one of the driving forces behind the evolution of the coleoids was competition from that other group of big metazoans, the fish.

The nautiloids…well, the nautiloids weren’t so successful, evolutionarily speaking. Only one genus, Nautilus has survived to the modern day, and all the others followed the stem-group cephalopods into extinction.

The coleoids, on the other hand, have done relatively well. The number of species have fluctuated over time, but currently there are about 800 known species, which is respectable. The fish have clearly done better, with about 30,000 extant species, but that could change — there are signs that cephalopods have been thriving a little better recently in an era of global warming and acute overfishing, so we humans may have been giving mobile molluscs a bit of a tentacle up in the long evolutionary competition.

There was another major event in coleoid history. During the Permian, about 276 million years ago, there was a major radiation event, with many new species flourishing. In particular, there was another split: between the Decabrachia, the ten-armed familiar squid, and the Vampyropoda, a group that includes the eight-armed octopus, the cirroctopodes, and Vampyroteuthis infernalis. The Vampyropoda have had another locomotor shift, away from rapid jet-propelled movement to emphasizing their fins for movement, or in the case of the benthic octopus, increasing their flexibility to allow movement through complex environments like the rocky bottom.

Time for the big picture. Here’s the tree of cephalopod evolution, using dates derived from a combination of the available fossil evidence and primarily molecular clocks. The drawings illustrate the shell shape, or in the case of the coleoids, the shape of the internal shell, or gladius, if they have one.





A molecularly calibrated time-tree of cephalopod evolution. Nodes marked in blue are molecular divergence estimates (see methods in Supplemental Material). The divergence of Spirula from other decabrachiates are from Warnke et al. [43], the remaining divergences are from analyses presented in this paper. Bold lineages indicate the fossil record of extant lineages, stippled lines are tentative relationships between modern coleoids, partly based on previous studies [41, 76, 82] and fossil relationships are based on current consensus and hypoth- eses presented herein. Shells of stem group cephalopods and Spirula in lateral view with functional anterior left. Shells of coleoids in ventral view with anterior down. The Mesozoic divergence of coleoids is relatively poorly resolved compared to the rapid evolution of Cambro- Ordovician stem group cephalopods. Many stem group cephalopod orders not discussed in the text are excluded from the diagram.

The story and the multiple lines of evidence hang together beautifully to make a robust picture of cephalopod evolution. The authors do mention one exception: Nectocaris. Nectocaris is a Cambrian organism that looks a bit like a two-tentacled, finned squid, which doesn’t fit at all into this view of coleoids evolving relatively late. The authors looked at it carefully, and invest a substantial part of the review discussing this problematic species, and decided on the basis of the morphology of its gut and of the putative siphon that there is simply no way the little beast could be ancestral to any cephalopods: it’s a distantly related lophotrochozoan with some morphological convergence. It’s internal bits simply aren’t oriented in the same way as would fit the cephalopod body plan.

So that’s the state of cephalopod evolution today. I shall be looking forward to the Next Great Paper, and in particular, I want to see more about the molecular biology of tentacles — that’s where the insights about the transition from monoplacophoran to cephalopod will come from, I suspect.

Kröger B, Vinther J, Fuchs D (2011) Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules: Extant cephalopods are younger than previously realised and were under major selection to become agile, shell-less predators. Bioessays doi: 10.1002/bies.201100001.



This material is from the 4th edition of The Zebrafish Book. The 5th edition is available in print and within the ZFIN Protocol Wiki.




Modified from: Kimmel et al., 1995. Developmental Dynamics 203:253-310. Copyright © 1995 Wiley-Liss, Inc. Reprinted only by permission of Wiley-Liss, a subsidiary of John Wiley & Sons, Inc.

Ballard (1981) coined the term “pharyngula” to refer to the embryo that has developed to the phyolotypic stage, when it posesses the classic vertebrate bauplan. According to von Baer’s famous laws (discussed by Gould, 1977) this is the time of development when one can most readily compare the morphologies of embryos of diverse vertebrates, and for the zebrafish we approximate the period as the second of the three days of embryonic development (Fig. 29). The embryo is most evidently now a bilaterally organized creature, entering the pharyngula period with a well-developed notochord, and a newly-completed set of somites that extend to the end of a long post-anal tail. The nervous system is hollow and expanded anteriorly. With the rapid cerebellar morphogenesis of the metencephalon (Fig. 30A), just preceding the pharyngula period, the brain is now sculptured into 5 lobes (Fig. 23C).

The period name focuses attention on the primordia of the pharyngeal arches, present but at early times difficult to distinguish individually. The pharyngeal arches develop rapidly during this second day from a primordial region that can be visualized ventral to, and about twice as long as the otic vesicle (Fig. 31). Seven pharyngeal arches in all develop from this primordium, a prominent boundary within it (arrow in Fig. 31) occurring between pharyngeal arches 2 and 3. This boundary is important, for later the arches anterior to it (the mandibular and hyoid arches) form the jaws and the operculum, and arches (branchial arches) posterior to it will form the gills.

The cells of the hatching gland, with their brightly refractile cytoplasmic granules, are prominent features of the pericardial region throughout the pharyngula period (Fig. 32).

During the first few hours of the pharyngula period the embryo continues the rapid lengthening that started at 15 h, but then the rate of lengthening abruptly decreases. The time of the change, at 31-32 h, correlates approximately with the end of the rapid morphogenetic straightening of the tail, discussed above. The new rate of lengthening is maintained throughout the rest of embryogenesis (Fig. 16).

The head also straightens out. It lifts dorsalwards fairly rapidly during the pharyngula period and then more slowly, and one can use this change to quickly determine the approximate stage of the embryo (Fig. 33). We imagine two lines from a side view: One, a line through the middle of the ear and eye, is the head axis. The other, along the notochord, and parallel to the horizontal myosepta at about somites 5-10, is the trunk axis. A way to estimate the angle between the two lines, the head-trunk angle (HTA), is to position the embryo in its dish with its tail pointing towards the observor, and mentally superimpose a clock face upon it. One of the hands of the clock, the trunk axis, points towards 6 o’clock. The position of the other hand, the head axis, changes with developmental time as as shown in Fig. 33.

The morphogenesis accompanying head-straightening dramatically shortens the head, in absolute terms, making it more compact along the anterior-posterior axis. As can be seen from Fig. 1, the rudiments of the eye and the ear approach one another rapidly, thus providing a second new staging index. Simply estimate the number of additional otic vesicles that could fit between the eye and the otic vesicle. We term this number “otic vesicle length (OVL)“. It decreases from about 5 at the beginning of the pharyngula period to less than 1 at the end.

During most of the period, until about 40 h, the most precise staging method, and the most difficult, depends on using Nomarski optics to locate the leading tip of the migrating portion of the posterior lateral line primordium, as it moves steadily along the length of the trunk and tail (Fig. 34A). It leaves behind cells that form the ganglion of the lateral nerve, and as it moves it deposits cells that form the neuromasts along the nerve. The primordium migrates in the skin, superficially to the horizontal myoseptum (Fig. 34B), on each side of the body, at an approximately linear rate of 100 µm/hour (Metcalfe, 1985), or 1.7 myotomes/hour. Determine which myotome, from 1-30, the advancing (posterior) tip of the primordium overlies. We define primordium (“prim”) stages by this index (Fig. 35). The method is tedious, and the migrations of the primordia on both sides of a single embryo are not always synchronous. After 40 h the primordium is far posterior, small, and indistinct.

In addition to these general features, and novel ones that characterize particular stages, there are several important developments during the pharyngula period that we now outline below, and then, following the same order of presentation and setting each topic off into a paragraph of its own, we add details in the stage descriptions.

The fins begin to form. The median fin fold, barely present at the onset of the period, becomes prominent, and forms collagenous strengthening fin rays, or actinotrichia (Fig. 28D). The rudiments of the bilaterally paired pectoral fins begin their morphogenesis: Mesenchymal cells gather together to form fin buds that serve as probably the single-most useful staging feature during the second half of the pharyngula period (Fig. 36, and Fig. 37). As the buds develop, an apical ectodermal ridge becomes prominent at their tips. Whether the ridge plays a morphogenetic role similar to that of the limb bud of tetrapods is unknown, but a hint that it might do so comes from the fact that it is positioned at the exact boundary of the ventrally located expression domain of the engrailed1 gene (Hatta et al., 1991a; Ekker et al., 1992). A most significant connection between the zebrafish fin bud and the tetrapod limb bud is the domain posterior mesenchymal domain of sonic hedgehog gene expression in both, corresponding to the zone of polarizing activity (ZPA; see Krauss et al., 1993).

Pigment cells differentiate. They are easy to see and we use them for staging landmarks. The pigmented retinal epithelium, and the neural crest-derived melanophores begin to differentiate at the onset of the period, and pigmentation gets rather far along during the period. The melanophores begin to arrange themselves in a characteristic pattern that includes a well-defined set of longitudinal body-stripes (Milos and Dingle, 1978).

The circulatory system forms (Reib, 1973). The heart begins to beat just at the onset of the period, and forms well delineated chambers. Blood begins to circulate though a closed set of channels. A bilateral pair of aortic arches appears just at the outset of the pharyngula period, this is aortic arch #1, the earliest and most anterior arch of the eventual serial set of six. The others develop rapidly near the end of the period. The blood flows into each side of the head from the anterior two arches via the carotid artery and returns via the anterior cardinal veins. The more posterior aortic arches (arches #3-6) also connect to the left and right radices (roots) of the dorsal aortae, which anastomose in the trunk to form an unpaired midline vessel lying just ventral to the notochord. The dorsal aorta is renamed the caudal artery as it enters the tail (Reib, 1973). At a point along the tail the channel makes a smooth ventrally directed 180 degree turn to form the caudal vein, returning the blood to the trunk. The vein continues in the posterior trunk as the unpaired median axial vein, lying just ventral to the dorsal aorta. Just posterior to the heart, the vein then splits into the paired left and right posterior cardinal veins. In turn, each posterior cardinal joins with the anterior cardinal to form the common cardinal vein (or duct of Cuvier) that leads directly to the heart’s sinus venous. The name sometimes used for the common cardinal as it crosses the yolk sac, the vitelline vein, is not very appropriate, because the vessels named vitelline veins in other fish have different connections (see Reib, 1973). The common cardinal veins, at first very broad and not very well-defined, carry the blood ventrally across the yolk. As development continues the common cardinals become narrower channels, and relocate to the anterior side of the yolk.

Finally, there is marked behavioral development. Tactile sensitivity appears, and the flexions that occurred in uncoordinated individual myotomes during the late segmentation period become orchestrated into rhythmic bouts of swimming.




U.S. National Library of Medicine
National Institutes of Health

Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules: Extant cephalopods are younger than previously realised and were under major selection to become agile, shell-less predators.

Kröger B, Vinther J, Fuchs D.


Museum für Naturkunde Berlin, Berlin, Germany.


Cephalopods are extraordinary molluscs equipped with vertebrate-like intelligence and a unique buoyancy system for locomotion. A growing body of evidence from the fossil record, embryology and Bayesian molecular divergence estimations provides a comprehensive picture of their origins and evolution. Cephalopods evolved during the Cambrian (∼530 Ma) from a monoplacophoran-like mollusc in which the conical, external shell was modified into a chambered buoyancy apparatus. During the mid-Palaeozoic (∼416 Ma) cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish and octopods) internalised their shells and, in the late Palaeozoic (∼276 Ma), diverged into Vampyropoda and the Decabrachia. This shell internalisation appears to be a unique evolutionary event. In contrast, the loss of a mineralised shell has occurred several times in distinct coleoid lineages. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour.

Copyright © 2011 WILEY Periodicals, Inc.

 [PubMed – as supplied by publisher]



The Monoplacophora


Living fossils from the ocean deep


Once known only from Paleozoic fossils, living monoplacophorans were discovered in 1952 in one of the most important discoveries in modern biology. Since that first recent species (Neopilina galathaea) was discovered, around 20 other species have been identified.

One reason for having evaded detection for so long is that they are generally found in the deep ocean. Finding them has been quite a boon to malacologists however, as monoplacophorans are often thought to be among the most primitive of molluscs. Indeed, many researchers believe that monoplacophoran-like ancestors gave rise to the rest of Mollusca.

Modern systematic research has borne out the idea of Monoplacophora being the basal member of the Mollusca clade. Their morphology then, proves to be remarkably important in understanding what the first molluscs may have looked like, as well as how the other major groups such as bivalves and gastropods may have evolved.

As only a few species of living monoplacophorans are known, and all being somewhat similar, much of our knowledge of the group comes from fossils.

Fossil record
Monoplacophorans are the first undoubted molluscs, being found in rocks from the earliest Cambrian. The fossil record indicates that the group was quite diverse during the Paleozoic.

Recent monoplacophorans form a distinct clade, and their similarities and differences with the other extant molluscan groups are easily recognized. There is little question that some Paleozoic taxa are also members of this clade. However, the characters that distinguish some Paleozoic monoplacophorans from the torted gastropods and vice versa are open to alternative interpretations and the relationships of several major groups of early-shelled molluscs have therefore been the subject of much debate.

Life history & ecology
Monoplacophorans are found on both soft bottoms and hard substrates on the continental shelf and seamounts, generally in the very deep sea. However, some Paleozoic taxa are associated with relatively shallow water faunas (greater than 100 m), indicating that their relegation to the deep sea is a more recent phenomenon.

Unfortunately, there have thus far been no developmental studies done on monoplacophorans. Indeed, most of our knowledge about Monoplacophora comes from the first description of Neopilina galathaea by Lemche and Wingstrand in 1959.

More on morphology
Monoplacophorans are small and limpet-like, having a single, cap-like shell. Some organs (kidneys, heart, gills) are repeated serially, giving rise to the now falsified hypothesis that they may have a close relationship with segmented organisms such as annelids and arthropods.

In fossil monoplacophorans, the aperture (shell opening) varies in shape from almost circular to pear-shaped. Shell height is also variable and ranges from relatively flat to tall. The monoplacophoran animal has a poorly defined head with an elaborate mouth structure on the ventral surface. The mouth is typically surround by a V-shaped, thickened anterior lip and post-oral tentacles; post-oral tentacles come in a variety of morphologies and configurations. Below the head lies the semi-circular foot. In the pallial groove, between the lateral sides of the foot and the ventral mantle edge, are found five or six pairs of gills (there are fewer in very tiny taxa).



In Recent and fossil limpet-like monoplacophoran shells the apex is typically positioned at the anterior end of the shell, and in some species the apex actually overhangs the anterior edge of the shell.

Internally the monoplacophoran is organized with a long, looped alimentary system, two pairs of gonads, and multiple paired excretory organs (four of which also serve as gonoducts). A bilobed ventricle lies on either side of the rectum and is connected via a long aorta to a complex plumbing of multiple paired atria that in turn are connected to the excretory organs. The nervous system is ladder-like and has weakly developed anterior ganglia. Paired muscle bundles enclose the visceral mass. Large, dorsal paired cavities are extensions of glands associated with the pharynx. The monoplacophoran radula is docoglossate, i.e., each row having a central tooth, three pairs of lateral teeth, and two pairs of marginal teeth.
Original text by Paul Bunje, UCMP. Monoplacophoran anatomy by Ivy Livingstone, © BIODIDAC.

Drug Enforcement Administration agents arrested ten people in an elaborate drug bust Tuesday that spanned both coasts, and seized 2 million dollars worth of the designer drug “bath salts” over the course of a five month investigation. (ABC News)





ABCNews.com, July18, 2011  —  Dr. Jeffrey J. Narmi could not believe what he was seeing this spring in the emergency room at Schuylkill Medical Center in Pottsville, Pa.: people arriving so agitated, violent and psychotic that a small army of medical workers was needed to hold them down.

They had taken new stimulant drugs that people are calling “bath salts,” and sometimes even large doses of sedatives failed to quiet them.

“There were some who were admitted overnight for treatment and subsequently admitted to the psych floor upstairs,” Dr. Narmi said. “These people were completely disconnected from reality and in a very bad place.”

Similar reports are emerging from hospitals around the country, as doctors scramble to figure out the best treatment for people high on bath salts. The drugs started turning up regularly in the United States last year and have proliferated in recent months, alarming doctors, who say they have unusually dangerous and long-lasting effects.

Though they come in powder and crystal form like traditional bath salts — hence their name — they differ in one crucial way: they are used as recreational drugs. People typically snort, inject or smoke them.

Poison control centers around the country received 3,470 calls about bath salts from January through June, according to the American Association of Poison Control Centers, up from 303 in all of 2010.

“Some of these folks aren’t right for a long time,” said Karen E. Simone, director of the Northern New England Poison Center. “If you gave me a list of drugs that I wouldn’t want to touch, this would be at the top.”

At least 28 states have banned bath salts, which are typically sold for $25 to $50 per 50-milligram packet at convenience stores and head shops under names like Aura, Ivory Wave, Loco-Motion and Vanilla Sky. Most of the bans are in the South and the Midwest, where the drugs have grown quickly in popularity. But states like Maine, New Jersey and New York have also outlawed them after seeing evidence that their use was spreading.

The cases are jarring and similar to those involving PCP in the 1970s. Some of the recent incidents include a man in Indiana who climbed a roadside flagpole and jumped into traffic, a man in Pennsylvania who broke into a monastery and stabbed a priest, and a woman in West Virginia who scratched herself “to pieces” over several days because she thought there was something under her skin.

“She looked like she had been dragged through a briar bush for several miles,” said Dr. Owen M. Lander, an emergency room doctor at Ruby Memorial Hospital in Morgantown, W.Va.

Bath salts contain manmade chemicals like mephedrone and methylenedioxypyrovalerone, or MDPV, also known as substituted cathinones. Both drugs are related to khat, an organic stimulant found in Arab and East African countries that is illegal in the United States.

They are similar to so-called synthetic marijuana, which has also caused a surge in medical emergencies and been banned in a number of states. In March, the Drug Enforcement Administration used emergency powers to temporarily ban five chemicals used in synthetic marijuana, which is sold in the same types of shops as bath salts.

Shortly afterward, Senator Bob Casey, Democrat of Pennsylvania, asked the agency to enact a similar ban on the chemicals in bath salts. It has not done so, although Gary Boggs, a special agent at D.E.A. headquarters in Washington, said the agency had started looking into whether to make MDPV and mephedrone controlled Schedule I drugs like heroin and ecstasy.

Mr. Casey said in a recent interview that he was frustrated by the lack of a temporary ban. “There has to be some authority that is not being exercised,” he said. “I’m not fully convinced they can’t take action in a way that’s commensurate with the action taken at the state level.”

Senator Charles E. Schumer, Democrat of New York, introduced federal legislation in February to classify bath salts as controlled Schedule I substances, but it remains in committee. Meanwhile, the drugs remain widely available on the Internet, and experts say the state bans can be thwarted by chemists who need change only one molecule in salts to make them legal again.

And while some states with bans have seen fewer episodes involving bath salts, others where they remain fully legal, like Arizona, are starting to see a surge of cases.

Dr. Frank LoVecchio, an emergency room doctor at Banner Good Samaritan Medical Center in Phoenix, said he had to administer general anesthesia in recent weeks to bath salt users so agitated that they did not respond to large doses of sedatives.

Dr. Justin Strittmatter, an emergency room doctor at the Gulf Coast Medical Center in Panama City, Fla., said he had treated one man whose temperature had shot up to 107.5 degrees after snorting bath salts. “You could fry an egg on his forehead,” Dr. Strittmatter said.

Other doctors described dangerously elevated blood pressure and heart rates and people so agitated that their muscles started to break down, releasing chemicals that led to kidney failure.

Mark Ryan, the director of the Louisiana Poison Center, said some doctors had turned to powerful antipsychotics to calm users after sedatives failed. “If you take the worst attributes of meth, coke, PCP, LSD and ecstasy and put them together,” he said, “that’s what we’re seeing sometimes.”

Dr. Ryan added, “Some people who used it back in November or December, their family members say they’re still experiencing noticeable paranoid tendencies that they did not have prior.”

Before hitting this country, bath salts swept Britain, which banned them in April 2010. Experts say much of the supply is coming from China and India, where chemical manufacturers have less government oversight.

They are labeled “not for human consumption,” which helps them skirt the federal Analog Act, under which any substance “substantially similar” to a banned drug is deemed illegal if it is intended for consumption.

Last month, the drug agency made its first arrests involving bath salts under the Analog Act through a special task force in New York. Undercover agents bought bath salts from stores in Manhattan and Brooklyn, where clerks discussed how to ingest them and boasted that they would not show up on a drug test.

“We were sending out a message that if you’re going to sell these bath salts, it’s a violation and we will be looking at you,” said John P. Gilbride, special agent in charge of the New York field division of the D.E.A.

The authorities in Alton, Ill., are looking at the Analog Act as they prepare to file criminal charges in the death of a woman who overdosed on bath salts bought at a liquor store in April.

“We think we can prove that these folks were selling it across the counter for the purposes of humans getting high,” said Chief David Hayes of the Alton police.

Chief Hayes and other law enforcement officials said they had been shocked by how quickly bath salts turned into a major problem. “I have never seen a drug that took off as fast as this one,” Chief Hayes said. Others said some people on the drugs could not be subdued with pepper spray or even Tasers.

Chief Joseph H. Murton of the Pottsville police said the number of bath salt cases had dropped significantly since the city banned the drugs last month. But before the ban, he said, the episodes were overwhelming the police and two local hospitals.

“We had two instances in particular where they were acting out in a very violent manner and they were Tasered and it had no effect,” he said. “One was only a small female, but it took four officers to hold her down, along with two orderlies. That’s how out of control she was.”