Restore Default

research journal
Demystifying the Mythical Seahorse

Download PDF Version

Norah Saarman, Conservation and Resource Studies '06, explains how genetic sleuthing led her to the medicinal herb shops of Chinatown and beyond.

When Dr. Healy Hamilton invited Norah Saarman, to do an undergraduate research project on seahorse genetics, she felt a tingle of excitement. "I've always had a crush on Syngnathidae, the family of fishes including pipefish, pipehorses, seadragons and

seahorses, and now I would get to study the most lovable member of the group!" she remembers. Her brief experience in corn genetics research had more than paid off, opening the door to a whole new realm of conservation biology.

The appearance of seahorses is exciting enough. As their scientific name Hippocampus implies, seahorses have the head of a horse (hippo = horse, campus = head). This, combined with a curvy prehensile tail and a series of armor like body rings, complete a mythical image. Exotic stripe-ringed eyes move independently to scope out tiny floating prey.

The uses of seahorses
Seahorses have an astonishing and endearing reproductive strategy. A male seahorse receives between 5 and 2,000 eggs directly into his brood pouch. The eggs are fertilized and then nourished as they develop in this internally regulated environment. His stomach becomes distended just like a pregnant woman until he gives birth to the young, which emerge fully formed at the end of gestation, and rise to the surface to disperse on ocean currents. The appreciative female performs courtship dances daily to exhibit her loyalty.

As Saarman began her research, she became aware that she had stumbled upon a group that is not only unique and captivating, but also understudied, overexploited and in grave danger of extinction. In 2004, seahorses were added to Appendix II of the Convention on International Trade of Endangered Species agreement to protect them from exploitation. The 167 nations who have signed the agreement are responsible for controlling cross-boarder trade and regulating fishing practices so that sustainable populations of all 35 seahorse species can persist. One might say that seahorses are the charismatic ambassador of the coral reef and mangrove forest.

Seahorses are found in various marine habitats close to the coast. Because the coastal areas that seahorses call home are some of the most threatened marine ecosystems of the world, protecting seahorses will ensure the continued vitality of the whole ocean floor community.

These communities provide many services to humans including invaluable nutrition, lumber, fuel wood, carbon sequestration and medicinal ingredients. Seahorses are not only endangered because of their ecological fragility, they are also threatened by their overexploitation in trade for traditional Chinese medicine.

Seahorses as medicinal ingredients

An estimated 24.5 million or 70 tons of seahorses are sold annually for use in Chinese medicine. Most seahorses on the market are caught accidentally by shrimp trawlers who later handpick them from the net and sell them for additional income on the international market. In some countries, seahorses are targeted by lantern fishers who fish by night when seahorses are most active.

Seahorses are reputedly high in yang, the active male force, and are a respected treatment for many ailments associated with a cold kidney system. As a source of fire energy, seahorse can be used to treat many symptoms including impotence, urinary incontinence, wheezing, abdominal pain, toxic swelling and debility in the elderly.

But seahorses are a fragile species that respond quickly to habitat destruction and overfishing and may not be able to survive the current rate of harvest. Seahorses are sparsely distributed and don't travel much, so once they're removed from an area they don't return easily. They also remain faithful to their mate and don't reproduce quickly, making them exceptionally vulnerable to population reduction when too many are caught at sexual maturity.

The international seahorse trade

Why does trade continue despite the negative impacts? The seahorse trade is widespread and affects millions of people whose income is so low that the economic value cannot be represented effectively in US dollars.

Some of the world's poorest fishermen target seahorses. Because the average income in some poor countries is just one or two dollars a day, seahorses can greatly increase a fisherman's income. Even though most fishermen sell their catch to distributors at the low price of $0.10 to $1.56 USD per kilo, the profit is a strong incentive. Desiccated seahorses sell for between $333 and $666 USD per kilo in San Francisco.

Enforcement of fishing regulations are expensive, and management plans are difficult to implement. With such a high incentive driving the seahorse market the challenge of maintaining seahorse populations will require extensive research, more careful documentation and international cooperation.

H. ingens

Trade is well documented for species such as H. trimaculatus, which originate in Asia. However the 'giant' Pacific seahorse, H. ingens, the only species which occurs along the Pacific coast of North and South America, remains an unrecognized component of Chinese medicine. If Saarman could prove that giant Pacific seahorses were being traded often for Chinese medicine, it might provide incentive for more careful documentation.

Journey to Chinatown

Saarman's research quickly snowballed into different disciplines, and she made a trip to Chinatown, San Francisco. There she interviewed seahorse specialists and acupuncturists alike to answer her questions about the cultural and economic value of seahorses.

Two years after placement on Appendix II of CITES, Saarman found large jars and trays of seahorses available in almost every herbal supply shop in Chinatown, San Francisco. There are usually two different types of whole, dried seahorses, sold in pairs to be used in home made formulas: "dark" seahorses and "light" seahorses. According to storeowners, the dark seahorses were bought from providers in South America, and the light seahorses were bought from providers in China. Dark seahorses were priced at about $15 to $25 per pair, and light seahorses were priced at about $3 per pair.

Saarman wasn't able to talk freely with storeowners, because they fear repercussions for illegally obtained seahorses, and are unwilling to risk their business to provide information to researchers. Instead, she sent representatives into shops to purchase seahorses for various hypothetical illnesses. Saarman then sampled the dried seahorses and identified the species. The wildlife trade monitoring network, TRAFFIC, provides a seahorse guide - using this key she was able to identify the seven specimens collected from the shops. The small white seahorses were of three different species (H. kelloggi, H. spinosissimus, and H. trimaculatus) all found in the indo-Pacific. The large dark seahorses were in fact the 'giant' Pacific seahorse or H. ingens. It was interesting to find that the 'giant' Pacific Seahorse is significantly more valuable in San Francisco than the Asian species.

Tracking down H. ingens

Although H. ingens is frequently sold for Chinese medicine, no one knows where they are harvested. The population size, how different populations interact, and how genetically diverse the populations are, is also unknown. Taking a tiny step toward better understanding of seahorses, Saarman completed a new research project using genetic markers to examine the relationship between giant pacific seahorses in different parts of their range.

Saarman looked at genetic diversity in a small part of the H. ingens mitochondrial DNA in the hopes that patterns of variation found in the DNA could be enough to tell her where the seahorses come from. She looked at 86 different specimens from five different eastern Pacific locations (California, Mexico, Guatemala, Ecuador, and Peru). For each seahorse she analyzed the same 438 base pair fragment of mitochondrial DNA.

Unfortunately, the differences in DNA between seahorses in different locations were small, suggesting either movement of individuals between populations (contrary to expectations), or that the differences were too small to show up in the analysis. Only seahorses from California and Mexico were different enough to distinguish between the two. It is possible that very recent separation of populations created changes in DNA profiles that were unrecognizable in the mitochondrial DNA fragment she looked at.

Although the fragment of DNA Saarman studied wasn't able to tell her where undocumented seahorses were coming from, there are other even smaller bits of DNA with more genetic diversity that could help find the answer. These are called microsatellites. Because microsatellites change rapidly, two populations separated for even a small amount of time will result in detectable differences. As a contracted technician at the California Academy of Sciences, Saarman is now working on developing microsatellite markers that she believes will elucidate the true evolutionary story of the 'giant' Pacific seahorse.

-Norah Saarman

comments

hello, my self karan veer singh working as scientist in INDIA,at national bureau of fish genetic resources,lucknow. i working on seahorses ( microsatellite work)mainly indo pacific spp. i know the difficulties that lies in this type of work,i would like to join as i would get lot of help from you people as i am freshly introduced to seahorses and in india we have to work a lot on them, thanks and best of luck

posted by karan veer singh | 2008-01-23 01:28:26

If you are interested in contacting me, please email nsaarman@biology.ucsc.edu. Thanks!!!

posted by Norah | 2008-11-04 16:37:00

DNA based identification of seahorse (Syngnathoides : Hippocampus) using cytochrome c oxidase subunit I (coI) variation Karan Veer SINGH # , W. S. LAKRA, A. Gopalakrishnan, & R. C. SOBTI* National Bureau of Fish Genetic Resources, Canal Ring Road P.O. Dilkusha, Lucknow * Dept of Biotechnology, Panjab University, Chandigarh # communication kvsingh@nbfgr.res.in Phone 91-522-2442440 Introduction The seahorse in Indian Ocean are represented by five species of seahorses belonging to one genus Viz. Hippocampus kuda Bleeker 1852, H. histrix Kaup 1856, H. fuscus Ruppell 1838, H .trimaculatus Leach 1814 and H. kelloggi Jordon and Snyder 1902 and also H. spinosissimus to have suspected distribution in Indian waters (Lourie 2004 & Lipton and Thangaraj 2002). These species shows overlapping features during morphometric diagnosis and its very difficult sometimes to clearly separate out as one species with H.kuda, H fuscus and H. spinosissimus as one group while H. trimaculatus, H kelloggi and H. histrix as separate species. Thrity four species are believed to be true species inhabiting the world (Lourie et. al., 1999). Seahorses are moderately well defined but the Indo-Pacific species are difficult to classify. H. kuda is a default name for at least 10 distinct species since seahorses are so flexible in their appearances identification is often very difficult. We were able to clearly identify, H. kuda, H. trimaculatus, H. spinosissimus, H. histrix, and H. kelloggi based on the morphometric characteristics. And few samples as a group with overlapping feature for H borboneinsis / H. fuscus / H. kuda into one group with more abundant ones are the H. kuda. DNA barcoding It has been proposed that the gene sequence of the cytochrome c oxidase subunit I (COI) gene could serve as the basis for a global identification system for animals, (Hebert et al. 2003). The suggestion was that each species would be delineated by a particular sequence or a tight cluster of very similar sequences. The total length of cytochrome oxidase I in vertebrates is about 1545 base pairs (bp), and a region about 650 bp long commencing near the start of the COI reading frame was nominated as the ‘barcode’ region.We analysed 655 bp region of the mitochondrial cytochrome c oxidase subunit I gene (COI) using universal primers. Finclipings sample were used for DNA isolation followed by PCR and sequencing. DNA Barcodes for all putative fish species collected in the Indian Ocean waters were constructed using softaware like Bioedit, MEGA4, and compared the resultant molecular data with field-based morphological identifications, and additional sequence data obtained from GenBank. There was high congruence between morphological and molecular classification, and COI provided effective species-level discrimination for nearly all putative species. The utility of DNA barcoding for species identification using mitochondrial cytochrome c oxidase subunit I (COI) has been established from a number of invertebrate and in vertebrate taxa (Hebert et. al. 2003, 2004). Although DNA barcoding aims to develop species identification systems, some phylogenetic signal was apparent in the data. Supporting morphological evidence for each of these being separate species. We conclude that COI sequencing, or 'barcoding', can be used to identify fish species. Sequences has been submitted to the NCBI GenBank Accession Nos : FJ176578, FJ176581, FJ176586 - FJ176592, EU930325 - EU930330. Barcoding Animal Life: Cytochrome c Oxidase Subunit 1 Divergences among Closely Related Species Paul D. N. Hebert; Sujeevan Ratnasingham; Jeremy R. deWaard Proceedings: Biological Sciences, Vol. 270, Supplement: Biology Letters. (Aug. 7, 2003), pp.S96-S99. DNA barcoding Australia’s fish species Robert D. Ward,Tyler S. Zemlak, Bronwyn H. Innes, Peter R. Last and Paul D. N. Hebert Phil. Trans. R. Soc. B (2005) 360, 1847–1857 Biological Identifications through DNA Barcodes Paul D. N. Hebert; Alina Cywinska; Shelley L. Ball; Jeremy R. deWaard Proceedings: Biological Sciences, Vol. 270, No. 1512. (Feb. 7, 2003), pp. 313-321.

posted by karan veer singh | 2009-07-30 02:29:53

post a comment