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Dangerous Marine Animals
The What, Where, Avoiding and Otherwise Dealing with Biological Stinger, Biters, Pokers as a Diver.

Sea Urchins: Some Toxic, Some Spiky, Others…  



By Bob Fenner



Of all marine organism groups that divers are likely to avoid, urchins are good candidates. The ones with long, pointed spines are obviously dangerous to get too close to; can and do puncture… through wet suits, even thick booties given enough mechanical force. What may be news to you is that several of these “aquatic hedgehogs” are actually venomous; some very much so.

Look; don’t touch! Toxopneustes pileolus (Lamarck 1816), Flower Urchin. Indo-Pacific. Very toxic to touch.  To 12 cm. in diameter. One showing venomous spines and extension of searching tube feet Here in N. Sulawesi. 


What are Echinoids?
Sea Urchins and Sand Dollars, Class Echinoidea

Friends and associates who know me to be an avid diver frequently ask whether I'm concerned with potential underwater encounters with sharks, barracudas, giant squids and the like. My standard reply is that it is much more dangerous time-wise driving on the freeway. However, in the way of moments spent underwater, Sea Urchins are some of the most realistically harm/hurtful organisms.

Urchins perform invaluable service as scavengers of over-abundant, fouling algae; preventing overgrowth of benthic habitat, excluding corals and more. For divers, some also present considerable risk.

Classification: Taxonomy, Relation with Other Groups

Urchins and their allies the sand dollars and heart urchins make up the Class Echinoidea in the phylum Echinodermata. You're familiar with this phylum's other four living Classes, the Sea Stars, Brittle stars, Sea Cucumbers and Sea Lilies & Feather Stars. Collectively the echinoderms or spiny-skinned animals are grouped as radially symmetrical, with a water-vascular system (ambulacral) responsible for their peculiar locomotory tube feet. They have a true body cavity (coelom) supporting a calcareous internal or external skeleton... in the case of urchins, called the test.

The Class Echinoidea including the Urchins are discoidal, ovate or globose echinoderms having bodies covered with spines and no arms. The name Echinoidea is actually Greek for "like a hedgehog" referring to these spines. Their mouths are aboral, that is, directed against the substrate. Distributed between these spines are beak-like pedicellariae, specialized tube feet used for cleaning and defense. Some of these structures are termed globeriferous pedicellariae (now that's a mouthful!) and contain poison glands. About 800 species of urchins have been described.

Examples (to avoid):

Vanna… White? No, Vanna, OW!

            Several years back, friend MichelleM was visiting out on Kona (Hawai’i’s Big Island for you haoles); when we decided to have a night swim in front of the main drag (Ali’i Dr.), just south of the King Kam. I had warned her to not stand up twixt the sandy beaches to the ends, north and south; as the urchins come out and scour the rocks next to the concrete breakwater at night. As the lack of luck would have it, she did stop a bit short on the return leg and got poked but good by the local wana (pronounce “van nah”; Hawaiian for urchins).

            We did a quick look, see at the local stores to see if any had a handy sharp tool for easing the broken spine segments out, but gave up after a cursory go with a straightened out large metal staple. I told Mich not to worry; as the pieces would dissolve in a few to several days… and she limped along with the help of NSAIDs. And yes; the spines did dissolve in time; sans infection.

Mich’s nemesis: Diadema paucispinum (A. Agassiz 1863), a Long-Spined Sea Urchin. Pacific; Hawai'i and islands of the South Pacific. To about twelve inches maximum diameter, with spines. Usually in 60 or more feet of water on a vertical surface. Common name means "few spines" which you may not agree with if you get poked but good. Kona pix.


Isla Socorro by Night:

            In the early 1970’s I had the good fortune of meeting up with the Huffman family maintaining their aquariums at home and offices in San Diego, CA. They owned a fab “six pack” boat, the Reward, 78 feet in the water; which occasionally they used themselves for outings al sur to the Islas Revillagigedos; and a guyot called Hurricane. Occasionally they allowed me to haul along as a safety diver and erstwhile boat helper; including some tropical fish collecting. It will come as no surprise to you if you’ve been night diving that many fishes “lay down to sleep” on the bottom, near rock and reef structure; providing a great boon for collectors willing to dive nocturnally.

            On one such night, the freshly recruited skipper, JohnF; went out with me looking for juvenile Clarion Angelfish… and though he was a more than competent hunter/diver, ended up disoriented, laying directly down on a group of Diadema urchins… puncturing his suit, knee and upper leg.

            JohnF’s intake of spines was far more numerous, deeper and involved larger pieces than Michelle’s… And he was adamant that he was going to “dig them out”, no matter how much I tried to dissuade him. He did cut into himself, lancing with a single edge razor, and gingerly (gripping too hard just breaks the spines) pulled out much of the remnants. We applied a topical antibiotic cream after washing the damaged area with hydrogen peroxide, and that was the end of below water action for the skipper that trip.

Secretive by day, Diadema mexicanum A. Agassiz 1863, Needle Sea Urchin; comes out to scour the reef at night. Costa Rica (Pacific side).


Lembeh Strait Coleman Shrimp Burns:

            One benchmark photo experience for macro divers in the coral triangle involves searching symbiotic (toxic) fire urchins and their Coleman Shrimp, Zebra Crab, Squat Lobster… hosts. Often the close ups are really close… involving the use of diopters with a need for proximity to their subjects… and the urchins in question here are quite social, living and moving about in a grouping. As you’ve likely surmised, this is a recipe for mis-engagement. In the several times I’ve been to Lembeh; I’ve noted as many occasions of these “burning” encounters on unwary divers hands, arms and exposed legs.

A pair of Periclimenes colemani ensconced on their customized urchin home… The shrimp eat away at the tube feet and remove spines to suit the urchin’s test (exoskeleton) for their purpose… The urchin providing food and habitat… and transport!

A vacant Asthenosoma varium Grube 1866, the Pinhead Sea Urchin. Family Echinothuriidae. Indo-West Pacific; Red Sea to Indonesia. Test size to six inches in diameter; spines to twelve. Nocturnal; generally hiding out of the light by day. Walks on spines and/or tube feet. This one in S. Leyte; P.I.


For Spine Punctures:

            Easier to say than do; but once you realized you’ve been punctured, do your level best to not over-react by touching the area. As calmly as you’re able, surface and once on land or boat, expose the area for a clear view. IF spine parts are exposed, GENTLY pull on them to remove. IF too deeply lodged, it is best to leave small pieces embedded, treating the pierced area as a wound to prevent infection. Soap and water will do; followed by flushing with fresh water. NSAIDs are of use for pain relief and anti-inflammation action.  Hot water immersion (some folks advocate for vinegar, lime juice, urine…) may lessen pain.

            Deep wounds and ones where spines are lodged in joints are another matter; and should you feel faint, nauseous, have breathing troubles, muscle fatigue or even paralysis; you’re encouraged to seek medical help. 

Pedicellariae: Chemical Burns:

            For toxic exposures, some sources encourage the immersion of the affected area in very warm water for a few tens of minutes for denaturing probable protein toxins. IF there is attached urchin material on the wound, this is best removed using a bit of shaving cream and a simple throw-away razor.

Avoiding Troubles:

            Most issues with urchins are  avoided by simply being aware of their presence and your own body while in the water. Take care whenever entering and exiting ocean shallows to assure there are none to be encountered. At all times watch where your body goes… with current; especially during night dives; when it’s very easy to lose your sense of hydrostatic balance.

            Mmm; and there are danger-free urchins, like Pencils and Slates… though, as always, it’s best for all to not be touched. Simply put: Don’t handle marine life and you won’t be mal-affected by it.

Still to be left untouched, pencil and slate urchins bear non-piercing spines.

Heterocentrotus mammillatus (Linnaeus 1758), the (Red) Pencil Urchin. Indo-Pacific; Red Sea to Hawai'i. Nocturnal, hiding in crevices by day in depths to thirty feet, emerging at night to rasp rocks. To one foot overall diameter. Hawai'i picture.  Eucidaris thouarsii (Valenciennes 1846), Slate Pencil Urchin. Family Cidaridae. To 10.2 inches in diameter. Sea of Cortez to Ecuador and Galapagos Islands. Ten rows of 5-8 variously sharp/dull club-like spines. Found on rocky shore shallows to 150 meters depth. Galapagos pic.




            So; as with all dangerous marine animals; forewarned is fore-armed: be aware of, and avoid coming in physical contact with too-spiny and toxic sea urchins. This is easily done given good buoyancy control, awareness of your surroundings; and the usual good placement of your hands and body en toto. Should you get barely spined unintentionally there is likely little you can and should do other than ameliorative analgesic action. Too many, too deep spines breaking off in you or too extreme effects of duration call for prompt medical attention.

Warm colors, sharp spines? Watch out! Astropyga radiata (Leske 1778), the Radiating Hatpin Urchin. Indo-Pacific; Africa to Hawai'i. Out during both day and night. On sand to rubble substrates. One among many (with a juv. Lutjanus sebae hitchhiking for safety) in Manado, N. Sulawesi, Indo.


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