Pygmy Seahorses: Life Aquatic

Text and photos by Richard Smith, Ph.D.
In the gloomy depths at 100 Ft on a coral covered wall in Komodo, Indonesia, I caught my first glimpse of a pygmy seahorse. Like most first experiences with these tiny animals, it was fleeting, and I wasn’t able to observe them as I would have liked.
When I had this encounter in 2002, researchers knew next to nothing about pygmy seahorse biology, and only one species was named. Little did I know that a decade later I would be the first person in the world to complete a doctorate on the biology of these diminutive fishes and would subsequently name new species of them. Since the turn of the millennium, there has been a flurry of new pygmy seahorse discoveries.
We now have seven named species across the Indo-Pacific. Georges Bargibant, a researcher in New Caledonia, discovered the first pygmy seahorse when he was collecting a gorgonian coral for the Noumea museum and found a pair of tiny seahorses on its surface. Bargibant’s pygmy seahorses are extreme habitat specialists that live only on the surface of Muricella
gorgonians. Also known as sea fans, these corals can reach monumental sizes, measuring a couple of meters across.
In the gloomy depths at 100 Ft on a coral covered wall in Komodo, Indonesia, I caught my first glimpse of a pygmy seahorse. Like most first experiences with these tiny animals, it was fleeting, and I wasn’t able to observe them as I would have liked.
When I had this encounter in 2002, researchers knew next to nothing about pygmy seahorse biology, and only one species was named. Little did I know that a decade later I would be the first person in the world to complete a doctorate on the biology of these diminutive fishes and would subsequently name new species of them. Since the turn of the millennium, there has been a flurry of new pygmy seahorse discoveries.
We now have seven named species across the Indo-Pacific. Georges Bargibant, a researcher in New Caledonia, discovered the first pygmy seahorse when he was collecting a gorgonian coral for the Noumea museum and found a pair of tiny seahorses on its surface. Bargibant’s pygmy seahorses are extreme habitat specialists that live only on the surface of Muricella
gorgonians. Also known as sea fans, these corals can reach monumental sizes, measuring a couple of meters across.

Denise’s and Walea pygmies also live in close association with certain corals. Through my research I have found Denise’s pygmy seahorses living with 10 different kinds of gorgonians, including whip coral bushes. The Walea pygmy, however, lives only with beige soft corals and in only one small bay in central Indonesia. Other pygmies are much more cosmopolitan in their habitat choices. Pontoh’s, Satomi’s and Coleman’s pygmies live almost anywhere on the reef, which makes finding and studying them more challenging because we have to scour more places to find them. My colleagues and I found a new pygmy species in 2018; we named this resident of Japan and Taiwan japapigu.
My involvement in the naming of Hippocampus japapigu came about after I visited Hachijō-jima, a tiny island just a 45-minute flight from Tokyo. In 2013 I was in Okinawa for a fish biologist conference, but I also planned a side trip to look for an odd pygmy seahorse that I had seen in a picture. Japapigu looks similar enough to Pontoh’s pygmy seahorse that no one had further investigated the odd fish in the photo; having seen many pygmies over the years, I was sure this seahorse was a different species. Not being a taxonomist, I was thwarted for a few years until I met seahorse taxonomist Graham Short at another conference, and we started talking about this unusual pygmy.
My involvement in the naming of Hippocampus japapigu came about after I visited Hachijō-jima, a tiny island just a 45-minute flight from Tokyo. In 2013 I was in Okinawa for a fish biologist conference, but I also planned a side trip to look for an odd pygmy seahorse that I had seen in a picture. Japapigu looks similar enough to Pontoh’s pygmy seahorse that no one had further investigated the odd fish in the photo; having seen many pygmies over the years, I was sure this seahorse was a different species. Not being a taxonomist, I was thwarted for a few years until I met seahorse taxonomist Graham Short at another conference, and we started talking about this unusual pygmy.

On much closer inspection, Japapigu turned out to be quite different:
Genetic analysis showed that it split off from all other pygmies around 8 million years ago.
Pygmy seahorses are very small, measuring half an inch to just over an inch (1.4 to 2.7 centimeters) in length. The smallest, Satomi’s pygmy seahorse, barely stretches across a dime. In addition to their size, true pygmies are slightly different morphologically from their larger cousins. As adaptations to their small sizes, pygmy seahorses have a single gill opening at the back of the head, and males brood their fry in a special pouch within the body cavity rather than in a pouch on the tail like other seahorses.
To confuse matters, there are also a few species of tiny non-pygmy seahorses, such as the dwarf seahorse found in parts of the southeastern United States; these are morphologically tiny versions of the larger seahorses. Like all other seahorses, pygmies have the reproductive quirk of male pregnancy. In a process known as egg hydration, females internally ready a clutch of eggs about four days before they are due to mate. Daily dances and behavioral rituals with their
partners allow pairs to synchronize their reproductive cycles, minimizing the time between broods to produce as many young as possible. When a pair mates, the female transfers her unfertilized eggs into the male’s brood pouch. The male fertilizes the eggs as they go into his pouch, as such he can be certain that he is the father of each baby he carries, which is almost unique in the animal kingdom. For this reason the male seahorse becomes pregnant and puts so much effort into raising the fry.
My research focused on the biology and conservation of Bargibant’s and Denise’s pygmy seahorses, the two gorgonian-living pygmies. I investigated their population sizes, the
impacts of diver interactions, and how they use the space on gorgonian corals. One of the most unexpected aspects of my research, however, was their social and reproductive biology. Although reproductive biology is fairly well-documented in other seahorses, no one had studied reproduction in pygmy seahorses. For much of my work I was based at a dive resort with an extraordinarily rich house reef where these seahorses are common.
Over six months I dived several times a day to study different groups of Denise’s pygmies, discovering that once settled on a gorgonian as a tiny juvenile, they wouldn’t leave it again. After I selected a group at a suitable depth that enabled me to visit frequently, I began to collect data. I took close-up images under the trunk of each pygmy, which allowed me to identify the sex of the animals: Females have a tiny raised circular pore, and males have a slitlike opening from where the babies will eventually emerge.
Genetic analysis showed that it split off from all other pygmies around 8 million years ago.
Pygmy seahorses are very small, measuring half an inch to just over an inch (1.4 to 2.7 centimeters) in length. The smallest, Satomi’s pygmy seahorse, barely stretches across a dime. In addition to their size, true pygmies are slightly different morphologically from their larger cousins. As adaptations to their small sizes, pygmy seahorses have a single gill opening at the back of the head, and males brood their fry in a special pouch within the body cavity rather than in a pouch on the tail like other seahorses.
To confuse matters, there are also a few species of tiny non-pygmy seahorses, such as the dwarf seahorse found in parts of the southeastern United States; these are morphologically tiny versions of the larger seahorses. Like all other seahorses, pygmies have the reproductive quirk of male pregnancy. In a process known as egg hydration, females internally ready a clutch of eggs about four days before they are due to mate. Daily dances and behavioral rituals with their
partners allow pairs to synchronize their reproductive cycles, minimizing the time between broods to produce as many young as possible. When a pair mates, the female transfers her unfertilized eggs into the male’s brood pouch. The male fertilizes the eggs as they go into his pouch, as such he can be certain that he is the father of each baby he carries, which is almost unique in the animal kingdom. For this reason the male seahorse becomes pregnant and puts so much effort into raising the fry.
My research focused on the biology and conservation of Bargibant’s and Denise’s pygmy seahorses, the two gorgonian-living pygmies. I investigated their population sizes, the
impacts of diver interactions, and how they use the space on gorgonian corals. One of the most unexpected aspects of my research, however, was their social and reproductive biology. Although reproductive biology is fairly well-documented in other seahorses, no one had studied reproduction in pygmy seahorses. For much of my work I was based at a dive resort with an extraordinarily rich house reef where these seahorses are common.
Over six months I dived several times a day to study different groups of Denise’s pygmies, discovering that once settled on a gorgonian as a tiny juvenile, they wouldn’t leave it again. After I selected a group at a suitable depth that enabled me to visit frequently, I began to collect data. I took close-up images under the trunk of each pygmy, which allowed me to identify the sex of the animals: Females have a tiny raised circular pore, and males have a slitlike opening from where the babies will eventually emerge.

One group of four individuals I studied included three males and one female — a perfect composition for investigating their social and reproductive biology. Over the years I had observed many groups with anodd number of animals, which made me wonder what would happen to the odd one out. All previous research has found seahorses to be monogamous,
with neither male nor female mating again while the male was pregnant. This pair-bonding often lasts a season or even a lifetime, so a group with three males and one female would
allow fascinating insight. After two months of recording every interaction for several hours each day, I found that pygmies are somewhat more risqué than their larger cousins.In their battles over the female, the three males were quite pugnacious and would frequently attempt to strangle each other with their tails. One epic battle involved all three males and
resulted in one of them having a sprained tail for several days afterward. Like giraffes, the males also tried to use their necks to push each other over in displays of dominance. I was lucky enough to witness births on several occasions, with remating occurring just a few minutes later. I unexpectedly discovered that the female would alternately mate with the two largest males. With a 12-day gestation period, the female would mate with the second male six days after mating with the first male. This cycle continued for several pregnancies. The third male never had any offspring during my study and was relegated to watching these mating behaviors, presumably hoping that one of the other males would eventually
die and free up a spot for him. Like many marine creatures, pygmy seahorses have a precarious place in our oceans. I found them to have some of the lowest population densities of any seahorses yet studied. Furthermore, the species that directly rely on gorgonians or soft corals for their existence require a healthy host. Reefs throughout their ranges are heavily degrading, destroying the fragile hosts for pygmies. Divers can help through thoughtful and careful interactions with these delicate creatures. Do not touch the animal or its habitat, and avoid disturbing them with bright lights and excessive use of strobes.
As is the case with many marine animals, we still have much to learn about pygmies. My colleagues and I are working on naming yet another new species of pygmy seahorse, which appeared in a most unexpected location. Keep your eyes open while diving — most pygmies have been found by eagle-eyed recreational divers and dive guides, revealing new
species to the scientific community at an unprecedented rate. AD
with neither male nor female mating again while the male was pregnant. This pair-bonding often lasts a season or even a lifetime, so a group with three males and one female would
allow fascinating insight. After two months of recording every interaction for several hours each day, I found that pygmies are somewhat more risqué than their larger cousins.In their battles over the female, the three males were quite pugnacious and would frequently attempt to strangle each other with their tails. One epic battle involved all three males and
resulted in one of them having a sprained tail for several days afterward. Like giraffes, the males also tried to use their necks to push each other over in displays of dominance. I was lucky enough to witness births on several occasions, with remating occurring just a few minutes later. I unexpectedly discovered that the female would alternately mate with the two largest males. With a 12-day gestation period, the female would mate with the second male six days after mating with the first male. This cycle continued for several pregnancies. The third male never had any offspring during my study and was relegated to watching these mating behaviors, presumably hoping that one of the other males would eventually
die and free up a spot for him. Like many marine creatures, pygmy seahorses have a precarious place in our oceans. I found them to have some of the lowest population densities of any seahorses yet studied. Furthermore, the species that directly rely on gorgonians or soft corals for their existence require a healthy host. Reefs throughout their ranges are heavily degrading, destroying the fragile hosts for pygmies. Divers can help through thoughtful and careful interactions with these delicate creatures. Do not touch the animal or its habitat, and avoid disturbing them with bright lights and excessive use of strobes.
As is the case with many marine animals, we still have much to learn about pygmies. My colleagues and I are working on naming yet another new species of pygmy seahorse, which appeared in a most unexpected location. Keep your eyes open while diving — most pygmies have been found by eagle-eyed recreational divers and dive guides, revealing new
species to the scientific community at an unprecedented rate. AD
Posted in Alert Diver Spring Editions
Tagged with Conservation, Fish Identification, Sea Horses, Hippocampus
Tagged with Conservation, Fish Identification, Sea Horses, Hippocampus
Categories
2020
January
February
Group Fitness at the PoolHow to Rescue a Distressed diver at the SurfaceHow to manage Near-DrowningNo Sit-ups no problem How to manage MalariaHow to manage Oxygen Deficiency (Hypoxia)What to do when confronted by a sharkHow to manage Scombroid PoisoningHow to perform a Deep Diver RescueHow to perform One-rescuer CPRHow to perform a Neurological Assessment
March
DAN’s Quick Guide to Properly Disinfecting Dive GearCOVID-19 : Prevention Recommendations for our Diving CommunityGermophobia? - Just give it a reasonable thoughtScuba Equipment care – Rinsing and cleaning diving equipmentCOVID-19 and DAN MembershipFurther limitations imposed on travels and considerations on diving activitiesDAN Membership COVID-19 FAQsLancet COVID-19 South African Testing SitesCOVID-19 No Panic Help GuideGetting Decompression Sickness while FreedivingDown in the DumpsCardiovascular Disease and DivingDelayed Off-GassingDiving after Dental surgeryDiving with Multiple MedicationsPygmy Seahorses: Life AquaticAfrica DustCOVID-19 Myth BustersScuba Units Are Not Suitable Substitutes for VentilatorsDisinfection of Scuba Equipment and COVID-19Physioball Stability Exercises
April
COVID-19 AdvisoryScuba Equipment Care - Drying & Storing Your GearTransporting Diving Lights & BatteriesHow to Pivot Your Message During a CrisisTourism Relief FundCOVID-19 Business Support ReviewDiving After COVID-19: What We Know TodayEUBS-ECHM Position Statement on Diving ActivitiesPart 2: COVID-19 Business Support ReviewPress Release
May
Diving in the Era of COVID-19Dive Operations and COVID-19: Prepping for ReturnCOVID-19 & Diving Activities: 10 Safety RecommendationsCOVID-19: Surface Survival TimesThe Philippines at its FinestThe Logistics of ExplorationThe Art of the Underwater SelfieShooter: Douglas SeifertFAQs Answered: Disinfecting Scuba EquipmentStock your First-Aid KitResearch and OutreachCovid-19 ResearchOut of the BlueEffects of Aspirin on DivingThe New Pointy end of DivingDiving and Hepatitis CCaissons, Compressed-Air work and Deep TunnellingPreparing to Dive in the New NormalNew Health Declaration Form Sample Addressing C-19 IssuesDiving After COVID 19: What Divers Need to Know
June
Travel Smarter: PRE-TRIP VACCINATIONSAttention-Deficit/Hyperactivity Disorder and DivingCOVID-19: Updated First Aid Training Recommendations From DANDiving with a Purpose in National Marine SanctuariesStay Positive Through the PandemicFor the Dive Operator: How to Protect Your Staff & ClientsStudying Deep reefs and Deep diversAsking the Right QuestionsLung squeeze under cold diving conditions
July
Dive DeprivationVolunteer Fish Surveys: Engage DiversDAN Member Profile: Mehgan Heaney-GrierTravel Smarter: Don’t Cancel, Reschedule InsteadDive Boat Fire SafetyRay of HopePartner ExercisesDiving at AltitudeAluminium ExposureHip FracturesAcoustic NeuromaGuidelines for Lifelong Medical Fitness to DiveNew Dive Medical Forms
August
Women in Diving: Lauren Arthur, Conservationist & Natural History Story TellerWomen in Diving: Dr Sara Andreotti White Shark ResearcherTiming ExerciseWomen in Diving: The Salty Wanderer, Charlie WarlandWomen in Diving: Beth Neale, Aqua soul of freedivingWomen in Diving: Diving and spearfishing Diva, Jean HattinghWomen in Diving: Zandile Ndhlovu, The Black Mermaid
September
October
Freediving For ScienceStep Exercises with CardioFluorescence Imaging help Identify Coral BleachingChildren and DivingThe Watchman device and divingScuba Diving and Factor V Leiden gene mutationNitrogen Narcosis at shallow depthsOil and Particulates: Safe levels in Breathing Air at depthDive Principles for Coping with COVID-19The Importance of a Predive Safety CheckTalya Davidoff: the 'Plattelandse Meisie' Freediver
2019
February
April
May
DAN Press ReleaseYour Dive Computer: Tips and tricks - PART 1Your Dive Computer: Tips and tricks - PART 2Aural HygieneDCS AheadHow Divers Can Help with coral conservationRed Tide and shellfish poisoningDiving after Kidney DonationDiving with hypertrophic cardiomyopathyEmergency Underwater Oxygen Recompression
June
July
September
October
November
Exercise drills with DowelsHeart-rate TrainingCultivating ConservationTRavel Smarter : Evaluating an unfamiliar Dive operatorChallenging the Frontiers of Decompression ResearchTravel Smarter: Plan for Medical EmergenciesWhen should I call my Doctor?DAN Student Medical Expense CoverageAdvice, Support and a LifelineWetsuits and heat stressDiving after Chiropractic adjustments
2018
April
Flying after pool diving FAQLung squeeze while freediving FAQDiving after Bariatric surgery FAQMarine injuries FAQVasovagal Syncope unpredictable FAQIncident report procedure FAQDiving after knee surgery FAQDiving when in RemissionDive with orbital Implant FAQInert gas washout FAQOxygen ears FAQPost Decompression sicknessChildren and diving. The real concerns.Diving after SurgeryPhysiology of Decompresssion sickness FAQDiving and regular exerciseGordon Hiles - I am an Underwater Cameraman and Film MakerScuba Air QualityBreath-hold diving. Part 3: The Science Bit!Compensation Legislation and the Recreational DiverCape Town DivingFive pro tips for capturing better images in cold waterThe Boat Left Without You: Now What?
May
When things go wrongEmergency Planning: Why Do We Need It?Breath-hold diving: Running on reserve -Part 5 Learning to RebreatheSweet Dreams: When Can I Resume Diving Post Anaesthesia?Investing in the future of reefsTo lie or not to lie?THE STORY OF A RASH AFTER A DIVEFirst Aid KitsTaravana: Fact or Falacy?
June
Oxygen Unit MaintenanceKnow Your Oxygen-Delivery Masks 1Know Your Oxygen-Delivery Masks 2Emergency Oxygen unitsInjuries due to exposure - HypothermiaInjuries due to exposure - Altitude sicknessInjuries due to Exposure - Dehydration and other concernsHow to plan for your dive tripThe Future of Dive MedicinePlastic is Killing our ocean
September
Return to DivingDiagnoses: Pulmonary blebSide effects of Rectogesic ointmentDiving with ChemotherapyReplacing dive computers and BCDsCustomize Your First-Aid KitPlan for medical emergenciesHow the dive Reflex protects the brain and heartDry suits and skin BendsAltitude sickness and DCSScuba Diving and Life Expectancy
2017
March
April
Incident Insight: TriageA Field Guide to Minor MishapsSnorkels: Pros & ConsTime & RecoveryMedication & Drug UseDiving with CancerNitrox FAQCOPD FAQHyperbaric Chamber FAQJet Lag FAQHydration FAQAnticoagulant Medication FAQFluid in the Ear FAQEye Surgery FAQElderly Divers FAQNitrogen FAQHealth Concerns FAQMotion Sickness FAQMicronuclei FAQ
June
August
2016
February
March
Breath-Hold Diving & ScubaReturn to Diving After DCITiming Exercise & DivingHot Tubs After DivingSubcutaneous EmphysemaIn-Water RecompressionDiving at AltitudeFlying After DivingDiving After FlyingThe Risks of Diabetes & DivingFlu-like Symptoms Following a DiveHand & Foot EdemaFrontal HeadachesBladder DiscomfortLatex AllergiesRemember to BreatheProper Position for Emergency CareAches & PainsCell Phones While DrivingSurfers Ear Ear Ventilation TubesDealing with Ear ProblemsDiving with Existing Ear InjuriesPerforated Ear DrumENT SurgeryUnpluggedCochlear ImplantsPortuguese Man-of-WarJellyfish StingsLionfish, Scorpionfish & Stonefish EnvenomationsStingray Envenomation Coral Cuts, Scrapes and RashesSpeeding & Driving Behaviour
June
Newsflash! Low Pressure Hose DeteriorationItching & rash go away & come back!7 Things we did not know about the oceanMigraine HeadacheAttention Deficit Disorder Cerebral Vascular AccidentEpilepsyCerebral PalsyHistory of SeizuresMultiple Sclerosis Head TraumaBreast Cancer & Fitness to Dive IssuesLocal Allergic ReactionsSea LiceHow ocean pollution affects humans Dive Fatality & Lobster Mini-Season StatisticsPregnancy & DivingReturn to Diving After Giving BirthBreast Implants & DivingMenstruation During Diving ActivitiesOral Birth ControlBreast FeedingPremenstrual SyndromeOsteoporosisThe Aftermath of Diving IncidentsCompensation Legislation & the Recreational DiverNoise-Induced Hearing LossLegal MattersThe Nature of Liability & DivingDAN Legal NetworkWaivers, Children & Solo DivingHealthy, but overweight!Taking Medication while Scuba DivingGetting Fit for the Dive SeasonBone Considerations in Young DiversAsthma and Scuba DivingHepatitisDiving with HyperglycemiaShoulder PainDiving After Spinal Back Surgery
August
Hazard Identification & Risk AssessmentCaring For Your People Caring For Your FacilitiesCaring For Your BusinessScuba Air Quality Part 1Scuba Air Quality Part 2Chamber Maintenance Part 1Chamber Maintenance Part 2The Aging Diver Propeller SafetyRelease The PressureDon't Get LostMore Water, Less Bubbles13 Ways to Run Out of Air & How Not To7 Mistakes Divers Make & How To Avoid ThemSafety Is In The AirHow Good Is Your Emergency Plan
2015
January
March