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Reproductive husbandry of the weedy sea dragon, Phyllopteryx taeniolatus, at the Aquarium of the Pacific in Long Beach, California

By Kristy L. Forsgren, Aquarium of the Pacific, Long Beach, California. Reprinted with permission.

Weedy Seadragon in the wild. Photo courtesy of saspotato via flickr.

Author’s Note: “They are a precious species that is best left in its natural environment.  In addition to the difficulty in obtaining them, they are extremely expensive to maintain and require an enormous amount of time!  When I took care of the seadragon collection at the Long Beach Aquarium, it was my full-time job caring for and maintaining their exhibits.  Often times I worked more than 40 hours a week and almost 15+ hours a day at one point once I was able to breed them!”

Abstract

The weedy sea dragon, Phyllopteryx taeniolatus, is a member of the family Syngnathidae, which includes the seahorses, pipehorses, and pipefishes. The weedy sea dragon is a monotypic species endemic to southern coastline of Australia. Male sea dragons become pregnant after female sea dragons transfer eggs onto a specialized patch of skin on the underside of the male’s tail. Due to the difficulty and cost associated with maintaining sea dragons in captive environments, reproductive success and rearing of hatchlings has never been documented. During the summer of 2001, two weedy sea dragons became pregnant at the Aquarium of the Pacific. Embryos were incubate for 34
days (X + SD = 34 + 12.73, N=2) and hatched over a 13-day period (X + SD = 13.5 + 9.19, N=2). A total of 40 juveniles were raised, 35 were distributed to zoos and aquariums throughout the United States, and the others are on exhibit with the adults at the Aquarium of the Pacific. While there may be speculation regarding the effect of seasonality on sea dragons, the Aquarium of the Pacific believes that their successful breeding may have been the result of simulating natural environmental conditions.

Introduction

The weedy sea dragon, Phyllopteryx taeniolatus, is a monotypic species endemic to the southern coastline of Australian, from Sydney on the east coast to Perth on the west coast and to the tip of Tasmania and inhabit rocky reefs, seaweed beds, and sea grass meadows (Kuiter, 2000). These extraordinary fish have elaborate appendages on their head and body that resemble blades of algae (Kuiter, 2000). This camouflage allows them to ambush their planktonic prey of larval fishes and mysid shrimp (Kuiter, 2000).

Weedy Seadragon with eggs. Photo courtesy of saspotato via flickr.

Paternal brooding is a peculiar reproductive strategy characteristic of syngnathids in which the males incubate developing embryos. Females transfer eggs to a specialized patch of skin on the underside of the male’s tail (Kuiter, 2000). Embryos are incubated for several weeks (Kuiter, 2000). Hatching is staggered and occurs over several days aiding in the dispersal of the offspring and thereby decreasing competition for food (Kuiter, 2000).

The difficulty involved with collecting sea dragons, and providing them with live food have contributed to the challenges associated maintaining them in public aquaria. During the summer of 2001, two weedy sea dragon successfully received eggs from a female. A total of 40 juveniles were raised, 35 have been distributed to zoos and aquariums throughout the United States making this the first transfer of aquarium-bred weedy sea dragons in the world. The remainder of the juveniles are on display with the adult population at the Aquarium of the Pacific. The reproductive success at the Aquarium may have been associated with simulating seasonality by changing the temperature and photoperiod of the exhibit on a monthly basis.

Methods

The Aquarium of the Pacific’s weedy sea dragon population consists of five males and two females. The sea dragon habitat consists of a 1.2 m deep cylindrical exhibit tank that contains 5200 liters of water with a calculated turnover of 40 minutes. The exhibit bottom is covered with 1.3 – 2.5 cm Mexican Beach Pebble (Blue Daisy Cement Products, Inc., Gardena, California). Artificial macro algae are cemented to dead rock and artificial Sargassum floats at the surface.

The exhibit is lit with two 250-watt, 20,000 Kelvin metal halide light fixtures and a 30-watt lamp used as a night-light when exhibit lighting is off. The life support components include an ultraviolet sterilizer, a UMI barrel heat exchanger, a sand filter, protein skimmer, and a bio-tower.

Water quality parameters were checked weekly and adjustments were made to maintain healthy ideal conditions; salinity was kept at 33 ppt, pH was between 8.2 and 8.3, alkalinity between 2.5 and 3.0, and ammonia was below 0.05 mg/L, nitrite was below 0.080 mg/L and nitrate were kept below 0.005 mg/L.

Water temperature and day length data for southern Australia were obtained from the Australian Oceanographic Data Centre, these data were converted into a schedule of monthly seasonal changes (Table 1). The metal halides and heat exchanger were manually changed to regulate seasonal variation within the exhibit.

In order to care for the pregnant males and hatchlings, a holding basket for pregnant males, a modified tank for raising hatchlings, and an automatic feeding bucket were constructed. A cylindrical basket (56 cm x 81 cm) was constructed using 100 micron screening and reinforced with 1.3 cm plastic mesh, this basket was hung at the surface of the sea dragon exhibit.

An acrylic tank (37.9 liters) was modified and placed on the same filtration as the sea dragon exhibit (Figure 1). A 2.5 cm bulkhead was installed into the top center of the tank and an overflow drain was plumbed with 2.5 cm PVC. Silicone was used to attach 500 micron screening onto the inside of an acrylic frame that was placed at a 40o angle over the inside of the bulkhead, a thin flexible plastic was glued into the bottom corners of the tank, creating a rounded surface on the bottom. Three sides of the tank were covered with a blue gel (Just Blue, #79, LEE Filters, Hampshire, England).

An automatic feeding bucket was made and programmed to feed the sea dragon hatchlings (Figure 2). A 2.5 cm bulkhead was plumbed into the bottom of a plastic 7.6 liters bucket, a PVC thread to hose thread adapter connected the bulkhead to a programmable garden timer and an adjustable hose valve was attached to the garden timer and a barbed nipple with a piece of clear vinyl tubing was attached. The bucket was hung above the modified juvenile tank and programmed per manufacture’s instructions.

Food was supplemented prior to feeding the sea dragons. Brine shrimp nauplii, (Artemia salina) were enriched with Selco (Inve Aquaculture, Belgium) 24 hours before feeding. Mysids (Mysidopsis bahia) were enriched with Selco-ed Artemia nauplii and frozen Cyclop-eeze product (Argent Laboratories, Redmond, Washington). Frozen mysis shrimp (Tropical Marine Centre Ltd., England) were supplemented with vitamins (VitaFish, Marine Enterprises Intl., Maryland).

Results

Spawning occurred from May 2001 to late June 2001 resulting in two male weedy sea dragons successfully receiving clutches of eggs. Incubation varied from 25 days to 43 days (X + SD = 34 + 12.73 days, N=2) and hatching varied 7 days to 20 days (X+SD = 13.5 + 9.19, N=2). Of the first weedy sea dragon’s hatchlings, 68.1% survived and 65.8% of the second male’s young survived.

Juvenile Weedy Seadragons

Discussion

Seasonal variations may have contributed to the weedy sea dragons successfully breeding at the Aquarium of the Pacific in Long Beach, California by stimulating reproductive behavior. Breeding occurred during the spring and early summer of 2001, when water temperatures ranged between 16.1 C and 17.8 C and the photoperiod was between 13 and 14 hours of daylight.

Seasonality was accomplished by altering the water temperature and photoperiod each month according to a schedule based on southern Australia’s regional seasonality. Breeding occurs in the wild between October and January when water temperature varies from 18 C to 22 C and photoperiod is between 13-14 hours (Powell, 1999). Due to the differences in seasonality between the northern and southern hemispheres, a direct seasonality schedule of southern Australia would have resulted in the exhibit being dark at times during the Aquarium’s open hours. Therefore, a few alterations had to be made in order to adapt Australia’s seasonal changes to Long Beach, California. The day length schedule and consequently the water temperature schedule, was adapted to meet guest needs while still accomplishing seasonal fluctuations. No adverse affects were observed due to these environmental changes.

Several aquariums have observed the weedy sea dragon’s mating behavior fewer have witnessed egg transfers. The Aquarium of the Pacific is the first aquarium worldwide to successfully raise weedy sea dragon hatchlings. Mating behavior and egg droppings have been observed throughout the year in facilities that do not implement a seasonality schedule similar to that of the Aquarium of the Pacific’s, several observations resulting from life support malfunctions resulting in a temperature change (Powell, 1999). However, at the Aquarium of the Pacific, reproductive behaviors increase in frequency and intensity associated with seasonal temperature increase and extended day length.

Weedy sea dragon mating behavior observed at the Aquarium of the Pacific involved several dragons swimming 2-3 cm apart with their tails curled outward. These interactions have been observed between males and between males and females, but never between two females. An interaction that has been frequently observed is one in which the animals move their heads toward, then away from one another, a propulsion similar to that of two opposing magnets being forced together. No physical contact actually occurs and shortly after this behavior, the sea dragons separate. Although the nature of these interactions are unknown, they may be related to territory disputes or mate selection.

On the morning of May 5, 2001, a pregnant weedy sea dragon carrying approximately 50 eggs was discovered. A second dragon became pregnant on June 23, 2001, with approximately 75 eggs. The males were placed in a floating basket that remained in the exhibit for the duration of the pregnancy preventing the need to transport or acclimate them to another location. The basket prevented physical contact with other dragons thus protecting the eggs and made daily observations of the dragons and the developing embryos possible.

Pregnant sea dragons refused to consume frozen mysids; therefore they were fed only live mysids (Mysidopsis bahia) consuming nearly 1500 mysids per day for the first four weeks. Later, the dragon’s appetite decreased to approximately 100 mysids per day, and they discontinued eating while the young were hatching. The dragons were returned to the exhibit after the young hatched and they began eating live mysids the following day. Frozen mysids were consumed within a week.

Incubation of eggs has been estimated to be 6 weeks, although young began hatching at an average of 34 days (34 + 12.73, N=2) after egg transfer and hatching of the entire clutch averaged 13.5 days (13.5 + 9.19, N=2). The hatchlings were scooped out of the male’s basket in a small container to avoid being netted or touched while transferring them into the flow through tank. The first hatchlings were 2 cm in length and were born curled around a large pink yolk sac. The hatchling’s mouths and fins were underdeveloped at birth but began developing quickly as the yolk sac was being absorbed. Sea dragons born later were more developed and had smaller yolk sacs.

At seven days of age, the first hatchling’s yolk sacs had been completely absorbed and they began swimming and eating one-day old Artemia nauplii. Sea dragons that hatched after this time were ready to swim and eat. In addition to continuous daily feedings, an automatic feeding bucket was set to feed five times throughout the night.

Although it is not known how much food was actually consumed during the night, the feeding bucket provided food during the evening and early morning. Artemia nauplii were fed to the hatchlings until brine shrimp remnants no longer appeared in the dragon’s fecal pellets. This occurred about 5 days after first eating nauplii at that point, the hatchlings began eating one-day old mysids (Mysidopsis bahia). As the young sea dragons grew, the size of the food they were eating was increased, allowing them to feed more efficiently. The dragons began eating 2-day old mysids at 10-19 days old, 3-4 day-old mysids when they were 19-33 days of age, and 5-7 day-old mysids at 33-42 days of age. Adult mysids were eaten when the juveniles were 12 weeks of age.

When the juveniles were five months old, several were shipped to other zoos and aquariums within the United States. Each dragon was triple bagged with approximately 11.4 liters of exhibit water supersaturated with oxygen. Dragons were packed in a styrofoam insulated container lined with plastic and a frozen gel pack, then shipped overnight to their respective destinations.

It is important to continue sharing the knowledge gained from sea dragons in public aquariums. The life cycle of the sea dragon is more attainable than ever before and with continued research, the mysteries of the sea dragon can be unlocked. In addition to fulfilling biological interest, the sea dragons amaze aquarium visitors each day, making them increasingly important ambassadors to the sea in particular to the waters of Australia.

Table 1. Aquarium of the Pacific’s schedule of monthly water temperature (+/- 0.1 to 1.5o C in Adelaide, South Australia, Australia) photoperiod and day length changes for the sea dragon exhibit.

Figure 1. Diagram of modified acrylic tank used to raise weedy sea dragon hatchlings at the Aquarium of the Pacific.

Figure 2. Overnight feeding bucket used to raise weedy sea dragon hatchlings at the

Aquarium of the Pacific.

Acknowledgments

The generous support and enthusiasm of the Aquarium of the Pacific has made the breeding and rearing of the weedy sea dragons was possible. I’d like to thank the husbandry and life support staff for their assistance, patience and support. I would especially like to thank Sandy Trautwein, Curator of Fishes and Invertebrates, who always believed in accomplishing this unique event and to Charlie, my husband, who has shared my devotion and enthusiasm for sea dragons.

References

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Kuiter, Rudie. 2000. Seahorses, pipefishes and their relatives. TMC Publishing.

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MacKay, Bruce. YEAR? Seadragons in wild and captive environments. Today’s

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