Breeding the Weedy Sea Dragon (Phyllopteryx taeniolatus), a first successful attempt Elevage du dragon de mer commun (Phyllopteryx taeniolatus) en Aquarium : premier succès




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Breeding the Weedy Sea Dragon (Phyllopteryx taeniolatus), a first successful attempt
Elevage du dragon de mer commun (Phyllopteryx taeniolatus) en Aquarium : premier succès

Isabel Koch, Thomas Seitz



Zoologisch-botanischer Garten Wilhelma, Stuttgart, Germany




Abstract
Weedy Sea Dragons (Phyllopteryx taeniolatus / Syngnathidae) from the temperate waters of the south coast of Australia have become very famous aquarium inhabitants within the last years, because of their strange appearance. Up to now all specimens were caught wild or tank-reared from pregnant males caught in the wild. True breeding of this species in an aquarium was not possible though many other species in the same family are bred in tanks without problems.

In April 1999, one male sea dragon, part of a group of seven individuals in the Stuttgart Aquarium for two, was observed carrying eggs at the base of his tail. The complete birth process was observed until the birth of five young. Information is also provided on the tank, feeding, behaviour and socialization with other species in the tank.




Résumé

Venant des eaux tempérées de la côte sud de l’Australie, les dragons de mer communs (Phyllopteryx taeniolatus), famille des Syngnathidae, rencontrent depuis plusieurs années dans les Aquariums un succès phénoménal auprès du public en raison de leur apparence très étrange, de leur faculté de camouflage et de leur grande beauté. Jusqu’à présent, tous ces poissons provenaient directement de captures dans le milieu naturel, ou bien d’élevages effectués à partir de mâles prélevés en mer et portant des œufs. Bien que plusieurs espèces d’hippocampes et de syngnathes aient déjà été élevées sans problème majeur en Aquarium, l’élevage du dragon de mer commun n’avait pas encore été possible en captivité.

En avril 1999, à Stuttgart, un dragon de mer commun mâle, faisant partie d’un groupe de sept individus présenté à l’Aquarium depuis deux ans, fut observé avec environ 120 œufs sous la base de la queue. Le développement complet des œufs a ainsi pu être étudié et suivi, jusqu’à la naissance de cinq dragons de mer.

Introduction

Since February 1997, a group of seven Weedy Sea Dragons (Phyllopteryx taeniolatus / Syngnathidae) has been living at the Aquarium of the Zoological and Botanical Garden Wilhelma in Stuttgart. They were purchased from Ascidian (Perth/Australia), arrived as adult or sub-adult animals in Stuttgart. Thanks to information from other colleagues and from Roger Wilson, the fish were treated with great caution and quarantined as recommended. The Sea Dragons proved to be quite resistant: even when the chiller failed they had no severe problems and were moved into the exhibition tank two months later.




The Tank

2000 l of artificial seawater (Instant Ocean) at an average temperature of 17°C and 1.022 specific gravity, 250 W HQI 12 h/d plus natural day- and moonlight, permanent water clearance by UV light (36 W), slow filtration (2x800 l/h) and very slow current, nitrate around 20 mg/l. Decoration: gravel, natural rockwork, artificial kelp-like algae (Carl Gage) and natural algae, which soon grew on the artificial ones (species unknown). Measurements of the tank: 1.5 m long, 1.3 m wide and 1.0 m high, semi-oval shape.



Co-inhabitants:
Invertebrates: Polychaetes, sponges, brittle stars and ascidians (species not identified). Vertebrates: One Talma (Chelmonops truncatus), a group of Potbellied Seahorses (Hippocampus abdominalis) and - during 2.5 years - two Pigmy Leatherjackets (Brachaluteres jacksoniensis).
The Pigmy Leatherjackets were nice friendly inhabitants of the tank and died for unknown reasons. One was still alive at the time of pregnancy and had to be removed from the tank during those weeks, because of nibbling at the eggs. The Talma was also removed despite its lack of interest in the eggs. The Potbellied Seahorses are perfect companions for Sea Dragons: They occupy different places in the tank from the Dragons and do not interact with them (except when they sometimes attach with their tails to the Sea Dragons if the latter remain too close to a suitable attaching structure) and they feed as slowly as the Sea Dragons.
What we have observed so far is that mating occurs in some relation to the phases of the moon, mostly three or four days after the full moon. The main season for mating is late spring/early summer, but some of this behaviour is displayed all year.


Report of the Pregnancy





  • 6th April 1999: Surprise: a male was observed with 120 eggs at the base of his tail! Eggs whitish with a little orange inside. Male displays no more interaction with group, refuses feeding, rolling himself slowly in the current.

  • 2nd week: Eggs 50% of their size embedded in the skin, male continues as before.

  • 3th week: At the end of this week two-thirds of the eggs are lost (reason unknown).

  • 4th week: Male frequently changes place, starts feeding and interacting with the group.

  • 5th week: Only 25 eggs left.

  • 6th week: 15 eggs left; first structure visible inside.

  • 7th week: 5 eggs left; eyes visible, father separated, 5 young hatched (25 mm long) but died after 2-4 days.


Feeding & Behaviour

The only fact that makes it difficult to keep Weedies in an aquarium is providing them with suitable food: they refuse to feed on anything other than their native food or live mysiid shrimps - both sometimes not easy to get for non-coastal-aquariums.


Weedy Sea Dragons are not aggressive towards their own species or other fishes. Only from time to time do males seem to fight each other gently with their snouts (especially during mating time), but without any of them getting hurt. Swimming side by side with curved tails is also part of male fighting and mating behaviour. In both cases the colours become brighter and the dark spot at the cloaca turns to purple-red. The Dragons do not seem to be very upset during this phase, and continue feeding as usual.
For mating it seems that the female needs a great deal of time to chose a suitable male - in case of success they perform a perfectly synchronized dance swimming parallel from bottom to surface several times. The egg transfer was not observed, as most of the mating happens during the night. In our case there was no change of skin structure on the tail of the male, only the female seemed to be a little thicker than usual, with a slightly swollen cloaca.
What we have observed so far is that mating occurs in some relation to the phases of the moon, mostly three or four days after the full moon. The main mating season is in late spring/early summer, but some of this behaviour is displayed all year.


Discussion

Since, to date, there is little experience with successful egg transfers and even less with complete pregnancy of sea dragons, it would be important to have more breeding groups of sea dragons to obtain more information. This is why we should think about keeping larger groups of Sea Dragons, not just small groups or pairs.


But even though the Weedy Sea Dragon is not rare in his natural habitat, it seems to be impossible in the past two years to get additional specimens. As the dragons already present in various aquariums are getting older and older, nobody can say what influence this may have on the chances for breeding success!





Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)


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