aqua, International Journal of Ichthyology Larval development of laboratory-reared Green Mandarinfish, Synchiropus splendidus (Teleostei: Callionymidae) Matthew L. Wittenrich1, Carole C. Baldwin2, Ralph G. Turingan1 1) Florida Institute of Technology, Department of Biological Science, 150 W. University Blvd., Melbourne, FL, 32901, USA 2) Division of Fishes, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, DC 20013-7012, USA * Corresponding author: Matthew L. Wittenrich, Phone: 321-674-7222, Fax: 321-674-7222. Email: [email protected] Received: 24 September 2009 – Accepted: 3 January 2010 Abstract 20 Tagen DPH statt. Die Ontogenese, einschließlich der Larvae of Synchiropus splendidus (Herre, 1927) were Knochenentwicklung, wird vom Schlupf bis zum Jugendsta- obtained from natural spawnings of two wild-collected dium beschrieben. pairs of adults. Egg and larval development of S. splendidus is similar to that described for other callionymids. Eggs Résumé measure 0.8 mm in diameter and hatch after 13-16 hours Des larves de Synchiropus splendidus (Herre, 1927) ont at 26°C. Newly hatched larvae measure 1.56 ± .04 mm NL été obtenues de pontes naturelles de deux couples d’adultes and begin feeding four days post-hatching (DPH) at 1.74 capturés dans leur milieu. Le développement de l’oeuf et ± .06mm NL. The notochord accounts for 20% of the de la larve de S. splendidus est semblable à celui décrit pour body length at 12 DPH. Larvae lack heavy ventral pig- d’autres Callionymidés. Les oeufe font 0,8 mm de dia mè - mentation, but have three distinctive lines of pigment on tre et éclosent au bout de 13-16 heures, à 26°C. Les larves the posterior portion of the body – one along the base of qui viennent de naître font 1,56 ± ,04 mm NL et com- the dorsal fin, one along the base of the anal fin, and one mencent à se nourrir 4 jours après l’éclosion à la taille de along mid-body. Larvae exhibit an ontogenetic color 1,74 ± ,06 mm NL. La notocorde représente 20% de la change from yellow to orange prior to settlement. Inci- longueur du corps 12 H aprés l’éclosion. Les larves n’ont dence of settlement was highest between 16-20 DPH. pas de forte pigmentation ventrale, mais ont trois lignes Ontogeny, including osteological development, is des - nettement pigmentées sur la portion postérieure du cribed from hatching to the juvenile stage. corps – une le long de la base de la dorsale, une le long de la base de l’anale et une le long du milieu du corps. Les Zusammenfassung larves montrent un changement de couleur ontogénique Die untersuchten Larven von Synchiropus splendidus (Herre, du jaune à l’orange avant fixation. La survenue de cette fi - 1927) entstammten dem natürlichen Laich von zwei in der xation a lieu majoritairement entre 16 à 20 heures après Natur gefangenen erwachsenen Paaren. Die Ei- und Larven - l’éclosion. L’ontogénie, y compris le développement ostéo - entwicklung ähnelt bei S. splendidus der von anderen lo gique, est décrite depuis l’éclosion jusqu’au stade juvénile. Callionymiden beschriebenen. Die Eier haben einen Durchmesser von 0,8 mm; bei 26° C schlüpfen die Larven Sommario nach 13 bis 16 Stunden. Die frisch geschlüpften Larven Larve di Synchiropus splendidus (Herre, 1927) erano ot - haben eine Länge von 1,56 ± 0,04 mm NL und fangen 4 tenute in condizioni naturali da due coppie di adulti raccolti Tage nach dem Schlupf (DPH = days post-hatching) an zu in natura. Lo sviluppo embrionale e larvale di S. splendidus è fressen, bei einer Länge von 1,74 ± 0,06 mm NL. Nach 12 simile a quello descritto per gli altri callionimidi. Le uova mi - DPH macht die Rückensaite (Notochord) 20 % der Körper- su rano 0.8 mm di diametro e schiudono dopo 13-16 ore a länge aus. Bei den Larven fehlt eine starke ventrale Pigmen- 26°C. Alla schiusa le larve misurano 1.56 ± 0.04 mm NL e tation, doch weisen sie drei deutliche Pigmentlinien im hin- cominciano a nutrirsi 4 giorni dopo la schiusa (DPH, days teren Teil des Körpers auf – eine an der Basis der Rücken- post-hatching) quando raggiungono 1.74 ± 0.06 mm NL. flosse, eine an der Basis der Afterflosse und eine in Längsrich- Dopo 12 DPH la notocorda comprende il 20% della lun - tung in der Körpermitte. Im Laufe der Ontogenese zeigen die ghezza del corpo. Le larve mancano di pigmentazione ven- Larven einen Farbwechsel von Gelb zu Orange kurz vor der trale, ma posseggono tre marcate linee pigmentate sulla parte Ansiedlung. Diese findet am wahrscheinlichsten nach 16 – po steriore del corpo – una lungo la base della pinna dorsale, 7 aqua vol. 16 no. 1 - 20 January 2010 Larval development of laboratory-reared green mandarin, Synchiropus splendidus (Teleostei: Callionymidae) un’altra lungo la base della pinna anale e la terza sulla parte MATERIALS AND METHODS me diana del corpo. Le larve mostrano una variazione onto - Larvae described herein were obtained from natural ge nica della colorazione dal giallo all’arancio prima dell’in se - spawnings of two wild-collected pairs of Synchiropus dia mento. Il grado di insediamento era più elevato a 16-20 splendidus. Eggs were collected shortly after spawning DPH. L’ontogenesi, incluso lo sviluppo osteologico, è de - and transferred to cylindrical incubation tanks (15 l) scritta a partire dalla schiusa fino agli stadi gio vanili. provided with gentle aeration from an open-ended air diffuser. Two days after fertilization embryos were INTRODUCTION transferred to 150 l black conical rearing tanks and Dragonets of the genus Synchiropus Gill, 1859, are reared at densities of no more than 1.5 larvae l-1. small, bottom-dwelling fishes from the tropical Water quality in each rearing tank was maintained by Indian and Pacific Oceans and comprise approxi- a biological filter tower, ultraviolet sterilizer, and pro- mately 27 species (Fricke 1983). The Green Man- tein skimmer with an exchange rate of 0.5 l-1 min. darin, Synchiropus splendidus (Herre, 1927), is a small Natural seawater filtered through a 10 µm closed- (6 cm) species that occurs in shallow protected pore filter was maintained at 26°C, salinity 35 ppt, lagoons and reefs in the western Pacific; it is distrib- pH 8.2, NH3 and NO2 < 0.02 ppm, and NO3 < 10 uted from the Ryukyu Islands of southern Japan to ppm (Red Sea marine lab test kit). Water changes New Caledonia and Australia (Myers 1999). were performed every other day by replacing 10% of Together with S. picturatus (Peters, 1877), S. stellatus the total system water from the sump. Photoperiod Smith, 1963, and S. ocellatus (Pallas, 1770), S. splen- was maintained at 14 hrs light and 10 hrs dark with didus is hugely popular in the world aquarium trade. two 40W fluorescent bulbs (6500 K) mounted 20 To date, all specimens offered in the trade are cap- cm above the water surface. Greenwater was main- tured from the wild, and concern over the sustain- tained in the rearing tanks during all trials by adding ability of this selective fishery has been raised (Sadovy 0.5 ml of diluted Nannochloropsis oculata algae paste et al. 2001, Vincent & Sadovy 1998). (Reed Mariculture) to the tanks each morning. Despite initial successes in the propagation and Larvae were provided with rotifers (Brachionus pli- rearing of Synchiropus spp. (Wittenrich 2009; Mai catilis, average lorica length ranged from 180-277 2000, 2006; Sadovy et al. 2001; Wilkerson 1996), µm) and copepod-dominated, size-sorted wild plank- limited descriptive information is available pertain- ton (55-90 µm) as initial feed 4 DPH and subse- ing to the development of these popular fishes. quently provided with larger copepod-dominated, Improved larval rearing techniques and knowledge size-sorted wild plankton (110-500 µm) 8 DPH of the life-history requirements of Synchiropus have through settlement. Prey density of rotifers was main- recently enabled continuous production of larval tained from 3-5 DPH at 10 ml-1 and subsequently and juvenile S. splendidus for observation. Sadovy et lowered to 5 ml-1 until 12 DPH when rotifers were al. (2001) described the fishery, reproduction, and removed from the diet. Wild plankton was main- early life history of S. splendidus. Herein, we expand tained at 2 ml-1 throughout the larval period. on their description of larval development and Beginning at hatching (0 DPH), 20 larvae were describe for the first time the development of cer- sampled from the rearing tank, initially every other tain osteological features. We describe morphology, day and subsequently every 2-6 days, anesthetized color pattern, and growth of larvae and juveniles to with tricaine methanosulphonate (MS-222) and 50 days post-hatching (DPH). Additionally, we fixed in 5% seawater-buffered formalin for 24 hours compare larval S. splendidus to known larvae of before transfer to 70% ethanol for later analysis. other Callionymidae. Developmental characters Notochord length (NL) or standard length (SL) of may be of value in future phylogenetic investiga- freshly collected larvae was measured using an ocular tions of callionymid fishes. We hope that this infor- micrometer fitted to a stereomicroscope prior to mation will prove useful in providing a rearing pro- preservation. Twelve larvae from samples taken at 5, tocol for future scientific investigations and hatch- 7, 9, 12, 15, 17 and 23 DPH were cleared and ery applications. Aquaculture potential and proto- stained following the methods described by Potthoff cols will be addressed in future work. Cultured fish (1984). Elements of the viscerocranium were do indeed exhibit long-term success in aquariums described following Hunt Von Herbing et al. (1996), and commercial production is underway at one US- Liu (2001) and Moteki (2002).