Female maturation, egg characteristics and fatty acids profile in the seahorse Hippocampus guttulatus
Planas, M. | Quintas, P. | Chamorro, A. | Silva, C.
Knowledge of the biology and ecology of seahorses (Hippocampus spp.) is scarce, but has been increasing in recent years due to their conservation status. Captivity breeding programmes can be a valuable source of information on the reproductive biology of seahorses. A captive broodstock of Hippocampus guttulatus Cuvier 1829 was established in 2006 and kept under natural-like photoperiod and temperature. Female maturation was studied during the whole reproductive season in 2007. Most egg clutches were released from May (17°C; 15L:9D) to October (18°C; 13L:11D), with peak releases occurring in June-August (20°C; 16L:8D-14L:10D). Throughout the study, four egg morphotypes were found; two regression equations were proposed for estimating egg/yolk volume based on measurements of egg and yolk biometrics. Female weight was positively correlated with yolk volume/egg volume ratio (Y v/E v) (r s =0.523, n =21, P <0.05) but not with E v or Y v. Egg dry weight (567±141μg) was correlated with Y v (r s =0.384, n =31, P <0.05). Mean clutch size and clutch biomass were 242±142 eggs and 137±87mg dry weight, respectively. Clutch size was positively correlated to female weight (r s =0.479, n =25, P <0.05). Inter-clutch intervals (days) were affected by temperature (°C) as described by the following equation: Interval =357.55e⁻⁰.¹²⁸³ Temp. Estimated inter-clutch intervals at 16, 18 and 20°C were 45.9, 35.5 and 27.5 days, respectively. Egg total lipids accounted for 31.9±3.1% dry weight. Absolute lipid content in eggs was correlated with egg dry weight (r s =0.907, n =41, P <0.001) and Y v (r s =0.384, n =41, P <0.5). In decreasing order of relative percentage, the most important fatty acids, were 18:1n9, 16:0, 18:2n6, 20:5n3, 18:0 and 22:6n-3. The level of n-3 HUFA was 18.5±0.7% (38.4±3.3mg/g dry weight). The profile of fatty acids in eggs resembled that displayed by the broodstock diet (enriched adult Artemia).
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