Early development of the longsnout seahorse Hippocampus reidi (Syngnathidae) within the male brood pouch.

Fertilized and unfertilized eggs and embryos of the longsnout seahorse Hippocampus reidi were collected at different stages of development and provided the basis for a description of morphological development from fertilization until release from the paternal pouch. Images of fertilized eggs, as well as their rupture after a few minutes in seawater are reported for the first time. The yolk sac transitioned from ovoid to spherical shape and was reabsorbed progressively until release. The tail began rising from the surface of the deuteroplasm while embryos were in the egg envelope. Embryos lacked a primordial fin fold and developed some species characteristics, such as rays in the dorsal fin, before resorption of the yolk sac. At release, juvenile seahorses were in an advanced stage of development even if they lacked important adult characteristics, such as ring plates and coronet. The tail was not prehensile in juveniles at release; a small caudal fin was present, although this fin is lost in adults.

Development of short-snouted seahorse (Hippocampus hippocampus, L. 1758): osteological and morphological aspects.

Information about early development after male release lags behind studies of juveniles and adult seahorses, and newborn seahorses, similar in shape to adults, are considered juveniles or fry. During early life, Hippocampus hippocampus present behavioural (shift in habitat, from planktonic to benthic) and morphological changes; for this reasons, the aims of this study are to define the stage of development of H. hippocampus after they are expelled from the male brood pouch and to establish direct or indirect development through an osteological analysis. The ossification process was studied in 120 individuals, from their release to 30 days after birth. To analyse the osteological development, Alcian Blue-Alizarin Red double staining technique for bone and cartilage was adapted to this species. At birth, H. hippocampus presents a mainly cartilaginous structure that ossifies in approximately 1 month. The bony armour composed of bony rings and plates develops in 10 days. The caudal fin, a structure absent in juveniles and adult seahorses, is present at birth and progressively disappears with age. The absence of adult osteological structure in newborns, like coronet, bony rings and plates, head spines and components allowing tail prehensile abilities, suggests a metamorphosis before the juvenile stage. During the indirect development, the metamorphic stage started inside brood pouch and followed outside and leads up to reconsider the status of H. hippocampus newborns.

Development of seahorse (Hippocampus reidi, Ginsburg 1933): histological and histochemical study.

Biological aspects and global demand for aquarium promote seahorses as new species with high potential for commercial purposes; however, the low newborn survival rate represents the main bottleneck of seahorses farming. In this study, the organogenesis of the Hippocampus reidi was analysed from release until the 30th day after birth, using histological and histochemical approaches. To study the stages of their early life, 360 individuals were killed, sectioned, and stained with haematoxylin and eosin, periodic acid-Schiff, and Sudan Black B techniques. At birth, mouth and anus were open, the swim bladder inflated, and the visual system highly developed. Among the results, it was emphasized the presence of the yolk sac until the 2nd day after birth, the loops of the intestine to accommodate its elongation, and the ability of the larvae to absorb lipids in the anterior and posterior tract of the intestine. A short time (7/8 days) between reabsorption of yolk sac and formation of gonads was registered, with primordial follicles visible from the 10th day after birth. For the first time, organogenesis in H. reidi was described in detail; seahorses underwent a marked metamorphosis, and the indirect development observed in this species lead up to reconsider the term "juvenile" used for H. reidi during this period.

Occurrence of skeletal deformities and osteological development in red porgy Pagrus pagrus larvae cultured under different rearing techniques.

The present study describes the osteological development and the occurrence of skeletal deformities in red porgy Pagrus pagrus larvae in relation to the intensification of the rearing system. Eggs obtained from natural spawning were cultured under two different rearing systems: intensive (100 eggs l⁻¹) in 2000 l and semi-intensive (mesocosm) system (5 eggs l⁻¹) in 40,000 l conico-cylindrical tanks. Fish samples were periodically collected along the development from hatching to juveniles at 95 days post hatching (dph). Osteological development, meristic counts and the presence of skeletal deformities were evaluated. Despite the external appearance of the juveniles being similar to wild standards, X-ray studies revealed a high number of fish (semi-intensive: 37·8%; intensive: 45·5%) with skeletal deformities. Regardless of the rearing system, no significant interaction was found between the per cent of the most common deformities, axial deviations (lordosis and presence of fused vertebrae). Cranial deformities and kyphosis incidences, however, were significantly higher in intensively cultured P. pagrus. Also, the fused vertebrae in these fish were located mainly in the caudal area instead of pre-haemal area for semi-intensively reared P. pagrus. Moreover, a significant interaction was found between the total number of vertebrae and the type of rearing system used; fish from the intensive system showing a higher number of fish with an extra vertebrae (10 abdominal + 15 caudal). Present results suggest a relationship among feeding sequence, osteological development and deformity incidence and location in P. pagrus larvae.