Mouth Growth and Prey Selection in Juveniles of the European Long‐snouted Seahorse, Hippocampus guttulatus

Abstract

Seahorses are ambush predators that swallow the prey through their tubular snout. In order to better understand mouth growth and its effect on prey preference by juveniles of the seahorse Hippocampus guttulatus, experimental assays were carried out by feeding juveniles (0-30 -d after male's pouch release [dar]) on a mixture of rotifers, Brachionus plicatilis; Artemia nauplii; and copepods; Acartia tonsa. Mouth development in juveniles was accomplished by growth of upper and lower jaws, which were linearly correlated with juvenile length, whereas mouth width (MW) and height (MH) grew exponentially with juvenile size. Additionally, MW and MH were exponentially correlated, so that the transversal section of the mouth increased linearly with juvenile age and length. Gut content and Ivlev' selectivity index demonstrated a permanent rejection of rotifers for the whole experimental period and a clear preference of juveniles for copepods from 0 to 15 dar and for Artemia nauplii afterwards. Results also suggest that juveniles are able to ingest larger prey than those provided as the limiting factor in prey ingestion was not MW, as for many marine fish larvae, but mouth area. A tentative feeding schedule to successfully feed H. guttulatus juveniles from 0 to 30 dar is proposed.

Histological development of the long‐snouted seahorse Hippocampus guttulatus during ontogeny

“…At birth, eyes were already pigmented and the visual system was fully functional, allowing H. guttulatus to be excellent visual predators (Blanco & Planas, ; Celino et al ., ; Roos et al ., ; Van Wassenbergh et al ., ). The fovea, a depression in retinal tissue, is a specialized area for high acuity vision in many vertebrates.…”

“…The growth of seahorse juveniles in the present study was in accordance with previous studies (Planas et al ., ). Major developmental changes occurred during the first month of development, coincident with the duration of the planktonic phase of the species after male pouch release (Blanco & Planas, ; Olivotto et al ., ).…”

Application of Effective Day Degrees in the Assessment of Stable Isotope Patterns in Developing Seahorses under Different Temperatures

“…Seahorse juveniles were fed for 30 days according to an optimized feeding schedule for growth and survival maximization [34]. Three feeding periods were established from male's pouch release (day 0): Copepods were cultivated in 250-500 L tanks at 26-27 • C and 38 salinity and fed every two days on mixtures of the microalgae Isochrysis galbana and Rhodomonas lens (10 3 cells mL −1 ).…”

Application of Effective Day Degrees in the Assessment of Stable Isotope Patterns in Developing Seahorses under Different Temperatures

“…Immediately after male's pouch release, juveniles from each batch were randomly transferred (5 Seahorse juveniles were fed for 30 days according to an optimized feeding schedule for growth and survival maximization [34]. Three feeding periods were established from male's pouch release (day 0):…”