Early developmental stages of the sea urchin Sphaerechinus granularis (Lamarck, 1816) (Echinoidea: Toxopneustidae)

ABSTRACT

Early developmental stages of echinoids have been thoroughly studied but continue to offer remarkable insights for the current understanding of biological sciences. The sea urchin Sphaerechinus granularis has been commonly tested by exposing its developmental stages to a variety of stressors, but current descriptions about developmental time and morphological features are lacking. This study aimed to describe for the first time the embryonic and larval development of Sphaerechinus granularis with detailed light micrographs and morphological measurements. Adult sea urchins were obtained and spawned to rear embryos and larvae in laboratory conditions at 19°C until competence. Development was monitored by observing individuals in a light microscope and taking microphotographs for description. Embryonic development from fertilization to two-arm pluteus lasted 72 h post fertilization and larvae reached a competent stage 33 days post fertilization. Skeletal post oral rods in larvae from this research lacked lateral spines, which were illustrated by other authors in previous studies. This intraspecific variation should be further studied to understand changes in functional morphology of populations from the same species. Development from fertilization to metamorphosis of S. granularis can be achieved under laboratory conditions in less than 40 days. This original article offers the first detailed description for both embryonic and larval stages of this species, including light microphotographs, and can be used as a comprehensive description of S. granularis larval development, as well as a baseline to establish a rearing protocol.

KEYWORDS:

• Embryogenesis
• larval biology
• planktotrophic larvae
• echinopluteus
• intraspecific variation

Acknowledgements

Funding for DGS’s short research duration at Universidad de La Laguna was awarded through financial aid from the Departamento de Bienestar Estudiantil, Universidad Nacional de Costa Rica. The authors are grateful for assistance provided by Beatriz Alfonso, Adriana Rodríguez, Sara González-Delgado and Saray Pérez during the experiment. We also thank Éinar Hernández-Alfonso for insightful comments on early versions of this manuscript, as well as two anonymous reviewers for their valuable input that improved this research article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Departamento de Bienestar Estudiantil: [Grant Number ].