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Early life cycle and effects of microalgal diets on larval development of the spiny rock-scallop, Spondylus limbatus (Sowerby II, 1847)

Abstract:

The Spondylus limbatus fishery in most of the eastern Pacific is restricted due to a decline in natural populations. The aquaculture production of seedlings applying proper larviculture techniques could contribute to the restoration programs of this valuable fishing resource. However, literature of proper culture techniques for S. limbatus is scarce. We describe the embryonic, larval and post-larval development of S. limbatus raised in the laboratory, and the effect of two monoalgal (Chaetoceros gracilis, CG; and Isochrysis galbana, IG) diets and a combination of different cell ratios (3CG:1IG, 1CG:3IG and 1CG:1IG) on growth and survival of S. limbatus larvae. Fertilized eggs had a diameter of 60.2±1.3μm. Swimming D-larvae, with a shell length of 98.0±2.2μm, were obtained within 26h; and pediveligers (185.2±3.9μm) in 12days. At day 16 (>200μm) pediveligers metamorphosed into postlarvae and the dissoconch appeared. After metamorphosis, we did not observe byssus production and post-larvae were capable of remaining free (in plantigrade stage) for 2-3months, with crawling movements until settlement by cementation took place on hard substrates. The post-larval settling behavior is suggested to be characteristic of the genus Spondylus. The algal diet experiment revealed significantly larger larvae (164.0±1.8μm) and faster growth (5.5±0.0μmday-1) with 3CG:1IG treatment, while survival was higher when fed CG alone (18.8±4.3%). The embryogenesis and larval development of S. limbatus are similar to other Pectinidae species. The combination of C. gracilis and I. galbana (3:1) could be used as an appropriate diet for S. limbatus larval culture. Future research will be focused on improving survival of competent S. limbatus larvae by implementing water treatment systems and consequently testing preference substrates that potentially stimulate attachment and cementation on this species.Statement of relevance. This study presents a complete description of the embryonic and larval development of S. limbatus. Additionally, we determined an appropriate diet (C. gracilis, I. galbana; 3:1) for enhancing larval growth and survival of this commercially and ecologically important species. Finally, we provide unpublished observations about the settling behavior and physiological characteristics of S. limbatus postlarvae and their implication for aquaculture.