The advantages of Ulva (Chlorophyta) as an additive in sea urchin formulated feeds: effects on palatability, consumption and digestibility

Abstract

The present study was performed to determine whether the palatability, consumption and digestibility of an artificial sea urchin diet could be improved by the addition of a highly preferred seaweed. Four species of macroalgae (Ulva rigida, Ecklonia maxima, Porphyra capensis and Gigartina polycarpa) were assessed by pairwise preference tests. Each macroalgal species was consumed at least once by Tripneustes gratilla and significant preferences always involved Ulva as the most preferred species. Four proteinrich artificial diets supplemented with varying amounts of Ulva [0, 50, 150 and 200 g kg À1 designated 0, 5, 15 and 20U, respectively] were then developed and fed to urchins over a 20-day period. Inclusion of 200 g kg À1 dried Ulva significantly improved the palatability of the artificial diet and mean dry feed consumption rates were higher in urchins fed the 20U and 15U diets compared with urchins fed diets with a lower Ulva content. Daily digestible protein (DP) intake also differed significantly, with urchins fed the 20U diet having a significantly higher DP intake compared with the 15U, 5U and 0U treatments. These results indicate that inclusion of the palatable seaweed Ulva acted as a feeding stimulant, increasing the acceptability of the diets and boosting protein intake.

The use of stable isotope ratios δ 13 C and δ 15 N to track the incorporation of Ulva and other important dietary ingredients into the gonads of the sea urchin Tripneustes gratilla

“…We demonstrated that Ulva added to artificial feeds makes a significant contribution (~35%) to the final composition of the urchin gonad and incorporation of other proteins, particularly fishmeal, appears to increase with increasing dietary Ulva content. These results support the findings of Cyrus et al (), who demonstrated that dietary Ulva inclusion improved protein retention as well as the palatability of formulated feeds. Stable isotopes have been used previously to provide information about the natural feeding habits of sea urchins in the wild (Prado, Carmichael, Watts, Cebrian, & Heck, ; Rodríguez, ; Tomas, Alvarez‐Cascos, Turon, & Romero, ; Vanderklift, Kendrick, & Smit, ; Yatsuya & Nakahara, ); however, this is the first time that duel stable isotope analysis has been used to estimate the contribution of specific dietary ingredients to the development of the sea urchin gonad.…”

“…The proximate composition and nutrient analysis of the four dietary treatments are presented in Table . The Ulva used in this study, identified as U. armoricana by gene sequencing (see Cyrus, Bolton, Scholtz, & Macey, ), was produced in paddle raceway aquaculture systems at Irvine and Johnson (I&J) Cape Abalone farm [Ulva is used as a bio‐filter, where effluent water is directed from the abalone culture system to large shallow paddle raceways where the Ulva is therefore fertilized.] (34°34′60 S; 19°21′00 E) (Bolton, Robertson‐Andersson, Shuuluka, & Kandjengo, ) and processed for inclusion in the formulated feeds as described in Cyrus et al ().…”

Can artificial diets be a feasible alternative for the gonadal growth and maturation of the sea urchin Paracentrotus lividus (Lamarck, 1816)?

“…As the formulation method was the same for the three diets (6% agar), it is easier to focus only on the nutritional aspect of the ingredients. In fact, food type affects ingestion rates in sea urchins as reported by Vadas (1977), Anderson and Velimirov (1982), De Ridder and , Frantzis and Grémare (1993), Fernandez and Pergent (1998), Fernandez and Boudouresque (2000), Cyrus et al (2015), and Vizzini et al (2015). Furthermore, protein levels seem to also be correlated to ingestion rates (Fernandez & Boudouresque 1998).…”

“…Therefore, palatability and attraction were successfully achieved, which are key factors for artificial feeds (Cirino, Ciaravolo, Paglialonga, & Toscano, 2017;Cyrus, Bolton, Scholtz, & Macey, 2015;Fabbrocini et al, 2015;Lawrence, Lawrence, & Watts, 2013), as well as a suitable texture and form (Klinger, 1982;Spirlet et al, 2001). The inclusion of fresh triturated L. digitata in Diet B might have acted as a feeding stimulant, assuming its chemosensory characteristics were preserved (Cyrus et al, 2015;Klinger & Lawrence, 1984). As the formulation method was the same for the three diets (6% agar), it is easier to focus only on the nutritional aspect of the ingredients.…”

An Ocean Acidification Acclimatised Green Tide Alga Is Robust to Changes of Seawater Carbon Chemistry but Vulnerable to Light Stress

“…Ulva , a cosmopolitan genus which is common in tide-pools, has been gaining significant interest due to its potential value in animal feed [20,21], human food [22,23], biofuel [24,25] as well as the delivery of crucial ecosystem services such as wastewater bioremediation [26,27] and CO 2 removal [28,29]. Meanwhile, Ulva is the only genus contributing to reported green tide events [30,31].…”