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Effects of delayed metamorphosis on larval survival, metamorphosis, and juvenile performance of four closely related species of tropical sea urchins (genus Echinometra).

Rahman MA, Yusoff FM, Arshad A, Uehara T - ScientificWorldJournal (2014)

Bottom Line: Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species.Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec.Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Marine Biotechnology, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.

ABSTRACT
We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22-24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10 rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis.

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Effects of delayed period on larval competence to metamorphosis (%) of Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo) in response to coralline red algae. Larvae attained metamorphic competence within 24 days after fertilization were on month 0. Each value represents the mean ± SD of 12 replicate experiments from each species with 15 larvae per replicate for each delayed period. Results of one-way ANOVA (F value and P value) are presented above each set of bars. Columns with the same letter represent means that are not significantly different (Tukey's test, P > 0.05).
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fig2: Effects of delayed period on larval competence to metamorphosis (%) of Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo) in response to coralline red algae. Larvae attained metamorphic competence within 24 days after fertilization were on month 0. Each value represents the mean ± SD of 12 replicate experiments from each species with 15 larvae per replicate for each delayed period. Results of one-way ANOVA (F value and P value) are presented above each set of bars. Columns with the same letter represent means that are not significantly different (Tukey's test, P > 0.05).

Mentions: Complete metamorphosis from feeding larvae to feeding juveniles took place in about 1 day after settlement on coralline red algal substratum. This included the complete development of internal organs as well as formation of adult mouth, anus, tubefeet, and spines. Completion of metamorphosis was the same and the rate of development was equivalent among the four species. Moreover the time required to complete metamorphosis was similar and no particular deformities/defects were observed in the juveniles among the four species at various delayed periods. The percentage of Echinometra spp. larvae that metamorphosed was typically greater for 0 delayed larvae than for delayed larvae whose metamorphosis was postponed (Figure 2). Competent larvae (0 month delayed) of Echinometra spp. showed highest metamorphic success and no significant differences (Tukey's test, P > 0.05) were recognized among the four species (Figure 2). Similar but significantly lower metamorphosis rate was observed in the metamorphosis of 1-month delayed larvae (Figure 2). Moreover, postponing metamorphosis of 2–5-month delayed larvae had significant effect on metamorphosis. Despite these discriminations, an extended larval period resulted in lower metamorphic success in such a way that Em showed significantly (Tukey's test, P < 0.05) higher values than those of Ea and Eo, while Ec showed significantly the lowest values among the treatments (Figure 2).


Effects of delayed metamorphosis on larval survival, metamorphosis, and juvenile performance of four closely related species of tropical sea urchins (genus Echinometra).

Rahman MA, Yusoff FM, Arshad A, Uehara T - ScientificWorldJournal (2014)

Effects of delayed period on larval competence to metamorphosis (%) of Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo) in response to coralline red algae. Larvae attained metamorphic competence within 24 days after fertilization were on month 0. Each value represents the mean ± SD of 12 replicate experiments from each species with 15 larvae per replicate for each delayed period. Results of one-way ANOVA (F value and P value) are presented above each set of bars. Columns with the same letter represent means that are not significantly different (Tukey's test, P > 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3927581&req=5

fig2: Effects of delayed period on larval competence to metamorphosis (%) of Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo) in response to coralline red algae. Larvae attained metamorphic competence within 24 days after fertilization were on month 0. Each value represents the mean ± SD of 12 replicate experiments from each species with 15 larvae per replicate for each delayed period. Results of one-way ANOVA (F value and P value) are presented above each set of bars. Columns with the same letter represent means that are not significantly different (Tukey's test, P > 0.05).
Mentions: Complete metamorphosis from feeding larvae to feeding juveniles took place in about 1 day after settlement on coralline red algal substratum. This included the complete development of internal organs as well as formation of adult mouth, anus, tubefeet, and spines. Completion of metamorphosis was the same and the rate of development was equivalent among the four species. Moreover the time required to complete metamorphosis was similar and no particular deformities/defects were observed in the juveniles among the four species at various delayed periods. The percentage of Echinometra spp. larvae that metamorphosed was typically greater for 0 delayed larvae than for delayed larvae whose metamorphosis was postponed (Figure 2). Competent larvae (0 month delayed) of Echinometra spp. showed highest metamorphic success and no significant differences (Tukey's test, P > 0.05) were recognized among the four species (Figure 2). Similar but significantly lower metamorphosis rate was observed in the metamorphosis of 1-month delayed larvae (Figure 2). Moreover, postponing metamorphosis of 2–5-month delayed larvae had significant effect on metamorphosis. Despite these discriminations, an extended larval period resulted in lower metamorphic success in such a way that Em showed significantly (Tukey's test, P < 0.05) higher values than those of Ea and Eo, while Ec showed significantly the lowest values among the treatments (Figure 2).

Bottom Line: Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species.Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec.Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Marine Biotechnology, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.

ABSTRACT
We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22-24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10 rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis.

Show MeSH
Related in: MedlinePlus