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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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Distribution patterns of common Echinometra spp. on the Pacific reef (after Palumbi [49]). Species are designated according to the published documents [8, 49–58]: Ea, Echinometra sp. A; Em, E. mathaei; Ec, Echinometra sp. C; and Eo, E. oblonga. Localities are C, Isla del Coco, Costa Rica; H, Hawaiian Islands; G, Guam; O, Okinawa; B, Bali; GB, Great Barrier Reef; R, Rottnest Is.; F, Fiji; N, Niue; and T, Tahiti.
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fig6: Distribution patterns of common Echinometra spp. on the Pacific reef (after Palumbi [49]). Species are designated according to the published documents [8, 49–58]: Ea, Echinometra sp. A; Em, E. mathaei; Ec, Echinometra sp. C; and Eo, E. oblonga. Localities are C, Isla del Coco, Costa Rica; H, Hawaiian Islands; G, Guam; O, Okinawa; B, Bali; GB, Great Barrier Reef; R, Rottnest Is.; F, Fiji; N, Niue; and T, Tahiti.

Mentions: All of the four species of Echinometra occur on reefs in Okinawa and Indonesia. It is more common, however, to find only two sympatric species in island archipelagoes of the central/western pacific. At the edge of the tropical pacific, Echinometra species are often found alone (e.g., E. oblonga in Cocos Is., Costa Rica and E. mathaei at Rottnest Is., SW Australia) [49]. Until now, there have been no detailed information of the distribution patterns of Echinometra, but from the recently incomplete survey done by Palumbi [49], it is clear that discontinuities of species ranges are common for Pacific Echinometra (Figure 6). For example, E. mathaei and E. oblonga are found together in Hawaii and in Niue. In Fiji, 1300 km to the west of Niue, there are also two species of Echinometra but not E. mathaei and E. oblonga. Instead, E. sp. A and E. sp. C are common (Figure 6). To the east of Niue, in the Society Islands, only E. mathaei and E. sp. A are common. As a second example, E. mathaei and E. sp. A are the common calm-water species in Guam and Papua New Guinea. In Palau (1300 km SW of Guam) E. sp. C is the commonest species of Echinometra with E. sp. A occurring rarely. Highly realized dispersal in the Pacific is suggested by the discovery of indistinguishable mtDNA sequences in individuals collected from distant localities [49]. For E. sp. A, identical sequences were seen in the individuals collected from Guam and Bali (4000 km distant), Fiji and Papua New Guinea (4500 km), and Okinawa and Guam (2600 km). The observation of indistinguishable mtDNA sequences in geographically distant localities is common for marine species with high dispersal potential [95–97]. If a reef can support populations of several species of Echinometra, and Echinometra species have high dispersal potential from reef to reef, why are not all four species found in all available reef habitats? One potential explanation for the heterogeneous distribution of species in the Pacific is that local populations are founded on archipelagoes largely by chance. If these founder events are relatively rare, there may not have been enough time since these species formed for the colonization of all available reefs in the Pacific by all species [49]. Micronesian ostracods also show this pattern [98], with distinct heterogeneity between atolls in species composition but no clear relationship between species similarity and distance between atolls.


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)

Distribution patterns of common Echinometra spp. on the Pacific reef (after Palumbi [49]). Species are designated according to the published documents [8, 49–58]: Ea, Echinometra sp. A; Em, E. mathaei; Ec, Echinometra sp. C; and Eo, E. oblonga. Localities are C, Isla del Coco, Costa Rica; H, Hawaiian Islands; G, Guam; O, Okinawa; B, Bali; GB, Great Barrier Reef; R, Rottnest Is.; F, Fiji; N, Niue; and T, Tahiti.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig6: Distribution patterns of common Echinometra spp. on the Pacific reef (after Palumbi [49]). Species are designated according to the published documents [8, 49–58]: Ea, Echinometra sp. A; Em, E. mathaei; Ec, Echinometra sp. C; and Eo, E. oblonga. Localities are C, Isla del Coco, Costa Rica; H, Hawaiian Islands; G, Guam; O, Okinawa; B, Bali; GB, Great Barrier Reef; R, Rottnest Is.; F, Fiji; N, Niue; and T, Tahiti.
Mentions: All of the four species of Echinometra occur on reefs in Okinawa and Indonesia. It is more common, however, to find only two sympatric species in island archipelagoes of the central/western pacific. At the edge of the tropical pacific, Echinometra species are often found alone (e.g., E. oblonga in Cocos Is., Costa Rica and E. mathaei at Rottnest Is., SW Australia) [49]. Until now, there have been no detailed information of the distribution patterns of Echinometra, but from the recently incomplete survey done by Palumbi [49], it is clear that discontinuities of species ranges are common for Pacific Echinometra (Figure 6). For example, E. mathaei and E. oblonga are found together in Hawaii and in Niue. In Fiji, 1300 km to the west of Niue, there are also two species of Echinometra but not E. mathaei and E. oblonga. Instead, E. sp. A and E. sp. C are common (Figure 6). To the east of Niue, in the Society Islands, only E. mathaei and E. sp. A are common. As a second example, E. mathaei and E. sp. A are the common calm-water species in Guam and Papua New Guinea. In Palau (1300 km SW of Guam) E. sp. C is the commonest species of Echinometra with E. sp. A occurring rarely. Highly realized dispersal in the Pacific is suggested by the discovery of indistinguishable mtDNA sequences in individuals collected from distant localities [49]. For E. sp. A, identical sequences were seen in the individuals collected from Guam and Bali (4000 km distant), Fiji and Papua New Guinea (4500 km), and Okinawa and Guam (2600 km). The observation of indistinguishable mtDNA sequences in geographically distant localities is common for marine species with high dispersal potential [95–97]. If a reef can support populations of several species of Echinometra, and Echinometra species have high dispersal potential from reef to reef, why are not all four species found in all available reef habitats? One potential explanation for the heterogeneous distribution of species in the Pacific is that local populations are founded on archipelagoes largely by chance. If these founder events are relatively rare, there may not have been enough time since these species formed for the colonization of all available reefs in the Pacific by all species [49]. Micronesian ostracods also show this pattern [98], with distinct heterogeneity between atolls in species composition but no clear relationship between species similarity and distance between atolls.

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