Larval ecology of the fluted giant clam, Tridacna squamosa, and its potential effects on dispersal models

Neo, Mei Lin; Vicentuan, Kareen; Teo, Serena Lay‐Ming; Erftemeijer, P.L.A.; Todd, Peter A.

doi:10.1016/j.jembe.2015.04.012

Cited by 16 publications

(7 citation statements)

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“…Our biophysical model (IBOD) considered the PLD, larval survival, and ability for larvae to settle when crossing a suitable substrate. Available computer time limited our ability to run dedicated sensitivity analyses for each of these parameters, but all are expected to influence the dispersal kernel [ 40 ] and warrant further investigation. A number of other processes also deserve more attention for future modelling of larval dispersal, including 1) the movement of gametes before fertilization, which last several to tens of hours for giant clams [ 40 ] and may significantly influence dispersal kernel; 2) larval swimming speed, which may also affect the path of larvae and is low for T .…”

Section: Discussionmentioning

confidence: 99%

“…A number of other processes also deserve more attention for future modelling of larval dispersal, including 1) the movement of gametes before fertilization, which last several to tens of hours for giant clams [ 40 ] and may significantly influence dispersal kernel; 2) larval swimming speed, which may also affect the path of larvae and is low for T . squamosa (104.0 to 1010.6 μm.s -1 , [ 40 ]) but remains unestimated for T . maxima (though larval behaviour experiments reveal active swimming, [ 39 ]); 3) factors inducing settlement, including crustose coralline algae [ 40 ] or conspecifics [ 39 ]; and 4) spatial differences in larval survival, such as from spatial variation in predation or food availability.…”

Section: Discussionmentioning

confidence: 99%

“…squamosa (104.0 to 1010.6 μm.s -1 , [ 40 ]) but remains unestimated for T . maxima (though larval behaviour experiments reveal active swimming, [ 39 ]); 3) factors inducing settlement, including crustose coralline algae [ 40 ] or conspecifics [ 39 ]; and 4) spatial differences in larval survival, such as from spatial variation in predation or food availability. Finally, it is worth noting that despite the recent advances in characterizing the circulation around New Caledonia [ 32 ], ROMS models continue to have difficulty simulating currents along the coastlines, particularly in the Loyalty channel where the modeled Vauban current is too strong.…”

Section: Discussionmentioning

confidence: 99%

“…During the competency period (after 9 days), we allowed larvae to settle as soon as they crossed a patch of favourable habitat [ 39 , 40 ]. We considered a competency period ranging from 9 to 19 days on the basis of Jameson [ 37 ] and Neo et al [ 40 ], with the number of surviving larvae exponentially decreasing with time. We used a survival curve similar to Wood et al [ 41 ] (See S1 Fig ).…”

Section: Methodsmentioning

confidence: 99%

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Considering reefscape configuration and composition in biophysical models advance seascape genetics

et al. 2017

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Previous seascape genetics studies have emphasized the role of ocean currents and geographic distances to explain the genetic structure of marine species, but the role of benthic habitat has been more rarely considered. Here, we compared the population genetic structure observed in West Pacific giant clam populations against model simulations that accounted habitat composition and configuration, geographical distance, and oceanic currents. Dispersal determined by geographical distance provided a modelled genetic structure in better agreement with the observations than dispersal by oceanic currents, possibly due to insufficient spatial resolution of available oceanographic and coastal circulation models. Considering both habitat composition and configuration significantly improved the match between simulated and observed genetic structures. This study emphasizes the importance of a reefscape genetics approach to population ecology, evolution and conservation in the sea.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Considering reefscape configuration and composition in biophysical models advance seascape genetics

et al. 2017

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“…squamosa larvae, although the animal phyla are completely different. Neo et al [41] reported that the settlement competency period in T . squamosa is 14 days, and until then, the larvae actively swim and are able to alter the depth distribution and settlement location.…”

Section: Discussionmentioning

confidence: 99%

Study on expelled but viable zooxanthellae from giant clams, with an emphasis on their potential as subsequent symbiont sources

et al. 2019

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Unlike most bivalve shellfishes, giant clams (tridacnines) harbor symbiotic microalgae (zooxanthellae) in their fleshy bodies. Zooxanthellae are not maternally inherited by tridacnine offspring, hence, the larvae must acquire zooxanthellae from external sources, although such algal populations or sources in the environment are currently unknown. It is well known that giant clams expel fecal pellets that contain viable zooxanthellae cells, but whether these cells are infectious or just an expelled overpopulation from the giant clams has not been investigated. In this study, we observed the ultrastructural and photosynthetic competencies of zooxanthellae in the fecal pellets of Tridacna crocea and further tested the ability of these cells to infect T . squamosa juveniles. The ultrastructure of the zooxanthellae cells showed that the cells were intact and had not undergone digestion. Additionally, these zooxanthellae cells showed a maximum quantum yield of photosystem II ( Fv/Fm ) as high as those retained in the mantle of the giant clam. Under the assumption that feces might provide symbionts to the larvae of other giant clams, fecal pellets from Tridacna squamosa and T . crocea were given to artificially hatched 1-day-old T . squamosa larvae. On the 9 th day, 15–34% of the larvae provided with the fecal pellets took up zooxanthellae in their stomach, and on the 14 th day, zooxanthellae cells reached the larval margin, indicating the establishment of symbiosis. The rate reaching this stage was highest, ca. 5.3%, in the larvae given whole (nonhomogenized) pellets from T . crocea . The composition of zooxanthellae genera contained in the larvae were similar to those in the fecal pellets, although the abundance ratios were significantly different. This study is the first to demonstrate the potential of giant clam fecal pellets as symbiont vectors to giant clam larvae. These results also demonstrate the possibility that fecal pellets are a source of zooxanthellae in coral reefs.

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Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

Lee

Neo

Lim

et al. 2022

Aquatic Conservation

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1. With the increasing demand for giant clams in the ornamental trade as well as habitat destruction of coral reefs, giant clam populations have been threatened across the Indo-Pacific. This study documents the population status and genetic diversity of giant clams in Perhentian Islands Marine Park (PMP), a Marine Protected Area (MPA) on the east coast of Peninsular Malaysia, plus Rhu Island, an adjacent island outside the MPA.2. Of the 13 reef sites surveyed across an area of 11,200 m 2 , two giant clam species were recorded: Tridacna squamosa and Tridacna maxima, with average densities of 1.5 ± 2.2 and 5.2 ± 6.0 ind. 100 m À2 , respectively. The size-class survey revealed a higher number of T. maxima recruits (88 recruits) as compared to T. squamosa (only three recruits), suggesting a disparity in recruitment in the area.3. The genetic diversity of T. squamosa (n = 83) and T. maxima (n = 104) was explored using the mitochondrial cytochrome c oxidase I (COI) and 16S rRNA gene markers. Interestingly, a higher genetic diversity was detected in COI than 16S for both species. No significant genetic differentiation was detected between the populations of PMP and Rhu Island, while a low but significant genetic structure was detected in both species across the sites of PMP (COI datasets, AMOVA, T. squamosa, F CT = 0.14, P < 0.05; T. maxima, F CT = 0.11, P < 0.05).4. In general, the results of this study revealed healthy giant clam populations in PMP, but the decline warrants urgent attention to integrating conservation strategies such as restoration programmes in conjunction with a sustainable giant clam fishery. Given the relatively high genetic diversity of T. maxima at Rhu Island, expansion of the current MPA is needed for better conservation coverage.

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Larval ecology of the fluted giant clam, Tridacna squamosa, and its potential effects on dispersal models

Cited by 16 publications

References 50 publications

Considering reefscape configuration and composition in biophysical models advance seascape genetics

Considering reefscape configuration and composition in biophysical models advance seascape genetics

Study on expelled but viable zooxanthellae from giant clams, with an emphasis on their potential as subsequent symbiont sources

Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

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