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. 2022 Jan 19:10:e12589.
doi: 10.7717/peerj.12589. eCollection 2022.

Effective asexual reproduction of a widespread soft coral: comparative assessment of four different fragmentation methods

Sohyoung Kim  1 , Christian Wild  1 , Arjen Tilstra  1
Affiliations

Effective asexual reproduction of a widespread soft coral: comparative assessment of four different fragmentation methods

Sohyoung Kim et al. PeerJ. .

Abstract

Background: Many coral reefs worldwide are experiencing declines in hard corals, resulting in other benthic organisms, e.g., soft corals, becoming more dominant. As such, more studies on the ecophysiology of soft corals are needed. Despite many methods for asexual reproduction of hard corals, effective methods for soft corals, i.e., without a hard skeleton, are scarce. This study, thus, assessed four fragmentation methods, the glue, rubber band, tunnel mesh, and plug mesh method for the pulsating soft coral Xenia umbellata that is widely distributed in the tropical Indo-Pacific.

Methods: Methods were comparatively assessed by determining the required time and labor for the fragmentation plus the health status of the fragmented corals by measuring their oxygen fluxes and pulsation rates, i.e., a special feature of this soft coral that can be used as a proxy for its health.

Results: There were no significant health status differences between methods. This was indicated by similar gross photosynthesis (between 7.4 to 9.7 μg O2 polyp-1 h-1) and pulsating rates (between 35 and 44 pulses min-1) among methods. In terms of time/labor intensity and success rates, i.e., the percentage of fragments attached to the desired surface, the plug mesh method was the most efficient method with a significantly higher success rate (95 ± 5%), while the others had a success rate between 5 ± 5 and 45 ± 15%. The time needed for fragmentation, though not significant, was also the shortest (78 ± 11 s fragment-1), while other methods required between 84 ± 14 and 126 ± 8 s frag-1. The plug mesh method may thus be a valuable tool related to the reproduction of soft corals for use in subsequent experimental work.

Keywords: Asexual reproduction; Fragmentation methods; Soft coral research.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1. Illustration of (A) tunnel mesh method and (B) plug mesh method.
All components are fixed with two to four rubber bands on the sides. An extra egg crate is an important factor so that there can be water circulating through the egg crate holes. Once the coral fragment is attached to the mesh fabric or plug beneath, the egg crate and mesh fabric on top can be removed. Mesh fabrics are differentiated by diameter size of 3.5 mm (Large mesh: Mesh L) and 2.0 mm (Small mesh: Mesh S) per opening.
Figure 2
Figure 2. (A) Attachment success rate and (B) fragmentation time of four different fragmentation methods as an assessment of time- and labor-efficiency.
Four methods are the glue (Glue), rubber band (Rubber), tunnel mesh (Tunnel), and plug mesh method (Plug). Values are given as means ± SE of N = 3–4 replicates. Different letters (a, b) indicate significant differences between the methods (one-way ANOVA, F[3,12] = 21.75, p < 0.001).
Figure 3
Figure 3. (A) Oxygen fluxes and (B) pulsating rates measured on the twelfth-day post fragmentation as health assessments of three different fragmentation methods.
The three methods are the rubber band (rubber), tunnel mesh (tunnel), and plug mesh method (plug). Pgross = gross photosynthesis, Pnet = net photosynthesis, Rdark = dark respiration. Values are given as means ± SE of N = 3-4 replicates. Asterisks (*p < 0.01, **p < 0.001) indicate significant differences between the methods, while letters (c: Control, p: plug mesh method, r: rubber band method) indicate between which methods they differed in. Note: The glue method was not assessed as only one out of 20 replicates successfully attached to the plug.
Figure 4
Figure 4. Attachment success rates of the best assessed method, the plug mesh method, over a period of 72 h.
Fragments are either unattached to anything (Unattached: dark gray) or attached to the egg crate wall (Egg crate: light gray) or the plug (Plug: black). Values are given as means ± SE of N = 3 replicates.
Figure 5
Figure 5. (A) Oxygen fluxes and (B) pulsating rates of the plug mesh method.
Oxygen fluxes were measured after 7 days of fragmentation while pulsating rates were measured every 24 h starting from 24 h after fragmentation as health assessments. Pgross = gross photosynthesis, Pnet = net photosynthesis, Rdark = dark respiration. Values of bars are given as means ± SE of N = 3 replicates. Asterisks (*p < 0.01, **p < 0.001) indicate significant differences between treatments. Top bracket applies to Pgross only.
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