Fig 1.
(A) Plate-like adult M. capitata found in Hawaii. (B) Light micrograph of M. capitata eggs demonstrating size and appearance of vertically transmitted intracellular zooxanthellae. (C) Transmission electron micrograph of a single M. capitata egg demonstrating the size and appearance of white yolk droplets and deep blue membrane-bound endogenous zooxanthellae.
Fig 2.
Toxicity of intact and crushed M. capitata (A) eggs and (B) larvae against endogenous zooxanthellae determined by quantum yield.
Bars indicate SEM.
Fig 3.
Dose response curve of M. capitata eggs on exogenous zooxanthellae.
(A) Preliminary experiments on the dose response curve of the toxins found in M. capitata eggs were conducted against P. compressa zooxanthellae. Both 100 and 250 µl of egg volume reduced the P. compressa zooxanthellae y-values within 10 min, whereas the smaller volumes took 30 min to do the same. (B) These experiments were repeated with a larger number of P. compressa zooxanthellae samples (n = 10 individuals) split into two sub-samples treated with either 100 µl of crushed M. capitata (at the 0 min mark indicated by the arrow) or 100 µl of FSW. Only the M. capitata eggs reduced the Y-values. Bars indicate SEM.
Fig 4.
M. capitata sperm does not contain the same toxic properties as its eggs.
P. compressa zooxanthellae from 8 individuals were split into 5 sub-samples and exposed to five different treatments: 1) frozen/thawed F. scutaria sperm, 2) frozen/thawed M. capitata sperm, 3) toxic eggs: frozen/thawed crushed M. capitata eggs, 4) frozen/thawed crushed M. capitata larvae, and 5) FSW. After 20 min, the crushed M. capitata eggs and larvae reduced quantum yield greater than 90% (P < 0.05), while the other treatments remained unchanged at 0.4 (P > 0.05).
Fig 5.
Toxins with the frozen, crushed M. capitata eggs destroyed the tissue and the zooxanthellae of living P. compressa fragments.
(A) Only the addition of the caps with the M. capitata eggs caused tissue necrosis. (B, C) Twenty-four h later, only the caps with the M. capitata eggs reduced the quantum yield, indicating that the zooxanthellae in those areas were impaired (P< 0.05). Both the F. scutaria larvae and the M. capitata eggs caused a changed color on the fragment (P< 0.05), but only addition of the M. capitata eggs led to complete tissue necrosis under the cap 6 days later. Bars with the same letter indicate (P > 0.05), but bars with different letters indicate (P < 0.05). Bars indicate SEM.
Fig 6.
The addition of crushed M. capitata eggs negatively impacted sperm motility and in vitro fertilization success.
(A) When 5 µl of FSW was added to M. capitata sperm, its motility remained constant over time, however when 5 µl of crushed M. capitata eggs were added to M. capitata sperm, the motility decreased greater than 90% after 15 and 30 min. (B) After 30 min, the uncrushed- and crushed egg-treated sperm were tested in in vitro fertilization assays. The sperm exposed to the crushed eggs showed little fertilization success (1.3%), whereas the freshly collected bundles from two individuals (positive control) and the uncrushed egg-treated sperm had excellent fertilization success at 72 and 79%. Bars indicate SEM.
Fig 7.
The reduction in the quantum yield of F. scutaria zooxanthellae due to M. capitata egg chemical fractions.
The zooxanthellae from two individuals were divided up into 5 sub-samples and exposed to 30 µl of FSW, dimethyl sulfoxide (DMSO), frozen crushed M. capitata eggs, water fraction, butanol fraction (BuOH) or ethyl acetate fraction (EtOAc). The quantum yield of FSW and DMSO, were not different (P>0.05, ANOVA, Dunnett’s Multiple Comparison Test). But adding 30 µl of each of the chemical fractions or frozen eggs caused a reduction of 25 to 44% in the quantum yield over 40 min over the FSW values (P> 0.05, ANOVA, Dunnett’s Multiple Comparison Test). Bars with different letters were (P < 0.05). Bars indicate SEM.