Field estimates of planktonic larval duration in a marine invertebrate

Abstract

Planktonic larval durations (PLDs) affect the ecology and evolution of benthic marine populations through their effects on dispersal distance, the spread of sibling larvae, the level of larval mortality, and population connectivity. Despite the importance of PLDs, field estimates of PLDs in marine invertebrates are rare and restricted to specific taxa. The size of the first postmetamorphic feeding structure (the ancestrula lophophore) in Bugula neritina has been shown previously to decline with increases in larval duration. We hypothesised that if the relationship between larval duration and the size of the ancestrula lophophore can be estimated in the laboratory, then it should be possible to infer the PLD of B. neritina settlers in the field. We manipulated the length of the larval period in the laboratory and quantified the relationship between larval duration and the volume of the ancestrula lophophore. We then measured the size of lophophores in field-settled individuals at 2 sites on multiple days over a 2 yr period, and predicted their planktonic durations based on our laboratory-derived classifications. The average percentage of individuals in the field with short (0 to 1.5 h), intermediate (1.5 to 6.5 h), and long (6.5 to 32 h) PLDs was 54, 27, and 19%, respectively. Despite being competent to settle upon release from the colony, a significant proportion of settlers in the field experienced metamorphic delays that would incur significant post-settlement costs. Furthermore, there was a positive relationship between settlement density and the proportion of settlers in any one cohort that had experienced short PLDs. The extended planktonic periods that we predicted are likely to affect the dynamics of adult populations directly via reductions in settlement density and indirectly via reductions in the postsettlement performance of individuals that experienced a metamorphic delay before settling. KEY WORDS: Delayed metamorphosis · Dispersal · Larval quality · Larval mortality · Population connectivity Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 440: [151][152][153][154][155][156][157][158][159][160][161] 2011 PLDs have a number of important implications for the ecology and evolution of marine populations. Planktonic durations place a maximum limit on the distance that offspring can disperse from their sessile or 'site-attached' parents, which can influence population connectivity, population persistence, and the scale of local adaptation (Holt & Gaines 1992, Lenormand 2002, Palumbi 2003, Botsford et al. 2009). The length of the larval period also influences the spread of sibling larvae relative to each other (Strathmann 1974, Palmer & Strathmann 1981, Ronce 2007. PLDs affect not only how far larvae move, but also how much mortality they are likely to suffer. The plankton is thought to be a risky place for small, relatively unprotected larvae, and mortality rates can be high and longer planktonic periods probably entail significant mortality cos...

Desmophyllum dianthus (Esper, 1794) in the Scleractinian Phylogeny and Its Intraspecific Diversity

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Genetic diversity increases population productivity in a sessile marine invertebrate

“…Furthermore, in the congener B. stolonifera, Johnson (2010) showed that although selffertilized offspring can develop into reproductively mature adults, adults produced by selfing are incapable of producing viable offspring. After brooding, mothers release swimming, non-feeding larvae that typically settle and metamorphose within hours (Keough 1989, Marshall and, limiting the potential for long-distance dispersal (Burgess and Marshall 2011a). Independent feeding on planktonic particles commences with the formation of the lophophore.…”

Why does offspring size affect performance? Integrating metabolic scaling with life-history theory

“…In our system, larval period and temperature are key modifiers of the length of the dependent phase. For our study species, the larval phase varies in nature between a few minutes and up to 24 h [43]. A relatively long larval period of 12 h (and the same size-specific metabolic rate) would therefore yield an almost twofold increase in the differential of efficiency between big and small larvae in B. neritina and W. subtorquata (1.8 and 1.6 times, respectively).…”

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