Planulation periodicity, settlement preferences and growth of two deep-sea octocorals from the northwest Atlantic

Abstract

Adaptations and life history strategies have rarely been studied in deep-sea corals. Here we present laboratory data on the timing of larval release, reproductive output, substratum selectivity and growth of 2 alcyonaceans (Cnidaria, Octocorallia) from the bathyal zone of eastern Canada. Planulation patterns in 2 Drifa species were significantly influenced by seasonal productivity and the lunar cycle, and larval output was greater in larger colonies (from shallower depths). After release, planulae of Drifa sp. shifted their buoyancy to move between the bottom and the water column, whereas planulae of D. glomerata were largely demersal and crawled on the substratum until settlement (typically occurring after 1 to 30 d in both species). Settlement trials showed that planulae settled more readily on rough natural surfaces covered with biofilm than all other substrata tested and that larvae of colonies from deeper habitats were less selective than those originating from shallower habitats. In both species, the 8 primary mesenteries (and tentacle buds) appeared within 24 h post settlement, and polyps reached a maximum size after 2 to 3 mo. The first branching polyp was observed after ca. 9 mo of growth in D. glomerata, whereas no direct evidence of branching was detected in Drifa sp. over 21 mo of observation, although 2-and 4-polyp colonies were later discovered in the holding tank with adults. Together, these findings highlight dual traits of resilience (i.e. extended breeding period, long-lived larvae) and vulnerability (i.e. substratum selectivity, slow growth) in deep-sea corals.KEY WORDS: Deep-sea · Corals · Reproduction · Brooding · Settlement · Growth · Drifa Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 410: [71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87] 2010 the widely distributed Nephtheidae (Farrant 1986, Dahan & Benayahu 1997, Hwang & Song 2007, Sun 2009.The production and release of offspring is the initial step in a suite of processes that allows populations of benthic invertebrates to be replenished and maintained. Sexual modes of reproduction in corals include broadcast-spawning and brooding. In the deep ocean (below 200 m), broadcasting appears to be the dominant trait, and reports of brooding species are rare (Cordes et al. 2001, Waller et al. 2008, Sun 2009, Sun et al. 2009. However, investigations of reproductive patterns in deep-sea corals are fraught with difficulty, and knowledge about these remains embryonic at best. Studies of shallow-water corals have shown that they may undergo synchronous or asynchronous spawning, seasonal or so-called continuous reproduction, and lunar or shifted lunar spawnings, and that their patterns of sexual reproduction could be correlated to several factors, such as temperature, depth, and tidal, lunar and solar cycles (Jokiel & Guinther 1978, Stimson 1978, Benayahu & Loya 1983, 1984, Benayahu 1997, Ben-David-Zaslow et al. 1999.After release, larvae must recruit through settlement...

Internal brooding favours pre-metamorphic chimerism in a non-colonial cnidarian, the sea anemone Urticina felina

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Diversity, distribution and spatial structure of the cold-water coral fauna of the Azores (NE Atlantic)

“…In the deep sea, however, the effects of low temperature (O'Connor et al, 2007;Bradbury et al, 2008) and pressure (Somero, 1998) on larval metabolism may extend planktonic larval duration, leading to an increase of dispersal potential. In addition, some lecithotrophic coral larvae have the ability to delay metamorphosis for months, thus greatly prolonging the dispersive phase (Cordes et al, 2001;Sun et al, 2010).…”

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“…), with clear local substratum selectivity being exhibited by the larvae of sessile fauna, such as deep‐sea alcyonaceans (Sun et al . , ) and sponges (Whalan et al . ).…”

“…These changes in the composition of assemblages of sessile marine species are primarily driven by physical habitat complexity, particularly fine-scale variations in water flow (Smith & Witman 1999;Witman et al 2004;Palardy & Witman 2011) that control larval and food supply (Soltwedel et al 2013), and biological factors, such as larval supply rates and the regional species pool (Witman et al 2004). The biogeochemical composition of the rocky substratum determines larval selection and attachment processes (Dorschel et al 2009;S anchez et al 2009;Watanabe et al 2009;Wienberg et al 2013), with clear local substratum selectivity being exhibited by the larvae of sessile fauna, such as deep-sea alcyonaceans (Sun et al 2010(Sun et al , 2011 and sponges (Whalan et al 2008). Changes in the geomorphology at a broader scale are also important in driving ecological patterns (Schneider et al 1987;Jones et al 2013a,b), primarily because of their effect on local hydrography (Duineveld et al 2004(Duineveld et al , 2007.…”