Permanent ectoplasmic structures in deep-sea <i>Cibicides</i> and <i>Cibicidoides</i> taxa – long-term observations at in situ pressure

Abstract

Abstract. Deep-sea Cibicidoides pachyderma (forma mundulus) and related Cibicidoides spp. were cultured at in situ pressure for 1–2 d, or 6 weeks to 3 months. During that period, fluorescence analyses following BCECF-AM (2′,7′-bis(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester) or calcein (bis[N,N-bis(carboxymethyl)aminomethyl]-fluorescein) labelling revealed a persisting cytoplasmic sheet or envelope surrounding the Cibicidoides tests. Thus, the Cibicidoides shell can be considered as an internal rather than an external cell structure. A couple of days to a week after being transferred into high-pressure aquaria and adjusted to a pressure of 115 bar, the foraminifera changed from a mobile to a more or less sessile living mode. During this quasi-sessile way of life, a series of comparably thick static ectoplasmic structures developed that were not resorbed or remodelled but, except for occasional further growth, remained unchanged throughout the experiments. Three different types of these permanent structures were observed. (a) Ectoplasmic “roots” were common in adult C. pachyderma, C. lobatulus, and C. wuellerstorfi specimens. In our experiments single ectoplasmic roots grew to a maximum of 700 times the individuals' shell diameter and were presumably used to anchor the specimen in an environment with strong currents. (b) Ectoplasmic “trees” describe rigid ectoplasmic structures directed into the aquarium's water body and were used by the foraminifera to climb up and down these ectoplasmic structures. Ectoplasmic trees have so far only been observed in C. pachyderma and enabled the tree-forming foraminifera to elevate itself above ground. (c) Ectoplasmic “twigs” were used to guide and hold the more delicate pseudopodial network when distributed into prevailing currents and were, in our experiments, also only developed in C. pachyderma specimens. Relocation of a specimen usually required it to tear apart and leave behind the rigid ectoplasmic structures and eventually also the envelope surrounding the test. Apparently, these rigid structures could not be resorbed or reused.

Large-scale culturing of the subpolar foraminifera Globigerina bulloides reveals tolerance to a large range of environmental parameters associated to different life-strategies and an extended lifespan

“…In the later stages of their lifecycle, some G. bulloides individuals began to use their spine and cytoplasm as skeletons for the construction of solid organic structures, comprising both foraminifera cytoplasm and biological matter scavenged from the culture medium. While observed in deep-sea benthic species ( Wollenburg et al., 2021 ) this had not been reported in planktic species before Greco et al. (2023) .…”

“…These structures did not begin to form until at least day 16 and did not become fully developed until day 30 at the earliest, which given the generally short culturing period for G. bulloides in earlier work, would likely explain why they have gone unreported before. It was theorized in the case of deep sea benthic species that ectoplasmic twigs provide a supportive framework from which the rhizopod network can extend and catch food ( Wollenburg et al., 2021 ). As the aggregated particles within the structures on G. bulloides were retained and not consumed it supports the theory that they themselves were not the food source and may have had a role stabilizing and reinforcing the spine and rhizopod network.…”

Benthic foraminifera and gromiids from oxygen-depleted environments – survival strategies, biogeochemistry and trophic interactions

“…(Corliss and Chen, 1988;Lutze and Thiel, 1989). These species have the advantage that they are well adapted to collect fresh food supply from above (Wollenburg et al, 2021) but usually cannot withstand longer O 2 -depleted periods (Mackensen et al, 1995). Nevertheless, recent genetic data indicate that Cibicidoides wuellerstorfi clusters very close to known denitrifying species in the phylogenetic tree, so it cannot be excluded that some Cibicides spp.…”

“…The latter two are not discussed in detail, since they mainly apply to abyssal species that inhabit more oxygenated environments. Nevertheless, some Cibicides and Planulina species can also inhabit environments with relatively low O 2 concentrations (Erdem and Schönfeld, 2017;Rathburn et al, 2018;Hoogakker et al, 2018b;Glock et al, 2022), and at least some of these Cibicides species are certainly suspension feeders (Wollenburg et al, 2018(Wollenburg et al, , 2021. The trophic types that have been introduced above suggest that foraminifera mainly feed on a low trophic level, and it has been suggested that they constitute a trophic link to higher levels in the food chain (Lipps and Valentine, 1970;Gooday et al, 1992;Nomaki et al, 2008).…”

Reviews and syntheses: Foraminifera from anaerobic environments – Survival strategies, biogeochemistry, ecology and applications for paleoceanography

“…(Corliss and Chen, 1988;Lutze and Thiel, 1989). These species have the advantage that they are well adapted to collect fresh food supply from above (Wollenburg et al, 2021) but usually cannot withstand longer anaerobic periods (Mackensen et al, 1995). Nevertheless, recent genetic data indicates that Cibicidoides wuellerstorfi clusters very close to known denitrifying species in the phylogenetic tree, so it cannot be excluded that some Cibicides spp.…”