The morphological adaptation of Lithocodium aggregatum Elliott (calcareous green alga) to cryptic microhabitats (Lower Aptian, Spain): an example of phenotypic plasticity

Abstract

Lithocodium aggregatum Elliott is interpreted as a heterotrichale chlorophycean alga with a prostrate and erect system within a well-calcified tissue. Within Lower Aptian coral rubble of the western Maestrat Basin, Spain, it forms thick masses of juxtaposed crusts around the bioclasts. In achieving a rapid and complete encrustation of the available bioclasts, Lithocodium applied several strategies, e.g., filling voids of structured surfaces with a special fabric or forming erect extensions to bridge adjacent substrates. In these deposits, different types of poorly if ever illuminated cryptic microhabitats can be distinguished: (1) existing crypts such as empty shells or structural voids within bioclasts (2) crypts resulting from the complete encrustation of adjacent bioclasts by Lithocodium itself and (3) syndepositionally created crypts, e.g., boreholes produced by lithophagid bivalves. In these cases, Lithocodium developed a poorly calcified structure of large cells with thin microcrystalline walls indicating a high degree of variability (phenotypic plasticity). This cryptic growth stage is interpreted as an adaption to the poorly illuminated crypts (photoadaption) in order to maximize light capture for photosynthesis. The Lower Cretaceous Lithocodium is therefore not per se a cryptoendolithic microorganism, but may show adaptation to develop and survive also in these already existing or newly created niches.

Paleobiology of firmground burrowers and cryptobionts at a Miocene omission surface, Alcoi, SE Spain

“…To a lesser extent, even the activity of infaunal soft- and mainly hard-substrate cryptobionts is known in marine paleoenvironments (see Uchman et al, 2003 and references therein). Today, the most common organisms with cryptic habits are algae, foraminifera, sponges, corals, polychaetes, mollusks, bryozoans, and brachiopods (Kobluk and Lysenko, 1993; Lukeneder and Harzhauser, 2003; Taylor and Wilson, 2003; Zuschin and Mayrhofer, 2009; Schlagintweit and Bover-Arnal, 2012).…”

Geological reservoir characterization of the Lower Cretaceous Dariyan Formation (Shu'aiba equivalent) in the Persian Gulf, southern Iran

“…According to many authors (e.g., Tucker and Wright, 1990;Leinfelder, 2001;Schlagintweit and Bover-Arnal, 2012), Lithocodium aggregatum is a depth indicator (representing a water depth of 10 to 20 m) and occurrence of this flora suggests a shallow-water settings above the fair-weather wave base, such as inner ramps. On the other hand, Banner and Simmons (1994) stated that the micritic matrix of lithocodium indicates low paleocurrent velocities (less than 10 cm/sec), and there considered more likely to have been in warm, marine, well oxygenated settings.…”

Investigation of Microfacies—Electrofacies and Determination of Rock Types on the Aptian Dariyan Formation NW Persian Gulf

“…8) MF8 Foram-Algal Floatstone/Wackestone Description: The most characteristic component of the facies is large Lithocodium aggregatum clasts (green algae sensu) [24], associated with various large and small foraminifers (Orbitolina, Miliolids, Valvulinid) and oncoids. Other bioclasts are ostracods, algal debris (Salpingoporella), gastropod, and echinoderms debris.…”

“…According to many authors [24] [26] [27], Lithocodium aggregatum is a depth indicator (representing 10 to 20 m) and occurrence of this flora suggests the shallow-water settings (such as inner ramps) above fair-weather wave base. On the other hand, the micritic matrix of Lithocodium indicates low palaeocurrent velocities (less than 10 cm/sec), and it is more likely to have been in warm, fully marine, well oxygenated mid ramp (15 to 60 m) [28].…”