Disrupted spiculogenesis in deep‐water Geodiidae (Porifera, Demospongiae) growing in shallow waters

Abstract

Environmental conditions can affect the morphology and distribution of sponges. In particular, depth is known to influence the morphology of shallow-water sponges; however, the influence of depth on deep-water sponges has never been investigated. Although boreal Geodiidae (Demospongiae, Astrophorida) are deep-water species, in fjords and along the Norwegian coast Geodia barretti, G. simplicissima, and Pachymatisma normani can occasionally be found at shallow depths (20-40 m). In this study, we examine new shallow specimens from the Norwegian coast to compare their morphological and molecular characteristics with those of their deep-water counterparts. Morphology was studied at the level of the organism, skeletal organization, and the spicules, and a fragment of the cytochrome oxidase 1 gene was sequenced for shallow and deep specimens. Twelve specimens of Geodia spp. and five specimens of P. normani were collected in shallow waters. The majority of the Geodia spp. were identified as G. simplicissima, a species that has not been reported since its original description in 1931. However, we propose that G. simplicissima, only found in shallow waters, is a junior synonym of G. barretti. When comparing shallow and deepwater specimens of G. barretti and P. normani, we found phenotypic differences with respect to color, external morphology, cortex organization, and, above all, spicule morphology. In shallow specimens, microrhabds, sterrasters, and triaenes were smaller and irregular or underdeveloped. Oxyasters and strongylasters were normal in form, but smaller. We hypothesize that the lower silica concentration in shallow waters is primarily responsible for the disruption of spiculogenesis in shallow-water specimens of G. barretti and P. normani. The underdeveloped sterrasters observed in shallow-water specimens provide new insights into the formation of these particular microscleres. Finally, we discuss how the colonization of shallow waters by deep-water sponges may have strongly influenced spicule evolution and speciation.

The presence of the diagnostic character of the genus Paraleucilla (Amphoriscidae, Calcarea, Porifera) may depend on the volume and body wall thickness of the sponges

“…; Cavalcanti et al. ; Cárdenas & Rapp ). For P. magna , among the parameters tested to provide an explanation for the variability in the composition of its skeleton, only rainfall and those parameters related to the “size” of the sponge (volume and BWT) were good predictors of the presence or absence of the DZ.…”

Integrative taxonomic description of Plakina kanaky, a new polychromatic sponge species from New Caledonia (Porifera: Homoscleromorpha)

“…Nevertheless, the presence or absence of a spicule type could be also the result of bio availability of silica in the surrounding waters (Maldonado et al . ; Cárdenas & Rapp ). Only two other Plakina species described from the Pacific Ocean, Plakina australis (Gray ) and Plakina corticolopha Lévi & Lévi ; lack diods and triods, but they differ from P. kanaky sp.…”

“…; Meroz‐Fine et al . ; Cárdenas & Rapp ), to biotic factors such as predation (Loh & Pawlik ) or to the occurrence of photosynthetic symbionts, such as cyanobacteria for instance. In some cases, individuals of a given species can appear less similar than those of different species (Ackers et al .…”

Assessing the Potential of Sponges (Porifera) as Indicators of Ocean Dissolved Si Concentrations

“…Additional information about variations in the shape, or size of sponge spicules, or about disrupted spiculogenesis (shape changes, atrophies or other malformation of spicules) in relation to dSi concentration is scattered throughout the literature (Jørgensen, 1944;Hartman, 1958;Stone, 1970;Yourassowsky and Rasmont, 1984;Zea, 1987;Bavestrello et al, 1993;Rützler and Smith, 1993;Schönberg and Barthel, 1997;Mercurio et al, 2000;Valisano et al, 2012;Cárdenas and Rapp, 2013). Overall these studies show that the availability of dSi is a factor that can affect the morphology, composition or size of spicules in some species.…”