The Journal of Experimental Biology

The Journal of Experimental Biology

582

larval behaviour (Leys and Degnan, 2001; Leys et al., 2002; Leys

and Degnan, 2002). Investment in sequencing ESTs provided early

hints of interesting genomic complexity (Degnan et al., 2008), which

led the way to sequencing the first sponge genome (Srivastava et al.,

2010). But Amphimedon queenslandica is only available in eastern

Australia, cannot be cultured in the lab and broods its larvae, so

embryos are inaccessible to manipulation. Tethya wilhelma lives

easily in aquaria and has an interesting contraction behaviour

(Nickel 2001; Nickel, 2004). Sponges in the genus Tethya are

thought to be oviparous, but because reproduction has not been

observed in lab specimens, so far work has been on buds. If these

buds could be grown in thin ‘sandwich’ cultures under a coverslip,

however, it would allow a greater range of experimental approaches.

There is published work on the physiology (Lentz, 1966) and

recently also the molecular biology (Leininger et al., 2014) of Sycon,

a genus of calcareous sponge. The embryos and larvae are brooded

and so are inaccessible to manipulation in vitro, but the sponge is

small and therefore lives well in flow-through seawater tanks; it thus

has the potential to be adapted more widely as a cold-water model

species.

By far the easiest sponges to maintain and study in culture world-

wide are spongillids. These are a group of haplosclerid

demosponges which colonized freshwater between 183 and 141

million years ago (Meixner et al., 2007). A suite of papers describing

the morphology and development of canals, choanocytes and

spicules established this as an easy-to-use system (Weissenfels,

1976; Weissenfels and Landschoff, 1977; Weissenfels and Striegler,

1979; Weissenfels, 1980; Weissenfels, 1981; Weissenfels and

Hündgen, 1981; Weissenfels, 1982; Weissenfels, 1983; Weissenfels,

1984; Wachtmann et al., 1990; Weissenfels et al., 1990; Weissenfels,

1992). The attractiveness of this model, which was highlighted by

Yoko Watanabe through the film ‘Life of the freshwater sponge’

(Tokyo Film Corporation http://tokyocinema.net/EnglVieo.htm), has

led to more recent studies on signalling and coordination of sponge

behaviour (Elliott and Leys, 2007; Elliott and Leys, 2010), epithelia

(Leys et al., 2009; Adams, 2010), patterning (Windsor and Leys,

2010) and most recently, sensory cells (Ludeman et al., 2014). And

since freshwater sponges are easily obtained and cultured in Europe,

Japan and North America, there is a body of knowledge on the

genetics of development (Richelle-Maurer et al., 1998; Richelle-

Maurer and Van de Vyver, 1999; Nikko et al., 2001; Funayama et

al., 2005a; Funayama et al., 2005b; Mohri et al., 2008; Funayama et

al., 2010; Holstien et al., 2010; Funayama, 2013) and even the

possibility of using RNA interference methods (Rivera et al., 2011).

Typically, gemmules are collected during winter months and kept

refrigerated to hatch as needed in the lab, but it is also possible to

keep a population over the long term by returning hatched batches

to lakes. Individuals of freshwater sponges – and therefore all

gemmules from one individual – are either male or female, and

gametes can be obtained from cultures maintained in lakes (Mukai,

1989; Mukai, 1990).

Ecology of Ediacaran seas, sponge function and behaviour

What food would have been available to the first metazoans?

Bacteria, flagellates and other early phytoplankton would probably

have been the primary prey (Lenton et al., 2014). With no life yet

on land, bacteria-rich seas fertilized by aggregates of faeces would

not have existed and without that it is unlikely there would have

been high levels of dissolved organic carbon (DOC). Paleontological

evidence for high levels of dissolved organic matter in deep

Ediacaran oceans is equivocal (Halverson et al., 2009), as is fossil

evidence for larger animals at that time (e.g. Maloof et al., 2010).

Capture of prey would be best achieved by filtration and

concentration of food, which favours the idea of a filter/suspension

feeder arising before the evolution of complex nervous systems. If

filtration was the mechanism of feeding, it may have been

energetically expensive (Leys et al., 2011), so it is unlikely to have

originated in deep oxygen-poor oceans. Therefore, this animal

would most likely have evolved in shallow waters in competition

with other flagellates and have specialized to be efficient at filtering.

REVIEW

The Journal of Experimental Biology (2015) doi:10.1242/jeb.110817

Rhabdocalyptus dawsoni

Sycon coactum

Sycon ciliatum

Oscarella lobularis

Ephydatia muelleri

Oscarella carmela

Oopsacas minuta

Tethya wilhelma

Amphimedon queenslandica

Suberites domuncula

Fig. 1. Model sponge species

studied world-wide.

Hexactinellids: Rhabdocalyptus

dawsoni, Oopsacas minuta;

Calcarea: Sycon coactum, Sycon

ciliatum; Homoscleromorphs:

Oscarella lobularis, Oscarella

carmela; Demosponges: Tethya

wilhelma, Suberites domuncula,

Amphimedon queenslandica,

Ephydatia muelleri. Stars indicate

locations where freshwater sponges

are studied. Photos: R. dawsoni, 

S. coactum, O. minuta, E. muelleri,

T. wilhelma, A. queenslandica, 

S. Leys; O. carmella courtesy of 

S. Nichols; O. lobularis reprinted

with permission from Van Soest 

et al. (Van Soest et al., 2012); 

S. domuncula, reprinted with

permission from Müller et al. 

(Müller et al., 2012).

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