4 



SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES 



FIGURE 2A. Clathromorphum compactitm buildup (clathrostrome) crowning large cobble in cor-strome, including branching Lithoth amnion 

 spp. at 20 m depdi in southern Labrador. Crusts are 2-4 cm thick and 100-250 years old. Green sea urchins (Strongylocentrotus droebachien- 

 sis) are 30-50 mm in diameter. © Nick Caloyianis. Reprinted with permission. 



introduce the term clathrostrome to refer to extensive carbonate 

 crustal buildups dominated by the two Clathromorphum spe- 

 cies, C. compactum and C. nereostratwn. 



Biology and Ecology of Clathromorphum 



As with most red algae, crustose corallines have a basic 

 filamentous structure; in this group, the filaments are fused into 

 a calcified crust (Figures 2A-2C). As described by Adey (1964, 

 1965, 1966a, 1966b) and Adey et al. (1982; 2005), crustose 

 corallines combine these filaments into complex tissues with 

 the filaments linked by fusions and/or secondary pits. Also, sev- 

 eral different patterns of growth, within the carbonate frame- 

 work, characterize different genera (Adey et al., 2005). In many 

 cases the development of reproductive structures occurs within 

 perithallial tissue and is integrated with the growth of that tissue. 

 Given damage to the overlying meristem or in the formation of 

 conceptacle fertile discs, meristematic activity can be reinitiated 



within the uppermost years of perithallial tissue (forming char- 

 acteristic wound repair tissue). 



Like many higher plants and unlike all other red algae, cor- 

 allines have an intercalary meristem (Adey, 1964; Adey et al., 

 2005; Figure 2C); along with other elements of their anatomy 

 and reproduction, this characteristic has led to their separation 

 as an order of red algae (Corallinales; Silva and Johansen, 2007). 

 Recent phylogenetic work suggests the group may be separable 

 at the level of subclass on the basis of the structure of cell pit 

 connections (Bittner et al., 2011). In a multigene analysis of gen- 

 era with multipored conceptacles, currently under development 

 with colleagues (Adey et al., unpublished), we are able to show 

 that Clathromorphum forms a distinct clade most closely related 

 to Leptophytum and distant from the Lithothamnion and Phy- 

 matolithon clades. 



Corallines occurring on hard bottoms in shallow seas can 

 be reef formers in the tropics (Adey, 1998) and rock-blanketing 

 carbonate formers (cor-stromes) in colder waters. They are often 



