NUMBER 4 0 . 15 



TABLE 1. Summer reproductive state as a percentage of specimen surface. 









Mature 



Conceptacles 



Faint conceptacic 





Not reproductive'' 



Initial state'' 



conceptacles 



growing out 



remains 



Subregion 



(%) 



(%) 



(%) 



(%) 



(%) 



Northern Labrador 



19 



0.3 



40 



36 



3.5 



Southern Labrador 



32 



0 



32 



31 



4.5 



NE Newfoundland 



62 



0 



3 



15 



20 



Northern Gulf of St. Lawrence 



52 



0 



Trace 



3.1 



45 



Gulf of Maine" 



30 



0 



0 



10 



60 



■'Midsummer (July-August) reproductive (asexual) state in Clathromorlihiim compactiim from northern Labrador to the Gulf of Maine. The values 

 for each of the Subarctic subregions are estimated from 40 haphazardly selected sets of undamaged specimens with a 20-50 cm- surface, estimated 

 using a dissecting microscope. 

 ''Conceptacle caps. 

 ^From Adey (1965). 



Figure lOA. The sporangia! caps (plugs), which are embedded in 

 the calcified conceptacle roof tissue, and the uncalcified sporan- 

 gial mother cells are together about 150 pm long at maturity (be- 

 fore spore formation). The sporangia and surrounding vegetative 

 filaments form a developmentally uncalcified fertile cylinder that 

 is approximately 100 pm in diameter and 100 pm long before 

 final expansion to sporangial maturity. As we shall show, fertile 

 cylinder development requires the accompanying production of 

 about 10-12 cells in each filament of the surrounding vegetative 

 tissue. Near sporangial maturity, the carbonate component of an 

 80-pm-thick underlying vegetative tissue is dissolved beneath the 

 enlarging sporangia, with an additional 70-80 pm of carbonate 

 also dissolved laterally, to make room for the large sporangia to 

 fully mature. The sporangia produce bispores, each of which is 

 approximately 1,000 times greater in volume than the individual 

 surrounding vegetative ceils. The total noncalcified, organic vol- 

 ume of crushed vegetative cells is approximately ecjual to the 

 final spore volume. In the southwestern Labrador Sea, this final 

 expansion phase occurs in late spring and early summer, just 

 after ice breakup, when available light should be at a maximum. 

 Figure lOB, reduced to show primarily sporangial development, 

 provides a mean pattern for northern Labrador, where concep- 

 tacle maturation is delayed even longer into the next summer. 



Sporangial conceptacle development is initiated in early au- 

 tumn, and at maturity carbonate solution and crushing of previ- 

 ously formed summer vegetative tissue occurs to about 80 pm 

 below the plane of sporangial initiation. In southern Labrador 

 and northernmost Newfoundland, there is a greater level of veg- 

 etative cell fusion for a limited period at the time of sporangial 

 initiation. This cell fusion creates a weak zone in the carbonate, 

 and horizontal fractures are easily induced on this plane, as can 

 be seen in Figure 11. 



As shown by Adey (1965) for the Gulf of Maine and here 

 for the core Subarctic (Table 1), 20%-30% of the plant surface 

 in each year does not become reproductive. This is seen in an 



analysis of conceptacle bands in a C. compactum plant from Lab- 

 rador (Figure I2A,B), where every fifth to seventh year a growth 

 ring is devoid of a conceptacle band. Specimens have been found 

 in which extensive conceptacle production has occurred for sev- 

 eral consecutive years, followed by years with few or no con- 

 ceptacles (Figure 2B). In one very old specimen from northern 

 Labrador, several hundred years' worth of missing ct)nceptacle 

 bands were seen. This phenomenon implies that anatomy must 

 be consulted, in addition to measuring tiie number of concep- 

 tacle bands or the thickness between bands, in order to obtain 

 an accurate yearly archive. If it is suspected that several years are 

 missing, this suspicion is relatively easy to confirm with anatomy. 

 If conceptacles were apparently missing for many years, it would 

 be necessary to confirm by counting each year's Mg cycle. As 

 shown in Figure I2B, broken-out conceptacles can "grow in" 

 by regrowth of vegetative cells from the base and sides, nearly 

 obliterating evidence of the presence of the conceptacle in a su- 

 perficial analysis. The perithallial tissue that has grown back into 

 the conceptacle cavity will have formed several months later than 

 the surrounding tissue, depending on geographic latitude. 



In the specimen shown in Figure 12B, the years 2005 and 

 2006 lack buried conceptacles. For the year 2007, a broken- 

 out conceptacle appears on the right (note the presence of a full 

 conceptacle farther to the left). During the summer following 

 breakout, new tissue formed at the base of the conceptacle and 

 refilled the cavity during the following summer. This new tissue 

 was formed months later than the surrounding vegetative tissue. 

 A laser scan passing through the broken-out and grown-in con- 

 ceptacle would show carbonate chemistry totally out of phase 

 with that of the larger specimen on the same plane, unless the 

 presence of this grown-out conceptacle were taken into consid- 

 eration. Conceptacle cavities are oblate spheroids; because spo- 

 rangial formation begins in autumn (see Figure 10), a horizontal 

 plane through the principal diameter of the spheroid approxi- 

 mately marks the beginning of October. 



