FISHERY BULLETIN: VOL. 71, NO. 4 



It should be borne in mind that not all coral 

 damage can be attributed to A. ellisii. The report 

 of predation by Pharia pyramidata (Dana and 

 Wolfson, 1970) is the first indication that the 

 smaller asteroid, which occurs throughout the 

 coral areas of the Gulf, is also a coral-feeder. 

 And, of course, certain fishes are well known to 

 be coral-browsers and commonly leave gouge 

 marks on the coralla. 



The amount of Porites available to A. ellisii 

 in the preferred small form is difficult to evalu- 

 ate. The vast numbers of small encrustations 

 have, perhaps, been unappreciated by coral 

 workers in the Gulf. Dana and Wolfson (1970) 

 estimate approximately 3% coral coverage in 

 their survey areas. While our attempt to count 

 the numbers of Pontes at Pink Cliff station 

 does not warrant critical treatment, we estimated 

 that the encrustations covered roughly 10% of 

 the substrate. 



The important question of how much coral is 

 necessary to maintain the A. ellisii population 

 in the Gulf of California must await some defini- 

 tive information on coral growth rates in that 

 physical regime. Dana and Wolfson (1970) 

 calculated that an average-sized specimen would 

 consume 5.3 m- of coral per year. Our rough 

 estimate of 10% coral coverage at Pink Cliff 

 station would provide 20 m- of Porites per 

 individual. If that can be extrapolated to the 

 Gulf as a whole, even with an allowance for 

 competition, it would appear that A. ellisii is 

 living well within the available resources of its 

 environment. 



Miscellaneous Observations 



In its natural environment, A. ellisii reacts 

 to a touch or a cast shadow with a rapid re- 

 traction of the dermal papulae, resulting in 

 an overall color change from dark red (or orange 

 or yellow) to dull gray. If not further disturbed, 

 the papulae are soon extruded, restoring the 

 original color; if removed from the water, how- 

 ever, the gray persists. This habit reconciles 

 the conflicting descriptions of the species as 

 gray (Steinbeck and Ricketts. 1941) and as 

 rufous (Ziesenhenne, 1937). Madsen (1955) 

 mentions the same phenomenon for A. planci. 



When feeding or at rest, the aboral spines 

 are partly hidden in the papulae, and A. ellisii 

 presents a deceptively harmless appearance. 

 Although it can be more easily removed from 

 the substrate than most asteroids, it should be 

 handled with caution. Ziesenhenne (1937) was 

 uncertain of the toxicity of the spines, but two of 

 us (Barham and Wolfson) can attest to the pain- 

 ful and long-lasting effects of a puncture. 



To augment the meager morphological data 

 available for A. ellisii, we collected and mea- 

 sured six specimens at the termination of the 

 1971 study. Number of arms varied from 12 to 

 15, madreporic bodies from 5 to 9. Overall 

 diameters ranged from 10.7 to 15.4 cm, disk 

 diameters from 7.6 to 9.1 cm. Ratios of disk 

 diameter to arm length (calculated from overall 

 diameter minus disk diameter) ranged from 1.3 

 to 1.6. 



(In comparing specimens, it should be noted 

 that their general appearance will differ mark- 

 edly, depending on the method of preservation. 

 Dried specimens tend to "collapse" and appear 

 less spiny, much flatter, and more bat-armed 

 than if either fixed in preservative before drying 

 or maintained in the preservative. Our speci- 

 mens were preserved in Formalin-' and then 

 dried.) 



Distribution of Adtuthuster 

 adjacent to the Gulf of California 



We have found no Acanthaster at Banderas 

 Bay, our most southerly station, although the 

 environment seems ideal for the sea star. Speci- 

 mens designated as A. ellisii have been reported! 

 at Clarion, Roca Partida, and Socorro Islands I 

 in the Revillagigedo Group, some 24° south ofj 

 the tip of Baja California (Ziesenhenne, 1937), j 

 and the subspecies, A. ellisii pseudoplanei, was I 

 described (Caso, 1962) from specimens collected 

 at various locations in those islands. Whether 

 these identifications will survive taxonomic 

 review of the genus remains, of course, to be| 

 seen. 



3 Reference to trade names does not imply endorsement 

 by the National Marine Fisheries Service, NOAA. 



940 



