Preliminary Observations on the Development 

 of Leptasterias hexactis 



H. L. OSTERUD, 



University of Washington, Seattle 



Leptasterias is a genus of small starfishes eonimon on the Pacifiic 

 ("oast from northern Alaska to California. Some species extend in their 

 distribution into Puget Sound and abound on the shores of the San Juan 

 Islands and adjacent territory; but to the best of the writer's knowledge, 

 they are confined to this northern region of the Sound and are not recorded 

 from regions south of Port Townsend. Of the species given by Verrill 

 (1914), 3 appear to be found in the San Juan Island region. Lepasterias 

 hexactis, L. aequalis, and L. epichlora. It is indeed difficult in the region 

 of Friday Harbor to find specimens that answer well to the specific de- 

 scriptions of these starfishes. There are apparently so many local varie- 

 ties, and intergradation is so close, possibly through extensive hybridiza- 

 tion, that the distinction of species with certainty, at least by the non- 

 specialist, becomes very difficult or quite impossible. The adult Leptas- 

 terias may be readily found under rocks at low tide. These animals are 

 grayish to brownish-green in color, closely similating the color of the 

 rocks to which they cling; occasionally they may be reddish-brown. Some 

 reach the maximum size of 120 mm. in diameter, while the average of those 

 collected for this study was about 54. mm. Specimens measuring 24 mm. 

 have been found sexually mature and reproducing. The Leptasterias of 

 the San Juan Island region is normally 6-rayed (Fig. 1) tho rarely a 5- 

 or a 7-rayed specimen is collected. The females of the genus brood their 

 young, which never assume a free swimming stage, but pass through their 

 entire metamorphosis j^rotected by the mother. The young are therefore 

 very easily obtained. All the young of a given female are, as would be 

 expected, approximately in the same stage of dev<loi)meiit. 



Material for the study of the development of Lejitasterias was col- 

 lected in 3 visits to the Puget Sound Biological Station, in April, 1912, 

 .March, 1913, and February, 1911. On account of other duties it has not 

 been ])ossible at these times of the year to remain at the station for a 

 period sufficiently extended to follow the development in the living condi- 

 tion; and on account of the brevity of the visits the series of stages 

 secured is still incomplete in the early development. The attempt was 

 made to transfer the animals to Seattle and there rear the young, but with 

 disastrous results, the young dying very quickly. It seems advisable, how- 

 ever, to make known the general character of the develoi)ment and the 



(1) 



