ON ADAPTATIONS IN STRUCTURE AND HABITS OF SOME MARINE 

 ANIMALS OF TORTUGAS, FLORIDA. 



By J. F. McClendon. 



In June, 1908, at the laboratory of the Carnegie Institution of Wash- 

 ington, at Tortugas, Florida, I began the study of the habits of some reef 

 animals with a view to some comparative studies of behavior. The 

 results were written up in the Zoological Laboratory of the University 

 of Missouri. 



It was found that many of these animals were thigmotatic and 

 remained in glass tubes rather than in the open. They also learned 

 to find the tubes when removed from them. Such was the case with 

 five species of the Alpheidae, one of the Pontoniidse, Typton tortugcs 

 Rathbun, and Gonodactylus cerstedii. All the anemones were thigmo- 

 tactic on their bases. These same animals were heliotropic. The Crus- 

 taceans were negatively heliotropic and the anemones kept their bases 

 from the light, while Cradactis variabilis Hargitt hid all but the tips 

 of the fronds and tentacles from the light. In removing its base from 

 the light, Stoichactis helianthiis, which lives on coral heads, makes snail- 

 like movements similar to Metridium,^ while Cradactis, which lives in 

 holes in decaved coral heads, crawls on its tentacles. 



ON ADAPTATIONS OF SYNALPHEUS BROOKS! AND TYPTON 



TORTUG.C. 



In lagoons between the reefs is found the loggerhead sponge, Hir- 

 cinia acuta, which grows to 3 feet or more in diameter, but is of no com- 

 mercial value. The passages in this sponge are thickly populated by 

 Synalpheus brooksi Coutiere. These Alpheids are thigmotactic and 

 negatively heliotropic and seldom come outside the sponge, which they 

 do only at night and then rarely leave its surface. The only other 

 animals seen in the interior of the sponge were a small species of Amphi- 

 pod and a Pontoniid. The Alpheids were several hundred times as 

 numerous as the Amphipods or Pontoniids. Near or at the surface crabs 

 and worms were sometimes found. 



Both Alpheid and the Pontoniid, Typton tortugce, have the fourth 

 and fifth pairs of thoracic appendages pincer-like (plate i, figs, i and 3). 

 In the Alpheid the fourth and in the Pontoniid the fifth pair are asym- 

 metrically hypertrophied. In the Alpheid the asymmetry is very great, 

 and the large chela can be snapped with such vigor as to produce a loud, 

 clicking sound. When this claw is removed its mate grows to replace 



' McClendon, 1906, On the Locomotion of a Sea Anemone, Biol. Bull. 10. 



57 



