Color. — Pale gray flecked with small blue spots ; 

 uropods pale blue (Hedgpeth, 1949). 



Habitat. — This species lives in rivers and 

 estuaries. 



Type locality. — Ohio Kiver at Cannelton, Ind. 



Known range. — A narrow zone along Atlantic 

 seaboard from James River, Hopewell, Va. 

 (Hobbs and Massmann, 1952), to southern 

 Georgia; widespread from coastal Alabama to 

 Aransas Bay, Tex.; Mississippi River and tribu- 

 taries upstream to McCurtain County, Okla. ; 

 Fort Smith, Ark.; St. Louis, Mo.; Washington 

 County, Ohio. 



Remarks. — This species is distributed chiefly in 

 brackish and fresh water, ranging far inland in 

 the Mississippi River drainage. It is abundant 

 enough, especially in Louisiana, to provide a 

 fishery of some importance though the exact mag- 

 nitude is not known. Gunter (1937) described 

 the Louisiana fishery and gave information on 

 ecology of the species. Commercially, the shrimp 

 are taken in traps made of. wooden slats, similar 

 to lobster traps, baited with meat scraps or cotton- 

 seed cake. The shrimp are sometimes captured 

 by lifting submerged willow branches from the 

 water and catching the animals as they drop off. 

 Such catches are best made at night. Commer- 

 cial shrimping is done in the warmer months, as 

 the animals are scarce in winter. The shrimp 

 will attack fish kept in live boxes in the river, and, 

 though the feeding habits of the species are not 

 known completely, the animals are thought to 

 be primarily carnivorous. 



During a period of study from November to 

 early July, Gunter found that ovigerous females 

 first appeared in mid- April, and egg-bearing fe- 

 males were still present when the work was ter- 

 minated in July. Ovigerous females have been 

 found in April and May in North Carolina. 

 McCormick (1934) stated that eggs in various 

 stages of development were found in females at 

 the same time that thqy were in berry, which 

 indicates a long egg-laying season. Gunter found 

 females to outnumber males by more than 3 to 

 1. However, this ratio varied. When females were 

 carrying eggs, males made up only 9 percent of 

 the captured individuals, but prior to the egg- 

 laying season males made up 31.8 percent of the 

 total. He concluded that this indicated a change 

 in sex ratio at the egg-bearing period. 



Thirteen percent of the females caught were 

 ovigerous, and these ranged in length from 38 to 

 76 mm. Eggless females ranged from 23 to 93 

 mm. in length. From November to December, the 

 population was made up of individuals 60-80 mm. 

 long. In January, shrimp below 30 mm. average 

 length predominated, but from then until April 

 the average length increased to about 50 mm., and 

 thereafter the range of variation widened as 

 smaller animals came into the catch. 



Gunter found ovigerous females in bay water 

 with salinities ranging from 1.38 to 14.24 °/ 00 . 

 He noted that when the river was on a rise, with 

 turbidity high, few shrimp were taken in water 

 over 20 feet deep, and these were sometimes dead. 

 He conjectured that because these shrimp were 

 not buried in mud, high turbidity in deep water 

 during flood may have an adverse effect on respira- 

 tion. Hedgpeth (1949) suggested that silt causing 

 interference with respiration may drive the 

 shrimp from rivers to estuaries during such 

 seasons, but he also suggested that in regions 

 such as the Atlantic seaboard, where the species 

 is apparently a comparatively recent immigrant, 

 it may still depend on bay waters to complete its 

 breeding cycle. In any case, it is thought that 

 these shrimp and other species of the genus move 

 from river to river through the salty estuaries 

 at the river mouths (Gunter, 1937). 



Especially interesting is the fact that this 

 species and M. acanthurus are forms which may 

 be advanced in the process of moving from the 

 sea to fresh water. Few such examples exist. 



Genus Leander Desmarest, 1849 



Holthuis, 1952, p. 167. 



Leander tenuicornis (Say) 



Figure 46 



Palaemon tenuicornis Say, 1818, p. 249. — Hay and Shore, 1918, 

 p. 392, pi. 27, fig. 6. 



Leander tenuicornis: Holthuis, 1952, p. 155, pi. 41, figs, a-g ; 

 pi. 42, figs, a-f (rev.). 



Recognition characters. — Rostrum well devel- 

 oped ; high in female, more slender in male ; reach- 

 ing about to end of antennal scale; upper margin 

 with 8 to 14 regularly spaced teeth, first two 

 behind orbit; lower margin with 5 to 7 teeth 

 partially concealed by double row of setae. 

 Carapace smooth; antennal spine present, and a 

 branchiostegal spine placed some distance behind 

 anterior margin; branchiostegal groove absent. 



MARINE DECAPOD CRUSTACEANS OF THE CAROLINAS 



55 



