THE BRINE SHRIMP. 



Bv W. T. CALMAX. D.Sc. 



The pretty little Crustacean known as the Brine 

 Shrimp was first discovered about the middle of the 

 eighteenth centur\at L\"mington. in Hampshire. In 

 those da\s, and for something like a century after- 

 wards, the manufacture of salt from sea water was 



carried on there and at 

 other places on our coasts, 

 the hrst stage of the pro- 

 cess being the concentration 

 of the sea-water by exposing 

 it to evaporation by the 

 heat of the sun in large 

 shallow ponds. The con- 

 centrated brine was then 

 into open vats known 



run 



to 

 b\- 



Figure 1. 



The Brine Shrimp. 



Artciiiiii salina. 

 Female, from below. 



The line indicites actual length. 

 (.\fter G. O. Sars). 



as " salterns." previous 

 being further evaporated 

 artificial heat, and 

 it was in these 

 vats that the Brine 

 Shrimps, or " brine- 

 \\orms" as thev were 

 called, appeared in 

 such numbers as 

 to give the brine 

 a reddish tinge. 

 Thev were believed 

 to be of service in 

 clearing the liquid from im- 

 purities, and the workmen 

 were in the habit of trans- 

 ferring some of them from 

 one " saltern " to another, 

 when they did not make their appearance naturallw 

 to ensure their presence when the brine had 

 reached the proper degree of concentration. Brine 

 Shrimps ha\e since been found in many parts 

 of the world in natural or artificial brine-pools 

 and lagoons and in salt lakes, and, although 

 a number of species have been described, there 

 is reason to believe that they are all forms of 

 a single variable and cosmopolitan species, Arteinia 

 salina, which ranges from Greenland to Australia, 

 and from the Great Salt Lake of Utah to Central 

 Asia. 



The Brine Shrimp belongs to the sub-class 

 Branchiopoda, which includes the most primiti\e 

 of existing Crustacea, and it is closely allied to 

 the " Fairv Shrimp," Chirocephaliis diaphaiiits. 

 recentlv described in the pages of "Knowledge" 

 (July, igiO), by Mr. G. W. Pyman. 



The body of Arteinia is usually about half-an-inch 

 in length. Like that of Cliiroceplialiis it is worm- 

 like and completely divided into segments, without 

 a protecting shield or carapace, such as is found in 

 most other Crustacea. The first eleven segments 

 behind the head each carry a pair of flattened fin-like 



Figure 2. 



Nauplius larva, 

 just hatched, 

 highly magnified. 



feet, bv the rhythmical movements of which the 

 animal swims. The hinder part of the body forms 

 a slender tail and is without appendages. The head 

 bears a pair of compound eyes set on movable stalks 

 and a third eye, very small and of simple structure, 

 in the middle line in front : the three e3-es are 

 coloured with dark reddish-brown pigment. There 

 are two pairs of feelers, the first pair, or antennules, 

 slender and thread-like, the second, or antennae, 

 short and stumpy in the female, but \er\- large in 

 the male, and forming a pair of curiously-shaped 

 claspers for seizing the female. The female, when 

 fullv mature, carries her eggs in a sac-like receptacle 

 on the under-side of the body at the base of the tail. 

 The animals are generally of a pale reddish colour, 

 owing, as Sir Rav Lankester first showed, to the 

 presence in the body fluids of haemoglobin, the 



substance which gives its colour to the 



blood of \'ertebrates but is not often found 



in Invertebrate animals. 

 The Brine Shrimp 



Branchiopoda. usually 



wards, and it feeds 



on minute floating 



organisms and parti 



like most of the 

 swims back down- 



cles of organic matter 



(Afler G. O. S.-irb). 



which are drawn in 



towards the mouth by 

 the movements of the feet. 

 The phenomena of re- 

 production are of particular 

 interest. Like many, but 

 not all. of the Branchiopoda 

 the Brine Shrimp repro- 

 duces extensively by par- 

 thenogenesis, that is to 

 say, the females lay eggs 

 w hich are capable of devel- 

 opment without being ferti- 

 lised. In some localities, 

 in fact, it appears that 

 males are never found, 

 the colonies consisting 

 entirelv of females. In 

 other localities the two 

 sexes occur in nearly 

 equal numbers, and repro- 

 duction takes place by 

 fertilised eggs. There 

 is some evidence to show that there may be two 

 races of Brine Shrimps, the one e.xclusively 

 parthenogenetic, the other sexual, but it is by no 

 means clearlv ascertained what the exact relations 

 between the two forms are. 



The eggs are globular in shape, about one- 

 hundredth of an inch in diameter, and when 

 deposited are enclosed in a tough shell which 



Figure 3. 



The Brine Shrimp, 



Art cm ia salina, 



Male, from above. 



(After G. O. Sar>). 



227 



