CAPRELLIDAE OF WESTERN NORTH ATLANTIC 3 



The number of articles in the flageUum of antenna 1 varies consider- 

 ably, depending upon the size and sex of the individual. The greatest 

 number of articles may be useful for characterizing some species with 

 an unusually long flagellum. The relative lengths of the proximal and 

 distal flagellar articles have been used to characterize some species but 

 probably do not have generic significance. Mayer divided Caprella 

 scaura into groups on the basis of the number of fused proximal articles 

 of the flagellum; however, in most species this number is proportional 

 to the size of the individual and is of Httle value. 



Most capreUid genera have 2 articles in the flagellum of antenna 

 2; however, some genera such as Phtisica and He wi^J/'oto have more 

 than 2. Phtisica lacks a molar on the mandible. The lack of a molar 

 and the multiarticulate flagellum on antenna 2 may be correlated 

 ^\dth the fact that Phtisica is frequently found in plankton samples and 

 therefore subject to dietary habits different from those of benthic 

 forms. 



Mayer (1903, p. 47) used the presence of swimming setae on antenna 

 2 to characterize Tritella. Later Dougherty and Steinberg (1953) 

 described Tritella tenuissima which lacked swimming setae, and they 

 expressed the opinion that the presence or absence of swimming setae 

 w^as not a good generic character. Since T. tenuissima shares more 

 characters with Triliropus (p. 57) than with the members of Tritella, 

 Mayer's beUef that the presence of swimming setae is a valid generic 

 character seems justified. 



The mouthparts offer, in my opinion, some of the best, although 

 virtually neglected, taxonomic characters. The mouthparts reflect 

 feeding habits and thereby, at least to some extent, the niche of an 

 organism. Mayer (1903, p. 13) admitted that he neglected the mouth- 

 parts except for the proportions of the maxiUipedal lobes and the 

 mandibular palp. Regrettably, he (1890, p. 107; 1903, p. 73) believed 

 that the mouthparts of the Caprella species were all quite sunilar and of 

 little value in classification. Most of the mouthparts of Caprella 

 species are similar; however, the lacinia mobihs of the right mandible 

 offers a useful character for subdividing this large genus. The left 

 lacinia mobihs is usually 5-toothed apically, while the right lacinia 

 mobihs may be either 5-toothed, serrate, or smooth. Phtisica and 

 allied genera have developed ^ several accessory plates iu addition to 

 the lacinia mobihs, and these genera usually lack a molar (fig. 47i-j). 

 This unusual type of mandible undoubtedly reflects genetic relation- 

 ships and will probably form a basis for separation of the Caprelhdae 

 into subfamihes or other higher taxa. 



2 Assuming that the caprcllids arose from a podocerid type gammaridean having 

 a typical mandible with incisor, lacinia mobilis, setal row, and molar. 



