FISHERY BULLETIN: VOL. 73, NO. 4 



Table 2.-Body lengths (mm) of furcilia stages of six species of Nematoscelis. 

 (Medians were based on 6 to 20 individuals of each species for each stage.) 



'Data taken from Gopalakrishnan (1973). 



species (Table 2). Between the species pair N. 

 megalops and A'', difficilis, there is a significant size 

 difference during both the calyptopis and furcilia 

 stages. 



Juveniles of all species of Nematoscelis are 

 identified on the basis of their morphological 

 similarities to adults, especially in such characters 

 as the carapace, the rostrum, and the eye. During 

 the juvenile stages of A'^. tenella, the carapace 

 becomes elongate and narrow as in adults; the 

 dorsal keel on the carapace elongates anteriorly 

 and posteriorly; the broad and curved larval ros- 

 trum becomes short and pointed; and the larval 

 eye develops narrow upper and lower lobes (in the 

 adult eye only the lower lobe remains narrow). 

 These diagnostic features help to distinguish 

 juveniles of N. tenella from similar stages of other 

 species. 



The propodus of the first thoracic leg (max- 

 illiped) is a useful character to identify juveniles, 

 as it is in adults. Although the number of setae on 

 the propodus of this leg is fewer in juveniles than 

 in adults, it is possible to examine the differences 

 in the "style" of setation among juveniles of 

 Nematoscelis. For example, in adults of A^. gracilis 

 there are two rows of setae on the propodus of the 

 maxilliped (Figure 6c); in the juvenile stage this 

 segment develops at least one seta from each 

 position of these two rows. In A^. atlantica the 



same segment has only one row (marginal) of se- 

 tae in adults, and in juveniles at least one seta is 

 present at the position of this marginal row. This 

 difference in the style of setation can be used to 

 distinguish A'', gracilis and A^. atlantica juveniles. 

 The propodus of the maxilliped of N. microps also 

 has one row of marginal setae, but its inner mar- 

 gin is convex; the carpus of this appendage is 

 shorter than its propodus. The prominent dorsal 

 keel on the carapace is a good diagnostic feature of 

 A'', microps juveniles. 



Nematoscelis G. O. Sars— Generic Characters 



The shape of the rostrum variable in males and 

 females; eyes large and bilobed; the peduncle of 

 the first antenna slender in females and thicker in 

 males. Dactylus of the first thoracic leg (max- 

 illiped) triangular, flattened and furnished with 

 comblike setae on its inner lateral margin. The 

 second pair of legs greatly produced and with 

 spines on the distal segment or on both the penul- 

 timate and the distal segments. The endopod of 

 the seventh leg biarticulate in the female, lacking 

 in the male. Eighth leg a simple setose plate. All 

 the four processes— proximal, terminal, lateral, 

 and spine-shaped process— present in the petasma; 

 the spine-shaped process always straight and the 

 lateral without any hooks. 



Key for Identifying Adult Species of Nematoscelis 



The following key is adopted from Hansen (1910, 1912), Boden (1954), Boden et al. (1955), and Mauchline 

 and Fisher (1969). It is modified to include additional information: 



la. Second pair of thoracic legs with long spines from both terminal segment (dactylus) and 

 distal end of propodus. Third to sixth thoracic legs with three segments beyond knee. 

 Maxillule with well-developed pseudexopod. Basis of maxilla bilobed. Ventrolateral spine 

 on coxa of antenna greatly produced (Figure 4A,e,f ). Carapace with conspicuous cephalic 

 ridge (Figure 5f ,g). Eyes large (Figure 4B,e,f ). Propodus of first thoracic leg with setae 



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