KNIGHT: DEVELOPMENT OF EUPHAUSIA GIBBOIDES 



entire margin of carapace, not only the rostral 

 hood, is spinose. Euphausia brevis, E. krohnii, 

 and E. eximia, unlike E. gibboides, have two 

 small dorsal spines on the carapace; E. dio- 

 mediae, the only other species of Group A identi- 

 fied has instead a "sharp eminence" which, as 

 figured (Ponomareva 1969, Figure Ic), is con- 

 siderably higher and sharper than the dorsal 

 prominence of E. gibboides. The metanauplius 

 o{ E. pacifica has a dorsal crest more like that 

 ofE. gibboides but may prove, with further study, 

 to be consistently smaller; 25 specimens mea- 

 sured from one location by the author ranged 

 from 0.44 to 0.48 mm in total length with an 

 average of 0.46 mm. A metanauplius with fringed 

 rostral hood and two small dorsal spines is 

 figured by Boden (1955) as one of the larval stages 

 o{E. lucens. It appears, however, that the larvae 

 are those of another species of the genus (Bary 

 1956), and the form of the metanauplius suggests 

 that it might belong to a species of Group A 

 Euphausia. 



Calyptopis stages with spinose anterior margin 

 of carapace are found in all of the species listed 

 above excepts, pacifica. The calyptopes of Group 

 A species may be easily distinguished from those 

 of E. gibboides by relative width of carapace; 

 they do not have the anterolateral expansion over 

 the eyes. The carapace of the two species of 

 Group D is wide but, unlike E. gibboides, with 

 a very high peaked dorsal crest. Also, the entire 

 margin of the carapace of E. longirostris is 

 spinose, the first calyptopis is not described but 

 presumably it does not differ from calyptopes II 

 and III in this respect. The third calyptopis of 

 Lebour's E. sp. (1949, Figure 4, 3-4) resembles 

 E. gibboides in width of carapace, but the lateral 

 margins of the carapace are spinose. The carapace 

 of the calyptopis I described by Boden (1955, 

 Figure 12) is expanded anterolaterally, but it 

 appears to be proportionally longer than the 

 carapace oiE. gibboides. The relative lengths of 

 the posterolateral spines of the telson also 

 differ; the 3rd posterolateral spine is relatively 

 short; as figured it is no longer than the terminal 

 spines. The second and third calyptopes of this 

 species have relatively narrow carapaces. 



The most useful character for the identifica- 

 tion of furcilia stages oiE. gibboides is the rela- 

 tively large 3-lobed eye; wddth of rostral plate 

 and form of pleopods and telson may be helpful 

 as well in differentiating furcilia with spinose 



anterior margin of carapace. Furcilia ofE. gib- 

 boides may be separated from those of Group A 

 Euphausia as follows: 



Furcilia with 1 pair of non-setose pleopods — 

 the rostral plate appears to be of greater 

 vddth \nE. gibboides; 



Furcilia with both setose and non-setose pleo- 

 pods — in Group AEuphausia there is usually 

 only one form and it has 1 setose plus 4 non- 

 setose pairs of pleopods on abdominal seg- 

 ments 1-5 respectively (Sheard (1953) reports 

 numerous variants in the furciliar develop- 

 ment of a species identified as E. recurua), 

 E. gibboides has two forms, 1 setose plus 3 

 non-setose and 4 setose plus 1 non-setose 

 pair of pleopods; 



Furcilia with 5 pairs of setose pleopods — the 

 inner margin of the 3rd (inner) posterolateral 

 spine of the telson is smooth except for tiny 

 distal spinules in larvae of £■. gibboides and 

 spinose in larvae of Group A. 



A single character is sufficient to separate 

 furcilia of E. gibboides from those of E. longi- 

 rostris and E. spinifera; both Group D species 

 have a dorsal spine on segment 3 of the abdomen 

 beginning in furcilia I. The furcilia with 1 pair 

 of non-setose pleopods figured asE. sp. by Lebour 

 (1949, Figure 4, 5-6) differs from E. gibboides 

 in relative length of posterolateral spines 2 and 

 3 of the telson; as drawn they are almost equal 

 in length. The telson of the second furcilia which, 

 like E. gibboides, has 1 setose and 3 non-setose 

 pairs of pleopods is not figured, and details of 

 the two forms are not described. The first furcilia 

 figured by Boden (1955, Figure 15) also differs 

 from E. gibboides in length of posterolateral 

 spines of the telson; the 2nd pair are almost the 

 same length as the 3rd pair and only a little longer 

 than the 1st pair. The second furcilia of the species 

 has 1 setose and 4 non-setose pairs of pleopods 

 as found in species of Group A Euphausia. 



ACKNOWLEDGMENTS 



I am grateful to E. Brinton for encourage- 

 ment and assistance as well as review of the 

 manuscript. The work was supported by the 

 Marine Life Research Program, the Scripps 

 Institution of Oceanography's component of the 

 California Cooperative Oceanic Fisheries In- 

 vestigations, a project sponsored by the Marine 



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