AHLSTROM ET AL.: ARGENTINOIDEI 



157 



Table 39. Characters of the Eggs of Argentinoidei. 



' First grouped at vegetal pole, then move to beneath embryo, then coalesce to one at each equatonal pole. 

 • Numerous globules at vegetal pole then coalesce to one clump at each equatonal pole. 



cially the mesopelagic ones, do presently available early life 

 history specimens help define the species composition of argen- 

 tinoid genera? 



Development 



Eggs are known for 1 3 species of argentinoids and larvae for 

 22 species (Table 38). We present in this paper eggs of 5 ad- 

 ditional argentinoid species and larvae of 8 additional species. 

 These are: eggs and larvae oi Argentina sialis. Microstoma sp., 

 Nansenia Candida and N. crassa; larvae only for Bathylagus 

 argyrogaster. B. bencoides. B. pacificus and Balhylychnops ex- 

 ilis: eggs only for Bathylagus ochotensis. 



Eggs 



The eggs of argentinoids are pelagic, round, have a moderate 

 to narrow perivitelline space, segmented yolk and a chorion 

 with distinctive pustules on the inner surface (Table 39, Fig. 

 82). Egg diameters and oil globule characters are given in Table 

 39. 



Argentinoid larvae hatch as relatively undifferentiated yolk- 

 sac larvae, regardless of egg size. That is, yolk-sac larvae of A. 

 silus at 7.5 mm, newly hatched from eggs 3.0-3.5 mm diameter, 

 are at about the same stage of development as 3 mm bathylagid 

 yolk-sac larvae which hatch from 1 mm eggs. In most marine 

 fishes larger eggs produce more highly differentiated hatchlings. 



Larvae 



Body form. — Argentinid and bathylagid larvae are slender, those 

 of microstomatids are deeper-bodied, and opisthoproctids have 

 a wide variety of body shapes ranging from the slender larvae 

 of Balhylychnops to the deep-bodied Opisthoproctus (Table 40, 

 Figs. 83-87). 



The gut is elongate and straight in argentinids and bathylagids, 

 with the exception of B. milleri where the gut is straight but 

 only about half the body length. In argentinids the gut is lined 

 with transverse rugae for almost the entire length. In most bath- 

 ylagids the gut has two distinct sections: an anterior section with 

 longitudinal internal ridges, separated by a valve from a shorter 

 posterior section with transverse rugae. The anterior section in 

 B. hericoides and B. longirosths is markedly smaller in diameter 

 compared with other species. Larvae of j5. wesethi. B. nigrigenys 

 and B. argyrogasterhave transverse rugae along the entire length 

 of the gut and the anterior section is relatively larger in diameter 

 and thin-walled. Also the posterior section is subdivided by a 

 second valve. B. ochotensis larvae develop a similar structure. 



The gut in microstomatid larvae is long, but anteriorly has 

 an elongate S-shaped fold that lies flat on the left side (Fig. 84). 

 The lumen of the anterior folded section is characterized by 

 longitudinal ridges whereas the posterior straight section has 

 transverse rugae. The short pyloric section has longitudinal ridges. 

 Schmidt (1918) shows the gut extended beyond the finfold mar- 

 gin in Nansenia ohlita and trailing in early stage Microstoma 

 microstoma larvae but we have not seen this in any specimens 

 of these genera. 



In opisthoproctids the gut is elongate in Balhylychnops and 

 Dolichoptery.x and relatively shorter in the deeper-bodied gen- 

 era, Macropinna. Rhyncholyalus and Opisthoproctus. In all gen- 

 era there is a sac-like stomach, which exits through a constricted 

 pyloric section to the intestine. In Balhylychnops and Doll- 

 chopteryx the sac is elongate and pointed at its tip whereas in 

 the other genera it is more rounded in form. The sac lies on the 

 left side, except in Balhylychnops where it lies on the right. In 

 the latter genus the pyloric constriction leads into a short but 

 prominent bulbous section. DoHchopteryx is similar but lacks 



