BRUCE: LARVAL DEVELOPMENT OF BLUE GRENADIER 



rion. Late-stage eggs are 1.08-1.18 mm in diame- 

 ter with a single oil droplet of 0.36-0.42 mm di- 

 ameter (Fig. lA). Reared larvae hatch at 2.2-2.3 

 mm after 55-60 hours ( 14'-19"C). Newly hatched 

 larvae have a posteriorly positioned oil droplet 

 and adopt a head down position in rearing con- 

 tainers. Yolk absorption was incomplete in speci- 

 mens reared to 3.7 mm (6 days posthatch), al- 

 though the smallest field-collected larvae (3.6 

 mm) had already completed yolk absorption. The 

 anus opened laterally to the right in all reared 

 larvae and 95*^ of field-collected larvae. The anus 

 becomes symmetrical by 5.1 mm. A lateral anal 

 opening in M. novaezelandiae is consistent with 

 the developmental pattern reported for other gad- 

 iform species (Marak 1967; Matarese et al. 1981; 

 Fahay and Markle 1984; Dunn and Vinter 1984). 

 Field-collected larvae are moderately elongate 

 with the greatest body depth (16-229? body 

 length) occurring at or near the pectoral fin base 

 (Table 1). Head length as a proportion of body 

 length (BL) remains relatively constant at about 

 22% BL throughout the larval phase, decreasing 

 to about \1'7( BL in juveniles. Eye diameter de- 

 creases from 99f BL in preflexion larvae to A'7c BL 

 in juveniles. Depth at anus remains relatively 

 constant at about 139^ BL in larvae and juveniles. 

 Distances from the snout tip to the first dorsal fin 

 and from the snout tip to the anal fin decrease 

 slightly during development from about 279?^ BL 

 to 2l7c BL and 519r BL to 469? BL respectively. 



in the number of melanophores and their degree 

 of expansion. Although Badcock and Merrett 

 (1976) suggested the appearance of melanophores 

 can change on a diurnal rhythm, in the blue 

 grenadier larvae examined, there was no conspic- 

 uous relationship between time caught and me- 

 lanophore expansion. 



Head Pigmentation 



Newly hatched larvae (2.2-2.3 mm) have 

 melanophores concentrated in front and behind 

 the eye (Fig. IB). Melanophores increase in num- 

 ber and extend over the sides of the head and 

 snout by 3.3-3.5 mm (reared larvae, Fig. IC). 

 Melanophores migrate dorsally to the top of the 

 head by 3.6 mm (Fig. ID). Eyes become pig- 

 mented at this size in reared larvae. By 4.5 mm, 

 the dorsal pigment on the head consists of a group 

 of 3-11 melanophores scattered over the hind- 

 brain and posteriorly to above the cleithrum. Pig- 

 ment gradually extends over the midbrain, with 1 

 or 2 melanophores usually present between the 

 eyes by 5.3 mm. Melanophores develop externally 

 over these initial mid- and hindbrain spots and 

 extend posteriorly as a double row to the dorsal 

 fin anlage by 7.2 mm. Dorsal pigment gradually 

 intensifies: melanophores increase in number 

 and form a cap over mid- and hindbrains by 16.0 

 mm. Melanophores extend down between the eyes 

 to the tip of the maxilla by 12.0 mm. Internal 



Table 1 — Body proportions of larvae and juveniles of Macruronus novaezelandiae (expressed as percentage NL or SL): mean, standard 



deviation, range. 



Pigmentation 



Although pigmentation in M. novaezelandiae is 

 variable, certain features persist that, when com- 

 bined with meristic and morphometric informa- 

 tion, enable identification. Variation in the ap- 

 pearance of pigmentation is a result of differences 



pigment expands over the forebrain in larvae 

 from 9.0 to 15.0 mm. 



Ventral pigment on the head first develops in 

 4.2 mm larvae as 3-5 melanophores between the 

 dentaries. The number of melanophores increases 

 to 10-12 by 12.0 mm. 



121 



