Stage One (fig. 3A, B, H), total length 4.0mm (4.25mm)

The first larval stage (fig. 3A) is described by Gurney (1924: 150–151, fig. 60). The protopod of the 2nd antenna has only one ventral spine. The second spine which Gurney attributes to all larval stages does not appear until stage two. The telson (fig. 3H) is deeply cleft, and comprises two narrow and tapering rami each bearing plumose setae posteriorly. The posterior border of the telson is fringed with fine hairs medially and between each of the inner five pairs of long plumose setae.

The first (outer) seta is smooth and does not articulate with the telson. Gurney (1924) records the second telson seta present as a fine, smooth hair, springing from the base of the third seta—a condition normal among anomuran and thalassinid larvae. This is commonly known as the "thalassinid hair". In the Wellington larvae this seta is conspicuous and fringed with fine hairs along its entire length (fig. 3B). This reduced seta was not seen in the larvae of the Sydney species (Dakin and Colefax, 1940: 180–181, fig. 269a) though specifically looked for by those authors, but is present in the Samoan species (Gurney, 1938), and in J. nocturna (Gurney, 1942, fig. 101b) though missed by Caroli (1924) and by Tattersall (1938).

In J. novaezealandiae the third, fourth and shorter seventh telson setae are each fringed with fine hairs and minute spines along their entire length, but the fourth seta may have two or three large basal spines (fig. 3B). The fifth seta has a row of about ten large, basal spines along both inner and outer margins, but is without fine hairs in this region. Minute spines and fine hairs decreasing in size distally, occur for the remainder of its length. The sixth seta is similar, but large spines without supplementary hairs fringe its outer margin for approximately half its length (fig. 3B).

The armature of these posterior telson setae is of specific significance and must therefore be placed on record. With the lateral cornu of the telson considered as a modified first seta (Gurney, 1924) the telson formula is 7 + 7 setae as is normal in stage one larvae of Anomura and Thalassinidea.

Chromatophore Pattern

Chromatophores of the stage one larva have been illustrated in a previous publication (Wear, 1965; text-fig. 5D). All chromatophores are orange, small, numerous and very diffuse. Concentrations of pigment are found below the eyes, above the mandibles and maxillae, in the basipods and exopods of the 1st and 2nd maxillipeds, in the last four abdominal segments and in the telson. In later larval stages chromatophores appear above the 3rd maxillipeds and the pereiopods.

Fig. 3.—Jaxea novaezealandiae n.sp., larval stages. A, stage one larva, lateral view; B, stage one larva, posterior telson processes (one to seven) of right side, ventral view; C, stage three larva, left 1st antenna, dorsal view; D, stage three larva, left 2nd antenna, ventral view; E, stage three larva, left pereiopods, lateral view; F, stage six a larva, pleopods of 2nd abdominal segment; G, stage six a larva, cephalic appendages, lateral view; H, stage one larva, telson, ventral view; I, stage two larva, telson, ventral view; J, stage three larva, uropods and telson, ventral view; K, stage four larva, uropods and telson, ventral view; L, stage five larva, left lateral telson cornu, dorsal view; M, stage five larva, left lateral telson cornu, dorsal view to show extension of third telson seta beyond first seta; N, stage six larva, uropods and telson, ventral view.

Stage Two (fig. 31), total length 4.9mm to 5.3mm (5.15mm to 5.55mm)

The second larval stage has also been described by Gurney. The protopod of the 2nd antenna now has a second spine ventrally. The 1st and 2nd maxillipeds have natatory exopods each with six long plumose setae, and the exopod of the 3rd maxilliped bears four such setae. The telson (fig. 31) is rather more triangular than in stage one and usually bears 10 + 10, 10 + 11 or occasionally 11 + 11 posterior setae. These setae, with the exception of the lateral cornu and the thalassinid hair, usually possess a few marginal basal spines.

Stage Three (fig. 3C, D, E, J), total length 7.4mm to 7.7mm (7.6mm to 7.9mm)

The third larval stage was not present in Gurney's material and has therefore not been described.

The peduncle of the 1st antenna is two-segmented, with eight plumose setae along its inner margin (fig. 3C). The unarmed inner ramus exceeds the length of the outer ramus.

The 2nd antenna possesses a two-segmented protopod, with two ventral spines arising from the anterior margin of the distal segment (fig. 3D). The endopod is three-quarters the length of the exopod (squama) and is without terminal plumose setae, but has a small, ventral subterminal hair. The exopod has 13 or 14 marginal plumose setae (fig. 3D).

The 3rd maxilliped has a natatory exopod with six terminal setae as in stage two, but the endopod is somewhat longer and more robust.

The 1st pereiopod comprises a long rod-like endopod and a natatory, two-segmented exopod with six terminal plumose setae (fig. 3E). The 2nd, 3rd and 4th pereiopods are biramous. The exopod of the 2nd pereiopod is a slender unsegmented rod without setae, and those of the 3rd and 4th pereiopods are undeveloped buds (fig. 3E).

The telson is now separate from the 6th abdominal segment which has ventral procurved hooks similar to those of the first five segments (fig. 3J). There is no sign of pleopods. Uropods are present but the endopod and exopod have not separated from the protopod. The exopod has about 12 marginal setae but no lateral tooth, and the much smaller endopod has about four marginal setae (fig. 3J). The telson is broadly triangular, with the concave posterior margin having 11 or 12 pairs of setae including those of the slender posterolateral cornua. The third visible pair of setae (probably the original 4th setae) is now smooth, has lost articulation with the telson and migrated towards the cornua giving the posterolateral angles a more or less bifurcate appearance. Within this bifurcation of the lateral process (1st seta) and the third visible pair of setae, the second seta is reduced to a small spine. This spine is probably the third seta of stage two, as the thalassinid hair is now absent. The inner eight (or nine) pairs of setae which articulate with the telson, each have a few marginal basal spines.

It is in the third and subsequent larval stages of J. novaezealandiae in which the telson bifurcates at the posterolateral angles, that specific distinction from the later stage larvae of J. nocturna, the Sydney species and Kurian's Adriatic species becomes really apparent. In these latter three species the posterolateral cornu of the telson remains as a single process.

Stage Four (fig. 3K), total length 9.3mm to 10.0mm (9.45mm to 10.15mm)

The stage four larvae of Jaxea novaezealandiae agree in essential detail with the larva Gurney describes as stage three. However the following additional points have been noted.

The endopod of the 2nd antenna does not exceed the length of the exopod as in Gurney's larva, but the two rami are subequal. The 2nd pereiopod has a natatory exopod with four or six terminal plumose setae. Pleopod buds are not usually visible, but in occasional larvae tiny pleopod rudiments may be seen on segments two to five. The telson is more usually of the form shown in fig. 3K rather than that drawn by Gurney (1924: 152, fig. 61g). The "serrations" present on the lateral distal third of the telson are in fact stout spines, each having a definite articulation with the telson (fig. 3K). These spines vary in number between four and seven, but larvae are rarely found with an equal number of these spines on each side of the telson. Telson spines of this type are rare among thalassinid larvae, and certainly unique in the Laomediidae.

Stage Five (fig. 3L, M), total length 11.6mm to 12.5mm (11.75mm to 12.65mm)

This stage agrees with Gurney's stage four. The third (unarmed) telson setae only rarely extend beyond the tips of the outermost pair (fig. 3M). However, this trend become more obvious in the sixth larval stage (fig. 3N).

Stage Six (fig. 3N), total length 13.8mm to 15.2mm (14.1mm to 15.5mm)

This stage agrees with Gurney's stage five. The third telson setae now extend well beyond the outermost pair. This sixth stage is abundant in the plankton, and is probably the final trachelifer stage in the life history, as the first post-larval stage was obtained from these in the laboratory. There are also six stages in J. nocturna (Caroli, 1924) and in the Sydney species (Dakin and Colefax, 1940). Although post-larvae were not obtained by Dakin and Colefax, their sixth larval stage (15mm in total length) is at a similar stage of development to J. novaezealandiae stage six, and it is not expected that further trachelifer stages would follow in the Sydney species.

Stage Six A (fig. 3F, G), total length 15.5mm to 17.0mm (15.9mm to 17.4mm)

Stage six a was not seen by Gurney. This larva differs from stage six in the following characters.

The endopod of the 2nd antenna extends beyond the 1st antenna, and the segments of the endopod are visible beneath the cuticle (fig. 3G). The pereiopods have increased in size and are visibly segmented beneath the cuticle. The abdominal pleopods are now long biramous rods without setae (fig. 3F) and are longer than half the length of the abdominal segments. The telson is similar to that of stage six, but the third telson setae are more strongly developed than the first setae which are now relatively reduced and subterminal.

The status of this six a trachelifer stage is uncertain, but it is not regarded as an essential stage in the larval life history of J. novaezealandiae. Stage six a was obtained by moult in the laboratory but is extremely rare in the plankton, and it seems probable that the majority of larvae bypass this stage and moult directly from stage six to the first post-larval stage. Stage six larvae showed no sign of a further trachelifer stage beneath the cuticle. However, larvae at a stage of development intermediate between stages five and six were found rarely in the plankton. These showed a further trachelifer moult beneath the cuticle, and although the casts of larvae from which the original stage six a larvae were obtained in the laboratory were unfortunately destroyed, it is likely that stage six a follows this intermediate stage between five and six. This alternative route to the first post-larval stage appears to be taken only rarely.