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Euphausia lucens Hansen, 1905

Etymology: Euphausia - brightly shining; lucens - visible shining

Eye: The eye is round and large (E. lucens eye & rostrum). The eye diameter : carapace length is about 0.24.

Peduncle of 1st Antenna: The 1st segment has a very acute, small, dentate process which projects anteriorly over the proximal part of the 2nd segment. The 3rd segment has a strong dorsal keel (E. lucens,).

Rostrum: There is no rostrum. The anterior margin of the short frontal plate forms an obtuse triangle (E. lucens eye & rostrum) (E. lucens dorsal head).

Carapace: There is one pair of lateral denticles (E. lucens carapace denticle).

Abdomen: There are no dorsal spines or specific features (E. lucens).

Length: Adults are 10-18 mm.

Petasma: The terminal process is considerably longer than the proximal process. The end of the terminal process is bifid, with the inner branch longer and stronger than the outer. On the end of the proximal process there is a membranous expansion that, at the widest point, is 3x wider than the base. (The membranous expansion gives the impression of a leaf.) On the inner side of the distal end of the process, between the membranous expansions, there is a small tooth. Below the membranous expansion there is a strong secondary process or spine which appears blade-like. The lateral process is strongly and sharply curved at the end and carries on the curve a strong tooth of a distinctive shape (E. lucens petasma).

Thelycum: Described by Lomakina, 1972; Guglielmo and Costanzo, 1978.

Comments: E. lucens is the smallest of the subantarctic Euphausia species.

ECOLOGY
E. lucens aggregates and is a food source for whales.

HORIZONTAL DISTRIBUTION
E. lucens is circumpolar in the southern temperate waters between about 40°S and 47°S (E. lucens distribution).

VERTICAL DISTRIBUTION
E. lucens is a vertical migrator, within depths of 0-300 m.

LARVAE
See the development summary (E. lucens Table) for the stage descriptors and length in stage.

Metanauplius - undescribed

Calyptopis - (3 stages) (E. lucens A)

Carapace:
Shape - The carapace is rounded, curving ventrally over the eyes in C1.
Marginal spines - absent
Postero-dorsal spine - absent
Lateral denticles - A pair of denticles is present in C3.

Telson:
Postero-lateral spines - PL3 is longer than PL2.

Furcilia - (6 stages) (E. lucens B), (E. lucens C)

Eye: The eye is round and becomes darkly pigmented.

Carapace:
Frontal plate / rostrum - The frontal plate is rectangular in F1, and becomes broadly triangular and acute in late stages.
Marginal spines - absent
Postero-dorsal spines - absent
Lateral denticles - A pair of denticles is present.
Dorsal keel - A keel is present.

Thoracic legs: There is sequential development without elongate leg (s).

Abdomen:
Mid-dorsal spines - absent

Pleopods: There is variabilty in development of pleopods, the common developmental pathway is 4' - 4"1' - 5".

Telson:
Postero-lateral spines - PL3 is longer than PL2.
Lateral spines - One pair of lateral spines is present.

Comments: The larvae of E. lucens are similar to, but smaller than, the larvae of E. frigida and E. vallentini .

Development
(E. lucens Table), development summary for the stage descriptors and length in stage.

Pictures
E. lucens, selected stages
E. lucens A [calyptopis 1-3]
E. lucens B [furcilia 1-2]
E. lucens C [furcilia 4-5]
E. lucens D [juvenile]
key to larval illustrations

Euphausia lucens