Euphausia spinifera G.O. Sars, 1883
Etymology: Euphausia - brightly shining; spinifera - bearing spines
Eye: The eye is round and large (E. spinifera eye & rostrum). The eye diameter : carapace length is about 0.22.
Peduncle of 1st Antenna: The 1st segment has a distal comb-like lappet with 4 to 6 spines. The 2nd segment carries a forward projecting bifid spine that extends over part of the 3rd segment. The 3rd segment has a high dorsal keel (E. spinifera,) (E. spinifera lappet).
Carapace: The gastric area is faintly convex but is sharply keeled in the mid-dorsal line. There is a strong post-ocular spine above each eye (E. spinifera post-ocular spine). On either side of the carapace at mid-eye level behind the orbit, there is a mound-like projection that gives rise to a small hepatic spine (E. spinifera hepatic spine). There is a lateral denticle set above an incision in the lower edge of the carapace (E. spinifera carapace denticle).
Rostrum: It is strong and long reaching forward beyond the front part of the eye but not to the distal end of the 1st segment of the peduncle of the 1st antenna (E. spinifera eye & rostrum).
Abdomen: The pleura of each of the 3rd-5th segments are strongly notched (incised) posteriorly (E. spinifera abdominal spines). The 3rd segment has a strong dorsal spine. Segments 4 and 5 have small mid-dorsal spines.
Length: Adults are 21-29 mm.
Petasma: The terminal process has a heavy foot-like base with a strong and high heel. There is a short blunt process on its inner edge. The proximal process tapers from a wide base, bends rather sharply inward and expands distally to a large membranous plate which curves backward and upward. The lateral process is hook-shaped and may sometimes carry a small spine. The median lobe has a small additional process (E. spinifera petasma).
Thelycum: Described by Lomakina, 1972; Guglielmo and Costanzo, 1978.
Comments: E. spinifera, E. hanseni, E. longirostris and E. tricantha form John's (1936) group d of Euphausia species. They all have spines on the 4th-5th abdominal segments and are similar in body size. E. spinifera can be separated from the other three by the 4 to 6 spines on the lappet of the 1st segment of the peduncle of the 1st antenna.
ECOLOGY
E. spinifera aggregates and is a food for whales.
HORIZONTAL DISTRIBUTION
E. spinifera occurs in the Atlantic, Pacific and Indian ocean basins between about 35°S and 50°S in the colder subtropical water southwards to the subtropical convergence (E. spinifera distribution).
VERTICAL DISTRIBUTION
E. spinifera is believed to live in the upper 300 m.
LARVAE
See the development summary (E. spinifera Table) for the stage descriptors and length in stage.
Metanauplius - undescribed
Calyptopis 2-3 (3 stages) (E. spinifera A)
Carapace:
Shape - The frontal hood is expanded over each eye.
Marginal spines - The frontal hood is fringed with small marginal spines.
Postero-dorsal spine - A postero-dorsal spine is present.
Lateral denticles - A pair of very small denticles is present in C3.
Dorsal crest - There is a high, conical crest without spines.
Telson:
Shape - The telson is broad distally.
Postero-lateral spines - PL2 is longer than PL3.
Furcilia - (7 stages) (E. spinifera B)
Eye: The eye is rounded.
Carapace:
Frontal plate / rostrum - The frontal plate is broad and rectangular with rounded corners. A small rostral spine may be present in F3 and is usually present in F4, it becomes strong and longer by F7.
Marginal spines - There are small spines on the frontal plate in all stages. They are also present on the anterior lateral margin through F2, and sometimes F3.
Postero-dorsal spines - The postero-dorsal spine is present and long through F5, it is shorter or rudimentary in F6, and a very small rudiment or missing in F7.
Lateral denticles - A pair of denticles is present.
Dorsal keel - There is a high conical dorsal keel through F2 and lower but distinct keel in later stages.
Thoracic legs: There is sequential development without elongate leg (s).
Abdomen:
Mid-dorsal spines - There is a dorsal spine on segment 3 from F1, segments 4 and 5 are without spines.
Pleopods: The common developmental pathway is 1' - 1"3' - 4"1' - 5".
Telson:
Postero-lateral spines - PL2 is longer than PL3 in F1, at least.
Lateral spines - One pair of lateral spines is present through F5, there are 1-2 pairs in F6, and 1-3 pairs in F7.
Comments: The larvae are relatively large. In calyptopis stages the shape of the carapace with its high conical crest is distinctive.
In the furcilia phase the larvae of E. spinifera may be distinguished from other spiecies with a mid-dorsal spine on abdomen segment 3 by 1) the position of marginal spines on the lateral margins of the carapace, 2) the reduction of the postero-dorsal carapace spine in late stages, and 3) the lack of marginal spines on the abdominal pleura.
Development
(E. spinifera Table), development summary for the stage descriptors and length in stage.
(Euphausia Table), developmental form frequency in 5 species of Euphausia furcilia larvae from the Southern Ocean.
Pictures
E. spinifera, selected stages
E. spinifera A [calyptopis 2-3]
E. spinifera B [furcilia 1, 4-6]
key to larval illustrations