Euphausia lamelligera Hansen, 1911
Etymology: Euphausia - brightly shining; lamelligera - bearing a thin plate, leaf
Eye: The eye is round and large (E. lamelligera eye & rostrum). The eye diameter : carapace length is about 0.21.
Peduncle of 1st Antenna: The 1st segment carries a small but conspicuous upward- and forward-pointing bifid lobe on its upper distal margin. There is a large moveable lamella (plate) attached to the upper distal margin of the 2nd segment and it extends forward, usually adhering closely to about half of the length of the upper part of the 3rd segment. The 3rd segment has a high dorsal keel on its distal half (E. lamelligera,).
Rostrum: There is no rostrum, the frontal plate is short and forms an obtuse angle along the frontal margin. The gastric region is sharply domed, but there is no gastric keel (E. lamelligera eye & rostrum) (E. lamelligera dorsal head).
Carapace: There is one pair of lateral denticles (E. lamelligera ).
Abdomen: The 3rd abdominal segment has a posterior mid-dorsal spine that is about 1/3 as long as the 4th segment (E. lamelligera abdominal spine).
Length: Adults are 7-11 mm.
Petasma: The terminal process has a short, rounded heel and the process curves as it tapers to an acute end. The proximal process has a heavy, curved base, but the mid-part of the process is thicker than the base. Beyond the mid-part the process becomes flattened and expanded and then tapers to a thin, round end. The median lobe carries, terminally, a narrow short lobe with a rounded end. This lobe is folded obliquely forward. The curved lateral process carries a sharp dorsal tooth on the outer part of the distal curvature (E. lamelligera petasma).
Thelycum: Described by Guglielmo and Costanzo, 1978.
Comments: This species is distinguished by the large, moveable lamella (plate) on the 2nd segment of the peduncle of the 1st antenna and the rather high elevation of the bifid lappet on the 1st segment.
ECOLOGY
The coastal niche of E. lamelligera appears to be complimentary to, though overlapping with, the generally more oceanic range of the related species E. distinguenda.
HORIZONTAL DISTRIBUTION
E. lamelligera is restricted to the eastern equatorial Pacific. It occurs in coastal waters of Mexico, Central America, and South America, from the Gulf of California to 10°S, and at least to 15°S during El Niño conditions (e.g. 1958) (E. lamelligera distribution).
VERTICAL DISTRIBUTION
E. lamelligera is common over the narrow shelf and, elsewhere, probably remaining above 200 m.
LARVAE
See the development summary (E. lamelligera Table) for the stage descriptors and length in stage.
Metanauplius - (1 stage) (E. lamelligera A)
Carapace:
Shape - The frontal hood is evenly rounded.
Marginal spines - The frontal plate is fringed with small marginal spines with larger spines interspersed.
Dorsal crest - There is a pointed crest without spines.
Calyptopis - (3 stages) (E. lamelligera B)
Carapace:
Shape - The carapace is slightly pointed posteriorly.
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. The spinules on the postero-lateral and terminal spines are relatively strong and evenly space.
Furcilia - (4 stages) (E. lamelligera C), (E. lamelligera D)
Eye: The eye is large, and the faceted area is rounded with dark pigment.
Carapace:
Frontal plate / rostrum - The frontal plate is broadly triangular. There is a small rostral spine.
Marginal spines - absent
Postero-dorsal spines - absent
Lateral denticles - A pair of denticles is present.
Dorsal keel - A small keel is present.
Thoracic legs: There is sequential development without elongate leg (s).
Abdomen:
Mid-dorsal spines - absent
Pleopods: The common developmental pathway is 1' - 1"3' - 4"1' - 5".
Telson:
Postero-lateral spines - PL3 is longer than PL2. The spinules on the postero-lateral and terminal spines are strong and evenly space in early stages.
Lateral spines - One pair of lateral spines is present.
Comments: The large, round, darkly pigmented eye and shape of the frontal plate distinguish the furcilia stages of E . lamelligera . It may be seen in the Developmental Summary that the reduction in terminal telson spine number begins before the acquisition of 5 setose (") pleopods, and that there is variability in the number of terminal spines within a stage.
See the related species E. sibogae for a lateral view of the pleopod development typical of E. lamelligera .
Development
(E. lamelligera Table), development summary for the stage descriptors and length in stage.
Pictures
E. lamelligera, selected stages
E. lamelligera A [metanauplius]
E. lamelligera B [calyptopis 1-3]
E. lamelligera C [furcilia 1-2]
E. lamelligera D [furcilia 3-4]
key to larval illustrations