Marine Species Identification Portal : Euphausia crystallorophias

Euphausia crystallorophias Holt and Tattersall, 1906

Etymology: Euphausia - brightly shining; crystallorophias - clear ice, glass

Eye: The eye is round and large (E. crystallorophias, ). The eye diameter : carapace length is about 0.21.

Peduncle of 1st Antenna: The 1st segment has a low, blunt lappet with a short, sharp spine at the outer distal end. The 3rd segment has a low dorsal keel (E. crystallorophias,).

Rostrum: It is long and sharp, reaching as far as the front of the eyes (E. crystallorophias,).

Carapace: There is a gastro-hepatic transverse groove. A low keel runs mid-dorsally along the rostrum. There is one pair of lateral denticles (E. crystallorophias ).

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

Length: Adults are 23-35 mm.

Petasma: The terminal process has a short projection near its base. The process curves distally with the outer edge of the curve serrate. A small finger-like projection parallels the distal curvature. The proximal process has a near-basal heel and expands distally into two unequal membranous plates, with the cleft separating them being finely serrate. The lateral process is hooked distally with short projection at the base of the hook (E. crystallorophias petasma).

Thelycum: Described by Lomakina, 1972; Guglielmo and Costanzo, 1978; Kittel and Presler, 1980; Thomas and Nash, 1987.

Comments: The very large eye and long acute rostrum readily distinguish E. crystallorophias from young E. superba.

ECOLOGY
E. crystallorophias is a neritic species, though larvae disperse seaward. It aggregates and is a food source for whales and seals. Based on observed stomach contents, this species can feed on detrital material. It is relatively unpigmented, possibly because it consumes little chlorophyll.

HORIZONTAL DISTRIBUTION
E. crystallorophias occurs in the slope waters in and around the Antarctic peninsula, the South Shetland Islands, and the Antarctic continent ([l][][f][/f]# E. crystallorophias , ).

VERTICAL DISTRIBUTION
E. crystallorophias is commonest in bays and straits where depths are less than 300 m.

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

Metanauplius - (1 stage) (E. crystallorophias A)

Carapace:
Shape - The frontal hood is moderately wide.
Marginal spines - The frontal plate is fringed with small marginal spines and there are larger spines interspersed in a characteristic pattern.

Calyptopis - (3 stages) (E. crystallorophias B)

Carapace:
Shape - The carapace is relatively short in relation to the abdomen length.
Marginal spines - absent
Postero-dorsal spine - absent
Lateral denticles - A pair of very small denticles may or may not be present in C3.

Telson:
Postero-lateral spines - PL3 is longer than PL2 in C2-C3.

Furcilia 1-2, 4-5 (E. crystallorophias C), (E. crystallorophias D)

Eye: The eye is rounded.

Carapace: The carapace is short relative to the abdomen length.
Frontal plate / rostrum - The frontal plate is rounded distally and without a rostal spine in early stages. It becomes triangular and acute in later stages.
Marginal spines - absent
Postero-dorsal spines - absent
Lateral denticles - A pair of denticles is present, they are small in early stages.
Dorsal keel - A keel is present in F4.

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

Abdomen:
Mid-dorsal spines - absent

Pleopods: The common developmental pathway is 5'- 5".

Telson:
Postero-lateral spines - PL3 is longer than PL2.
Lateral spines - One pair of lateral spines is present.
Shape - It is widened distally in F1-F2.

Comments: In C1-C3 the shape and length of the carapace distinguish the larvae. In F1-F2, the shape of the rostrum and relatively short carapace are characterstic of the species. The intermediate furciliae are undescribed.

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

Pictures
E. crystallorophias [selected stages]
E. crystallorophias A [egg, nauplius, metanauplius]
E. crystallorophias B [calyptopis 1-3]
E. crystallorophias C [furcilia 1-2]
E. crystallorophias D [furcillia 4-5]
key to larval illustrations

Euphausia crystallorophias