Nyctiphanes capensis Hansen, 1911
Etymology: Nyctiphanes - night visible/shining; capensis - of the Cape of Good Hope
Eye: The eye is round, large in size, and tends to remain black under preservation (N. capensis eye & rostrum). The eye diameter : carapace length is about 0.20.
Peduncle of 1st Antenna: In the female the upper dorsal distal surface of the 1st segment carries an upright lappet with a pointed tip bending anteriorly. In small males (<13 mm) the lappet is almost upright but in larger males it is directed backwards, to as much as 40° from vertical. In the male there is no keel or spine on the 2nd and 3rd segments, but in the female there is sometimes, but not always, a small spine at the inner distal margin of the 2nd segment. The 3rd segment is shorter than the 2nd, and in the male its outer side is roundly convex while the inner side bears 3 strong plumose setae (N. capensis,).
Rostrum: A rostrum is lacking; the frontal plate is short, downward-bending, and forms an obtuse trough-like triangle with raised margins (N. capensis eye & rostrum). In immatures, the anterior edge of the frontal plate is truncate (squared-off rectangularly).
Carapace: There are no lateral carapace denticles (N. capensis).
Thoracic legs: Legs 1-6 (endopods) are similarly developed, the 7th is nearly as long but consist of only 2 segments. Exopods present on legs 1-7 in males; in females 1-5. The 8th leg is rudimentary. In the female, paired eggs sacs are secreted adhering to the two posterior thoracic endopods (6th and 7th).
Abdomen: The 6th segment has a small mid-dorsal posterior spine.
Length: Adults are 12-21 mm.
Petasma: The spine-shaped process is strong and curved. The proximal and terminal processes are lacking. The lateral process is long and bends sharply to an acute end. The median lobe is reduced and is less than half the height of the lateral process. The inner lobe is serrate along its inner margin (N. capensis petasma).
Thelycum: Described by Guglielmo and Costanzo, 1983.
Comments: There are 3 other species in this genus, N. simplex, N. australis and N. couchi : of the males of the four species only N. capensis lacks armature or a keel on the 2nd segment of the peduncle of the 1st antenna (Nyctiphanes,).
ECOLOGY
N. capensis is a coastal species, regionally dominant in the Benguela Current zooplankton community. It is an important food source for whales, fishes and birds.
HORIZONTAL DISTRIBUTION
N. capensis occurs on the South African coastal region, Cape Verde Islands, Andreu and Cape Blanc. Its range has been reported to overlap that of N. couchi off North Africa and in the Straits of Gibraltar (N. capensis distribution).
VERTICAL DISTRIBUTION
N. capensis occupies shelf and slope waters to about 250 m depth.
LARVAE
See the development summaries (N. capensis Table 1) and (N. capensis Table 2) for the stage descriptors, length in stage, and two systems of staging furcilia larvae.
Metanauplius - (2 forms), only pseudometanauplius illustrated (N. capensis A)
Calyptopis - (3 stages) (N. capensis B)
Shape - The carapace is smoothly rounded.
Marginal spines - absent
Postero-dorsal spine - absent
Lateral denticles - absent
Telson:
Postero-lateral spines - PL3 is longer than PL2.
Furcilia - (6 stages) (N. capensis C), (N. capensis D), (N. capensis E)
Eye: The eye is relatively large, round, and dark.
Carapace:
Frontal plate/rostrum - The frontal plate is truncated and concave. In late stages, the anterior margin may be almost flat. The antero-lateral angles may be acute.
Marginal spines - absent
Postero-dorsal spines - absent
Lateral denticles - A pair of denticles is present.
Thoracic legs: There is sequential development without elongate leg(s).
Abdomen:
Mid-dorsal spines - absent
Pleopods: There is a variety of forms in F1 and F2 with different levels of pleopod development. The developmental pathway varies, for example 1'- 1"3' - 4"1' - 5", and 2' - 2"3' - 5".
Telson:
Postero-lateral spines - PL3 is longer than PL2.
Lateral spines - One pair of lateral spines is present.
Comments: In the furcilia phase the larvae of N. capensis are characterized by the large round eyes and the shape of the carapace frontal plate.
N. capensis is separated geographically from the other three species of the genus, N. australis , N. couchi , and N. simplex . In two of the species, N. capensis and N. simplex , the carpace frontal plate is truncated, the anterior margin is concave, and the antero-lateral angles may be acute. In N. australis and N. couchi , the anterior margin of the frontal plate appears usually to be flat, it may be slightly indented in F1.
Development
(N. capensis Table 1) and (N. capensis Table 2), development summaries for the stage descriptors and length in stage, and two systems of staging furcilia larvae.
Pictures
N. capensis, selected stages
N. capensis A [egg, pseudometanauplius]
N. capensis B [calyptopis 1-3]
N. capensis C [furcilia 1-2]
N. capensis D [furcilia 3-4]
N. capensis E [furcilia 5-6]
key to larval illustrations