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Thysanopoda pectinata Ortmann, 1893

Etymology: Thysanopoda - tassel foot; pectinata - with a comb

Eye: The eye is small (T. pectinata eye & rostrum). The eye diameter : carapace length is about 0.14.

Peduncle of 1st Antenna: The lobe on the basal segment extends forward over the base of the 2nd segment as a pectinate flap, with 10-13 comb-like spines (T. pectinata lappet). The distal dorsal surface of the 2nd segment is expanded anteriorly as a low covering for a portion of the 3rd segment. The 3rd segment has a low keel.

Rostrum: A small upward-directed tooth is situated at the anterior limit of the broadly triangular, thickened frontal plate (T. pectinata eye & rostrum ).

Carapace: There are no lateral denticles or processes other than the rostal tooth (T. pectinata).

Abdomen: There are no dorsal spines.

Length: Adults are 29-44 mm.

Petasma: The terminal process is broadly based and distally expanded into a rounded end, concave on the inner surface. The proximal process above the base, bends inward, then sharply, outward, before terminating in an inward directed flattened plate with a distal tooth or teeth. The lateral process is distally hooked. The additional process is broad, curved, and distally acute (T. pectinata petasma).

Thelycum: Described by Guglielmo and Costanzo, 1977.

Comments: The pectinate lobe on the basal segment of the peduncle of the 1st antenna (T. pectinata,), together with the conical, sharply upturned rostral process, characterize this species.

ECOLOGY
T. pectinata is a mesopelagic species, with adults remaining below the thermocline.

HORIZONTAL DISTRIBUTION
The range is 45°N-30°S in the Atlantic, 10°N-40°S in the Indian Ocean (hence, excluding the Arabian Sea and Bay of Bengal), and about 35°N-35°S in the Pacific (excluding the eastern boundary waters) (T. pectinata distribution).

VERTICAL DISTRIBUTION
Adults are below about 150 m, larvae above 200 m.

LARVAE
See the development summary (T. pectinata Table) for the stage descriptors and length in stage.

Metanauplius - undescribed

Calyptopis 3 (3 stages) (T. pectinata A)

Carapace:
Shape - The carapace is large and pointed posteriorly. There is an angular projection on the lateral margin below the eye.
Marginal spines - absent
Postero-dorsal spine - absent
Lateral denticles - A pair of denticles is present in C3.

Furcilia - (number of stages unknown) (T. pectinata B), (T. pectinata C)

Eye: The eye becomes bilobed during the furcilia phase.

Carapace:
Frontal plate / rostrum - The rostrum is long and acute.
Marginal spines - absent
Postero-dorsal spines - absent
Lateral denticles - A pair of denticles is present.
Dorsal keel - There is a low short keel.

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

Abdomen:
Mid-dorsal spines - absent

Pleopods: The developmental pathway reported is 3'- 3"2'- 5".

Comments: The long nearly straight rostrum, the bilobed eye, and the low, short carapace keel are characteristic of the furcilia stages of the species. The furciliae resemble those of T. cristata but are smaller with a less conspicuous dorsal carapace keel.


Development
(T. pectinata Table), development summary for the stage descriptors and length in stage.

Pictures
T. pectinata, selected stages
T. pectinata A [calyptopis 3]
T. pectinata B [furcilia 1-2]
T. pectinata C [furcilia, juvenile]
key to larval illustrations

Thysanopoda pectinata