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

Kingdom Animalia
Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Superorder Eucarida
Order Euphausiacea
Family Euphausiidae
Genus Thysanopoda
Species Thysanopoda pectinata

Status in World Register of Marine Species

Accepted name: Thysanopoda pectinata Ortmann, 1893

Scientific synonyms and common names

Thysanopoda pectinata n. sp. Ortmann, 1893
Parathysanopoda foliifera : Illig, 1909
Parathysanopoda foliifera : Hansen, 1911

Baker, A. de C., B. P. Boden and E. Brinton, 1990. A practical guide to the euphausiids of the world. British Museum (Natural History), London. 96 pp.

Baker, A. de C., 1970. The vertical distribution of euphausiids near Fuertaventura, Canary Islands ("Discovery" SOND Cruise, 1965). Journal of the Marine Biological Association of the United Kingdom 50: 301-342.

Boden, B. P., M. W. Johnson and E. Brinton, 1955. The Euphausiacea (Crustacea) of the North Pacific. Bulletin of the Scripps Institution of Oceanography, University of California 6: 287-400.

Brinton, E., 1962b. The distribution of Pacific euphausiids. Bulletin of the Scripps Institution of Oceanography, University of California 8: 51-270.

Brinton, E., 1975. Euphausiids of Southeast Asian Waters. Naga Report. Scientific Results of Marine Investigations of the South China Sea and the Gulf of Thailand 4(5): 1-287.

Guglielmo, L. and G. Costanzo, 1977. Diagnostic value of the thelycum in euphausiids. II. Oceanic species. Genus Thysanopoda Milne Edwards, 1830. Crustaceana 33: 275-283.

Hansen, H. J., 1912. Report on the scientific results of the expedition to the eastern tropical Pacific, in charge of Alexander Agassiz, by the U.S. Fish Commission steamer "Albatross," from October 1904 to March 1905, Lieut.-Commander L. M. Garrett, U.S.N. commanding. XXVI and XXVII. The Schizopoda. Memoirs of the Museum of Comparative Zoology, at Harvard College. 35: 175-296.

Hirota, Y., 1987. Vertical distribution of euphausiids in the Western Pacific Ocean and the Eastern Indian Ocean. Bulletin of the Japan Sea Regional Fisheries Research Laboratory 37: 178-224.

Mauchline, J. and L. R. Fisher, 1969. The biology of euphausiids. Advances in Marine Biology 7: 1-454.

Mauchline, J., 1980. The biology of mysids and euphausiids. Advances in Marine Biology 18: 1-681.

Ortmann, A. E., 1893. Decapoden und Schizopoden. Ergebnisse der Plankton-Expedition der Humboldt-Stiftung 2: 1-120.

Roger, C., 1971. Distribution verticale des euphausiaces (crustaces) dans les courants equatoriaux de l'Ocean Pacifique. Marine Biology 10: 134-144.

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