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Thysanopoda minyops Brinton, 1987

Etymology: Thysanopoda - tassel foot; minyops - small eyed

Eye: The round eye is very small, 0.79 and 0.81 mm in diameter (T. minyops eye & rostrum). The eye diameter : carapace length is about 0.02 in the two known specimens > 110 mm in length. The thick eyestalk (about 3x diameter of eye) has a large anterior laterally directed tubercle above the eye (T. minyops eye photo). The facets of the eye are large (ca. 0.8 mm in diameter), with well developed ommatidia, though few in number (ca. 100) in the adults. Photophores are not evident on the eyestalk.

Peduncle of 1st Antenna: The 1st segment bears a setose, dorsally and posteriorly rounded lobe terminating anteriorly at a blunt angle, about 90° in lateral view. There is a low, rounded, dorsal hump distally on the 3rd segment (T. minyops,) (T. minyops lappet).

Rostrum: The frontal plate is a thick lip, broadly rounded in dorsal view, extending forward to the posterior limit of the eyes (T. minyops eye & rostrum). None of the 3 known specimens appear to have a tooth, such as are in T. cornuta and T. spinicaudata, on the anterior apex of the frontal plate. However, at least 2 of the specimens are damaged in that area.

Carapace: The medial dorsal axis of the head region bears a narrow ridge extending posteriorly to a cervical groove. This ridge does not have the thickness of the keel on the carapace in T. cornuta. The cervical groove crosses the dorsal part of carapace, and an H-shaped pattern of lateral furrows connects with the cervical groove on each side of carapace, as in T. cornuta, T. spinicaudata, andT. egregia. There are no lateral carapace denticles (T. minyops).

Abdomen: Photophores are not evident. Between the 1st pair of pleopods there is an acute anteroventrally directed process. No such processes are present on segments 2-5. On each of the 4th and 5th segments there are 3 small, dorsal, longitudinal elevations (T. minyops abdominal keel). Along each elevation there is a single groove in which there are two longitudinal rows of porelike pits (T. minyops dorsal abdomen). The elevated areas have been called "keels" in the three other largeThysanopoda species possessing them (T. cornuta , T. spinidaudata, T. egregia ). The 6th abdominal segment is only about 1.1x the length of the 6th segment, and its dorsal posterior part is smoothly convex not depressed (as in T. cornuta and T. spinicaudata ). The telson is slender and long (2.3x the length of the 6th segment) and is armed dorsally with 7 or 8 pairs of small spines.

Length: The 3 known specimens are 114 (male), 124 (female) and 83 mm (female).

Petasma: As inT. cornuta andT. spinicaudata, the basal parts of the terminal and proximal processes are directed toward the setiferous lobe of the pleopod and then the processes bend inwardly, away from it. Near the spine-shaped process there are 2 short setae on the single male specimen at hand. The two hooked processes on the median lobe (lateral process and additional process) are stout (T. minyops petasma).

Thelycum: Described by Brinton, 1987.

Comments: T. minyops differs conspicuously from the 2 other giant Thysanopoda speciesT. cornuta and T. spinicaudata in having (1) eyes much narrower than the eyestalk, but with few, relatively large ommatidia, (2)the posterior dorsal surface of the 6th seg is not a flat trough bordered laterally by ridges, (3) a relatively long and slender telson.

T. minyops is known only from depths of near-bottom waters in deep ocean basins.

Two of the known specimens are from oceanic areas west of Southern California and north of Hawaii. The 3rd specimen is from South of Madagascar in the Indian Ocean (T. minyops distribution).

The male was in an opening-closing net from 3600 m depth in 4000 m of water. The females were from 5240 m in 5800 m of water in the Pacific and from 4900 m in the Indian Ocean. Hence, T. minyops is considered an abyssal species (T. minyops depth range).


Thysanopoda minyops