Comprehensive Description

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"Sergestes (Sergia) potens, sp. n.


Holotype ♂, St. 3975 VII. Carapace length 25.5mm., total about 85 mm.


Organs of Pesta absent, cornea of the eye much longer and broader than the stalk, numerous lensless dermal photophores including conspicuous unpaired median ones in pereionic sternites; nearly related to S. phorcus Faxon and S. grandis Sund.


Rostrum moderately long, very deep, subrectangular; with a minute slender tip and a rudimentary dorsal tooth. Cervical and post-cervical sulci very shallow laterally, hardly or not at all continued across the dorsum.


Unciliated part of the external margin of the uropodal exopod twice the ciliated part. Posterior arthrobranch of XII four-fifths the length of the anterior one; about one-tenth longer than the posterior gill of XIII; about equal to the anterior gill of XIII. Cornea of the eye enormous; its length and its diameter both twice that of the short, slender distal segment of the stalk; no trace of ocular tubercle.


Some of the photophores are as follows: Uropodal exopod, a single file of three to five organs distal to the muscle, none median to it. Antennal scale, a row of nine to twelve in the distal part, a short oblique stripe in the median side of the proximal part; no photophore in the centre of the base of the scale. Middle of pleonic sternites, a single one in advance of the first four pairs of pleopods, one between the last three pairs, a pair behind the first three pairs of pleopods, one behind the fourth and fifth pairs; sixth pleonic sternite with a median row of about five photophores, and one between the uropods. Pereiopods, one in the base of the ischium of all five legs; one in the tip of the ischium of the second through fifth legs; one in the tip of the merus of the fourth and fifth legs; one in the tip of the carpus of the fifth, 2 in the fourth leg; a row of 10 to 12 in the merus of the third, of 6 in the second leg.


Petasma much as in S. phorcus and S. grandis, with lobus connectens proximolaterally produced as an armed finger-shaped protrusion. Lobus armatus large as in S. phorcus, but with a well-defined lobus accessorius at base larger than that in S. grandis. Processus ventralis expanded at base with a slender tip; relatively short, not reaching as far as does lobus terminalis. Lobus terminalis bears an armed proximolateral lobule which is much better defined than in S. phorcus, but is much smaller than the well-developed distomedian part of lobus terminalis instead of much larger than a rudimentary distomedian part as in S. grandis.


Genital sternites and base of third leg of female not greatly different from these parts in S. phorcus."


(Burkenroad, 1940)


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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