Anuropus paci

Kensley, Rian & Chan, Tin-Yam, 2001, species of deep-sea flabelliferan isopods from Taiwan (Crustacea: Peracarida: Aegidae, Anuropidae), Journal of Natural History 35 (4), pp. 481-496 : 487-495

Anuropus paci ®cus Lincoln and Jones, 1973

(®gures 1B±D, 4±9) Anuropus paci W cus Lincoln and Jones, 1973: 80, ®gures 1±3.

Material examined

NTOU, larvigerous female, mid-dorsal total length 135 mm; brood pouch containing 52 manca each about 28 mm mid-dorsal length, Tai-Shi ®shing port, I-lan County, NE Taiwan, approx. 500 m, 16 April 1999 . NTOU, ovigerous female middorsal length 95 mm, ®shing pot, Tai-Shi ®shing port, I-lan County, NE Taiwan, approx. 500 m, February 1999 . NTOU, male mid-dorsal length 50 mm, Tai-Shi ®shing port, I-lan County, NE Taiwan, approx. 400±500 m, September 1998 .

BMNH 1972.523 . 2 male paratype of A. paci W cus, from stomach of waved albatross, Galapago s region .

Description

Manca. Body with integument soft, large amounts of oil visible; pereon dorsally strongly arched. Coxal plates all posteroventrally rounded. Abdominal epimera all rounded. Telson subcircular, lacking dorsal ornamentation.

Antennule consisting of two articles, basal about half length of distal, latter three times longer than wide, distally rounded. Antenna consisting of seven articles, two basal articles about as long as wide, distal ®ve articles narrow, cylindrical. Mandible roughly triangular, incisor a rounded ridge; molar a small semicircular ¯ap; palp of three subequal articles, distal article bearing six very short distal spiniform setae. Left and right mandibles identical. Maxilla 1, lateral ramus distal margin obliquely truncate, bearing nine short spiniform setae; mesial ramus half length of lateral, bearing four very short squat distal setae. Maxilla 2 consisting of two rounded lobes bearing three or four undiOEerentiated distal bumps. Maxilliped consisting of three articles, distal article broadest and longest, with few tiny setae distally, mesial margin with small barely diOEerentiated lobe. Pereopod 1, ischium basal width equal to posterior margin; carpus and merus each much shorter than wide, with three tiny setal precursors on posterior margin, carpus lacking free anterior margin; propodus somewhat ināted, slightly longer than wide, with about seven setal precursors on palmar margin; dactylus slender, about four times longer than wide. Pereopods 2± 6 similar but increasing in length posteriorly; basis longest article, somewhat expanded; ischium with lobed anterior region bearing setal precursors; carpus and merus each roughly rectangular; propodus cylindrical, from two and a half to three times longer than wide; dactylus about one-third length of propodus. Pereonite lacking pereopods. Pleopods 1±5, protopod lacking coupling hooks on mesial margin; biramous, margins of rami bearing tiny setal precursors. Uropod similar in size to pleopods, rami slightly narrower, protopod with short lobe-like extension along mesial margin of endopod.

Male. Body 2.8 times longer than greatest width at pereonite 4; pleon distinctly narrower than pereon. Cephalon much narrower than pereonite 1, anterior margin shallowly bilobed, with modi®ed antennules extending laterally, when seen in dorsal view. Pereonites increasing in length posteriorly; pleonites decreasing in length posteriorly. Telson slightly longer than wide, ovate, dorsally with broadly rounded lateral ridge, with two rounded submedian ridges contiguous anteriorly, diverging posteriorly.

Antennule highly modi®ed and ināted, consisting of two articles, basal article stout, distally wider than long; distal article with triangular ināted dorsal portion and ventral rounded ridge bearing dense fringe of ®ne setae. Antenna consisting of seven articles, reaching posteriorly to mid-length of pereonite 3; two basal articles subequal, short; articles 3±7 slender, cylindrical; article 3 about two and a half times length of article 2; articles 4 and 5 subequal; articles 6 and 7 subequal, half length of article 5; distal articles with two small simple terminal setae. Mandible heavily sclerotized, incisor with truncate corneous cutting edge; molar thin, triangular, with row of short setae along anterior margin, setal row extending on to body of mandible; palp of three articles, articles 1 and 3 subequal, article 2 slightly longer; article 3 with dense distolateral band of setae. Maxilla 1, lateral ramus with oblique distal margin bearing four large corneous spinose setae plus ®ve much smaller setae; mesial ramus rounded, lobe-like, much smaller than lateral ramus, bearing four stout bristly setae. Maxilla 2 consisting of two poorly diOEerentiated lobes, lateral lobe bearing about eight short simple setae; mesial lobe bearing six longer bristly setae. Maxilliped consisting of two articles, basal article proximally broad; distal article distally widened, bearing tiny bristle-like setae. Pereopod 1 subchelate; basis longest article with anterior margin hollowed to accommodate rest of ¯exed-back leg; ischium, merus, carpus and propodus each with patch of tiny bristle-setae on posterior surface; merus with hollowed anterior lobe; carpus much shorter than wide, with very short free anterior margin; propodus somewhat ināted, about twice longer than wide; dactylus slender, reaching back to carpus. Pereopods 2 and 3 similar, longer than pereopod 1, merus roughly rectangular, lacking anterior lobe; carpus rectangular, slightly longer than wide; propodus cylindrical, about three and a half times longer than wide; dactylus slightly less than half length of propodus. Pereopods 4±7 similar, increasing in length posteriorly; ischium, merus, carpus and propodus having patch of short bristle-setae on posterior surface; propodus cylindrical, ®ve or six times longer than wide. Submedian penes on ventrum of pereonite 7 blunt, club-shaped, about three and a half times longer than wide, distally broadly rounded. Pleopods 1±5 increasing in size posteriorly. Pleopod 1 protopod bearing about eight coupling hooks on mesial margin; exopod and endopod bearing distal fringe of short marginal setae. Pleopod 2, protopod bearing eight coupling hooks on mesial margin; copulatory stylet articulating at base of endopod, tapering distally, reaching to apex of endopod, apically acute. Pleopod 3, protopod bearing eight coupling hooks on mesial margin; exopod having transverse suture in proximal half. Pleopod 4, protopod bearing eight much shortened coupling hooks on mesial margin; exopod with transverse suture in proximal half. Pleopod 5, protopod lacking coupling hooks; exopod having transverse suture in proximal half. Uropod tucked under telson, rami broad, lamellar, as continuation of pleopod series, exopod distally rounded, endopod subacute.

Ovigerous female. Body with pereon distinctly broader than pleon, dorsally strongly convex. Pereonites 1±4 increasing in length, pereonite 4 longest. Coxae of pereopods 2±7 posteroventrally rounded. Brood pouch formed by lamellae of maxilliped and ®rst ®ve pairs of pereopods, oostegites overlapping in midline. Eggs purple in life, oval, about 6.5 Ö 5.0 mm. Pleonites subequal in length, epimera posterolaterally rounded. Uropods tucked under telson, part of pleopodal series. Telson subcircular.

Larvigerous female. Body shape as in ovigerous female. Telson subcircular, with two pairs of broadly rounded anterior ridges and shallow semicircular groove. Antennules and antennae as in male. Mandible strongly sclerotized, truncate incisor corneous; molar broadly triangular, with row of short setae on anterior margin; row of short stiOE setae on mesial face. Maxilla 1, lateral ramus with 10 corneous spinelike setae of varying lengths distally; mesial ramus with four bristly setae. Maxilla 2 consisting of two poorly de®ned lobes, lateral lobe bearing four long and several short simple setae; mesial lobe bearing four bristle setae and several simple setae. Maxilliped consisting of single broad article bearing short marginal setae, plus epipodite expanded into broad anterior and smaller posterior lobed lamellar oostegite. Pereopod 1 subchelate, ischium, merus, carpus and propodus each having patch of very short spine-like setae on posterior surface; basis strongly grooved on anterior surface; merus with cupped anterior lobe; carpus short, having almost no free anterior margin; propodus expanded, about 1.8 times longer than wide; dactylus elongate slender, reaching back to carpus. Pereopods 2 and 3 similar, not subchelate, carpus rectangular; propodus elongate, slender, about 3.5 times longer than wide. Pereopods 4±7, basis longest article, dorsally with strong gutter formed by lateral and mesial ¯ange; carpus rectangular, about twice longer than wide; propodus slender cylindrical, about four times longer than wide. Pleopods 1±4, protopodite bearing about 10 coupling hooks on mesial margin, pleopod 5 lacking hooks; rami broad, thin-walled, completely lacking marginal setae; exopods 3±5 lacking transverse suture as seen in male. Uropodal rami thin-walled, broadly lamellar, forming sixth pair of respiratory appendages.

Colour

Body orange-red overall, but anterior somites somewhat paler in males. Eggs purple.

Remarks

Species of the genus Anuropus (see table 1) have been described on the basis of very few specimens, usually of only one sex. In four species, the specimens came from the gut contents of oceanic birds such as petrels or albatrosses. Menzies and Dow (1958) described and recorded ®ve specimens of Anuropus bathypelagicus oOE California, observed many nematocysts in the gut of one specimen, and suggested that from their capture in mid-water depths, species of Anuropus are bathypelagic rather than benthonic in habit. Barham and Pickwell (1969) presented convincing evidence that species of Anuropus live in association with large scyphozoan jelly®sh, either as commensals or as parasites, which is consistent with Menzies and Dow’s observations, and would also explain the records of the isopods from oceanic bird stomachs. The present material was collected from the by-catch that had already been landed at the ®shing port, and no sign of associated jelly®sh was seen.

The only ovigerous female of Anuropus described is that of A. sanguineus Nunomura, 1983 , from Japan. The present case, in which a male, an ovigerous and a larvigerous female in excellent condition are available is thus unusual, and warrants descriptive comments on all three forms, as well as on the manca.

The present material closely resembles A. paci W cus Lincoln and Jones, 1973, from the stomach contents of a waved albatross from the Galapagos region. This species is known from three males, one of which was used in a comparison with present material. No diOEerences between the paratypic male of A. paci W cus and the present male could be detected; the shape of the pereopodal coxae, pleonal epimera, the pleotelson, and the structure of the antennules, antennae, mouthparts are all very similar (see Lincoln and Jones, 1973, ®gures 1±3). Only the anterior three pereopods of A. paci W cus were illustrated, the remainder were missing, presumably lost when eaten by the albatross. These legs, too, are very similar to those of the present species.

In Anuropus sanguineus from the Okhotsk Sea, the shape of the coxal plates diOEer considerably from the present ovigerous female, while the antennule is short but barely ināted as it is in A. paci W cus.