Cryptocopoides pacificus, Mclelland, 2007

Mclelland, Jerry A., 2007, Family Pseudotanaidae Sieg, 1976 *, Zootaxa 1599, pp. 87-99 : 88-93

Genus Cryptocopoides Sieg, 1977

Cryptocopoides pacificus , n.sp.

Figures 1–3

Material examined. Holotype, non-ovigerous female, 2.2 mm (KMNH IvR 500.183), station XR-5, 42°23.83’N, 145°31.06’E, Kamchatka Trench , North Pacific, 16 September 2001, 3145–3265 metres . Paratypes: 1 female, 1.6 mm and one female, 1.6 mm (dissected and slide mounted; KMNH IvR 500.184 and 185), both from type locality; 1 female, 1.3 mm (KMNH IvR 500.186), station TD-4, 39°27.08N’ 143°37.79’W, 3146–3272 metres, 28 September 2001; 8 females, 1.6–1.7 mm (KMNH IvR 500.187), station XR-12, 41º37.67’– 41º37.08’N 146º54.19’– 146º52.72’E, 5473–5484 metres, 4 m ORE beam trawl, 23 September 2001; 1 female, 2.3 mm (KMNH IvR 500.188), station XR-6, 42°21.90’– 42°23.50’N 145°50.40’– 145°51.81’E, 3393–3395 metres, 3m ORE BT, 16 September 2001.

Diagnosis. Cryptocopoides with dorso-lateral and ventro-lateral setae on all pereonites, article 2 of antenna with two distal setae, pair of basal setae and pair of submarginal endite setae on maxilliped, small proximal seta on cheliped dactylus, two carpal setae on pereopod 1, and two ischium setae and spatulate carpal setae present on pereopods 4 and 5.

Etymology. The name refers to the Pacific Ocean.

Description - based on non-ovigerous female holotype and dissected paratype. Body length 1.6–2.3 mm.

Body. 3.6 times as long as broad ( Figs. 1A,B).

Cephalothorax. Subequal to pereonites 1–3, rounded, becoming narrower anteriorly, with pair of anterolateral setae, 25.4 % of total length; eyelobes absent.

Pereon. 51.4 % of total length, no abbreviated pereonites, each pereonite with pair of dorso-lateral setae and pair of ventro-lateral setae (pereonite 1 with two and pereonite 2 with one additional pair of ventrolateral setae). Pereonite 1 with prominent hyposphaenial spur ( Fig. 1C). Subsequent pereonites with low crests.

Pleon. Subequal to pereonites 5 and 6 combined, 15.3 % of total length, each pleonite with pair of ventrolateral setae (pair on pleonite 5 much longer than others, extending beyond pleotelson). Pleonites 4 and 5 with pair of dorso-lateral setae.

Pleotelson. Subequal to pleonites 4 and 5 together, 5.9 % of total length, apex rounded, with one pair of disto-lateral setae.

Antennule ( Fig. 1E) 12.4 % of body length, with four articles. First article 46.1 % of total length, 1.7 times as long as broad, with three short medial simple setae, four short distal simple setae (three small hair-like) and one long distal simple seta. Second article 0.9 times as long as broad, with one long and one short distal simple setae, and one distal broom seta. Third article 0.9 times as long as broad, with one short and two long distal simple setae. Distal article 3.5 times as long as broad, terminating with one aesthetasc and five simple setae (four long, one short).

Antenna ( Fig. 1F) with six articles, 82.4 % length of antennule. Second article 1.1 times as long as broad, 1.7 times as long as third article, both articles distally with long, slender spiniform seta and article 2 with additional short distal simple seta. Fourth article 3.5 times as long as broad, with three short distal simple setae, one long distal spiniform seta, and one distal broom seta. Fifth article 2.3 times as long as broad, distally with one long simple seta. Sixth article small, terminating with five simple setae (two short, three long).

Mouthparts. Labrum not observed. Mandibles ( Figs. 2A,B) with distal margins bearing three blunt terminal teeth, right lacinia mobilis absent, left lacinia mobilis small, narrow, pars molaris broad, with six blunt terminal teeth and two short marginal setae. Labium not observed. Maxillule ( Fig. 2C) endite terminating with eight spiniform setae, including one with expanded, slightly bifid tip. Maxilla not observed. Maxilliped ( Fig. 2D) bases about half fused, with seta near each palp articulation; endites completely separate, each with two setae and smooth lateral margins; palp with four articles; article 1 without setae, tapered distally; article 2 with one medial extremely long simple seta, one inner-edge simple seta, one inner-edge setulose spiniform seta, and one outer-edge spiniform seta; article 3 with one short distal simple seta and two inner-edge setulose spiniform setae; article 4 with one small outer-edge simple seta, three inner-edge setulose spiniform setae, and one inner-edge simple seta. Epignath ( Fig. 2E) elongate, curved, slightly expanded at proximal end, tip unarmored.

Cheliped ( Fig. 1D) sclerite attachment well developed. Basis 1.6 times as long as broad, with finely setulose inferior margin. Merus triangular, with inferior seta. Carpus 1.3 times as long as broad, with two unequal medial inferior setae, one distal superior seta and one medial superior seta. Propodus 2.4 times as long as broad, about 1.4 times as long as carpus, palm with one long and two short comb setae plus row of several small setules. Fixed finger with two inferior setae, three superior setae, terminal unguis and subterminal innermargin notch which receives tip of dactylus. Dactylus 55.2 % of propodus length, width subequal to fixed finger, with one proximal simple seta and terminal unguis.

Pereopod 1 ( Fig. 3A) coxa with seta. Basis 9.1 times as long as broad, with proximal superior seta and finely setulose margins. Ischium with small seta. Merus 2.9 times as long as broad, distally with short inferior seta. Carpus 3.2 times as long as broad, 1.3 times as long as merus, with superior marginal spinules, distally with three short spiniform setae (one inferior, one superior, one anterior) and one short superior simple seta. Propodus 4.4 times as long as broad, with superior marginal spinules, distally with two unequal superior spiniform setae, short inferior spiniform seta, and setulose terminal margin at emergence of dactylus. Dactylus without seta, length with unguis subequal to length of propodus.

Pereopod 2 ( Fig. 3B) coxa with seta. Basis 8.9 times as long as broad, with two proximal superior setae. Ischium with short inferior seta. Merus 2.3 times as long as broad, distally with long inferior spiniform seta. Carpus 3.3 times as long as broad, about 1.7 times as long as merus, distally with one short superior spiniform seta, one short superior simple seta and two long inferior spiniform setae. Propodus 4.6 times as long as, with faintly setulose inferior margin, superior marginal spinules, two unequal distal superior spiniform setae, one long distal inferior spiniform seta and setulose terminal margin at emergence of dactylus. Dactylus without setae, length with unguis subequal to propodus.

Pereopod 3 ( Fig. 3C) basis with medial inferior seta. Carpus with additional short distal spiniform seta; propodus 4.3 times as long as broad. Otherwise similar to pereopod 2.

Pereopod 4 ( Fig. 3D) coxa with seta. Basis 5.1 times as long as broad, with two medial superior setae. Ischium with two short setae. Merus 2.1 times as long as broad, distally with two long inferior spiniform setae. Carpus 3.1 times as long as broad, 1.7 times as long as merus, distally with four long spiniform setae and one short spatulate seta. Propodus 4.4 times as long as broad, slightly longer than carpus, distally with two long inferior spiniform setae, one short terminal spiniform seta, one short medial superior simple seta, faintly setulose inferior margin and setulose terminal margin at emergence of dactylus. Dactylus not fused with unguis, length with unguis subequal to propodus.

Pereopod 5 ( Fig. 3E) basis with one medial simple seta. Ischium with two unequal setae, propodus 4.9 times as long as broad and lacking superior medial seta. Otherwise similar to pereopod 4.

Pereopod 6 ( Fig. 3F) basis 6.4 times as long as broad and lacking setae. Ischium with single short seta. Carpus distally with four spiniform setae (three long, one short) and short simple seta (instead of spatulate seta). Propodus with additional terminal spiniform seta and lacking medial superior seta. Otherwise similar to pereopod 4.

Pleopods ( Fig. 1G) rami elongate, with terminal and subterminal setae. Endopod slightly shorter than exopod, with one subterminal and five terminal setae. Exopod with seven terminal setae.

Uropods ( Fig. 1H) exopod with two articles, three fourths as long as endopod. Proximal article about half as long as ramus, with one distal simple seta, distal article with two unequal simple setae. Endopod with two articles, proximal article about half as long as ramus, with two short distal setae, distal article with four long and two short simple setae.

Remarks. Specimens examined from this study differed from Sieg’s (1977) description of Cryptocopoides arctica by the following characters: (1) a somewhat shorter carapace with the presence of antero-lateral setae, (2) the presence of dorso-lateral and ventro-lateral setae on all pereonites - an additional two ventro-lateral setae pairs on pereonite 1 - and ventro-lateral setae on all pleonites, (3) a somewhat longer pleon and pleotelson, (4) antenna article 2 with an additional seta (5) the left mandible’s lacinia mobilis is narrow and not bifid, (6) the maxillule endite has one of its spiniform setae with an expanded, slightly bifid tip, (7) the maxilliped basis is nearly v-shaped, has a seta near each palp, and is fused to a lesser degree, (8) the maxilliped endites each have two sub-marginal setae instead of one, (9) the cheliped dactylus has a small proximal seta and is shorter in relation to the total length of the propodus - 55 vs. 60 %, (10) pereopod 1 has an additional carpal seta, (11) the dactylus plus unguis lengths are subequal to the propodus lengths of all pereopods instead of being shorter, (12) a greater number of distal setae (four or five vs. two) occur on the carpus of pereopods 2 and 3, (13) the presence of setae on the basis of pereopods 2–5, (14) pereopods 4 and 5 have two ischium setae (instead of one) and have a small spatulate carpal seta, and (15) the pleopod endopods possess a subterminal seta in addition to five terminal setae.

Discussion. The genus Cryptocopoides was established by Sieg (1976) to distinguish those specimens in the former genus Cryptocope which possessed well-developed pleopods as opposed to those retained in Cryptocope which have rudimentary, non-setose pleopods. Other generic diagnostic characters include four-articled first antennae, completely separate maxilliped endites, and maxillule endite with eight terminal spiniform setae. To date the only described species of the genus is the apparently widely distributed Cryptocopoides arcticus ( Hansen, 1887) , reported from several locations in the North Atlantic and North Sea (Hansen 1887,1913; Stebbing 1900; G.O. Sars 1909; Just 1970), off the shelf of Antarctica in the South Atlantic ( Vanhöffen 1914; Kussakin 1967; Kudinova-Pasternak 1975), and also from the Kurile-Kamchatka Trench north of Japan ( Kudinova-Pasternak 1970). On the evidence of this study it is probable that Kudinova-Pasternak’s record from the Kurile-Kamchatka Trench actually refers to C. pacificus . Sieg (1977) examined Hansen’s (1913) specimens of Cryptocope arctica from the north Atlantic and Cryptocope antarctica collected off Antarctica by Vanhöffen (1914) and determined the two groups to be nearly identical with only small variations; thus he based his redescription of Cryptocopoides arctica (= arcticus ) on specimens from both areas. Ideally, additional specimens from both polar regions should be re-examined in greater detail to determine if these “variations” could be interpreted as representing two separate species.