Astacilla boreaphilis Stransky & Svavarsson, 2006, sp. nov.

Astacilla boreaphilis sp. nov.

(Figs 1–10)

Material examined

Holotype. Ψ (7.4 mm), BIOICE stn 2475, 63°04.20’N, 21°34.90’W, 842 m, 5.5°C, 5 July 1993, RP sled, IMNH 2006.06.0 1.1.

Paratypes. Allotype, ɗ (7.0 mm), same data as holotype, IMNH 2006.06.01.2; Ψ (7.5 mm), BIOICE stn 3069, 62°28.80’N, 14°29.94’W, 1602 m, 3.24°C, 11 July 1997, RP sled, IMNH 2006.06.01.3; Ψ (7.4 mm, IMNH 2006.06.01.4), preparatory Ψ (6.4 mm, IMNH 2006.06.01.5), ɗ (8.7 mm, IMNH 2006.06.01.6), precopulatory ɗ (5.8 mm, IMNH 2006.06.01.7), juvenile (manca 3) (4.9 mm, IMNH 2006.06.01.8), juvenile (manca 2) (3.2 mm, IMNH 2006.06.01.9), all same data as holotype; BIOICE stn 2257, 63°14.61’N, 26°29.14’W, 1209 m, 4.09°C, 5 September 1992, RP sled, 30 specimens, IMNH 2006.06.01.10; BIOICE stn 2427, 63°09.90’N, 20°03.69’W, 778 m, 5.5°C, 3 July 1993, RP sled, 185 specimens, IMNH 2006.06.01.11; BIOICE stn 2472, 63°06.70’N, 21°37.60’W, 666 m, 6.09°C, 5 July 1993, RP sled, 37 specimens, IMNH 2006.06.0 1.12, 2 specimens (1 Ψ, 1 ɗ), ZMH 41184, 2 specimens (1 Ψ, 1 ɗ), ZMUC­CRU­9892; BIOICE stn 2475, 63°04.20’N, 21°34.90’W, 842 m, 5.5°C, 5 July 1993, RP sled, 341 specimens, IMNH 2006.06.0 1.13, 28 specimens (11 Ψ, 12 ɗ, 5 mancas), ZMH 41185, 30 specimens (14 Ψ, 9 ɗ, 7 mancas), ZMUC­CRU­9893.

Greenland material: WH233 stn 1016, 63°33.69’N, 39°18.18’W, 219 m, 4.37°C, 25 October 2001, epibenthic dredge, 4 specimens (1 brooding Ψ, 1 ɗ, 2 manca 3), ZMH 41183.

Other non­catalogued material (deposited at IMNH)

BIOICE stn 2254, 63°14.61’N, 26°03.43’W, 999 m, 4.88°C, 5 September 1992, Sneli sled, 1 specimen; BIOICE stn 2293, 62°27.86’N, 22°40.24’W, 1203 m, 3.91°C, 9 September 1992, RP sled, 7 specimens; BIOICE stn 2299, 63°00.10’N, 22°39.61’W, 775 m, 5.53°C, 10 September 1992, RP sled, 28 specimens; BIOICE stn 2303, 63°03.88’N, 22°41.22’W, 600 m, 6.75°C, 10 September 1992, RP sled, 1 specimen; BIOICE stn 2340, 62°08.00’N, 13°20.00’W, 1302 m, 5 May 1993, RP sled, 26 specimens; BIOICE stn 2403, 63°02.90’N, 21°49.60’W, 838 m, 5.49°C, 1 July 1993, RP sled, 448 specimens; BIOICE stn 2404, 63°02.30’N, 21°50.80’W, 802 m, 5.49°C, 1 July 1993, Sneli sled, 12 specimens; BIOICE stn 2406, 62°59.20’N, 21°47.00’W, 934 m, 4.57°C, 1 July 1993, RP sled, 106 specimens; BIOICE stn 2407, 62°58.60’N, 21°49.30’W, 917 m, 4.57°C, 1 July 1993, Sneli sled, 47 specimens; BIOICE stn 2409, 62°52.37’N, 21°43.42’W, 1060 m, 4.0°C, 2 July 1993, Sneli sled, 1 specimen; BIOICE stn 2410, 62°51.60’N, 21°44.10’W, 1074 m, 4.0°C, 2 July 1993, RP sled, 168 specimens; BIOICE stn 2418, 63°09.93’N, 21°12.08’W, 256 m, 7.08°C, 2 July 1993, RP sled, 4 specimens; BIOICE stn 2424, 63°10.27’N, 20°09.54’W, 495 m, 6.46°C, 3 July 1993, RP sled, 2 specimens; BIOICE stn 2426, 63°10.30’N, 20°03.80’W, 800 m, 5.5°C, 3 July 1993, Sneli sled, 4 specimens; BIOICE stn 2430, 63°07.90’N, 19°57.20’W, 1016 m, 4.8°C, 3 July 1993, RP sled, 3 specimens; BIOICE stn 2435, 63°13.80’N, 19°31.70’W, 965 m, 5.48°C, 3 July 1993, RP sled, 2 specimens; BIOICE stn 2691, 64°26.10’N, 28°14.20’W, 1162 m, 3.72°C, 31 August 1994, Sneli sled, 7 specimens; BIOICE stn 2692, 64°26.60’N, 28°15.50’W, 1162 m, 3.72°C, 31 August 1994, RP sled, 10 specimens; BIOICE stn 2697, 64°10.20’N, 27°43.10’W, 1042 m, 4.2°C, 2 September 1994, RP sled, 364 specimens; BIOICE stn 2698, 64°10.50’N, 27°42.60’W, 1038 m, 4.2°C, 2 September 1994, Sneli sled, 2 specimens; BIOICE stn 2700, 64°05.60’N, 27°50.00’W, 1105 m, 3.84°C, 2 September 1994, Sneli sled, 39 specimens; BIOICE stn 2701, 64°05.50’N, 27°49.70’W, 1121 m, 3.84°C, 2 September 1994, RP sled, 173 specimens; BIOICE stn 2704, 63°50.50’N, 27°42.80’W, 1295 m, 3.8°C, 2 September 1994, RP sled, 114 specimens; BIOICE stn 2706, 63°55.80’N, 28°16.30’W, 1406 m, 3.71°C, 3 September 1994, Sneli sled, 1 specimen; BIOICE stn 2707, 63°55.30’N, 28°16.80’W, 1407 m, 3.71°C, 3 September 1994, RP sled, 6 specimens; BIOICE stn 2811, 62°39.84’N, 19°45.36’W, 1695 m, 3.31°C, 23 August 1995, RP sled, 11 specimens; BIOICE stn 2844, 63°05.40’N, 17°21.10’W, 1085 m, 4.48°C, 27 August 1995, RP sled, 1601 specimens; BIOICE stn 2846, 62°59.00’N, 17°50.10’W, 947 m, 3.48°C, 27 August 1995, RP sled, 43 specimens; BIOICE stn 2864, 62°04.21’N, 20°35.55’W, 1681 m, 2.67°C, 31 August 1995, RP sled, 315 specimens; BIOICE stn 2900, 65°25.48’N, 27°52.62’W, 855 m, 5.18°C, 24 August 1996, Sneli sled, 2 specimens; BIOICE stn 2901, 65°25.76’N, 27°53.60’W, 854 m, 5.18°C, 24 August 1996, RP sled, 47 specimens; BIOICE stn 2904, 65°23.27’N, 28°21.27’W, 1057 m, 4.78°C, 24 August 1996, RP sled, 1 specimen; BIOICE stn 2907, 65°15.95’N, 28°50.36’W, 1311 m, 3.96°C, 25 August 1996, Sneli sled, 6 specimens; BIOICE stn 2909, 65°15.61’N, 28°50.15’W, 1300 m, 3.96°C, 25 August 1996, RP sled, 28 specimens; BIOICE stn 2912, 65°11.01’N, 29°04.18’W, 1456 m, 3.9°C, 25 August 1996, RP sled, 77 specimens; BIOICE stn 2918, 65°12.57’N, 29°14.55’W, 1539 m, 3.22°C, 26 August 1996, Sneli sled, 2 specimens; BIOICE stn 3069, 62°28.80’N, 14°29.94’W, 1602 m, 3.24°C, 11 July 1997, RP sled, 13 specimens; BIOICE stn 3183, 61°14.25’N, 27°54.98’W, 1005 m, 4.6°C, 31 July 2000, triangle dredge, 1 specimen; BIOICE stn 3189, 62°08.63’N, 26°38.17’W, 950 m, 5.21°C, 10 August 2000, Agassiz trawl, 21 specimens; BIOICE stn 3259, 62°59.50’N, 19°11.10’W, 1311 m, 3.72°C, 11 September 2001, Sneli sled, 58 specimens; BIOICE stn 3260, 62°59.40’N, 19°10.90’W, 1308 m, 3.72°C, 12 September 2001, RP sled,>1000 specimens; BIOICE stn 3261, 62°59.70’N, 19°11.10’W, 1301 m, 3.72°C, 12 September 2001, Agassiz trawl, 23 specimens; BIOICE stn 3263, 62°31.50’N, 19°39.50’W, 1682 m, 3.3°C, 13 September 2001, RP sled, 81 specimens; BIOICE stn 3280, 62°53.50’N, 15°55.60’W, 1692 m, 2.85°C, 16 September 2001, RP sled, 18 specimens; BIOICE stn 3500, 62°59.90’N, 20°30.30’W, 814 m, 5.82°C, 31 August 2002, Sneli sled, 4 specimens; BIOICE stn 3501, 62°59.84’N, 20°30.25’W, 829 m, 5.82°C, 31 August 2002, RP sled, 373 specimens; BIOICE stn 3504, 62°01.46’N, 19°49.15’W, 1733 m, 3.09°C, 2 September 2002, RP sled, 1 specimen; BIOICE stn 3505, 61°46.53’N, 19°44.45’W, 1809 m, 2.55°C, 2 September 2002, RP sled, 2 specimens; BIOICE stn 3509, 62°02.40’N, 19°38.71’W, 1678 m, 2.7°C, 3 September 2002, RP sled, 5 specimens; BIOICE stn 3510, 62°14.41’N, 19°28.62’W, 1605 m, 2.67°C, 3 September 2002, RP sled, 178 specimens; BIOICE stn 3512, 62°14.34’N, 19°28.78’W, 1607 m, 2.67°C, 4 September 2002, Agassiz trawl, 33 specimens; BIOICE stn 3514, 62°25.59’N, 19°46.15’W, 1780 m, 2.93°C, 4 September 2002, RP sled, fragment; BIOICE stn 3515, 62°22.20’N, 18°23.35’W, 1331 m, 3.77°C, 4 September 2002, RP sled, 1 specimen; BIOICE stn 3527, 62°47.19’N, 17°20.37’W, 1662 m, 3.36°C, 8 September 2002, RP sled, 64 specimens; BIOICE stn 3528, 62°47.28’N, 17°07.67’W, 1749 m, 2.95°C, 8 September 2002, RP sled, 7 specimens; BIOICE stn 3535, 62°38.52’N, 14°15.11’W, 1596 m, 2.64°C, 9 September 2002, Sneli sled, 1 specimen; BIOICE stn 3536, 62°23.93’N, 14°13.20’W, 1514 m, 2.57°C, 10 September 2002, Sneli sled, 3 specimens; BIOICE stn 3537, 62°24.68’N, 14°13.23’W, 1511 m, 2.57°C, 10 September 2002, Agassiz trawl, 1 specimen; BIOICE stn 3539, 61°59.63’N, 13°33.09’W, 1377 m, 2.41°C, 10 September 2002, RP sled, 57 specimens; BIOICE stn 3547, 62°59.04’N, 18°09.23’W, 1233 m, 12 September 2002, RP sled, 1 specimen; BIOICE stn 3554, 64°16.74’N, 25°41.58’W, 304 m, 7.19°C, 2 September 2003, RP sled, 3 specimens.

Diagnosis

Eyes absent. Adult body strongly sexual dimorphic, with heavy spination. Anterolateral margins of head rounded in lateral view, with medial indentation, small rostral point evident in fully developed specimens. Fusion of head and pereonite 1 indicated by dorsolateral suture incised laterally; head and pereonite 1 with one small medial spine anteriorly, two dorsal spines medially and two dorsolateral spines distally.

Pereonites 2–7 with heavy spination. Pleotelson with dorsolateral posterior wings, a pair of dorsolateral spines and a small dorsal tubercle/spine at mid­length. Oostegites 2–4 ovaltriangular shaped, tapering distally; oostegites 2 and 3 simple, laminar­like; oostegite 4 approximately three times longer than wide, with strong ridge and tubercles/spines laterally, outer side strong.

Males with similar spination pattern, except on pereonite 4. Pereonite 4 without spines, only insignificant tubercles anteriorly. Pleotelson without dorsal tubercle/spine at mid­length.

Description of female holotype

Body 7.44 mm in length, elongate, strongly geniculate between pereonites 4 and 5, cylindrical. Anterolateral margins of head rounded in lateral view, with medial indentation, small rostral point evident in fully developed specimens. Head and pereonite 1 fused, laterally sinuate, with one small medial spine anteriorly, two dorsal spines medially and two dorsolateral spines distally; pereonites 2–4 all of different width; pereonite 2 with one dorsal spine and two dorsolateral tubercles; pereonite 3 with one dorsal spine and two dorsolateral spines; pereonite 4 elongate, being 1.6 times longer than head and pereonites 1–3 together and about 0.58 times the total body length, with five dorsal pairs of spines and up to four lateral spines; oostegites 2–4 oval­triangular shaped, tapering distally; oostegites 2 and 3 simple, laminar­like; oostegite 4 approximately three times longer than wide, with strong ridge and tubercles/spines laterally, outer side strong; pereonites 5–7 similar in spination pattern, with single dorsal spine and two dorsolateral spines, at pereonite 7 developed as tubercles. Pleotelson with dorsolateral posterior wings, two dorsolateral spines and a small dorsal tubercle/spine at mid­length.

Antenna 1 shorter than 0.3 of third peduncular article of antenna 2; flagellum with group of three sensory setae and with two aesthetascs, aesthetascs two­segmented.

Antenna 2 slender, more than 0.7 of body length, with many fine setae and several groups of three sensory setae; flagellum with two articles, with medial spines on middle and distal part of first article and few on second flagellar article, with distal claw.

Mandibles symmetrical but not identical. Spine row of right mandible with one dentate spine, left mandible with two spines; incisor with four lobes; lacinia mobilis with two major lobes and one small indication of third lobe.

Maxilla 1 inner lobe with three terminal setae and few simple setae on outer margin; outer lobe with 10 stout apical setae and 4–5 simple setae, with several simple setae over entire surface.

Maxilla 2 inner lobe with eight robust denticulate setae in apical row, three stout setae in second row and five setose setae proximal to middle lobe; inner surface proximally with several long fine setae and several small simple setae; middle lobe with three progressively longer setae, all pectinate; outer lobe with three long setae, all pectinate and finely setulate, proximal margin with fine setae.

Maxilliped with basal articulation; with one coupling hook and three denticulate setae on inner margin (one broken off), distal margin with several very fine simple setae and five short denticulate setae; palp segments all free.

Pereopod 1 setose, ischium­dactylus dorsally with long simple setae; merus–dactylus ventrally with numerous mostly plumose setae with plumose shaft and short setules on tip; dactylus with several robust setae with pectinate tip; unguis pectinate, 1.1 times longer than propodus.

Pereopods 2–4 setose, cylindrical, surface with scale­like structures; setae on merus to carpus in two ventral rows, mostly as long as segment or longer; dactylus absent. Pereopods 5–7 progressively shorter; with two ungui, secondary unguis robust. Pleopod 1 peduncle with three coupling hooks on inner margin; exopod without lateral notch or setae, with nine apical plumose setae of different length (middle longest); endopod with 11 apical plumose setae of different length (middle longest), with one small and one long slender seta on inner margin.

Pleopod 2 peduncle with three coupling hooks on inner margin (one broken off); exopod without lateral setae, with 12 apical plumose setae of different length (middle longest); endopod without lateral setae, with 10 apical plumose setae of different length (middle longest).

Pleopods 3–5 similar, exopod shorter than endopod; pleopod 3 exopod with two plumose distolateral setae; pleopods 4–5 exopods with one plumose distolateral seta.

Uropodal peduncle with four distal lateral plumose setae (one broken off); exopod present, shorter than half­length of endopod, with three setae of different length, setae plumose with plumose shaft and short setules on tip, outer seta more slender than other two.

Description of male allotype

Body 7.0 mm in length. Anterolateral margins of head rounded in lateral view, with medial indentation, small rostral point evident in fully developed specimens. Head and pereonite 1 with one small medial spine anteriorly, two dorsal spines medially and two dorsolateral spines distally; pereonites 2 and 3 of similar width and pereonites 3 and 4 of similar width. Pereonite 2 with one dorsal spine and two dorsolateral tubercles; pereonite 3 with two dorsolateral tubercles; pereonite 4 long and narrow, 2.25 times longer than head and pereonites 1–3 together, about 0.66 times the total body length, without spines, only insignificant tubercles anteriorly; pereonite 5 with two dorsolateral spines; pereonites 6–7 with two dorsolateral tubercles. Pleotelson with dorsolateral posterior wings, two dorsolateral spines, without dorsal tubercle/spine at mid­length.

Antenna 1 flagellum with two segmented aesthetascs along entire ventral margin.

Antenna 2 with row of medial spines along the entire flagellum.

Right mandible with two additional lobes; left mandible without lobes.

Maxilla 2 inner lobe with 10 robust denticulate setae in apical row, two simple setae and one pectinate seta proximal to middle lobe, inner surface with five simple setae and several small simple setae; outer lobe with three long setae, of which one is pectinate, margin without fine setae.

Maxilliped without basal articulation; dense setae distally on endite.

Pereopod 1 unguis pectinate; 1.6 times longer than propodus.

Penial plate straight and simple.

Pleopod 1 peduncle with four coupling hooks on inner margin; exopod with proximal lateral notch with four plumose setae, inserting not marginal but beneath; apically with 10 plumose setae of different length (middle longest), with one plumose seta on inner and outer margin respectively; endopod with 10 apical plumose setae of different length (middle longest), with two slender setae on outer margin and four plumose setae on inner margin.

Pleopod 2 exopod with 11 apical plumose setae of different length (middle longest); endopod with seven apical plumose setae of different length (middle longest), with one plumose setae on outer margin; appendix masculina straight, bifid.

Pleopods 3–5 similar, exopod shorter than endopod; pleopod 3 exopod with three plumose distolateral setae.

Uropodal peduncle with five plumose distolateral setae.

Remarks

Astacilla boreaphilis sp. nov. shows typical characters for this genus (King 2003), having pereopod 1 with unguis, absence of dactylus from pereopods 2–4, and having a claw on the tip of the flagellum of antenna 2. A. boreaphilis sp. nov. is easily distinguished from the other northern Astacilla species by the unique pattern of spination, with numerous and large dorsal and dorsolateral spines. In addition, the species differs from A. arietina, A. granulata, A. intermedia, A. longicornis and A. pusilla in the absence of eyes. A. boreaphilis sp. can be distinguished from A. caeca in the spination pattern (presence of small tubercles in A. caeca and in having three setae on uropodal exopod (two setae in A. caeca). A comparison with other Astacilla species, known from the southern North Atlantic (i.e. A. bocagei; A. depressa Castelló & Poore, 1998; A. cinguicula Castelló & Carballo, 2000) does not show any resemblance.

There is some variation in the spination pattern among brooding females. The pattern seen on the holotype reflects the form commonly observed among the brooding females. Some specimens (e.g. female paratype, IMNH 2006.06.01.3; Fig. 10 E) showed even more pronounced spines at the posterior part of pereonite 4 and on the oostegites than seen on the holotype.

Furthermore, specimens at BIOICE stations 3280 and 3539 and to some extent specimens at BIOICE station 3527 had additionally a long spine middorsally on pereonite 1 and two pairs of short spines/tubercles posteriorly on the pleotelson. The spination pattern may partly be influenced by local conditions, such as high currents. Stations 3280 and 3539 are located near the Iceland –Faeroe Ridge and station 3539 is the coldest one (2.41°C), indicating the presence of mixed water masses, partly originating from the Nordic Seas. These are known to overflow the ridge, often at high currents (Hansen & Østerhus 2000).

The mandibles vary further considerably in the presence of the two additional lobes, either being on the right or the left mandibles of the specimens.

There is further an indication of regional differences in body size. The brooding female from Greenland was considerably smaller (6.4 mm) than the brooding females collected off Iceland.

Etymology

Greek, boreas, northern, referring to the distribution area; Greek, phileas, fondness, love, referring to the fact that it was found only within a limited boreal distribution of South Iceland and East Greenland.

Development of post­marsupial stages

The individual developmental stages were identified on basis of the development of the seventh pair of legs (see Hessler 1970), the development of spines along the body and the presence of the marsupium in ovigerous females. A noticeable character, which appeared very irregularly was a line on the lateral side of pereonite 4 (Figs 6, 9 and 10), sometimes just indicated (Fig. 6 A), or sometimes a beginning of a continuous suture line (Figs 9 C and 10A, C). It was confirmed that these specimens were indeed males (except in young manca stages when sexual characters were not sufficiently developed). This line was also recognizable in immature females where the marsupium was not well developed. This line may show the zone where the specimen opens the cuticula for a further moult. That would explain the varying development of this line. In well developed females, this line is probably hard to recognize due to the ventral plate and the oostegites.

At the manca 2 stage (Fig. 10 C, D) pereonite 4 is elongated, being about 0.38 times the body length. This is further advanced in the manca 3 stage (Fig. 10 A, B), where pereonite 4 is about 0.49 times the total body length. The spination pattern observed in the adults is already easily recognizable, both in Manca 2 and Manca 3 stages. In particular, the anterior head spine becomes well developed in these stages. At the subsequent female preparatory stage and assumed precopulatory male stage, larger changes in the habitus occur. While in the precopulatory male (Fig. 9 C, D) the pereonite 4 remains slender and smooth and becomes even around 0.71 times the total body length, in the preparatory female, besides having two smaller spines already present, some tubercles along pereonite 4 were visible. Additionally to the spination, the female body gets broader at pereonite 4 and is easily distinguished from the male. At the brooding stage the spines are generally well developed, but their sizes on the posterior part of pereonite 4 in particular and on the oostegites may vary (compare oostegites in Figs 3 G and 10E).