Apseudes larseni, Knight, Julianne S. & Heard, Richard W., 2006

Knight, Julianne S. & Heard, Richard W., 2006, A new species, Apseudes larseni (Crustacea: Tanaidacea), from the marine waters of New Zealand, Zootaxa 1306, pp. 57-67 : 58-66

Apseudes larseni , new species ( Figs. 1–3 )

Material examined. Holotype: adult ♂ (12 mm), NIWA 25031, station Q719–DLB, 2 Mar 1982, 42°01.60’–05.59’S, 170°10.30’–12.70’E, 750– 793 m. Paratypes: 1 preincubatory Ψ (9 mm with developing oostegites), NIWA 25030, station Q694–TM, 20 Feb 1982, 42°48.49– 42°46.69’S, 169°53.50’E, 380–520 m; 1 preincubatory Ψ (7 mm with developing oostegites), NIWA 25029, station Q693–DBL, 19 Feb 1982, 42°49.99’–50.40’S, 169° 58.69’– 170°00.00’E, 260–297 m; 1 preincubatory Ψ (8 mm with developing oostegites), GCRL 2503, station Q692–TM, 19 Feb 1982, 42° 53.89’S, 170° 00.49’E, 245 m.

Additional material. (all NIWA) 1 undetermined sex, station Q700–DBL, 23 Feb 1982, 41°15.10’ S, 170°37.50’E, 560 m; 5 ΨΨ, 1 undetermined sex, station Q693–DLB, 19 Feb 1982, 42°49.99’–50.40’S, 169°58.69’– 170°00.00’E, 260–297 m; 1 dissected male, station F911–TM, 11 Oct 1968, 34°37.99’S, 174°36.00’E, 1295 m; 1 Ψ, station Q163–DR, 16 Dec 1978, 41°40.00’S, 175°15.00’E, 280 m; 1 ♂, station Q695–DBL, 20 Feb 1982, 42°41.89’–42.00’S, 169°46.79’–47.59’E, 808 m; 1 Ψ, station F881–TM, 4 Oct 1968, 37°07.05’S, 177°30.99’E, 1260 m; 1 undetermined sex, station A323–DC, 28 Jan 1957, 44°40.00’S, 167°55.19’E, 108 m; 1 Ψ, station F874–TM, 3 Oct 1968, 37°17.99’S, 178°10.99’E, 1357 m; 1 Ψ, station B632–DCMb, 20 Oct 1962, 43°40.69’S, 170°43.50’E, 289 m; 1 Ψ, station Q691–TM, 18 Feb 1982, 42°57.70’–58.00’S, 170°12.40’–13.00’E, 109 m; 1 undetermined sex, station Q723–DBL, 4 Mar 1982, 41°57.59–58.50’S, 170°28.09–28.60’E, 503–504 m; 1 undetermined sex, station E892–TAM, 24 Mar 1968, 37°19.99’S, 173°34.99’E, 1226 m; 1 undetermined sex; station F755–TM, 19 Aug 1966, 43°00.00’S, 174°30.00’E, 854 m; 1 undetermined sex, station F879–TM, 4 Oct 1968, 37°25.49’S, 177°30.00’E, 1267 m; dissected specimens, station F760–TM, 20 Aug 1966, 42°45.00’S, 176°30.00’E, 739 m.

Diagnosis: Carapace with pronounced acute rostrum, acute subrostral spines, one pair of strongly developed fused ocular spines, two pairs of lateral spines, posterior most spines more ventral. Pereonite 1 with one pair of small lateral spines, one hyposphenia. Pereonite 2 with four pairs of lateral spines, one hyposphenia. Cheliped having basis with one ventral spine; merus with one ventral spine; carpus with one dorsodistal spine; exopod present. Pereopod 1 having basis lacking ventral spines.

Description (adult male)

Body ( Fig. 1 A, C). 8–12 mm long, about seven to eight times longer than wide, with pronounced lateral spines and hyposphenia.

Cephalothorax ( Fig. 1 A, C). Carapace about 1.2 times longer than wide (including rostrum), with pronounced acute rostrum, one pair of acute subrostral spines, one pair of fused ocular spines, two pairs of lateral spines, posterior­most spine more ventral.

Pereon ( Fig. 1 A, C). Pereonite 1 wider than long (length: width = 0.3), with one pair of small lateral spines, one hyposphenia; pereonite 2 wider than long (length: width = 0.7), with one pair of well­developed lateral spines, three pairs of small lateral spines, one pair of dorsal, anterolateral, microspinule­covered tubercles, one hyposphenia; pereonite 3 as wide as long, with one pair of well­developed lateral spines, two pairs of small lateral spines, one pair of dorsal, anterolateral, microspinule­covered tubercles, one hyposphenia; pereonite 4 as wide as long, with two pairs of lateral spines, one pair of dorsal, anterolateral, microspinule­covered tubercles, two hyposphenia; pereonite 5–6 as wide as long, with two pairs of lateral spines, pereonite 5 with two hyposphenia, pereonite 6 with one hyposphenia, genital cone.

Pleon ( Fig. 1 A, C). Pleonites 1–5 subequal in size, wider than long (length: width = 0.3), with one pair of well­developed lateral spines, one hyposphenia.

Pleotelson ( Fig. 1 A–C). Longer than wide (length: width = 1.8), with lateral protuberances, tapering distally to apex.

Antennule ( Figs. 1 A, C; 2A). About twice length of cephalothorax. Article 1 about three times longer than articles 2 and 3 combined, with inner proximal teeth, several inner and outer simple and broom setae; article 2 about twice the length of article 3, with several distal simple setae; article 3 with few simple seta; common article with no seta; inner flagellum with five serial repeating articles, with simple, broom, or no setae; outer flagellum with 13 serial repeating articles, with simple or no setae, articles 6, 9, 11 (antepenultimate), and 13 (ultimate) each with one or two aesthetascs.

Antenna ( Figs. 1 A, C; 2B). About 0.7 length of antennule. Article 1 partially recovered, article 2 subequal in length to article 4, with two to six inner and outer simple setae; squama about 0.7 length of article 2, with numerous marginal simple setae; article 3 about 0.2 length of article 2, with zero to one spiniform seta; article 4 with zero to one spiniform seta; article 5 about 0.6 length of article 4, with few broom and simple setae; articles 6–18 are serial repeating articles, with simple, broom, or no setae.

Labrum ( Fig. 2 F). Distal margin medially depressed, with numerous setules, midlateral margin with numerous setules.

Right mandible ( Fig. 2 G). Molar not recovered; incisor 4­dentate; setal row with four bifurcate setae, one trifurcate seta; palp with three articles, article 1 with four simple setae, article 2 about two times length of article 1, with two pinnate setae, several simple setae, article 3 subequal in length to article 1, with two pinnate setae, several simple setae, one long simple seta at tip.

Left Mandible ( Fig. 2 H). Molar with slightly cupped tip, setules covering tip; incisor 4­dentate; setal row not recovered; lacina mobilis 4­dentate; palp similar to right mandible, except with more pinnate setae on article 3.

Labium ( Fig. 2 D). Partially recovered. Lobe with fine setules on dorsal surface, fine setules on anterior margin, fine setae on posterior margin, small spines near palp attachment point; palp with fine setules on dorsal surface, fine setae on inner margin, small spines on outer margin, palp tip with three serrated setae, fine setules.

Maxillule ( Fig. 2 E). Outer endite base with inner and outer setules and fine setae, three inner small spines; outer endite tip with ten blunt spines, two simple setae; inner endite base with inner and outer setules and fine setae, four inner small spines; inner endite tip with two feather setae, one pinnate seta, one feathered multifurcate seta, one serrated seta; palp with two articles, article 1 two times length of article 2, without setae, article 2 with one simple seta, six moderately long bipinnate setae, one very long bipinnate seta with two apical hooks.

Maxilla ( Fig. 2 I). Inner lobe of fixed endite with numerous simple setae, three bipinnate setae, four bipinnate circumplumose setae; outer lobe of fixed endite with one pinnate circumplumose seta, one trifurcate pinnate seta, four trifurcate setae, three circumplumose setae, five simple setae, outer fine setules; inner lobe of moveable endite with two circumplumose setae, two pinnate circumplumose setae, six simple setae, small setules; outer lobe of moveable endite with two pinnate setae, two pinnate circumplumose setae, one circumplumose seta, one simple seta, fine subdistal setules, fine setules on outer margin.

Maxilliped ( Fig. 2 C). Endite about three times area of palp article 1, with serrated outer margin, distal fine setules, four distal bifurcate setae, one distal trifurcate seta, three distal bifurcate circumplumose setae, one distal simple seta, six inner feather setae, three inner coupling hooks; coxa with numerous fine setules; basis with proximal fine setules, outer fine setules; palp with four articles, article 1 with one inner bipinnate seta, one outer broom seta, article 2 about three times longer than article 1, with four inner pinnate setae, numerous inner simple and spiniform setae, one outer spiniform seta; article 3 about 0.6 length of article 2, with two inner tapered pinnate setae, three inner tapered setae, several simple setae; article 4 about 0.8 length of article 3, with three distal tapered pinnate setae, two distal tapered setae, three distal simple setae, one long distal simple setae.

Epignath (Not illustrated). Slightly curved, with two lobes; terminal seta.

Cheliped ( Fig. 3 A). Basis subequal in length to carpus, few simple seta, one ventral spine, exopod with three articles, article 3 with usually four simple setae; merus widening distally, about 0.8 length of basis, with several ventral simple setae, one ventral spine, one dorsodistal simple seta; carpus with several simple setae, one dorsodistal spine; propodus (including fixed finger) subequal in length to basis, with one to two simple setae proximal to dactylus; fixed finger with flattened teeth on cutting edge, with setae extending from each, numerous simple setae on ventral margin near articulation with movable finger; movable finger (dactylus) subequal in length to fixed finger, with few simple setae proximal to articulation with propodus.

Pereopod 1 ( Fig. 3 B). With well­developed coxal spine. Basis subequal to length of merus and carpus combined, with several simple setae, one ventrodistal spiniform seta, exopod with three articles, article 3 with usually six simple setae; ischium about 0.1 length of basis, with about two ventrodistal simple setae; merus widening distally, about 0.7 length of basis, with numerous ventral and dorsal simple setae, one ventrodistal, distally setose spiniform seta, one dorsodistal spiniform seta; carpus paddle­like (length: width = 1.1), about 0.5 length of merus, with numerous ventral and dorsal simple setae, one ventral spiniform seta, one ventrodistal, distally setose spiniform seta; propodus paddle­like, subequal to carpus in size, with several simple setae, four ventral, distally setose spiniform setae, one dorsal spiniform seta, three dorsal tapered setae, one dorsodistal, distally setose spiniform seta; dactylus and unguis combined subequal in length to propodus, dactylus with simple setae proximally.

Pereopod 2 ( Fig. 3 C). Basis subequal in length to ischium, merus, and carpus combined, with several simple setae; ischium about 0.1 length of basis, with few simple setae; merus widening distally, about 0.3 length of basis, with some simple setae; carpus with numerous simple setae; propodus subequal to carpus in length, slightly narrower, with several simple setae, few spiniform setae, one ventrodistal pinnate setae; dactylus and unguis combined about 1.3 times length of propodus, dactylus with simple setae proximally.

Pereopod 3 ( Fig. 3 D). Basis about 1.3 times length of ischium, merus, and carpus combined, with broom and simple setae; ischium about 0.1 length of basis, with few simple setae; merus, widening distally, subequal to carpus in length, with some simple setae, one ventrodistal spiniform seta; carpus with some simple setae, two ventrodistal spiniform setae; propodus about 1.2 times length of carpus, slightly narrower, with numerous ventral and dorsal simple setae, one ventral spiniform seta, one ventrodistal spiniform seta, one ventrodistal pinnate seta, one dorsodistal spiniform seta; dactylus and unguis combined about 1.3 times length of propodus, dactylus with simple setae.

Pereopod 4 ( Fig. 3 E). Basis subequal in length to merus, carpus, and propodus combined, with few broom and simple setae; ischium about 0.1 length of basis, with one ventral simple seta; merus about 0.7 length of carpus, with simple and broom setae, one ventral spiniform seta; carpus with numerous simple setae, some spiniform seta, one distal pinnate seta, three distal, distally setose spiniform setae; propodus about 0.7 length of carpus, slightly narrower, with some simple and broom setae, numerous pinnate setae; dactylus and unguis combined about 0.6 length of propodus, dactylus with few simple setae proximally.

Pereopod 5 ( Fig. 3 F). Basis subequal in length to merus, carpus, and propodus combined, with some simple and broom setae; ischium about 0.1 length of basis, with few simple setae; merus widening distally, about 0.8 length of carpus, with some simple and spiniform setae; carpus with some simple and spiniform setae, one ventrodistal, distally setose spiniform seta; propodus subequal to carpus in length, slightly narrower, with simple and spiniform setae, numerous ventral pinnate setae; dactylus and unguis combined subequal in length to propodus, dactylus with few simple setae proximally.

Pereopod 6 ( Fig. 3 G). Basis subequal in length to ischium, merus, and carpus combined, with numerous ventral and dorsal feather setae, some broom setae; ischium about 0.1 length of basis, with few simple setae; merus subequal to carpus in length, with several simple, few feather setae; carpus with several simple setae, one ventrodistal spiniform seta; propodus about 0.8 length of carpus, slightly narrower, with many simple setae, few spiniform and broom setae; dactylus and unguis combined about 1.3 times length of propodus, dactylus with few simple setae proximally.

Pleopods ( Fig. 3 H). Five similar biramous pairs. Basal article with few simple setae; endopod about three times length of basal article, with many feather setae along each margin; exopod about 1.3 times length of endopod, with numerous feather setae along each margin.

Uropod ( Fig. 1 A–C). Basal article about 0.5 length of pleotelson; endopod with 25–30 articles, some with fine setae; exopod with 3–5 articles, some with fine setae.

Adult female (not illustrated). Body generally (7–9 mm long). Similar to male except with fewer aesthetascs on antennule (lacking on article 9), presence of oostegites, and loss of hyposphenia on pereonites 1–4 in adults with fully formed oostegites.

Var ia t io n. Except for some variation in the number of setae (apparently related to size), little or no significant differences were observed in the mouth parts, spine patterns, or proportions in the appendages of other material examined.

Type Locality. 42°01.60’–05.59’S, 170°10.30’–12.70’E, 750–793 m; northwest of Greymouth, South Island, New Zealand.

Depth Range. 108 m – 1357 m

Etymology. This species is named in honor of Kim Larsen, tanaidacean specialist and friend.

Remarks

Apseudes larseni , new species, belongs to a group of Apseudes species characterized by the presence of lateral spines on both the carapace and pereonites, nine of which are previously known: Apseudes abyssalis Blazewicz­Paszkowycz & Larsen, 2004 ; A. graciloides Stephensen, 1915 ; A. graziellae Băcescu, 1981 ; A. rotundifrons Băcescu, 1981 ; A. grossimanus Norman & Stebbing, 1886 ; A. [= Pectinapseudes sensu Guţu 2006: 96 ] sicilianus Băcescu,1980 ; A. siegi Kudinova­Pasternak, 1985 ; A. tenuis Hansen, 1913 sensu Băcescu, 1981 ; A. vicinus Hansen, 1913 . Apseudes larseni can be distinguished from all but one of these species, A. graciloides , by having two pairs of lateral spines on the carapace.

Apseudes larseni , like A. graciloides , has one pair of lateral spines on pereonite 1; however, the locations of these spines differ. In addition, Apseudes larseni has four pairs of lateral spines (one large and three small) on pereonite 2, as opposed to one pair in A.

graciloides . It further differs from A. graciloides by having the merus of the cheliped with a ventral spine (absent in A. graciloides ) and a cheliped with a distinctly shorter carpus than in A. graciloides . Additionally, A. graciloides , unlike Apseudes larseni , has the ventral margin of pereopod 1 armed with spines.

Except for the loss of the hyposphenia on pereonites 1–4 in adult females with fully developed oostegites and for a few additional aesthetascs on the antennule of the adult male, little sexual dimorphism is exhibited by this species. Further, there appears to be a reduced genital cone on some of the pre­incubatory and ovigerous females, suggesting the possibility that under some conditions Apseudes larseni may be hermaphroditic. Notwithstanding, the largest specimen (12 mm) examined was a male.

Figures

FIGURE 1: Apseudes larseni, male. A. Dorsal view. B. Uropods. C. Lateral view. (Scale = 1.0 mm)

FIGURE 2: Apseudes larseni, male. A. Antennule. B. Antenna. C. Maxilliped with enlarged endite. D. Labium. E. Maxillule. F. Labrum. G. Right Mandible. H. Left Mandible. (Scale a = 0.2 mm: A – C, G – I; Scale b = 0.2 mm: D – F, Maxilliped endite)

FIGURE 3: Apseudes larseni, male. A. Cheliped. B. Pereopod 1. C. Pereopod 2. D. Pereopod 3. E. Pereopod 4. F. Pereopod 5. G. Pereopod 6. H. Pleopod. (Scale a = 0.2 mm: A, B; Scale b = 0.2 mm: C – H)