Pseudoprellicana johnsoni, Guerra-García, 2006

Guerra-García, J. M., 2006, Caprellidae (Crustacea: Amphipoda) from the Great Barrier Reef and Adjacent Localities, Records of the Australian Museum 58, pp. 417-458 : 434-440

Pseudoprellicana johnsoni n.sp.

Figs 29–32

Type material. HOLOTYPE 3, AM P61737, between Bird Islet & South Island , Lizard Island, Queensland, Australia, 14°40'S 145°, sediment at reef base with mixed algae, 25 m, GBR 27, J.K. Lowry, 9 Oct 1978 . PARATYPES (all Lizard Island, Queensland): 1♀, AM P61738, between Bird Islet & South Island , 14°41'S 145°28'E, sediment at reef base with mixed algae, 25 m, GBR 29, J.K. Lowry, 9 Oct 1978 ; 1♀, AM P61739, between Bird Islet & South Island , 14°40'S 145°28'E sediment at reef base with mixed algae 25 m, GBR 28, P.C. Terrill, 9 Oct 1978 .

Etymology. The species is dedicated to Rick Johnson, Australian Museum, for patiently registering all the material in the collections, and for his help and friendship during my stay at the Australian Museum.

Diagnosis. As for genus.

Description

Holotype male. Body length 2.8 mm. Lateral view ( Fig. 29A). Body smooth without projections; head rounded; suture between head and pereonite 1 absent; pereonites 2– 5 increasing in size respectively; pereonite 7 the shortest. Gills ( Fig. 29A) present on pereonites 3–4, oval, length about 2 times width. Mouthparts. Upper lip ( Fig. 30B) symmetrically bilobed, lobes poorly demarcated, smooth apically. Mandibles ( Fig. 30D,E) without molar; left mandible ( Fig. 30D) with 5-toothed incisor and lacinia mobilis, followed by a row of plates decreasing in size; right mandible ( Fig. 30E) with 5-toothed incisor, lacinia mobilis coarsely toothed, followed by row of plates decreasing in size; palp 3-articulate, second article with one seta, distal article with two setae. Lower lip ( Fig. 30C) with inner lobes well demarcated; inner and outer lobes smooth, without setae. Maxilla 1 ( Fig. 30F) outer lobe with six robust setae; distal article of palp with three robust setae and three serrate teeth distally and row of three setae laterally. Maxilla 2 ( Fig. 30G) inner lobe oval with four setae; outer lobe rectangular, about 1.3 times longer than inner lobe, with five setae. Maxilliped ( Fig. 30A) inner plate distally forming molarlike process with two setae; outer plate with three simple setae and serrate margin; palp four-articulate, dactylus smooth. Antennae. Antenna 1 ( Fig. 31A) about 1 ⁄ 3 of the body length; flagellum 3-articulate. Antenna 2 ( Fig. 31B) almost half-length of antenna 1; swimming setae absent; flagellum 2-articulate. Gnathopods. Gnathopod 1 ( Fig. 31C) basis as long as the ischium, merus and carpus combined; ischium and merus rectangular; carpus triangular with serrate margin ventrally; propodus oval, length about 1.5 times width, palm with three proximal grasping spines, grasping margin serrate on anterior half; dactylus slightly curved, with a distal seta. Gnathopod 2 ( Fig. 31D) inserted on anterior part of pereonite 2; basis as long as pereonite 2; ischium rectangular; merus and carpus slightly elongate; propodus elongate (length about 2.5 times width), with three proximal grasping spines and row of setae along palm; dactylus short and slightly curved, smooth. Pereopods. Pereopod 3 and 4 absent ( Fig. 29A). Pereopod 5 3-articulate ( Fig. 32A). Pereopods 6 and 7 missing (described from the female paratype AM P61738) Penes ( Fig. 32C,D) elongate, three times as long as wide with small apical suture. Abdomen ( Fig. 32C,D) with two pair of appendages and small dorsal lobe; first pair of appendages long, 2-articulate; second pair shorter, uniarticulate.

Paratype female. Body length 2.7 mm. Oostegites ( Fig. 29B) not setose. Gnathopods and abdomen ( Fig. 32E) similar to those of holotype male. Pereopods 6 and 7 ( Fig. 32B) subequal, six-articulate, carpus and propodus elongate, with row of setae ventrally; dactylus with plumose seta distally.

Remarks. Despite extensive sampling at Lizard Island, only three specimens of Pseudoprellicana johnsoni n.sp. were found, all on sediments at 25 m depth. Whether the species is naturally uncommon, or has narrow habitat requirements, remains to be determined.

Distribution. Presently known only from Lizard Island, Queensland.

Etymology. Named after Jim Lowry, Australian Museum for his help and hospitality during my stay at the Australian Museum, and for his considerable contributions to the knowledge of the amphipod crustaceans along the world.

Diagnosis. Body dorsally smooth. Gills on pereonites 2–4. Pereopods 3 and 4 longer than pereonites 3 and 4 combined. Propodus of male gnathopod 2 without projection. Abdominal appendages uniarticulate.

Description

Holotype male. Body length. 6.2 mm. Lateral view ( Fig. 34A). Body smooth dorsally. Head rounded. Pereonite 1 fused with head, suture absent; pereonites 2–5 increasing slightly in length respectively; pereonite 7 the shortest. Gills ( Fig. 34A). Present on pereonites 2–4. Elongate, length about 4 times width. First pair, on pereonite 2, triangular. Mouthparts. Upper lip ( Fig. 35A) symmetrically bilobed, lobes well demarcated and smooth apically. Mandibles ( Fig. 36A,B) with 3-articulate palp; distal article of palp with two setae and two rows of minute setulae; mandibular molar absent; left mandible ( Fig. 36A) with incisor 5-toothed, lacinia mobilis 4-toothed followed by three plates and three plumose setae; incisor of right mandible ( Fig. 36B) 5-toothed, lacinia mobilis forming minutely serrate plate, followed by two more plates and three plumose setae; molar flake absent. Lower lip ( Fig. 35B) with inner lobes well-demarcated; inner and outer lobes provided with setulae on apical end. Maxilla 1 ( Fig. 35D) outer lobe with six robust setae serrate; distal article of palp with three robust setae and three teeth distally, and three setae medially. Maxilla 2 ( Fig. 35E) inner lobe oval, with six setae distally; outer lobe elongate, rectangular, 1.5 times as long as inner lobe, with five apical setae. Maxilliped ( Fig. 35C) inner plate with three robust nodular setae (like teeth) distally; outer plate smaller than inner plate with four setae; palp four-articulate, articles 1–3 rectangular, article 4 (dactylus) small and curved. Antennae. Antenna 1 ( Fig. 37A) almost as long as the body; flagellum 11-articulate; peduncular articles elongate.Antenna 2 ( Fig. 37B) flagellum six-articulate; proximal article of peduncle with small projection distally; articles 3 and 4 of peduncle elongate; swimming setae absent. Gnathopods. Gnathopod 1 ( Fig. 37C) basis as long as ischium, merus and carpus combined; ischium short and rectangular; merus with setulae and four setae on distal end; propodus triangular, palm with four proximal grasping spines; dactylus smooth and scarcely curved. Gnathopod 2 ( Fig. 37D) inserted on anterior half of pereonite 2; basis about three times as long as pereonite 2; ischium rectangular; merus elongate, about the half basis length; carpus short and triangular; propodus as long as merus; palm with proximal cavity filled with a membranous sack, followed by a grasping spine and two distal rows of smaller spines along the palm; dactylus smooth, strongly curved. Pereopods. Pereopods 3 ( Fig. 38A) and 4 ( Fig. 38B) six-articulate. Propodus with three grasping spines along palm on pereopod 3 and four spines on pereopod 4; merus and carpus longer on pereopod 3 than on pereopod 4. Pereopod 5 ( Fig. 38C) four-articulate. Pereopods 6 and 7 missing in holotype (described for female below). Penes. Reduced to a pair of tiny appendages situated medially ( Fig. 38F). Abdomen. ( Fig. 38F) with two pair of uniarticulate appendages (although the first pair is provided with a basal peduncle), and a dorsal lobe.

Paratype female. Body length 3.8 mm. Flagellum of antenna 1 seven-articulate; flagellum of antenna 2 3- articulate ( Fig. 34B). Carpus of gnathopod 2 ( Fig. 37E) about three times as long as wide, more elongate than in male, with 3 grasping spines and without membranous sack proximally. Pereopods 6 and 7 ( Fig. 38D,E, 34C) sixarticulate, propodus with four grasping spines and one setae on pereopod 6 and three grasping spines and one setae on pereopod 7. Oostegites not setose ( Fig. 34B).

Remarks. Quadrisegmentum lowryi n.sp is close to its only congener Q. triangulum . The main differences between the two species are: (a) the antennae, gnathopods and pereopods 6 and 7 are clearly longer in Q. lowryi ; (b) the propodus of the gnathopod 2 male is provided with a developed distal triangular projection in Q. triangulum while this projection is absent in Q. lowryi ; (c) the abdominal appendages are 2- articulate in Q. triangulum and one-articulate in Q. lowryi .

Besides these differences, the membranous sack present on the male propodus palm of Q. lowryi seems not to be present in Q. triangulum (Hirayama, 1988) . Nevertheless this character should be used carefully because it varies allometrically. For example, Krapp-Schickel (1993) figured the variation of the gnathopod 2 in adult males of Phtisica marina . Some males of Phtisica marina (superadult) bear the membranous sac and one grasping spine, while another lacks the membranous structure, having 3 grasping spines proximally.

Distribution. Inside Outer Barrier (10°56.90'S 144°1.22'E) and Lizard Island, Queensland, Australia.

Remarks. Quadrisegmentum was recently established by Hirayama (1988) for Q. triangulum . The material examined from Queensland agrees well with the specimens described by Hirayama (1988). This is one of the most abundant caprellid species on the Great Barrier Reef.

Distribution. West Islet, Ashmore Reef, Northwest Australia (12°14.28'S 122°59.14'E) (Hirayama, 1988), Papua New Guinea (Guerra-García, 2003); a new record for Queensland, Australia.