Podocerus miscix, Hughes, 2013

Hughes, L. E., 2013, Podoceridae of Tropical Australia (Peracarida: Amphipoda), Records of the Australian Museum 65 (1), pp. 1-37 : 16-17

Podocerus miscix sp. nov.

Figs 12–13

Type material. Holotype, male, 2.7 mm, dissected, 2 slides, MAGNT Cr 017403, Bedout Island, WesternAustralia (19°35'S 119°05'E), 3 m, reef flat, 4 June 1985, coll. B. C. Russell ( BCR85-9 ) . Paratypes: 1 female, 3.0 mm, dissected, 1 slide, MAGNT Cr 017404, Bedout Island , Western Australia (19°35'S 119°05'E), 3 m, reef flat, 4 June 1985, coll. B. C. Russell ( BCR85-9 ) ; 1 male, 3.2 mm, dissected, 1 slide, MAGNT Cr 017405, Bedout Island , Western Australia (19°35'S 119°05'E), 3 m, reef flat, 4 June 1985, coll. B. C. Russell ( BCR85-9 ) ; 2 specimens (1 hyperadult male, 1 male) MAGNT Cr 017406, Bedout Island , Western Australia (19°35'S 119°05'E), 3 m, reef flat, 4 June 1985, coll. B. C. Russell ( BCR85-9 ) .

Type locality. Bedout Island , Western Australia (19°35'S 119°05'E) .

Etymology. From the Latin miscix meaning changeable, inconstant, in reference to the male gnathopod 2 development with growth stage.

Diagnosis. Gnathopod 1 coxa subequal to coxa 2, longer than broad, anteroventral corner produced anteriorly, apically rounded; carpus rectolinear with truncate lobe; propodus subtriangular, produced distally, palm margin minutely crenulate. Gnathopod 2 carpus partially fused with propodus; propodus subovate, medial surface without setae, palm subacute, conveX, palm with 3 teeth, defined by tooth with 1 robust seta; dactylus posterior margin crenulate with proximal tooth. Uropod 1 biramus; peduncle with welldeveloped ventromedial spine, spine 3 times as long as broad.

Hyperadult male. Gnathopod 2 basis with medial acute projection; propodus subtriangular distal shelf, propodus palm with 1 subtriangular tooth.

Female Gnathopod 2 propodus, palm with 3 teeth, defined by tooth, with 2 robust setae.

Description. Based on holotype male, 2.7 mm, MAGNT Cr017403. Body cuticle dorsally and laterally smooth. Head dorsally smooth, rostrum short, one tenth of head length; eyes weakly bulging; lateral cephalic lobe rounded; anteroventral corner rounded.

Gnathopod 1 coxa subequal to coxa 2, longer than broad, anteroventral corner produced anteriorly, apically rounded; basis 3 times as long as broad, without anterodistal setae; carpus rectolinear with truncate lobe, 1.5 times as long as broad; propodus subtriangular, produced distally, anterior margin with clusters of long slender setae, palm margin minutely crenulate, with 1 robust seta near corner of palm; dactylus posterior margin with serrate teeth, cuticle surface smooth. Gnathopod 2 basis 1.5 times as long as broad, anterodistal corner with produced subacute lobes without setae; merus posterior margin with narrow produced lobe, lobe as long as broad, posterior margin apically subacute, anterior margin without short robust setae; carpus partially fused with propodus; propodus subovate, length 1.6 times width, anterior margin with a few long slender setae, medial surface without setae, palm subacute, convex, 3⁄4 the length of the propodus, with broad, well developed distal shelf, shelf margin strongly crenulate, palm with 3 teeth, defined by tooth with 1 robust seta; dactylus posterior margin smooth with proximal tooth, closing along palm.

Epimera 1–3 posteroventral corner rounded. Urosomite 1 length 1.5 times as long as broad. Uropod 1 biramus; peduncle 3 times as long as broad, with well-developed ventromedial spine, spine 3 times as long as broad; inner ramus length subequal to peduncule; outer ramus more than half the length of inner ramus. Uropod 2 biramous; peduncle ventromedial spine absent; outer ramus about half the length of inner ramus. Uropod 3 uniramus; ramus without setae. Telson dorsal lobe with 2 apical setae, lower margin with 2 pair of long slender lateral setae.

Male hyperadult (dimorphic characters) based on paratype male, 3.2 mm. MAGNT Cr017405. Gnathopod 2 basis with medial acute projection, anterodistal corner with produced rounded lobes without setae; merus posterior margin with narrow produced lobe, lobe as long as broad, posterior margin apically subacute without setae; propodus subovate, length twice width, palm with well-developed subtriangular distal shelf, propodus palm with 1 subtriangular tooth; dactylus posterior margin weakly denticulate with proximal subquadrate tooth, apically falcate.

Female (sexually dimorphic characters) based on paratype female, 3.0 mm. MAGNT Cr017404. Gnathopod 2 basis 3 times long as broad; anterodistal corner subquadrate, with short robust setae; merus posterior margin with broad lobe, lobe 1.3 times as long as broad, with 5 short robust setae; carpus free, distinct from propodus; propodus length 1.5 times width, anterior margin with a few robust setae, palm convex, with poorly developed distal shelf, shelf margin weakly crenulate, palm with 3 teeth, defined by tooth, with 2 robust setae.

Remarks. Material figured here of juvenile male, adult male and female share the same carina formulae and gnathopod 1 carpus, propodus and dactylus form, with all specimens from the same sample. The transition from the juvenile male to hyperadult male includes a variation in the number of gnathopod 2 propodus teeth and tooth size. The gnathopod 2 basis in the hyperadult male specimen has 2 anterior projections. The falcate dactylus and posterior margin crenulation indicate the male b specimen is a hyperadult and therefore it seems best to couple it to the other males in the sample with other similarities. The slight elongation of the gnathopod 1 carpus and propodus, and also the gnathopod 2 propodus are typical with increasing specimen size.

The P. miscix sp. nov. female gnathopod 2 propodus is relatively large compared to that of other female podocerids. Gravid females with enlarged and sexually dimorphic gnathopods are also known for P. orontes sp. nov.

Podocerus miscix sp. nov. is similar to P. clavicarius sp. nov. and P. tulearensis Ledoyer 1986 with a smooth dorsum and large spheroid gnathopod 2. The male gnathopod 2 dactylus extends along or beyond the propodus palm in P. miscix sp. nov. and P. tulearensis , while it closes short of the palm in P. clavicarius sp. nov. Podocerus tulearensis is known from a single male specimen where the gnathopod 2 palm has a distal shelf and no teeth (or sinus with weakly developed tooth) and the dactylus is straight, compared with P. miscix sp. nov. where the palm has 1 to 4 teeth and a recurved dactylus.

Distribution. WesternAustralia: Bedout Island (current study).

Figures

Figure 12. Podocerus miscix sp. nov. holotype male, 2.7 mm, MAGNT Cr017403, Bedout Island, Western Australia (scale 0.1 mm).

Figure 13. Podocerus miscix sp. nov. holotype male, 2.7 mm, MAGNT Cr017403, male b, 3.2 mm, MAGNT Cr017405, and female, 3.0 mm, MAGNT Cr017404, Bedout Island, Western Australia (scale 0.1 mm).