Harryplax, Mendoza, Jose C. E. & Ng, Peter K. L., 2017

Mendoza, Jose C. E. & Ng, Peter K. L., 2017, Harryplaxseverus, a new genus and species of an unusual coral rubble-inhabiting crab from Guam (Crustacea, Brachyura, Christmaplacidae), ZooKeys 647, pp. 23-35 : 24-26

Harryplax gen. n.

Type species.

Harryplax severus sp. n., by present designation.

Diagnosis.

Carapace transversely subovate; dorsal surface granular, regions poorly defined; front bilobed, produced beyond orbits; anterolateral margin arcuate, cristate, lined with granules, with two teeth after exorbital angle; posterolateral margins straight, converging posteriorly; endostomial ridge strongly developed. Antennules well developed; second and third articles relatively long, stout, partially retractable into antennular fossa, distal tip of second article reaching infraorbital tooth; basal article of antenna rectangular, slender (much longer than wide), subsequent two articles elongate, flagellum long. Thoracic sternum narrow, granulate; thoracic sternites 1 and 2 fused, triangular; thoracic sternite 3 demarcated from sternite 2 by distinct transverse suture; thoracic sternites 3 and 4 nearly fused except for notches restricted laterally, which continue medially as oblique grooves, forming wide V, and forming the boundary between the two sternites; sternite 4 long, tip of male telson not reaching level of P1 condyles when pleon folded against thoracic sternum; male press-button present as rounded tubercle on sternite 5, midway between sutures 4/5 and 5/6. Median line present on exposed portion of sternite 4, absent in sterno-pleonal cavity except at level of sternites 7 and 8. Penis protruding from gonopore anterior to coxo-sternal condyle of P5. Vulva large, on sternite 6 abutting against posterior border of sternite 5, sub-circular operculum present. Chelipeds robust, distinctly asymmetric, not exhibiting any sexual dimorphism; major chela with eroded molariform tooth on proximal cutting margin of dactylus, large molariform tooth on proximal cutting margin of fixed finger; carpus with broadly triangular, sharp tooth on inner margin; merus anterior margin lined with conical spines. Ambulatory legs long, slender; anterior margins lined with small spines. Male pleon relatively broad; all somites and telson freely articulated. G1 slender, slightly sigmoid, surfaces without spines or sharp granules, distal half lined with stiff, short simple setae; G2 stout, about one-third of G1 length, distal segment short, petaloid.

Etymology.

The new genus is named primarily in honor of the intrepid field collector, the late Harry T. Conley, who collected many interesting crustaceans in the rubble beds of Guam, including the species presently being described. The name is also an allusion to a famous namesake, Harry Potter, the magical hero of the popular book series by J.K. Rowling, and Mr. Conley’s uncanny ability to collect rare and interesting creatures as if by magic. The name is an arbitrary combination of “Harry” and the suffix “-plax”. Gender feminine.

Remarks.

Harryplax , new genus, is classified in Pseudozioidea following Naruse and Ng’s (2014) definition based on the following morphological features: 1) having all the somites of the male pleon and the telson freely articulated; 2) the G2 being about a third the length of the G1; 3) the penis emerging from a coxal (P5) gonopore that is anterior to the coxo-sternal condyle; and 4) the large vulvae which are positioned close to each other in the thoracic sternum. Naruse and Ng (2014) exhaustively discussed the comparative morphology of the pseudozioid families, viz. Pseudoziidae , Planopilumnidae , Pilumnoididae , and Christmaplacidae (see also Guinot and Macpherson 1987; Davie 1989; Ng and Wang 1994; Ng and Liao 2002; Ng 2010; Ng and Ahyong 2013). They highlighted the diagnostic characters of Christmaplacidae which effectively distinguish it from the rest of Pseudozioidea as follows: "The immobile eyes without pigmentation, elongated antennules that cannot retract into their fossae, large lobiform inner carpal spine of the cheliped, large lobiform and spiniform flexor margin of the merus of the cheliped, and the elongated ambulatory legs are unique characters in the Pseudozioidea." (Naruse and Ng 2015: 270, Table 1).

Harryplax is assigned to Christmaplacidae as it shares the following features with the type genus, Christmaplax : 1) a sub-ovate carapace with a strongly arcuate anterolateral margin armed with two well-spaced teeth after the effaced exorbital angle; 2) reduced and immobile eyes; 3) robust and similarly proportioned chelipeds, where the major chela has the two opposing modified teeth on the proximal cutting margins of the fingers; 4) long, slender ambulatory legs (unique in Christmaplacidae ); 5) a sternal press-button equidistantly positioned on sternite 5 between suture 4/6 and 5/6; 6) a penis emerging from a gonopore on the P5 coxa, anterior to its coxo-sternal condyle; and 7) a simple unarmed G1 with a relatively short and stout G2, the terminal segment of which is short and petaloid in shape.

There are several morphological features, however, that distinguish Harryplax from Christmaplax :

The carapace has the front more distinctly projecting beyond the supraorbital margin in dorsal view (Fig. 1A) (front only slightly projecting; cf. Naruse and Ng 2014: figs 1a, 2b, 3a);

There are no distinct notches separating the supraorbital margin from the front nor from the anterolateral margin (Fig. 1A) (slight notch between front and supraorbital margin, and deep, pronounced notch marking boundary with anterolateral margin; cf. Naruse and Ng 2014: figs 1a, 2b, 3a);

The anterior portion of the anterolateral margin is more gently arcuate (less convex) but is more strongly cristate (Figs 1A, B, 2A) (more strongly convex and with the crest less pronounced; cf Naruse and Ng 2014: figs 1a-c, 2a, 3a);

The teeth on the carapace anterolateral margin, especially the first, are more prominent, with the tips distinctly curved (Fig. 1A) (teeth relatively smaller with weakly curved tips; cf. Ng and Naruse 2014: figs 1a, 3a);

The eyes, while immobile and reduced, are relatively better developed with longer peduncles and bigger corneas, and are visible even from dorsal view (Fig. 1A, B, 2A) (hidden from dorsal view, sunken into orbit, with shorter peduncles and much reduced corneas; cf. Naruse and Ng 2014: figs 1a, c, 2a, b);

The basal article of the antenna is much longer and narrower (Fig. 2A) (shorter and wider; cf. Naruse and Ng 2014: figs 1c, 6a);

The second and third antennular segments are stout (especially the third), and, although the joint between two articles also reaches the mesial surface of infraorbital tooth when folded, the third article can be partially folded into antennular fossa (Figs 1B, 2A) (second and third antennular articles slender, too long to fold into antennular fossa; cf. Naruse and Ng 2014: fig. 2a, b);

The thoracic sternum is relatively narrower and the posterior end of sternite 3 is slightly wider than the anterior end of sternite 4 (Figs 1C, D, 3A, B) (thoracic sternum distinctly wider, posterior end of sternite 3 distinctly narrower than anterior end of sternite 4; cf. Fig. 1E; Naruse and Ng 2014: figs 1b, 3b, 6c);

Thoracic sternite 4 has a distinct median line in both the male and the female (Figs 1C, D, 3A, B) (median line absent on sternite 4; cf. Fig. 1E; Naruse and Ng 2014: figs 1b, 3b, 6c);

The vulvae are round, and their anterior edge is in contact with thoracic suture 5/6 (Figs 1D, 2H) (vulvae lunate, 'half-moon', in shape, anterior edge not touching suture 5/6; cf. Fig. 1E; Naruse and Ng 2014: fig. 5d);

The endopod of the third maxilliped is relatively narrower (esp. merus) and the lateral margin of the exopod is convex (Fig. 2B) (endopod broader, lateral margin of exopod straight; cf. Naruse and Ng 2014: fig. 6b).

The ambulatory legs are relatively shorter and stouter, and the dactyli are distinctly shorter than the propodi (Figs 1A, 2F, G) (ambulatory legs longer and more slender, dactyli subequal in length to propodi; cf. Naruse and Ng 2014: figs 1a, 3a);

The G1 is only slightly sinuous throughout its length, and the G2 is relatively stouter (Fig. 3E, F) (G1 distinctly sinuous, more pronouncedly curved, G2 more slender; cf. Naruse and Ng 2014: fig. 5b, c).

Naruse and Ng (2014: 265, 270) observed that there was a transverse ridge separating thoracic sternites 2 and 3 in Christmaplax mirabilis , but this is not an accurate description of the structures. What separates sternites 2 and 3 is a prominent transverse suture (as in Harryplax severus ) but the margin of sternite 2 adjacent to the suture is just slightly raised. The different morphological features of Harryplax require the emendation of the current diagnosis of the family Christmaplacidae (see above).