Research Article |
Corresponding author: Jose C.E. Mendoza ( jcmendoza@nus.edu.sg ) Academic editor: Sammy De Grave
© 2017 Jose C.E. Mendoza, Peter K.L. Ng.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Mendoza JCE, Ng PKL (2017) Harryplax severus, a new genus and species of an unusual coral rubble-inhabiting crab from Guam (Crustacea, Brachyura, Christmaplacidae). ZooKeys 647: 23-35. https://doi.org/10.3897/zookeys.647.11455
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Harryplax severus, a new genus and species of coral rubble-dwelling pseudozioid crab is described from the island of Guam in the western Pacific Ocean. The unusual morphological features of its carapace, thoracic sternum, eyes, antennules, pereopods and gonopods place it in the family Christmaplacidae Naruse & Ng, 2014. A suite of characters on the cephalothorax, pleon and appendages distinguishes H. severus gen. & sp. n. from the previously sole representative of the family, Christmaplax mirabilis Naruse & Ng, 2014, described from Christmas Island in the eastern Indian Ocean. This represents the first record of Christmaplacidae in the Pacific Ocean. With the discovery of a second genus, a revised diagnosis for Christmaplacidae is provided.
Pacific, Mariana Islands, taxonomy, Decapoda , Pseudozioidea , coral reef, coelobite, cryptofauna
In the early 2000’s, a collection of specimens made by the late Harry Conley from the reefs and rubble beds around the island of Guam, in the western Pacific, were presented by Gustav Paulay (then of the University of Guam) to the second author for study. This resulted in some important publications contributing to the knowledge on the brachyuran fauna of Guam and the Mariana Islands (
The present material was collected by excavating the rubble at low tide, to a depth of approximately 1–2 m. As noted in
Measurements are written as carapace maximum width × carapace median length, in millimeters. Material examined are deposited in the
Carapace subovate; anterior half of anterolateral margin arcuate, cristate, granulate, posterior half armed with two widely spaced sharp teeth. Eyes reduced, immobile; orbits with sunken exorbital angle, with strong, ridged, anteriorly projecting infraorbital tooth (inner orbital angle), the mesial surface of which receives the antennule. Antennules elongated, cannot be fully retracted into their fossae. Cheliped with large, sharp, triangular, lobiform inner carpal spine; merus with highly convex flexor margin lined with conical spines; major chela with modified opposing molariform teeth on proximal cutting margins of fingers. Ambulatory legs elongate, very slender, meri at least five times as long as wide. G1 sinuous, without spiniform granules; G2 short, about one-third length of G1, distal segment short, about one-fifth total length of G2, petaloid in shape (emended from
Harryplax severus sp. n., by present designation.
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.
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.
Harryplax, new genus, is classified in Pseudozioidea following
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.
There are no distinct notches separating the supraorbital margin from the front nor from the anterolateral margin (Fig.
The anterior portion of the anterolateral margin is more gently arcuate (less convex) but is more strongly cristate (Figs
Harryplax severus gen. & sp. n., holotype, female (
The teeth on the carapace anterolateral margin, especially the first, are more prominent, with the tips distinctly curved (Fig.
The eyes, while immobile and reduced, are relatively better developed with longer peduncles and bigger corneas, and are visible even from dorsal view (Fig.
The basal article of the antenna is much longer and narrower (Fig.
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
The thoracic sternum is relatively narrower and the posterior end of sternite 3 is slightly wider than the anterior end of sternite 4 (Figs
Thoracic sternite 4 has a distinct median line in both the male and the female (Figs
Harryplax severus gen. & sp. n., paratype, male (
The vulvae are round, and their anterior edge is in contact with thoracic suture 5/6 (Figs
The endopod of the third maxilliped is relatively narrower (esp. merus) and the lateral margin of the exopod is convex (Fig.
The ambulatory legs are relatively shorter and stouter, and the dactyli are distinctly shorter than the propodi (Figs
The G1 is only slightly sinuous throughout its length, and the G2 is relatively stouter (Fig.
Holotype ♀ (7.9 × 5.6 mm) (
Christmaplax mirabilis Naruse & Ng, 2014, holotype ♂ (11.0 × 7.9 mm) (
Carapace (Figs
Antennules (Figs
Eye (Figs
Third maxillipeds (Figs
Male thoracic sternum (Fig.
Chelipeds (Figs
Ambulatory legs (Figs
Male pleon (Fig.
G1 (Fig.
The specific epithet, severus (L., harsh, rough, rigorous), alludes to the rigorous and laborious process by which this crab was collected. It is also an allusion to a notorious and misunderstood character in the Harry Potter novels, Professor Severus Snape, for his ability to keep one of the most important secrets in the story, just like the present new species which has eluded discovery until now, nearly 20 years after it was first collected. The name is used here as a noun in apposition.
Harryplax severus sp. n., shares some key morphological features with C. mirabilis which are presumably adaptations to a stygobitic lifestyle (i.e. reduced eyes, well-developed antennules and antennae, and long, slender ambulatory legs), which in turn suggests that the environmental conditions under which the former thrives are probably similar to the conditions in underwater caves. Harryplax severus is clearly a chalicophilous species, as it was collected deep in coral rubble or under subtidal rocks. It is also possible that it is a cavity dweller, or coelobite (viz.
We are grateful to the late Harry Conley for collecting this important material. A soft-spoken ex-Marine with a steely determination and a heart of gold, his endeavours have substantially advanced the cause of marine science. Thanks are also due to our old friend, “master hunter” Gustav Paulay, who passed the second author the bulk of Conley’s material and got us started on our studies of the Pacific cryptofauna. We also thank Shane Ahyong, Paul Clark, and Tohru Naruse for their helpful comments and suggestions for the improvement of this paper.