On a new commensal species of Aliaporcellana from the western Pacific (Crustacea, Decapoda, Porcellanidae)
On a new commensal species of Aliaporcellana from the western Pacific (Crustacea, Decapoda, Porcellanidae)
Alexandra Hiller 0
0 Smithsonian Tropical Research Institute , Apartado 0843-03092, Panamá , República de Panamá 2 Institut für Tierökologie und Spezielle Zoologie der Justus-Liebig-Universität Giessen , Heinrich-Buff-Ring 29 (Tierhaus), D-35392 Giessen , Germany
Aliaporcellana spongicola sp. n. from the Philippines and Indonesia is described. The new species has been frequently photographed by divers because of its striking coloration, but has not been described yet. Aliaporcellana spongicola sp. n. is in fact a widespread commensal of barrel sponges of the genus Xestospongia and other sponges. Morphological characters and ecological information of all described species of Aliaporcellana, and of other porcellanids associated with sponges and soft corals, suggest that all members of the genus are commensals, and that similar morphological adaptations to dwelling on these hosts have evolved independently in different evolutionary lines within Porcellanidae. The porcellanid genus Aliaporcellana was established by Nakasone and Miyake (1969) for a group of Indo-West Pacific species previously assigned to Porcellana Lamarck and to one of three natural groups within Polyonyx Stimpson, designated by Johnson (1958) as the P. denticulatus Paul'son 1875, group. A diagnostic character considered
eol>Crustacea; Porcellanidae; Aliaporcellana; new species; Indo-West Pacific; commensalism; adaptation; sponge- and octocoral-dwelling
Nakasone and Miyake (1969)
to raise Aliaporcellana is the dactylus of all walking
legs bearing two or more distinctively well-developed fixed spines. Aliaporcellana
contained nine species until
restricted the genus to the species of the Polyonyx
denticulatus group, which now includes the type A. suluensis (Dana 1852), A. pygmaea
(de Man 1902) and A. telestophila
, and the species described by
Nakasone and Miyake (1969)
, A. kikuchii. A fifth species, A. taiwanensis, was subsequently
Dong et al. (2011)
Here we describe a new sponge-dwelling species of Aliaporcellana from material
collected in the Philippines and Indonesia. Despite having been frequently
photographed by divers because of its striking coloration and relatively large size, the species
has not been described. With the exception of A. telestophila , commensalism has never
been reported for other congeners. We highlight the characters distinguishing the new
species from its congeners, and discuss the morphological traits, present in all
Aliaporcellana species and other porcellanids associated with sponges, which we interpret as
adaptations to living on these hosts.
Material and methods
We found the new species in material collected in the Philippines by G. Paulay [Florida
Museum of Natural History, Gainesville, U.S.A. (UF)] and in Indonesia by C.H.J.M.
Fransen [Naturalis Leiden, The Netherlands (RMNH)]. The holotype is deposited in
the National Museum of Natural History, Philippines (NMCR). Color photographs
of the holotype and of the live crab in the field were provided by G. Paulay, and were
included in the description. Measurements of carapace length and width (in mm) of
type individuals follow collection information.
Aliaporcellana spongicola sp. n.
Material. Holotype: female (ovigerous), NMCR 4966, ex UF 43328, Philippines,
Oriental Mindoro Province, Mindoro, Puerto Galera, off Pt W of Bayanar Beach,
13.5118°N 120.9088°E, 10–13 m, sand slope, coll. G. Paulay, 02.04.2015, 6.8 × 7.0
mm. Paratypes: 2 females (ovigerous), UF 43328, same collection data as holotype, 7.4
× 7.6 mm, 5.2 × 5.2 mm;1 female (ovigerous), UF 42943, Philippines, Oriental
Mindoro Province, Mindoro, Puerto Galera, Batangas Channel, 13.5199°N 120.9604°E,
11 m, lagoon sand slope with sponge, coll. G. Paulay, 12.04.2015, 6.2 × 6.8mm; 2
males, 1 female (ovigerous), RMNH.CRUS.D.57287, Indonesia, SW Sulawesi,
Spermonde Archipelago, Bitung, sta. 17, 20 m, from large grey folious sponge, cleaning
station, coll. C.H.J.M. Fransen, 30.10.1994, 4.8 × 4.4 mm, 3.3 × 3.0 mm, 5.2 × 4.8 mm.
Description. Carapace rounded (Figures 1, 2), considerably variable in form and in
length-width ratio; larger females with carapace broader than long (ratio < 1), smaller
individuals with carapace relatively longer than broad (ratio > 1); dorsal surface convex,
glossy, with faint, transverse striae on branchial and intestinal regions; cervical grooves
gently depressed. Front (Figures 1, 2) broad, slightly produced beyond eyes, weakly
trilobate, somewhat deflexed; frontal lobe visible in dorsal view, grooved, overreaching
lateral ones. Distal margin of entire front lined with row of rounded, upwardly directed
small spines (Figure 3a), the largest on supraocular edges. Outer orbital angles (Figure
2) forming acute, bifid tooth followed by hepatic spine of similar size. Epibranchial
margin rounded, produced outwards, marked with epibranchial spine; cervical groove
faintly marked. Mesial branchial margins crested, with row of 5 or 6 strong, anteriorly,
upwardly directed spines of increasing size posteriorly. Sidewalls entire.
Eyes moderately large (Figures 1, 2, 3a), retracted, ocular peduncles short. First
movable segment of antennal peduncle (Figures 2, 3b) with strong, anteriorly curved
distal spine, second with smaller, anterodistal, acute protuberance, third one globular.
Basal segment of antennular peduncle (Figure 3c) with anterior surface transversely
rugose, surrounded with open ring of strong, conical spines. Third maxilliped (Figure
3d) slightly rugose, ischium sub-quadrate with inner lobe, inner margin of merus
semicircular; exopodite long, pyriform, reaching 2/3 of length of merus.
Third thoracic sternite (Figure 3e) broadly elliptic, with triangular, forwardly
produced, lateral projections. Telson with 7 plates.
Chelae moderately different in size and form (Figures 2, 4a-c); merus short, dorsal
surface faintly rugose, inner margin with strongly projecting, sub-rectangular
projection, fringed distally with cockscomb-shaped row of teeth, other large spines on
proximal and distal edge of outer margin, one on distal margin; ventral side with two large
spines on distal margin. Carpus 1.5 times as long as wide, dorsal surface evenly convex,
similarly structured as carapace, with some faint transversal plications; inner margin
with 3–5 low or sharply hooked teeth, decreasing in size distally, distal edge rounded.
Outer margin with a row of six or seven acute, upwardly directed spines, the last one
forming distal edge. Palm slender, surface rounded, similarly structured as carpus, with
faint, transverse striae. Smaller chela with outer margin bearing row of approximately
ten sharp spines on proximal half, with scattered, long, simple setae; fingers reaching
up to half length of chela, dactylus moderately twisted, opening vertically, cutting
edges denticulate, without teeth, both fingers with narrow fringe of fine, plumose setae
in proximal 2/3 of length. Larger chela somewhat stouter, outer margin with row of
spines less developed or disappearing in large specimens, with scattered, long, simple
setae, fingers relatively shorter as in smaller chela; dactylus moderately twisted, opening
vertically, cutting edges in pollex and dactylus with broad, shallow tooth, gape naked.
Walking legs (Figures 2, 3f, g) stout, merus with some transversal striae, with
scattered, long, simple setae, increasing in number towards dactylus; carpus in first and
second leg ending dorsodistally in two minute spines, propodus ventrally with 1
movable spine in addition to terminal triplet; dactylus terminating in bifurcate, curved claw.
Coloration. The background color of carapace and extremities is bright orange
(hexadecimal color #e86700), overlain with a reticulate bright blue (hexadecimal color
#000de8) pattern (Figures 1, 5). A broad, black band crosses the carapace transversely
at the level of the hepatic region; it is fringed on both sides by a small, blue line and
a broad, orange band. A similar band extends along the outer border of the chelipeds
from the carpus to the tip of the pollex. In a number of individuals the blue color
prevails over the orange, and the entire crab appears blue.
Ecology. Aliaporcellana currently consists of six species. Of all species, A. spongicola
sp. n. is by far the most strikingly colorful, and has, therefore, become popular among
underwater photographers and marine aquarists. Aliaporcellana spongicola sp. n. dwells
on large barrel sponges of the genus Xestospongia Laubenfels [family Petrosiidae; e.g.,
X. testudinaria (Lamarck 1815)] and on other types of sponges, like the “large, grey
foliose sponge”, on which the crabs from Sulawesi included in this study, were found.
The porcellanid lies in the sponge’s folds, where it is most protected from predators
Distribution. The type specimens come from the central Philippines and northern
Etymology. The name spongicola (from the Latin word spongia, meaning sponge,
and the Latin suffix cola, meaning dwelling) refers to the sponge-dwelling habit of the
Remarks. Aliaporcellana spongicola sp. n. is considerably variable in the shape of
carapace and the degree of spination on body and extremities. As in other porcellanid
species, the spines are more defined in smaller specimens. The new species is
distinguished from A. pygmaea and A. kikuchii by the lack of acute spines on the dactylus of
the smaller cheliped
(Osawa 2007; Dong et al. 2011)
, and by its smoother surface of
carapace and chelipeds
(Lewinsohn 1969; Nakasone and Miyake 1969; Werding and
Hiller 2007; Osawa and Chan 2010)
. Aliaporcellana spongicola sp. n. can be
distinguished from A. suluensis, A. telestophila and A. taiwanensis by its regularly denticulated
front (Figures 2, 3a), which is smooth in the other species, and by the basis of the
antennular peduncle, which is crowned with a ring of spines (Figure 3c) and is at most
granulate or faintly serrate in the compared species
(see Lewinsohn 1969; Werding and
Hiller 2007; Dong et al. 2011 for A. suluensis; Ng and Goh 1969 for A. telestophila;
Dong et al. 2011 for A. taiwanensis)
With the description of Aliaporcellana spongicola sp. n., the genus now comprises
Up to now, A. telestophila is the only species of the genus reported to live as
(Johnson 1958; Ng and Goh 1996)
. Johnson (1958) described this species
based on his own collections and observations, highlighting that A. telestophila was
found “strictly [in] commensalism with the octocoral Telesto”. However,
doubted the identification of the octocoral host and referred to it as
Solenocaulon Gray (family Anthothelidae Broch), instead.
Ng and Goh (1996)
Goh et al. (1999)
described the porcellanid as dweller inside of the hollow branches
of the octocoral, communicating with the outer medium through the openings of
these branches. The species lives in male-female pairs; sometimes two pairs are found
in one host colony.
Our own observations of the morphology and ecology of A. suluensis collected
from sponges in Saudi Arabia, and of all other Aliaporcellana species, led us to conclude
that perhaps all species of the genus are commensals. We base our conclusions on the
well-developed, fixed spines on the dactylus of the walking legs, a character present
in all Aliaporcellana species (see Figures 3f-g) and other porcellanid commensals that
(e.g., Pachycheles ackleianus A. Milne-Edwards, 1880, Polyonyx
hendersoni Southwell, 1909 and P. splendidus Sankolli, 1963; see Haig 1960; Hiller et al.
. This morphological trait is probably an adaptation to moving on the surface
of this type of host. We hypothesize that all members of the genus Aliaporcellana are
commensal of sponges or octocorals, and that this morphological trait has evolved
independently in different evolutionary lines within Porcellanidae. Aliaporcellana
spongicola sp. n. probably lives in male-female pairs, as A. telestophila does on the octocoral
(Ng and Goh 1996; Goh et al. 1999)
The association between crab and sponge may be easily overlooked because
sponges are often attached to each other and to rocks, and are damaged when the rocks are
lifted. More collection data of other Aliaporcellana species are needed to confirm the
commensal status of the genus.
We are grateful to G. Paulay, A. Bemis, and J. Slapcinsky (Florida Museum of Natural
History, Gainesville, U.S.A.) for giving us access to porcellanid material and
photographs, and for hosting us. We are also indebted to C.H.J.M. Fransen and K. van
Dorp, (Naturalis Leiden) for giving us access to porcellanid material. We also thank S.
Sereda for inking our drawings in pencil. We thank H.A. Lessios (STRI), E. Campos
(Universidad Autónoma de Baja California, México) and an anonymous reviewer for
comments that helped improve this manuscript.
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