Calliaxina thomassini, Ngoc-Ho, 2014

Ngoc-Ho, Nguyen, 2014, Six species of Axiidea and Gebiidea from the Indo-West Pacific (Crustacea, Decapoda), Zoosystema 36 (3), pp. 545-561 : 549-552

publication ID	https://doi.org/ 10.5252/z2014n3a1
persistent identifier	https://treatment.plazi.org/id/03C187FC-FF8A-696C-D0AE-FEEBFEEC9F4B
treatment provided by	Felipe
scientific name	Calliaxina thomassini
status	sp. nov.

Treatment

Genus Calliaxina Ngoc-Ho, 2003 Calliaxina thomassini n. sp.

( Fig. 2 View FIG )

MATERIAL EXAMINED. — Madagascar. All specimens small and damaged with most appendages lost except for holotype.

Holotype. Toliara (Tuléar) region (South-western Malagasy) Songoritelo fringing reef, 15 km northward of Toliara town, in seagrass beds on inner reef flats, coarse limestone sand, J. Picard coll. 3.VIII.1962: ♂, cl 5 mm, tl approx. 21 mm, specimen broken into three parts, all pereopods present, broken off, maxilliped 3 endopod lost, exopod present ( MNHN Th 1621) (figured).

Paratypes. ♀, same data as holotype, cl 5.5 mm, tl 20.5 mm, most appendages lost except for right pereopod 1, 2 and 3.( MNHN Th 1622) (figured) ; Toliara Great Barrier Reef , 10 m, clean coral sands, B. A. Thomassin coll. 19.IX.1969: 2 ♂, both pereopods 1 present, cl 5 mm, tl 17 mm ( MNHN Th 1623a), cl 4 mm, tl 15.5 mm (figured) ( MNHN Th 1623b) ; Nosy Bé Island (north-western Malagasy), Antafianambitry fringing reef, inner flats back of inner marine seagrass beds, sandy sediments, Mireille Pichon-Carles coll. 21.X.1964: 2 ♀, cl 5.5 mm, tl 19 mm ( MNHN Th 1624a), cl approx. 4 mm, dissected ( MNHN Th 1624b) .

Non type. Thomassin coll., data lost: ♀, cl 6.5 mm, tl approx. 23.5 mm, specimen much damaged, broken ( MNHN Th 1625).

DIAGNOSIS. — Rostrum slightly pointed or absent. Eyestalks about 1.25 times as long as broad at base, corneas rounded, subterminal. Telson approximately 1.60-1.70 times as broad as long, lateral borders rounded, posterior border slightly convex, a transverse carina in large specimens. Maxilliped 3 exopod present, articulated, overreaching ischium of endopod. Pereopod 1 subequal, slightly dissimilar, not sexually dimorphic. Pereopod 1 with faint longitudinal keel on upper border of propodus; fixed finger with pointed tip, cutting edge either with a small triangular median tooth along with two or three tufts of setae or unarmed with a longitudinal depression and row of long setae near the edge. Uropods longer than telson; exopod with rounded posterior border, dorsal plate and large pointed proximal spine.

ETYMOLOGY. — The species is named for Bernard A. Thomassin who collected and donated the studied material to the MNHN.

DESCRIPTION

Carapace lacking dorsal oval, frontal margin with small pointed rostrum ( Fig. 2A View FIG ) or flat ( Fig. 2B View FIG ). Linea thalassinica distinct, cervical groove and one transverse suture present, very faint. Eyestalks dorsally flattened, about 1.25 times as long as broad at base, corneas rounded, pigmented, subterminal.

Telson ( Fig. 2C, P, Q View FIG ) approximately 1.60- 1.70 times as broad as long, broader in larger specimen ( MNHN Th 1625, ♀ of tl 23.5 mm, Fig. 2P View FIG ), lateral borders rounded, posterior border slightly convex, a transverse carina interrupted medially bearing a few setae in large specimens, carina absent in small specimens ( Fig. 2Q View FIG ).

Antennule and antenna unbroken in one specimen ( MNHN Th 1624a) ; antennular peduncle shorter than antennal peduncle, reaching approximately 2/3 distal of last article.

Maxilliped 1 ( Fig.2H View FIG ) endopod absent or broken, epipod large with pointed anterior lobe.

Maxilliped 2 ( Fig. 2I View FIG ) epipod present, slightly overreaching ischium of endopod.

Maxilliped 3 ( Fig. 2J, K View FIG ) exopod present, articulated, overreaching ischium of endopod. Ischium of endopod slightly longer than broad, crista dentata on inner surface, holding 12 teeth in holotype; merus about 0.8 time as long as broad, carpus with convex lower border; propodus as long as broad; dactylus with rounded terminal border bearing close-set stiff setae.

Pereopod 1 subequal, slightly dissimilar, not sexually dimorphic. Ischium ( Fig. 2D, E View FIG ) approximately 2.5 times as long as broad at mid-length; lower border with two or three spinules followed by two or three denticles; merus about 0.8 times as long as broad, carpus as long as broad, both merus and carpus with convex lower and upper border, unarmed. Propodus about 1.2 times as long as broad in holotype ( Fig. 2D View FIG ), approximately as long as broad in other pereopods 1 examined ( Fig. 2E View FIG ); upper border with a longitudinal keel, very faint in holotype and paratypes, better defined in a larger specimen ( Fig. 2E View FIG ); fixed finger with pointed tip, cutting edge varies slightly in morphology: either carrying a small triangular tooth medially along with two or three tufts of setae on the side ( Fig. 2D, E View FIG ); or unarmed with a longitudinal depression and row of long setae near the edge ( Fig. 2F, G View FIG ); this shape occurs equally on right or left pereopod 1, more often on the right. Dactylus with pointed curved tip, unarmed.

Pereopods 2-5 ( Fig. 2 View FIG L-O) as figured. Pereopod 2 chelate; pereopod 3 with small postero-proximal lobe on propodus; pereopod 4 propodus slender; pereopod 5 subchelate.

Male pleopod 1, very small in holotype ( Fig. 2S View FIG ) uniramous, 2-articulated, distal article slender, with pointed tip; male pleopod 2 ( Fig. 2T View FIG ) biramous, exopod shorter than endopod, latter with spinule and outline of appendix interna.

Female pleopod 1 ( Fig. 2U View FIG ) in specimen MNHN Th 1625 (tl 23 mm) uniramous, bi-articulated, first article making a stout angle, distal article slender with a few setae; female pleopod 2 ( Fig. 2V View FIG ) biramous, exopod longer and slender than endopod, no visible appendix interna.

Pleopod 3-5 ( Fig. 2R View FIG ) biramous, foliaceous endopod bearing finger-like appendix interna.

Uropods ( Fig. 2C, P, Q View FIG ) exopod and endopod oblong, longer than telson, exopod with rounded posterior border, dorsal plate and large pointed proximal spine.

REMARKS

The genus Calliaxina was established by Ngoc-Ho (2003) with Calliax punica de Saint Laurent & Manning, 1982 as type species and including two others: C. novaebritanniae (Borradaile, 1899) and C. sakaii (de Saint Laurent & LeLoeuff, 1979) . The genus mainly differs from Calliax by having an exopod on the maxilliped 3.

This taxon has been disputed by Sakai. Sakai (2005: 197) stated that Calliaxina “is not accepted” and Calliaxina as well as Eucalliax were considered synonymous with Calliax . Sakai (1999) ignored Calliaxina all together. Sakai’s stance was criticized by Dworschak (2007: 159). Later, Sakai (2011a: 494) recognised Calliax , Eucalliax and Calliaxina as valid; nevertheless, he argued that the presence of an exopod on the maxilliped 3 was not “of vital importance” in the classification of the genera, in contrast, the presence of a sulcus was considered. According to his concept, Calliaxina was expanded to include eight species.

The cardiac sulcus is an uncalcified suture running across the carapace between the cervical groove and the posterior border. It is faint, much more indistinct than the linea thalassinica and is also variable. In the material of the new taxon studied, it is present only in the holotype and a specimen of cl> 4 mm (tl> approx. 15 mm) while the maxilliped 3 exopod is present in all. Similarly, in Calliaxina punica (de Saint Laurent & Manning, 1982) , type species of the genus, the cardiac sulcus is present but hardly visible in a ♂ of tl 26 mm (de Saint Laurent & Manning 1982: fig. 1a) belonging to the paratype lot MNHN Th 565 (6 ♂, 4 ♀, of tl 12-26 mm). In the rest of the lot and in the paratypes MNHN Th 563 (2 juveniles of tl 12 mm and 12.5 mm), the cardiac sulcus is absent.

In this work, the classification of Calliaxina as defined by Ngoc-Ho (2003) is adopted.

There are a few similarities between Calliaxina and Eucalliax , e.g., while comparing Calliaxina thomassini n. sp. with Eucalliax panglaoensis Dworschak, 2006 from Bohol, Philippines. Both species have a suture on the carapace, the pereopod 1 equal and chelate, pereopod 3 with a small proximal lobe on the propodus, telson with a transverse carina (not always present in Calliaxina thomassini n. sp.); however the rostrum is much more prominent in E. panglaoensis and the telson is broader. Above all, the main difference between the two genera is that Eucalliax panglaoensis as all species of Eucalliax has no exopod on maxilliped 3, while a large exopod is present on maxilliped 3 of Calliaxina thomassini n. sp.

The material examined comprises young specimens of small size. Consequently, a number of characters, especially male and female pleopods 1 and 2, are very small with no visible appendix interna or appendix masculina. Some other characters do not quite agree with the original diagnosis of Caliaxina presented by Ngoc-Ho (2003: 493): the maxilliped 3 is narrower (ischium + merus length about 2.5 times merus width) than in typical species where it is operculiform (ischium + merus length <twice merus width), the telson is about 1.60-1.70 as wide as long, slightly wider than in Calliaxina punica , type species of the genus.

Of the three Calliaxina species , the new taxon shows similarities with C. novaebritanniae :

1) Small slightly pointed rostrum; 2) maxilliped 3 exopod about as long as ischium; 3) telson broader than long with transverse carina interrupted medially by a tuff of setae; and 4) posterior border of telson straight or slightly convex.

Calliaxina thomassini n. sp. differs from C. novaebritanniae as well as C. punica and C. sakaii by: 1) rostrum minute or nearly absent; 2) row of long setae on the edge of the depression on one pereopod 1 fixed finger; and 3) large proximal spine on uropod exopod.