Colanthura gerungi, Annisaqois & Wägele, 2021

Annisaqois, Manikmayang & Wägele, J. Wolfgang, 2021, Morphology and Taxonomy of Isopoda Anthuroidea (Crustacea) from Sulawesi with description of six new species, European Journal of Taxonomy 768, pp. 1-52 : 39-50

Colanthura gerungi sp. nov.

urn:lsid:zoobank.org:act:1F397C5C-DDE1-440D-9B96-9B181CECA23D

Figs 27–35

Differential diagnosis

Species of Colanthura with expanded propodus of subchelate pereopod 1, palm with proximal triangular tubercle protruding at posterior margin; mesial surface beside this tubercle with row of 18 setae, propodus of subchelate pereopods 2–3 oval, 2 times long than wide, pereopod 2 with row of 5 medial sensory spines on propodus palm, six such spines on P3; uropod endopod ovate, about 0.8 times sympod length, exopod shorter and roughly triangular, margins of endopod, exopod and tip of telson weakly crenulated; telson tongue-shaped, rounded distal margin bearing 5 pairs of long setae, 2 pairs of short setae dorsomedially near apex, and 4 further pairs of dorsal setae near lateral margin.

Colanthura kensleyi Poore, 1984 from the Philippine and Sangihe Islands (north of the Sulawesi area sampled for this study) shows close affinities to the material from Bangka Island described herein; both species are best distinguished through the uropod exopod, which is triangular to oval in C. gerungi sp. nov.,while in C. kensleyi the uropod exopod has an elongate oval shape. Also, the propodus of pereopod 1 is wider in C. kensleyi , and lacks additional mesial setae distally. Three of these are present parallel to the palm of the female in our material. A redescription of C. kensleyi is needed for further comparison (see also Poore 1984).

Etymology

This species is dedicated to Dr Grevo Gerung, who sponsored and supervised the studies of the first author.

Material examined

Holotype INDONESIA • ♂ (3.8 mm); Bangka Island , west of Coral Eye Resort; 1°45′20.77″ N, 125°7′57.28″ E; 1–2 m depth; in seagrass bed; M. Annisaqois and J.W. Wägele leg.; Sep. 2019; MZB Iso 109.

Allotype INDONESIA • ♀ (3.9 mm); Bangka Island , west of Coral Eye Resort; 1´°45′19.92″ N, 125°7′58.96″ E; 1–2 m depth; on mangrove roots; M. Annisaqois and J.W. Wägele leg.; Sep. 2019; MZB Iso 110.

Paratypes INDONESIA • 1 ♂ (3.5 mm), 1 ♀ (3.7 mm), 11 immature specimens (1.6–3.9 mm); Bangka Island ; 1°45′20.77″ N, 125°7′57.28″ E; 1–2 m depth; in seagrass bed; M. Annisaqois and J.W. Wägele leg.; Sep. 2019; MZB Iso 111 • 1 immature specimen; Bangka Island ; 1°45′19.92″ N, 125°7′58.96″ E; 1 m depth; on mangrove roots; M. Annisaqois and J.W. Wägele leg.; Sep. 2019; MZB Iso 112 • 1 ♀; Bangka Island , off Coral Eye Resort; 1°44′22.04″ N, 125°8′41.19″ E; 1–2 m depth; in coral rubble; M. Annisaqois and J.W. Wägele leg.; Sep. 2019; MZB Iso 113 .

Description

Male

BODY. Slender, about 13 times as long as greatest width, dorsally weakly pigmented, scattered small cuticular scales on body and part of appendages. Cephalothorax in dorsal view roughly as long as wide, pair of compound eyes with few but distinct ommatidia. Body proportions: C<1<2 = 3>4> 5>6>>7. Pereonite 7 is strongly reduced, without appendages, not as long as pleonite 3 or 4. Pleonites 1–5 free, together length about as pereonite 6.

ANTENNAE. Antenna 1 with 6 flagellar articles, articles broader than long, many long aesthetascs surround flagellar segments, on last article 4 aesthetascs. Antenna 2 with short flagellum, basal flagellar article slightly as long as wide, followed by 3 minute articles. Mandible fused laterally to cephalothorax (see Fig. 31 ), palp and molar absent. Maxilla 1 slender lanceolate, apex laterally serrated, with 11 saw-teeth. Maxilliped uniarticulate without sutures separating articles, bearing 9 simple setae, 8 of them near apex.

PEREOPODS. Pereopods 1–3 subchelate. Expanded propodus of pereopod 1 with proximal triangular tubercle protruding at posterior margin; mesial surface beside this tubercle with row of 18 setae and further setae on palm. Propodus of pereopods 2–3 oval, 2 times long than wide, dactylus reaching nearly to tip of carpus. Pereopod 2 with row of 5 medial sensory spines on propodus palm, six such spines on P3. Pereopods 4–6 dactylus shorter than propodus, propodus as long as wide and slightly curved, in P6 narrower than in P4 and P5, two sensory spines on palm of P4, three on P5 and P6; carpus lenght as merus, nearly rectangular and as long as wide, with 2 sensory spines on ventral margin, carpus and merus together roughly lenght of ischium.

EXOPODS OF PLEOPOD. Exopod of pleopod 1 operculiform, distal margin with 13 feathered setae, endopod narrower, about ¼ of exopod width, margin with 13 feathered setae. Exopod of pleopod 2 distally with 7, endopod with 4 feathered setae. Appendix masculina surpassing tip of endopod, apex with a small hooked knob. Pleopods 3–4 endopod with 3, exopod with 6 distal feathered setae, on pleopod 5 only 5. Uropod endopod ovate, not surpassing telson. Endopod about 0.8 sympod lenght. Exopod of uropod shorter and triangular, with 12 simple setae and 8 feathered setae, most on margin. Margins of endopod, exopod and tip of telson weakly crenulated. Telson tongue-shaped, rounded distal margin bearing 5 pairs of long setae, 2 pairs of short setae dorsomedially near apex, and 4 further pairs of dorsal setae near lateral margin. Setation symmetry is imperfect.

Ovigerous female

Habitus resembling male (see Fig. 32 ). Antenna 1 with 4-jointed flagellum; first article of flagellum short, ring-shaped, with 1 feather-like seta; second article longest, distally 2 minute articles; last article with 3 aesthetascs and 4 setae. Antenna 2 flagellum apparently uniarticulate, with whorl of distal setae. Acute mouth parts. Mandible fused laterally to cephalothorax ( Fig. 31 ), without palp and without molar process. Maxilla 1 elongate, acute, distal part serrated with 10 saw-teeth. Maxilliped without sutures separating articles, apically 1 tiny and 4 longer setae. Pereopods 1–3 subchelate, propodi oval, width about two thirds of length, larger in pereopod 1, dactyli reaching to tip of carpus, carpus triangular. Propodus of pereopod 1 with mesial comb of 8 slender setae near proximal tubercle of palm, more distally three stouter mesial setae and further setae on palm. Palm of propodus of pereopod 2–3 with 5–6 sensory spines. Pereopods 4–6 dactylus shorter than propodus, propodus much as long as wide, slightly curved, with 2 (P4) or 3 (P5–6) sensory spines on palm; carpus dorsally with 1 feather like seta and ventrally 2 sensory spines. Exopod of pleopod 1 operculiform with 13 feathered setae on distal margin, endopod narrow, about ⅓ exopod width, distally with 9 feathered setae. Pleopods 2–5 endopod with 3 feathered setae and exopod with 8–5 feathered setae. Uropods not surpassing telson, exopod ovate, endopod shorter than sympod (0.6 sympod length) and smaller than exopod. Telson tongue-shaped, rounded distal margin bearing 5 pairs of long setae, 4 pairs of longer dorsal setae, and dorsally many irregularly scattered short setae.

Immature specimens

In all features quite similar to females. Total length 1.6–3.9 mm. The shape of the uropod exopod varies somewhat, but is in tendency triangular with rounded apex. The setation on the telson is not constant, with pairs of long setae on distal margin and further scattered setae dorsally (see Fig. 35 ).

Remarks

This species belongs to the Colanthura group of genera discussed by Poore (1984). The paranthurid genera Califanthura Schultz, 1977 , Colanthura Richardson, 1902 , Cruregens Chilton, 1882 and Cruranthura Thomson, 1946 share the absence of pereopod 7, the short pereonite 7, the fusion of maxilliped basis and palp. Cruregens is blind, Cruranthura has fused pleonites 2–5 and a pereonite 7 that is short but well visible (as in Cruregens ). Species of Califanthura and Colanthura are very similar, and it might be that the character distinguishing Colanthura from Califanthura (pleonites not fused in Colanthura ) has not always been seen in species assigned to Califanthura and vice versa. Since free pleonites is the plesiomorphic state, Colanthura might be a paraphyletic genus.

Good illustrations of the mandible in these genera are not available. For the Colanthura described herein, we discovered in SEM studies that the mandible is laterally fused to the cephalon and therefore it cannot be dissected with the other mouthparts (see Fig. 31 ). This fusion might have caused the absence of illustrations of the mandible in descriptions of other species, too. The fusion of the mandible with the head capsule is a unique feature among isopods. It implies that the most active mouthpart is the movable maxilla, which probably is used as a stinging tool in these paranthurids, while mandibles and hypopharynx form a rigid sheath.

We do not propose to place the genera with fused immobile mandible in a new family. This character evolved within the Paranthuridae , and to separate some genera would leave the remaining ones in a paraphyletic group. This should always be avoided, to prevent the subjective and arbitrary creation of taxa. There are 13 described species with free pleonites that can be assigned to the genus. Unfortunately, several published species descriptions are very incomplete. Most characters useful to distinguish the species can be found in the uropod shape and setation. Species of Colanthura have been found in tropical, temperate, and polar waters. Of the tropical species, Colanthura bruscai Poore, 1984 from Mexico and Costa Rica and Colanthura pigmentata Kensley, 1980 from Madagascar have a broader propodus of pereopod 1 than C. gerungi sp. nov. Müller (1993) reported a dorsally black Colanthura tenuis from Bora Bora, where the exopod of the uropod is more elongate than in C. gerungi sp. nov. Müller’s species is probably not the same as C. tenuis of Richardson (1902) (redescribed by Poore 1984), which occurs in the western Atlantic Ocean. Colanthura nigra Nunomura, 1975 from Japan is also dorsally black and easily distinguished from other Indo-Pacific species. The uropod sympod is wider than in the specimens described herein. The redescription of C. nigra by Poore (1984) shows a uropod exopod with a distally straight outer margin. Colanthura setouchiensis Nunomura, 1993 from Japan does not have the basal tubercle on the propodus palm of pereopod 1 that is present in most descriptions of Colanthura . Colanthura uncinata Kensley, 1978 b from South Africa has a small and narrow uropod exopod with very few setae. The exopod of the uropods of C. daguilarensis Bamber, 2000 (a species from Hong Kong) and C. bruscai Poore, 1984 has an outer margin that is distally slightly concave, while in C. gerungi sp. nov. the exopod is continuously oval. Colanthura gauguini Müller, 1993 from Moorea has a broad oval uropod exopod with only a few long setae on the distal half of the margin, where other species have in addition feathered setae. The Caribbean species C. ornata Carvacho, 1977 has been described with fused pleonites and might be a Califanthura . Uropod shapes have not been published.

Figures

Fig. 27. Colanthura gerungi sp. nov., ♂, holotype (3.8 mm), in dorsal and lateral view (MZB Iso 109). Abbreviations: A1 = antenna 1; A2 = antenna 2; Mx = maxilla; Mxp = maxilliped.

Fig. 28. Colanthura gerungi sp. nov., ♂, holotype (MZB Iso 109). Abbreviation: P1–P6 = pereopods 1–6.

Fig. 29. Colanthura gerungi sp. nov., ♂, holotype (MZB Iso 109). Abbreviation: Plp1–Plp5 = pleopods 1–5.

Fig. 30. Colanthura gerungi sp. nov., ♂, holotype (MZB Iso 109). Abbreviations: UEx = exopod of uropod; UEn = endopod of uropod; Tel = telson.

Fig. 31. Colanthura gerungi sp. nov., SEM-images of a male specimen. Cephalothorax in ventral and lateral view. The maxillipeds are flanked laterally by mandibles which are fused to the cephalothorax. This explains why mandibles are usually missing among dissected mouthparts of this genus. The part distally in between maxillipeds is the hypopharynx, which envelopes the maxillae and distal parts of the mandibles. Note the bulging lenses of lateral eyes.

Fig. 32. Colanthura gerungi sp. nov., ♀, allotype in dorsal and ventrolateral view (3.9 mm) (MZB Iso 110). Abbreviations: A1 = antenna 1; A2 = antenna 2; Mx = maxilla; Mxp = maxilliped.

Fig. 33. Colanthura gerungi sp. nov., ♀, allotype (MZB Iso 110). Abbreviation: P1–P6 = pereopods 1–6.

Fig. 34. Colanthura gerungi sp. nov., ♀, allotype (MZB Iso 110). Abbreviations: UEx = exopod of uropod; UEn = endopod of uropod; Tel = telson.

Fig. 35. Colanthura gerungi sp. nov., immature specimens of different sizes (body length in mm). (MZB Iso 111) Comparison of exopods of uropods and telson setations.