Anoplodactylus perissoporus, Arango, Claudia P. & Krapp, Franz, 2007

Arango, Claudia P. & Krapp, Franz, 2007, A new species of Anoplodactylus (Arthropoda: Pycnogonida) from the Great Barrier Reef and discussion on the A. tenuicorpus - complex *, Zootaxa 1435, pp. 19-24 : 20-23

Anoplodactylus perissoporus new species ( Figure 1 )

Holotype: S105845. 1 male with eggs. Great Barrier Reef (GBR), Central Section, Rib Reef, reef slope, in coral rubble, 8 m. 6 September 1998. Paratypes: S105846. 1 female; GBR, Central Section, Pandora Reef, 3– 6m in rubble with algae, 15 July 1999. S105847. 1 juvenile, instar with 4th legs developing. Coral Sea, Flinders Reef, front reef, 12m, in Halimeda . 3 July 1999. S105848. 1 female. Coral Sea, Flinders Reef, front reef, 12m, in Halimeda . S105849. 1 male with eggs, 3 females; GBR, Central Section, Pandora Reef, 4–6m in rubble, 19 April 2000. CA111 1male. GBR Central Section, Pandora Reef, 8m in rubble, 14 November 1999. CA141, 184. 1 female, 1 male. GBR, Central Section, Pandora Reef, 4–6m in rubble, 19 April 2000.

Diagnosis

Five to nine cement gland pores on femora of males. Smooth chelae. Tibia 2 the longest leg segment, tibia 1 slightly longer than femur; 13 or more crenulations on the distal margin of major heel spine; eight sole spines; tiny distal lamina. Body glabrous, segmentation lines faint or obliterated.

Description

Specimens of moderate size for genus, leg span about 7 mm. Body and legs extremely slender, very attenuate form. Lateral processes separated about four to six times their diameter, as long as two to four times their anterior diameter, the third and fourth pair shorter. Trunk segmentation lines almost indistinct ( Fig. 1 A). Ocular tubercle very low, rounded; eyes large, lightly pigmented. Proboscis with swelling at midpoint ( Fig. 1 B). Abdomen small, glabrous.

Chelifores long, slender, diverging in acute angle at base, chelae half the length of scape, palms rectangular, as long as fingers, fingers curved and overlapping at tips, no sign of teeth ( Fig. 1 C).

Ovigers arise ventrally on first lateral processes, bases seen dorsally near the middle (see Fig. 1 A). Third segment length more than 10 times its width, with short setae; fourth segment longer than fifth, with two ectal and one endal setae; fifth segment with five ectal setae and one endal strong seta, sixth as long as fifth, with three endal setae, one ectal and two distal setae ( Fig. 1 D, H).

Legs very slender, coxae 2 three times longer than 1 and 3, these two subequal, tibia 2 the longest segment, tibia 1 just slightly longer than femur ( Fig. 1 E), femur with five to nine low cement gland cups (right leg 1: 9, leg 2: 9, leg 3: 6, leg 4: 5; left leg 1: 8, leg 2: lost, leg 3: 7, leg 4: 6) ( Fig. 1 F). Tarsus small, propodus slender, with three heel spines, the most distal the largest, with 13 teeth; eight sole spines, tiny distal lamina. Propodal main claw long, auxiliaries absent ( Fig. 1 G). Genital pores ventrally on second coxae of third and fourth legs. Female slightly larger than male (2.3mm in body length), with slightly longer propodal claw, otherwise same characteristics as male. Genital pores ventrally on second coxae of all legs. One male from Pandora Reef (CA111) has dorsodistal setae on major leg segments and an incipient crenulation of second heel spine of some legs. This specimen has five to nine cement glands as the holotype, justifying its designation as A. perissoporus new species.

Measurements holotype: Body length (from tip of last lateral process to anterior margin of cephalic segment): 2.1mm; width (across second pair of lateral processes): 1.4 mm; second lateral process length: 0.45mm; chelifore scape length: 0.48mm; palm: 0.14mm; chela fingers: ~ 0.14mm; proboscis length: 0.39mm; proboscis width at midpoint: 0.135mm; femur: 1.46mm; tibia 1: 1.48mm; tibia 2: 1.76mm; propodus: 0.55mm; claw: 0.3mm; abdomen: 0.18mm.

Etymology

Gr. perissos, beyond the regular number, extraordinary, odd number. In reference to the numerous cement gland pores on the femora of males, an unusual feature in Anoplodactylus .

Discussion

The tenuicorpus complex seems to be confined to the Indo-West Pacific region ( Figure 2 ). In the case of specimens identified as A. tenuicorpus only the type locality (Siquijor Island, off Mindanao) yielded a male (= the holotype). Other records refer only to females (see Figure 2 ). Traditionally, most Anoplodactylus species can be readily identified only if male specimens are available (but see Arango & Maxmen 2006), because diagnostic characters are usually related to male secondary sexual characteristics such as form and number of cement gland openings and ovigers features. When Child reported the females with no accompanying males from Eastern Indian Ocean ( Child 1988a), he relied only on their thin appearance and the serrated heel spine. Now, with at least another well-definable species (from Socotra Island) known to occur in the northeastern part of the Indian Ocean, some doubt is cast upon whether the females recorded from Aldabra and the Seychelles should be conspecific with that first described based on a male from the Philippines ( Child 1988b).

Anoplodactylus is a relatively morphologically homogeneous genus, and species are usually described based on one or two distinct characters, or more or less unique combinations of characters, mostly of the males. We present a summary of main differences among the four species included in the complex ( Table 1 ), which are also characters used by Stock (1994). These differences might seem minor when defining separate entities or species, but they reflect the nature of variation among Anoplodactylus records in general, and the difficulties in defining species boundaries within this speciose genus.

The tenuicorpus complex seems related to Anoplodactylus pectinus , a widely distributed pantropical species ( Hedgpeth 1948; Stock 1975; Bamber 1998; Arango 2003; Child 2004 and other references therein) that shares morphological traits with the complex such as prolonged chelifores (but not the proboscis) and pectination of the largest spine on the propodal heel. However, A. pectinus is not as slender and lateral processes are not as long as in species of the tenuicorpus complex. Further material and detailed studies including additional sources of data are needed to understand the distribution patterns and affinities among the species and populations of such rare sea spiders as in the tenuicorpus complex.

Figures

FIGURE 1. Anoplodactylus perissoporus n. sp., from Rib Reef, Central Section of Great Barrier Reef, holotype male. A. Dorsal view (0.5 mm). B. Proboscis (0.1 mm). C. Chelae (0.1 mm). D. Oviger (0.3 mm). E. Third right leg (0.5 mm). F. Femur of third left leg (0.5 mm). G. Distal leg articles (0.25 mm). H. Distal oviger segments (details from D).

FIGURE 2. Distribution map of the species in the A. tenuicorpus complex. Records of single male and females of A. tenuicorpus are shown: Female paratype from Aliguay Island, Philippines (Child 1988 b), one female from Aldabra Atoll (Child 1988 a), one female from Seychelles (Child 1988 a), one female from Calalan Bank off Glass Breakwater, near Magundas, Guam (Child 1991), one female from Madang, Riwa Bay, Port Moresby Bootlet Inlet (Child 1996).

Tables

TABLE 1. Main characters distinguishing the four attenuated Anoplodactylus species in the tenuicorpus complex.

Characters perissoporus n.sp.	tenuicorpus Child	exaggeratus Stock	Socotra species
Chelae length 1/2 of scape	1/3 of scape	1/2 of scape	1/2 of scape
Chelae teeth number Not present	3+3	5+3	4–5 + 5
Teeth shape on chela N/A	triangles	needles	needles
Chelae palm 2 x largest diameter	2 x largest diameter	3 x largest diameter	2 x largest diameter
Propodal cutting lamina tiny, distal	tiny, distal	absent	absent
Propodal sole spines 8	~ 5	~ 7	~ 9
Heel spine crenulations +13+	7–8	12	9
Oviger articles 6	6	7 (pseudoarticulation)	6
Relative lengths leg segments Tibia 2>tibia 1>femur	femur>tibia 2>tibia 1	tibia 2> tibia 1> femur	tibia 2> femur> tibia 1
cement gland(s) 5–9 cups-mounds	2 mounds	one mound	one slit
Proboscis length 0.39	0.54	0.43	0.4
Proboscis width (inflation) 0.135	-	0.13	0.16
Body length 2.1	1.71	1.69 (by addition)	2.17
Body width (2nd segment) 1.4	0.89(first)	0.77	1.13
Body segmentation lines nearly obliterated	3 distinct	3 distinct	3 distinct