Rhopalorhynchus sibogae Stock 1958

Arango, Claudia P., 2009, New species and new records of sea spiders (Arthropoda: Pycnogonida) from deep waters in Western Australia, Zootaxa 1977, pp. 1-20 : 3-5

publication ID

https://doi.org/ 10.5281/zenodo.185190

DOI

https://doi.org/10.5281/zenodo.6213214

persistent identifier

https://treatment.plazi.org/id/039387DA-FF83-787D-FF7E-FB3DD1A7FE36

treatment provided by

Plazi

scientific name

Rhopalorhynchus sibogae Stock 1958
status

 

Rhopalorhynchus sibogae Stock 1958 View in CoL

( Figure 2 View FIGURE 2 )

Rhopalorhynchus sibogae View in CoL — Stock 1958: 114, 117, 124–125. — Child 1975: 7.

Material: AM P72804, 1female. 4 December 2005, Kalbarri, Western Australia, CSIRO station 096-025, collected by Sherman sled from 27.8126°S 113.2990°E to 27.8080°S 113.2970°E, soft bottom, 123m. AM P72807, 1 male. 7 December 2005, Carnarvon, Western Australia, CSIRO station 120-049 collected by Sherman sled from 112.6660°S 24.6194°E to 112.6660°E 24.6228°S, hard bottom, 100 m.

Remarks: Rhopalorhynchus sibogae had been reported from Australia only once ( Child 1975). I have compared these two specimens to the two juveniles in Child (1975) deposited at Western Australian Museum and, based on the proboscis, palps and leg configurations, they can be all attributed to the same species. The four specimens agree in the position of the proboscis tooth at 31–37% along the inflated part ( Figure 2 View FIGURE 2 B–D), and the proportion of the sixth:seventh palp segments being about 50% ( Figure 2 View FIGURE 2 E, F), in agreement to the type material ( Stock 1958). Strangely, these observations differ from the report in Child (1975), as he described the proboscis tooth on 24–26% the distance along the inflated part and the sixth-seventh palp segments proportion as 93%; the reason for this inconsistency is unclear. Tarsal ratio and length of the propodal claw are in agreement in the four specimens examined. Rhopalorhynchus sibogae and R. tenuissimum ( Haswell 1884) are very closely related species, if not the same, as there is an overlap in many of the diagnostic characters of the two species, at least based on the very few individuals available for measurements and according to the re-description in Staples (1982) and Takahashi et al. (2007). The main aspects that can be used to attempt differentiation of the two species are the position of the proboscis tooth, at near 44–50% the distance of the inflated part in R. tenuissimum ( Figure 2 View FIGURE 2 A) and between 30–40% in R. sibogae ( Figures 2 View FIGURE 2 B–D), the sixth and seventh palp segments ratio which is 0.65–0.70 in R. tenussimum and 0.5 in R. sibogae ( Figure 2 View FIGURE 2 E, F), and the main claw: propodus ratio, 69–85% in R. tenuissimum , 100% in R. sibogae .

The species of this genus are very homogeneous in their morphology and only subtle variations have been used to recognise species, at the same time stating that there is clear intraspecific variation of most characters depending on age and gender ( Stock 1958). In Australia, R. sibogae is known from Point Cloates to Rottnest Island in WA and R. tenuissimum is known from localities in Queensland on the Eastern coast. The two specimens reported herein are within the range of distribution of R. sibogae .

CSIRO

Australian National Fish Collection

Kingdom

Animalia

Phylum

Arthropoda

Class

Pycnogonida

Order

Pantopoda

Family

Colossendeidae

Genus

Rhopalorhynchus

Loc

Rhopalorhynchus sibogae Stock 1958

Arango, Claudia P. 2009
2009
Loc

Rhopalorhynchus sibogae

Child 1975: 7
Stock 1958: 114
1958
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