Pallenella pachycheira ( Haswell, 1885 )

Staples, David A., 2025, Pycnogonids, ‘ sea-spiders’ (Arthropoda, Pycnogonida) selected from the collections of the South Australian Museum with descriptions of new species and review of the genus Pallenella., Memoirs of Museum Victoria 84, pp. 1-47 : 42-44

Pallenella pachycheira ( Haswell, 1885)

Postscript: This reference is often cited incorrectly as Haswell, 1884. The paper was based on records for the year 1884 but published in 1885 (confirmed by Biodiversity Heritage Library and Museums Victoria Library).

Plate 16a–d

Possibly, non Pallenella pachycheira Brenneis et al. 2020 (earlier lit. and syn).

One male, ( SAMA E9442 ) South Australia, Coffin Bay , between Farm Beach and The Frenchman, under rocks on encrusting bryozoan, 6m ., K. Gowlett, 17 Jan 1988.

Plate 16. Pallenella pachycheira ( Haswell, 1885) . Unregistered specimens from Victorian waters: a, specimen amongst folds of bryozoan zooids (photo D. Staples); b, chelae; c. proboscis anterior view; d, whole specimen (photo Blair Patullo, Museums Victoria).

Remarks. The most common colouring of this species along the southern Australian mainland appears to match the be orangebrown, colour of the host bryozoan, but Arango and Brenneis (2013) recorded a yellow form with orange banding from Eaglehawk Neck Tasmania. Brenneis et al. (2020) again recorded the species from Eaglehawk Neck without commenting on colouring and markings but were able to confirm the genetic alignment of their two collection lots ( Arango and Brenneis, 2013). Unpublished records also place this colour form in central Bass Strait, Tasmania. Personal observations of other colour forms and variation in the size of mature specimens, suggest that more than one species has been assigned to P. pachycheira . This Plate 17. Pallenella reflexa ( Stock, 1968) , male, holotype (SAM E3418): a–c, trunk dorsal, lateral and anterior views; d, leg 3; e, propodus; f, left chela; g, juvenile ventral view; h, juvenile propodus.

South Australian specimen is largely consistent with Flynn’s (1919) redescription of Haswell’s holotype collected from New South Wales and typical of the form most often encountered along the Australian south-east coastline generally.Unfortunately, Flynn did not refigure the chela of the holotype but based on Haswell’s figure ( Haswell 1885, plate 57:6) the fingers of the present material and those described by Arango and Brenneis (2013) are far more strongly curved. For the time being this is attributed to differences in artistic interpretation. In agreement with the holotype, each finger of this specimen bears a single rounded projection on the inner central edge as opposed being present on the cutting edge of the moveable finger only, in the Tasmanian specimen. The “very short” proboscis of the holotype described by Flynn is consistent with this material whereas the proboscis of the Tasmanian specimen appears to be more slender and longer. Based on images and figures of the holotype and this specimen, the length of basal inflated part of the proboscis is about 1.4 times the width compared to about 2.7 times in the Tasmanian specimen. Differences in the shape of the propodus are also evident. This specimen has four eyes each with a single lens and shows signs of residual colour but no pattern markings.

Additional images of P. pachycheira collected from along the southern Australian mainland are included here for comparison (plate 16a–d).

The annular constrictions of the legs mimic bryozoan zooids and when combined with matching colouring of the host bryozoan, they are extremely difficult to detect in situ (plate 16a).

The legs of P. reflexa also share an irregular surface with P. pachycheira except that the constrictions of P. reflexa are subtle and take the form of undulations (plate 17d). Pallenella reflexa has eight eye lenses. Images of the Great Australian Bight specimen, Staples, (2005) are included here (SAM E3418, plate 17a–h).