Pallenella inflata ( Staples, 2005 )

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 : 23-24

Pallenella inflata ( Staples, 2005) .

Pseudopallene inflata ( Staples, 2005) : 164 Fig. 3 — Staples 2008,

129 Fig. 2E–F — Brenneis et al. 2020: 859, Fig 9.

Plate 8a–f

Material examined. One male carrying protonymphon and three juveniles] ( SAMA E9439 ). Cape Colbert, Port Lincoln , 34° 44´S, 135° 59´E, 2–7 m, W. Zeidler and K.L. Gowlett-Holmes, 4 Mar 1987 .

Remarks. Exuviae of protonymphon and juveniles are entangled amongst threads on the ovigers of this specimen (plate 8e). Three juveniles remain attached, the largest of which has one developing fourth leg which may be regenerating (plate 8f), otherwise all legs are segmented and equally developed. There is little to add to the original description of this species and to subsequent observations by Staples (2008) and Brenneis et al. (2020). Examination of this male reveals the presence of microscopic setae on the lateral processes, but trunk mid-dorsal setae are not evident. The dorsal inflation of the trunk segments may be marginally lower than in the holotype. Coxa 1 is fringed with short, sharp spinules. The legs are finely papillose. There are four, five or six primary spines on the propodal heel. Four eye lenses are present. The tiny oviger claw is difficult to orientate and its shape is not clear, but it appears to be of a similar shape to that of the male previously collected from the Investigator Group ( Staples 2008). The total oviger spine count of this Port Plate 8. Pallenella inflata , female holotype (SAM E3417): a, b, trunk dorsal and anterior view; c, right chela; d, leg 4. Male, ovigerous (SAMA E9439): e, lateral view: f, juvenile, anterior view.

Lincoln specimen and the holotype from Althorpe Island are much the same (41 spines compared to 39 spines in the P. inflata holotype). The subadult specimen identified as P. inflata by Brenneis et al. (2020) (DNA voucher specimen TAS35) formed part of the same phylogenetic analysis as P. cf. chevron (DNA voucher EN18), and P. cf. ambigua (DNA voucher EN10 and 11). These three voucher specimens were collected from Eaglehawk Neck. It is most unfortunate that the authors included subadult material in their morphological analysis. The subadult P. inflata (TAS35) voucherspecimenappearstohavegreatermorphological similarity to the subadult P. karenae holotype than it does to the adult P. inflata holotype. The P. karenae holotype is larger than the adult P. inflata holotype (leg length 11.72mm versus 8.5mm) but of similar size to the subadult P. inflata DNA voucher specimen from Eaglehawk Neck (leg length 11.57 mm). The authors attributed the size differences to a variance between populations and lead them to conclude that size alone is unsuitable for segregation of the two species, but whether such a conclusion can be reached in the absence of molecular support for the relationship between the adult P. inflata holotype and the subadult P cf. inflata is problematic. The similar leg spans of the subadult P. karenae and subadult P. inflata voucher specimen suggests a similar growth stage. The description of a “more pointed” oviger claw in the voucher specimen fits more closely with the “slender and tapering” description of P. karenae than it does with the rounded (scoop-shaped) claw of the P. inflata holotype from Althorpe Island South Australia. Staples (2008) described the male oviger claw of P.inflata from the Investigator Group South Australia as a “little more pointed” than that of the female holotype, but the figure of the oviger claw of the Fortesque Bay specimen ( Brenneis et al. 2020, Fig. 9G) shows an oviger claw that is clearly acute. The total oviger spine count of the P. karenae holotype and the P. inflata DNA voucher specimen is the same (30 spines) compared to 39 spines in the female P. inflata holotype and 43 spines in the male. In both P. karenae and the P. inflata DNA voucher specimen, the immoveable finger is marginally longer than the moveable finger, compared to marginally shorter in the P. inflata holotype. The authors did not comment on the wedge-shaped incision in the cutting edge of the moveable finger of the P.inflata voucher specimen ( Brenneis et al. 2020, Fig. 9C), or state whether both chelae were the same, but in any event, the incision on the moveable finger is not evident in either the P. inflata or P. karenae holotypes. The authors cited a “comparatively high number of teeth” along both margins of the oviger claw in the P. inflata voucher specimen ( Brenneis et al., 2020, Fig. 9G, in caption) to further distinguish that specimen from P. karenae but in the same paper, they noted that the number of teeth along the oviger claw margins of another species, P. baroni , was a variable character ( Brenneis et al. 2020). This suggests the same variability could extend to other species also and may not be a reliable diagnostic character. The relationship between the South Australian P. inflata holotype and the Tasmanian material needs greater scrutiny. Using the key provided by Brenneis et al. (2020), P. karenae and P. inflata can be followed down to couplet 9 where they are distinguished by rather nebulous characters. Unfortunately, the extent of dorsal inflation of the trunk described in the key as “moderate or strong” is subjective, and the citing of minute mid-dorsal setae on the trunk as a diagnostic character of P. karenae is questionable, particularly when those setae seem to be best diagnosed by scanning electron microscope ( Brenneis et al., 2020, Fig. 8). Whilst the presence of setae of this size is an interesting observation, they could easily have been overlooked in the original description of P. inflata . Significantly, the description of P. karenae is based on a solitary subadult female, and in a genus where ontogenetic changes are well documented, the inclusion of a subadult specimen in a key to “adult” Pallenella species is problematic. It is unfortunate that the authors did not discuss morphological differences that separated P. karenae from its congeners rather than rely on colour differences and comparison with an undescribed specimen preliminarily placed in the “ variabilis” complex (Brenneis et al., 2013). Specifically, P. karenae needs to be clearly distinguished from P. inflata and P. gracilis . Whilst the independence of these Eaglehawk Neck specimens based on morphological grounds is unclear, their independence does appear to be genetically well-supported ( Brenneis et al. 2020: Fig. 3). Images of the P. inflata holotype (SAM E3417) are provided to assist with comparisons (plate 8a–f). The holotype retains a pink hue in alcohol, perhaps a remnant of red markings prior to preservation (plate 8a, b).