Pallenopsis patagonica (Hoek, 1881)

Lucena, Ruda Amorim & Lindsey Christoffersen, Martin, 2022, Pycnogonida (Arthropoda) from Museu de Ciencias Naturais, Rio Grande do Sul, Brazil, Zoosystematics and Evolution 98 (2), pp. 305-312 : 305

Pallenopsis patagonica (Hoek, 1881)

Fig. 5

Phoxichilidium patagonicum Hoek, 1881: 84-86, pl. XII, figs 6-9.

Pallenopsis glabra Möbius, 1902: 184-185, taf. XXVII, fig. 1-6.

Pallenopsis hiemalis Hodgson, 1907: 17-20, pl. I, fig. 4, pl. II, fig. 3.

Pallenopsis meridionalis Hodgson, 1914: 158-165.

Pallenopsis moebiusi Pushkin, 1975: 80-83, fig. 4 a-m.

Material examined.

(FZB.Pyc-008) 1 female, St. 4512, 37°38'S, 56°56'W, Argentina, 25 Aug 1977 .

Distribution.

Antarctic (Ross Sea, Weddell Sea) to southern Argentina (up to approximately 37°15'S), southeast Pacific (Strait of Magellan up to 33°S) ( Weis et al. 2014; Scarabino et al. 2019).

Depth.

15-720 m ( Child 1995b).

Remarks.

Literature records large morphological variations for this species ( Hoek 1881; Hodgson 1907; Loman 1923; Gordon 1944; Child 1995b; Weis et al. 2014). These variations encompass mainly the proportion of the articles of the legs, the shape of the trunk, the structure of the propodus, the size and inclination of the abdomen and the size of the cement gland ( Stock 1957; Pushkin 1993; Child 1995b; Cano-Sanchez and López-González 2019; Scarabino et al. 2019).

Recent studies, based mainly on molecular data, have indicated the existence of cryptic species under the name P. patagonica , mainly from the Antarctic Region ( Weis et al. 2014; Harder et al. 2015; Dömel et al. 2017, 2019). These species form the P. patagonica sensu lato complex. Although no consensus exists concerning the number of possible new species (up to 19 clades have been proposed) and no morphological characterisation has been provided for the identified clades, specimens collected in the Falkland Islands and the Patagonian Region appear to belong to P. patagonica sensu stricto ( Weis et al. 2014; Harder et al. 2015; Dömel et al. 2017, 2019), the type locality of the species.

The specimen analysed herein comes from northern Argentina, close to the northern range of the species ( Child 1995b). This female individual has all the characters described by Hoek (1881), such as the indicated number of articles and the proportion established amongst the last articles of the ovigers, the same proportion amongst the articles of the legs and a similar body structure, with lateral processes separated by about less than half their own diameter and a cylindrical proboscis. In relation to subsequent descriptions, the present specimen is similar to P. meridionalis (today a synonym of P. patagonica ), particularly in the shape of the ocular tubercle, structure of the propodus and ornamentation of the lateral processes ( Pushkin 1993). However, the closest proximity is with P. yepayekae Weis et al. 2014, from which it may be distinguished by the number of articles on the oviger and in the number of setae on the abdomen (2 in the description, 4 in the individual at hand), including a cylindrical proboscis. However, we observed an undescribed character for P. patagoica , but reported for P. yepayekae and indicated as distinguishing the two species: the presence of brush-like setae in the ventral region of coxae 2 and 3. Hoek (1881) described the presence of setae in coxae 2 and 3, but did not illustrate them. In the cited material, such setae appear to be smaller and in lower number in the material analysed herein than in P. yepayekae .

Great morphological variation has been reported for several species from polar, temperate and tropical regions, where the genus is quite diverse ( Stock 1974). Our data are insufficient for advancing previous taxonomic conclusions. It becomes necessary to conduct more in-depth morphological analysis and to extend the investigation to include samples from wider geographical locations. Species-group and genus-level revisions are necessary to distinguish diagnostic species characters from intrapopulational variations ( Hennig 1950, 1968).

Figures

Figure 5. Pallenopsis patagonica (FZB. Pyc- 008), female. A. Dorsal view; B. Lateral view; C. Oviger; D. Propodus.