PUDEONISCIDAE Lemos de Castro, 1973

Campos-Filho, Ivanklin Soares, Teixeira Lisboa, Jonathas & Monticelli Cardoso, Giovanna, 2018, A new genus and two new species of Pudeoniscidae Lemos de Castro 1973 (Crustacea: Isopoda: Oniscidea) from Brazil, Journal of Natural History (J. Nat. Hist.) 52 (7 - 8), pp. 457-482 : 458-460

Family PUDEONISCIDAE Lemos de Castro, 1973

Diagnosis

Exoantennal conglobation; cephalon with well developed lateral lobes, triangular frontal shield, profrons strongly grooved to fit antennae, frontal line present delimiting the upper margin of frontal shield, supra-antennal line absent; dorsal cuticle with verrucalike scales or smooth; dorsolateral furrow scaled or with verruca-like scales; epimera of pereonites 1 – 7 slightly curved backwards; epimera of pereonite 1 with dorsolateral furrow to fit antennae during conglobation, sometimes reduced, absent in troglobionts; epimera of pereonites 1 – 3 with small ventral lobes or schisma on pereonite 1; one line of noduli laterales per side inserted almost at the same distance from lateral margin and gradually closer to posterior margin of pereonites 1 – 7; pleon outline continuous to that of pereonite 7; neopleurae 3 – 5 well developed and rectangular; telson triangular or trapezoidal with dorsal ovoid depression, proximal portion wider than distal portion and lateral sides concave; antennule of three articles; antenna covering eyes during conglobation, flagellum of three articles, second and third divided by suture; uropod protopod sub-quadrangular, exopod inserted on outer distal groove, endopod inserted proximally, not surpassing the distal margin of telson; pleopod exopods with respiratory structures of uncovered Atracheodillo - type or polyspiracular covered Eubelum - type, absent in troglobionts.

Remarks

Vandel (1963) erected the genus Pudeoniscus to allocate the new species P. birabeni from Pico da Tijuca, Rio de Janeiro state, Brazil. The author misinterpreted the dorsolateral furrow on epimera of pereonite 1 as a sulcus arcuatus, typical of Eubelidae , and incorrectly included the genus within this family (see the Eubelidae section in Schmidt 2003). In Pudeoniscus , the dorsolateral furrow differs in shape, position and function from the sulcus arcuatus of Eubelidae . Whereas the dorsolateral furrow of Pudeoniscus is used to fit the antennae during conglobation, the sulcus arcuatus of Eubelidae probably participates in the water-conducting system ( Ferrara and Paoli 2003).

Lemos de Castro (1973) created the family Pudeoniscidae to allocate P. birabeni and the new species P. obscurus ; the author also created the genus Brasiloniscus to allocate two new species, B. maculatus and B. verrucosus . The definition of Pudeoniscidae proposed by the author comprised the following characteristics: exoantennal conglobation; cephalon with triangular and well-developed frontal shield, frontal line present and with two frontal-lateral grooves to fit the antennae, lateral lobes well developed and eyes inserted in the frontal-lateral grooves, which are covered by antennae during conglobation; epimera of pereonite 1 with deep lateral furrows that accommodate the antennae during conglobation, and a lateral schisma, which is sometimes reduced to a small ventral lobe; epimera of the pereonites 2 and 3 with ventral lobe; pleon, telson, and uropods without any adaptation to conglobation; these last characteristics were also mentioned by Vandel (1963).

The ability to conglobate is considered as an eco-morphological strategy used by oniscideans to protect them from predators ( Schmalfuss 1984), and it is also useful to reduce water loss ( Edney 1951). Species with conglobation ability occur in Oniscidea families (e.g. Tylidae , Armadillidae , Armadillidiidae , Cylisticidae , Hekelidae and Scleropactidae ), indicating a convergent or parallel evolution of this feature ( Schmidt 2002). The triangular frontal shield is also present in the genus Exzaes Barnard, 1932 (see Ferrara 1977) – currently, the genus is considered as incertae sedis, and in the Armadillidiidae , but it differs in shape from that of Pudeoniscidae . The frontal shield of Exzaes is rhomboid, directed upwards and bent backwards over the vertex of the cephalon. In the Armadillidiidae the frontal shield is wider and the lateral sides are less concave; also it differs in the shape of telson and uropods, and in the respiratory structures on pleopod exopods (see the Armadillidiidae section in Schmidt 2003; and Eluma caelata ( Miers, 1877) in Taiti and Rossano 2015). Concerning the lack of conglobating mechanisms in the pleon, telson and uropods, the material examined here shows typical characteristics of conglobating animals such as: dorsally convex shape of pleon and telson; neopleurae well developed with rectangular or sub-rectangular shape, with outline continuous to that of pereonite 7; and uropods dorsoventrally flattened (see also Schmidt 2003). These characteristics are also present in Cylisticidae (e.g. Lepinisticus Ferrara and Taiti, 1983 ; Troglocylisticus, 1983 ). In comparison with Pudeoniscidae , the Cylisticidae has a narrower distal portion of the telson, with acute apex not covering the uropod endopods (see Ferrara and Taiti 1983; and Cylisticidae section on Schmidt 2003).

The phylogenetic position of Pudeoniscidae remains uncertain. Wägele (1989) allocated the family within an unresolved clade along with the families Hekelidae , Irmaosidae , Tendosphaeridae , Spelaeoniscidae and Stenoniscidae . The clade was defined by two synapomorphic characters: reduced body size and reduced respiratory areas, and cephalon with dorsolateral furrows that fit the antennae. Schmidt (2002) allocated Pudeoniscidae within an unresolved clade with several families of Oniscidea, without any synapomorphic characters. However, it was mentioned that the Oniscus - type respiratory areas or the Y- or T-shaped dorsal scale-setae could be regarded as such. As mentioned by Schmidt (2003), the dorsolateral furrows of cephalon are laterally disposed and connected with the antennary sockets in Pudeoniscidae , whereas in the above-mentioned families they are located in the dorsal vertex of cephalon (for a more comprehensive view see Pudeoniscidae section in Schmidt 2003; Hekelus episimus Barnard, 1932 , in Ferrara 1977; and Irmaos sechellanum Ferrara and Taiti, 1983 , in Ferrara and Taiti 1983). Species with reduced size occur broadly within Oniscidea, e.g. Styloniscus Dana, 1852 (Styloniscidae) , Androdeloscia Leistikow, 1999 (Philosciidae) , Stenoniscus Aubert and Dollfus, 1890 (Stenoniscidae) , Littorophiloscia Hatch, 1947 (Halophilosciidae) and Pseudodiploexochus Lewis, 1998 (Armadillidae) . This characteristic is observed in P. birabeni and it is probably related to the eco-morphological strategy adopted to respond to habitat/predator pressure. The respiratory areas of Oniscus asellus Linné, 1758 were defined as an uncovered lung and classified as Atracheodillo - type by Paoli et al. (2002); and considered as functional respiratory organs by Leistikow and Araujo (2001). The Atracheodillo - type respiratory areas can also be found in other Oniscidea families, e.g. Balloniscidae (see Araujo and Leistikow 1999), Dubioniscidae ( Cardoso et al. 2016) , Eubelidae (see Paoli et al. 2002), Philosciidae ( Campos-Filho et al. 2015a) and Trachelipodidae (see Schmidt 2003). The presence of scale-setae on the cuticular surface can be related to the eco-morphological categories of isopods; a good example is the fan-shaped dorsal scale-setae usually present in species classified as creepers ( Schmalfuss 1984) such as Caraiboscia Vandel, 1968 and Metaprosekia Leistikow, 2000 (Philosciidae) (see Leistikow 2001; Campos-Filho et al. 2014); Dubioniscus Vandel, 1963 and Novamundoniscus Schultz, 1995 (Dubioniscidae) (see Campos-Filho et al. 2014; Cardoso et al. 2016); Trichorhina Budde-Lund, 1908 , and Niambia Budde-Lund, 1904 (Platyarthridae) (see Schmidt 2003; Campos-Filho et al. 2016). Lemos de Castro (1973) and Schmidt (2003) did not describe the scale-setae of the genera within the family, even though, as observed here, Pudeoniscidae exhibit two different types of scale-setae, the fan-shaped as in P. obscuros , and the triangular-shaped as in P. birabeni . As mentioned, these structures probably differ because of the habitats of these animals, since P. obscurus was usually collected in the soil or under stones, whereas P. birabeni was found among leaf-litter (Campos-Filho and Cardoso personal observation).

Although the exoantennal conglobation of Pudeoniscidae is similar to that of Cylistidae, Hekelidae , Irmaosidae , Scleropactidae and Tendosphaeridae , Pudeoniscidae differs from these families in the following structures: epimera of pereonite 1 with dorsolateral furrow, sometimes reduced (absent in all mentioned families); furrow in the dorsal vertex of cephalon absent (present in Cylistidae, Hekelidae , Irmaosidae and Tendosphaeridae ); frontal shield triangular with antennary sockets laterally directed (triangular frontal shield and less pronounced in Cylistidae, triangular and directed backwards in Hekelidae , quadrangular and directed backwards in Irmaosidae and Tendosphaeridae , and rectangular frontal shield in Scleropactidae ); telson triangular or trapezoidal with concave sides and distal portion covering the uropod endopods (telson triangular with distal portion not elongated in Cylistidae, Hekelidae and Irmaosidae , short, rounded and not covering the uropod endopods in Scleropactidae ; and sub-quadrangular in Tendosphaeridae ); telson with dorsal ovoid depression (absent in all mentioned families); antennal flagellum with slender suture on the distal article (absent in all mentioned families); apical organ short (long in Hekelidae , Irmaosidae and Scleropactidae ); uropod protopod sub-quadrangular with outer portion slightly developed surpassing exopod insertion, exopod inserted in an outer lateral groove (protopod longer than wide, exopod inserted distally in Cylistidae; protopod with outer margin strongly developed, exopod sub-distally inserted in the median portion in Hekelidae ; protopod rectangular with outer portion not well developed, exopod short and sub-distally inserted near median portion in Irmaosidae ); and pleopod exopods with uncovered Atracheodillo - type or covered polyspiracular of Eubelum - type lungs, see scanning electron micrographs in Figures 10 – 13 ( Trachelipus - type in Cylistidae, see Schmidt 2003; absent in Hekelidae , Irmaosidae , Scleropactidae and Tendosphaeridae ).

Figures

Figure 10. Oxossioniscus akoko sp. nov., ♂ paratype MZUF 9660: (a) Habitus, lateral view; (b) Scaleseta; (c) Cephalon, antennae and pereonites 1 and 2, frontal view; (d) Cephalon, antenna and pereonite 1, dorsal view; (e) Pereonites 1–3, ventral view; (f) Pleonites 4 and 5, telson and uropods, dorsal view; (g) Pleonites 4 and 5, telson and uropods, ventral view; (h) Antennula; (i) Antenna.

Figure 11. Oxossioniscus akoko sp. nov., ♂ paratype MZUF 9660: (a) Left mandible; (b) Right mandible; (c) Maxillula; (d) Maxilla; (e) Maxilliped.

Figure 12. Oxossioniscus akoko sp. nov., ♂ paratype MZUF 9660: (a) Uropod; (b) Pereopod 1; (c) pereopod 7; (d) Genital papilla; (e) Pleopod 1; (f) Pleopod 2; (g) Pleopod 3 exopod; (h) Pleopod 4 exopod; (i) Pleopod 5 exopod.

Figure 13. Oxossioniscus akoko sp. nov. ♂ paratype UFRGS 5680. (a) Cephalon, frontal view; (b) Pereonite 1 epimeron, arrows showing the nodulus lateralis, verruca-like scales, and triangular scaleseta; (c) Antennal flagellum; (d) Pleopod 1 exopod; (e) Pleopod 4 exopod. Scale bars: (a, b) 200 µm; (c–e) 100 µm; (b) (enlarged boxes) 100 µm (upper) and 20 µm; (d, e) (enlarged boxes) 10 µm.