Sululana, Bruce & Shimomura, 2019

Bruce, Niel L. & Shimomura, Michitaka, 2019, A new genus and species of deep-water marine cirolanid isopod (Crustacea: Isopoda: Cirolanidae) from the Philippines, Raffles Bulletin of Zoology 67, pp. 1-13 : 2-4

Sululana , new genus

Type species. Sululana buta , new species, by monotypy and original designation.

Diagnosis (female). Head anterior margin weakly concave with minute rostral point. Frontal lamina posteriorly wide (0.8 as wide clypeus), anteriorly narrowly rounded; clypeus ventrally flat, without acute process. Pleonites all free, all visible in dorsal view, pleonite 5 with free lateral margins; pleonite 5 slightly wider than pleotelson anterior margin. Mandible incisor without cusps. Maxilla reduced, composed of one simple lateral lobe, small mesial lobe. Maxilliped endite distally narrowed, without coupling hooks. Pereopods 1–7 ambulatory; propodus and dactylus haptorial, dactylus elongate, longer than propodus; propodus without prominent RS opposing base of dactylus. Pereopods 1–3 with ischium and merus superior distal margins not produced, sparsely setose; pereopods 1–3 merus inferior margin without molariform RS; pereopods 5–7 basis without long PMS, ischium and merus distally without long setae; articles not flattened or otherwise expanded; propodus of pereopods 1–7 without RS opposing base of dactylus. Pleopod 1 exopod operculate, endopod reduced, less than 25% width and length of exopod. Uropodal peduncle with weak mesiodistal lobe; rami lammelar, exopod half as long as endopod, without marginal RS.

Description. Head approximately 71% as wide as pereonite 1. Body surfaces unornamented; pereonite 1 about 1.3 times as long as pereonite 2 in dorsal view. Pleon unornamented, about 10% BL, with 5 visible unfused segments, all with free lateral margins, all laterally acute. Pleotelson without longitudinal carinae, ridges or without tubercles; posterior margin without PMS and RS.

Antennula peduncle articles 1 and 2 not fused; peduncular articles 2 and 3 colinear with article 1; articles 1 and 2 combined lengths less than length of article 3; articles 2 and 3 collinear, flagellum 1.2× longer than peduncle; without callynophore. Antenna peduncle comprised of 5 articles, peduncular articles 1–3 shortest, articles 4 and 5 longest, 5 longer than 4; flagellum 0.6 as long as peduncle.

Frontal lamina short, posteriorly wide, ventrally flat, anterior produced to narrowly rounded point extending between antennal peduncle article 3, posteriorly abutting clypeus. Clypeus ventral surface not projecting relative to frontal lamina. Mandible incisors wide; spine row with 9 RS; mandible palp article 3 short, less than half as long as article 2. Maxillula mesial lobe with 3 weakly circumplumose RS and 1 short simple RS. Maxilliped palp article 4 mesial margin weakly lobed; lateral margins of articles 2–5 with long setae; articles 3 and 4 distal margin width greater than proximal margin of article 4 and 5 respectively.

Pereopods 1–7, secondary unguis absent. Pereopod 7 basis not noticeably broader in distal half compared to proximal half; margins with few discontinuous setae; ischium and merus not flattened, distal margin weakly expanded, inferior margins with few setae.

Pleopod 1 endopod about 0.1 as wide and 0.3 as long as exopod, 2.4 times as long as wide. Pleopods 2–5 with 4 or 5 PMS present on all exopods, 2 PMS on all endopods; endopods all less than half size of exopod; endopod of pleopod 5 without proximomesial lobe. Uropod rami with simple margins.

Male. Only one female specimen (described herein) has been collected.

Remarks. The Cymothoidea includes two superfamilies, the Cirolanoidea Dana, 1852 and the Cymothooidae Leach, 1814 and contains families that range across a spectrum from free-living carnivorous scavengers and predators to fully obligate parasites ( Brandt & Poore, 2003: table 3; Poore & Bruce, 2012; Smit at al., 2014). These families (the Anthuroidea Leach, 1814, Gnathiidae Leach, 1814 , and crustacean parasitic families are not here considered) are characterised by the mandible having a blade-like mobile molar process (reduced in parasitic and micro-predators families such as the Aegidae White, 1850 , Corallanidae Hansen, 1890 , Cymothoidae Leach, 1818 , and Tridentellidae Bruce, 1984 ), usually with five free pleonites (often reduced through differing fusions in cave dwelling cirolanids) and the biramous and lamellar (i.e., flat) uropods attached ventrally in an antero-lateral position and articulating laterally (see Brandt & Poore, 2003).

Cirolanids have long been characterised by and identified by the tridentate cultrate (cutting) mandibular incisor. The Cirolanidae in addition to the mentioned characters have a maxillula with the mesial lobe provided with three or four stout robust setae and the outer lobe with 11 to 13 serrated and simple large and curved robust setae. The present genus lacks an evident tridentate mandible incisor, but the mandible has the palp, molar and spine row that are all typical of the family. In addition, the mouthpart details clearly separate this genus from all other Cymothooidae by the broad mandibular incisor (narrow in all the other families). The Corallanidae , Tridentellidae , Aegidae , and Cymothoidae either have all pereopods prehensile ( Cymothoidae ), anterior pereopods prehensile ( Aegidae ), and the maxilliped with reduced articles and abrading spines ( Aegidae , Cymothoidae ). The Corallanidae , which are most similar to the Cirolanidae in general body morphology, have the maxillula and maxilla reduced to minute simple lobes, while the Tridentellidae have, among other characters, a maxilliped endite that is broad, flat and elongate.

Sululana , new genus has five unfused pleonites, each with free lateral margins, which places it in the group of genera that includes Eurydice Leach, 1815 , Excirolana Richardson, 1912 , Metacirolana Kussakin, 1979 (see Bruce, 1986; Brusca et al., 1995), Aphantolana Moore & Brusca, 2003 , and Pontogelos Stebbing, 1910 (see Bruce, 1995). These genera are further characterised by pleonite 5 not laterally overlapped or enclosed by pleonite 4 or pleonites 3 and 4, the clypeus with a varyingly developed ventrally or anteroventrally directed blade, and frontal lamina that is posteriorly narrow. These genera also show, where known, sexual dimorphism, with sexually mature males having longer antennula and antennal flagellum, larger eyes and a longer pleon than in the females. In all of these genera there are species both with and without eyes, and lack of eyes is not considered per se to be of generic merit. Typically, species in this group of genera have the appendix masculina attached in a basal or sub-basal position, and the pleopod rami are all approximately subequal in size.

The purported apomorphies that define Sululana , new genus are: the unicuspid mandible incisor; maxilla with two simple lobes with endopod less than half size of exopod; all pereopods haptorial (i.e., dactylus longer than propodus); pereopod dactylus lacking secondary unguis; pleopod 1 exopod opercular and indurate; and all endopods less than half the size of the exopod.

Relationships. Sululana , new genus has an operculate and indurate (thickened) pleopod 1, a character that occurs rarely in the Cirolanidae . Operculate pleopod 1 occurs in Conilera Leach, 1818 , Conilorpheus Stebbing, 1905 , Oncilorpheus Paul & Menzies, 1971 , and the unrelated genus Calyptolana Bruce, 1985 (see Bruce, 1985, fig. 1). In all these genera except Calyptolana pleopod 1 is also thickened. In Oncilorpheus the exopod forms the operculum while in the other genera both the endopod and exopod are together operculate; in Sululana it is the operculate exopod along with the greatly reduced endopod on all pleopods that is unique within the Cirolanidae . The morphology of the pleon and all appendages of Sululana in comparison with these genera are so different that no phylogenetic relationship can be seen.

The pereopods of Sululana can be considered as both ambulatory and haptorial, pereopods 5–7 with slender articles that lack abundant setae and are not flattened (as in so-called natatory pereopods of genera such as Natatolana Bruce, 1981 and Eurydice Leach, 1815 ), and dactyli that are longer than the respective propodus. Such pereopods are seen in genera related to Cirolana Leach, 1818 as well as Metacirolana and Aphantolana . There are few characters shared with Cirolana , though the articles of the antennal peduncle have similar proportions of articles 1–3 short, 4 and 5 long, a character also shared with Metacirolana . The antennula differs from Cirolana and related genera in having all three peduncular articles about equal in length, with article 3 shorter than article 2, a character shared with Metacirolana and Aphantolana . The maxilliped is also more similar in form to that of Metacirolana rather than Cirolana or Natatolana Bruce, 1981 and their related genera. Both Sululana and Metacirolana have maxilliped palp articles 3 and 4 with weak mesial lobes (vs well-developed in most other genera) and a short quadrate article 5 (vs. distally rounded, c. 3× as long as wide). However, the clypeus and frontal lamina are not of the form shown either by Metacirolana nor by Eurydice .

We conclude that Sululana shows some affinities to Metacirolana and related genera in the pleon, antennula, mouthpart and general pereopod morphology, with no evident potentially derived shared characters with any other group of genera.

Etymology. Named after the Sulu Sea in the Philippines. Gender is feminine.