Acuticoxa, Huys, Rony & Kihara, Terue Cristina, 2010

Huys, Rony & Kihara, Terue Cristina, 2010, Systematics and phylogeny of Cristacoxidae (Copepoda, Harpacticoida): a review, Zootaxa 2568, pp. 1-38 : 32-34

Relationships between Laophontisochra George, 2002 and Acuticoxa gen. nov.

George (2002) proposed the genus Laophontisochra for two deepwater species from the Magellan region which shared a cylindrical, slightly dorsoventrally depressed body shape, a large maxilliped, a spinous outgrowth on the coxa of leg 1, a prehensile P1 endopod, reduced P2–P4 and long caudal rami. Despite these similarities, the type species L. maryamae and the unnamed Laophontisochra sp. also display many important differences. George (2002) suggested that the discrepancies in body ornamentation, caudal seta V, antennule, antenna and P1–P5 were indicative of the presence of two distinct species. The discovery of our new species from the northern continental shelf off São Paulo State suggests, however, that the observed morphological variation between both Laophontisochra species is such that two distantly related lineages can be recognized. Laophontisochra sp. shows a close relationship with Acuticoxa ubatubaensis sp. nov. based on the following synapomorphies: (1) the presence of dense setular surface ornamentation on the body somites; (2) distal margin of antennary endopod with three geniculate and three non-geniculate setae; (3) P2–P4 with outer spinous projection on coxa; (4) P4 exopod 1-segmented; and (5) P5 exopod and baseoendopod fused in Ƥ, forming a single plate with 8 setae/spines. The plesiomorphic states of these characters are expressed in L. maryamae : body somites virtually smooth (except for spinular tufts on pleural areas of pedigerous somites), antennary endopod with four geniculate and two non-geniculate setae around apex, P2–P4 without coxal processes, P4 exopod 2-segmented, and P5 biramous in Ƥ. Autapomorphies for L. maryamae include (1) the dense setular ornamentation on the first antennulary segment; (2) loss of the abexopodal seta on the antennary allobasis; (3) loss of P2–P3 endopods; (4) the reduced armature on Ƥ P5, comprising 1 endopodal and 4 exopodal setae (the precise homology of these elements with respect to the 7 non-basal elements expressed in Laophontisochra sp. and A. ubatubaensis are difficult to assess but it is conceivable that 2 endopodal elements were lost in L. maryamae ); and (5) P6 Ƥ set on raised protuberance.

Given its close resemblance to A. ubatubaensis , Laophontisochra sp. (also based on a single female specimen) is here formally assigned to the genus Acuticoxa . The characters compiled in Table 2 show that both females cannot be conspecific and hence the specimen figured by George (2002: Figs 5–7 ) is here designated as the holotype of a new species, A. biarticulata sp. nov. (the specific name refers to the 2- segmented condition of the exopods of P2–P3), which can be differentiated from the type species by the diagnostic characters given in Table 2 . The holotype (dissected on 8 slides) was deposited in the collections of the AG Zoosystematik und Morphologie of the Carl von Ossietzky-Universität in Oldenburg ( Germany) (reg. nos UNIOL-1999.016/1–8). Acuticoxa biarticulata is known only from its type locality (53°59.7’S, 70°33.0’W) at 79 m depth in the Northern Magellan Straits.

As a result of the removal of Laophontisochra sp. to Acuticoxa an updated generic diagnosis of Laophontisochra is presented below:

Diagnosis (amended). Nannopodidae . Body cylindrical; slightly depressed dorsoventrally; somites with finely incised hyaline frills but no setular ornamentation dorsally; pleural areas of pedigerous somites with spinular tufts; original segmentation of genital double-somite Ƥ marked by lateral constrictions and transverse ribs. Rostrum prominent, bell-shaped. Anal operculum unknown. Caudal ramus long and rectangular; with 7 setae; seta V longest, spiniform, not composite.

Antennule without spinous processes; 4-segmented in female; segment I elongate, segments III–IV with aesthetasc and posteriorly directed. Antenna without abexopodal seta on allobasis; exopod represented by seta; endopod with 6 distal setae (4 geniculate and 2 simple) and 2 lateral spines. Mandible biramous with incorporated unisetose exopod and 1-segmented trisetose endopod; basis with 2 setae. Maxillule with 2 elements on coxal endite; basal endites represented by 3 and 2 setae, respectively; endopod incorporated into basis and represented by 2 setae; exopod absent. Maxillary syncoxa with 2 endites, each bearing 2 elements; allobasis with claw and 1 accompanying seta; endopod represented by 2 setae. Maxillipedal syncoxa and basis unarmed; endopod 1-segmented with long geniculate claw and 1 accompanying seta.

P1 with conical, distally pinnate protuberance on outer margin of coxa; basis with inner (arising from anterior surface) and outer seta; exopod 2-segmented, exp-1 with outer seta, exp-2 with 5 setae; endopod prehensile, enp-1 without inner seta, enp-2 with 1 claw and 1 long seta. P2–P3 (and almost certainly also P4) without spinous projections or protuberances on coxa; P2–P4 exopods 2-segmented; P2–P3 endopods absent, P4 endopod 1-segmented with single apical element. Spine and setal formula as follows:

P5 exopod and baseoendopod distinct in Ƥ; exopod small, with 4 elements; baseoendopod with weakly developed endopodal lobe bearing 1 spine. Genital field Ƥ with P6 represented by paired raised protuberances bearing 2 short setae; copulatory pore unconfirmed.

Type and only species: Laophontisochra maryamae George, 2002 (by original designation)

Figures

FIGURE 5. Noodtorthopsyllus tageae sp. nov. (Ƥ): (A) maxilliped; (B) P 1, anterior; (C) P 2, anterior. Scale bars: 12.5 μm.

FIGURE 6. Noodtorthopsyllus tageae sp. nov. (Ƥ): (A) P 3, anterior; (B) P 4, anterior; (C) P 4 endopod with aberrant armature pattern; (D) P 5, anterior. Scale bars: 12.5 μm.

FIGURE 7. Noodtorthopsyllus tageae sp. nov. (3): (A) habitus, dorsal; (B) urosome, ventral. Scale bars: 50 μm.

Tables

TABLE 2. Morphological differences between females of Acuticoxa species (P 5 setal numbering starting from outer basal seta = seta 1).

Antennule segment I	A. ubatubaensis sp. nov. without ornamentation	A. biarticulata sp. nov. with dense setules
Antennule segment II setae Antennary exopod	7 naked + 1 pinnate absent	9 naked minute unisetose segment
Maxillipedal seta accompanying endopodal claw	present	absent
P1 exp-1 outer seta P1 exp-2 setae	present with long pinnules	absent naked
P3–P4 outer coxal projections	short and broad, not reaching beyond basal setophore	long and narrow, reaching well beyond basal setophor
P2–P3 exopods P3–P4 distal outer element exp	1-segmented setiform, naked	2-segmented spiniform, bipinnate
P5 seta 4	subequal to seta 3	twice as long as seta 3
P5 element 5	spiniform	setiform