Ogleus Morales-Núñez & Heard, 2013, new genus

Ogleus, new genus

Synonymy. “undescribed genus” Morales-Núñez et al. (2013)

Diagnosis. Leptocheliid. Male: Antennule peduncle with three relatively narrow, sub-parallel articles; article-3 not “scale” or “saddle-shaped”; flagellum with six articles having five aesthetasc- bearing articles and minute terminal article with simple setae; flagellum article-1, distinctly smaller than other four aesthetasc-bearing flagella articles, “ring-like” and no longer that wide, bearing single aesthetasc cluster. Chela robust, forcipate (propodus having wide gap between proximal origin of fixed finger and distal insertion of dactylus); fixed finger of propodus directed downward, nearly at right angle to posterior (ventral) propodal margin; dactylus reaching to or beyond tip of fixed finger; carpus with broad lateral face, breadth greatest distally, over two thirds length; inserted into middorsal margin of merus; merus expanding distally, to proximal propodus. Mouth parts reduced, non-functional mass. Maxilliped vestigial. Female: Antennule with three articles and minute fourth article (vestige of flagellum). Antenna with article-2 having thorn-seta on dorso- and ventrodistal margins; article-3 with forwardly directed spinose process dorsally. Mandible molar process with ridged, grinding surface. Maxilliped with basis having three or four pairs of long, simple seta distally; endite with strongly developed simple seta (reaching to distal region of palp article-2), two tooth-like, modified setae, bidentate, denticle-like seta, and two minute coupling hooks on inner margin. Uropods in both sexes long and narrow; endopod with five articles or incipient articles, terminal article distinctly longer than article-1; exopod small, unarticulated.

Type species. Ogleus pilarae n. sp.

Etymology. Named for John Ogle in recognition of his pioneering work on the tanaidacean fauna of the Gulf of Mexico and his many contributions to marine aquaculture.

Remarks. The new monotypic genus Ogleus apparently can be distinguished from all other leptocheliids by the first flagellar article in the male being very short and “ring-like” with single distal cluster aesthetascs. Notwithstanding, it appears to have its closest affinities with Heterotanais Sars 1882, Makassaritanais, and Pseudonototanais. Besides the difference in the shape of flagellar article-1, Ogleus can be distinguished from these three genera by a combination of other characters.

The male cheliped of Ogleus appears most similar to that of Pseudonototanais; however, excluding its distinctive first flagellar article, Ogleus is further be distinguished by having the male antennule being composed of three distinct peduncular articles and the flagellum having five aesthetasc-bearing articles and a minute terminal article with simple setae (see Figs. 8 J and 8I, respectively). The female of the new genus is separated from that of P. werthi and P. modestus by having three or four rather than a single or two pairs, respectively, of simple subdistal setae near the margin of the maxillipedal basis. Further the uropodal endopod of Ogleus has five articles or incipient articles that are of nearly equal diameter, the last of which is distinctly longer than the first.

Ogleus is superficially similar and shares characters with the type species of Heterotanais, H. oerstedii (Krøyer, 1842). It differs from H. oerstedii by the terminal male form having a chela with a styliform fixed finger, which in H. oerstedii is distally expanded (“club shaped”) (see Figs. 9 E and 9A, respectively) and by having an antennule with five aesthetasc-bearing flagellar articles versus only two or possibly three in H. oerstedii (see Figs. 8 I and 8H, respectively) (see Sars 1899; Sieg 1973). Like Ogleus, however, article-1 of the antennular flagellum has only a single distal cluster of aesthetascs. The female of Ogleus differs from that H. oerstedii in several aspects, including differences in the setation of the maxilliped and antenna. There are three or four long simple setae instead of just one on the distal margin of the maxillipedal endite. As in the genus Leptochelia, there is a strongly developed anteriorly directed spiniform process on the distodorsal margin of the antenna article-3; whereas, on H. oerstedii there is a subterminal styliform, anterodorsally, directed seta, one of the characters used by Bird &Larsen (2009) in separating Leptochelia and its allies from the Heterotanais complex.

The males of Makassaritanais differ from that of Ogleus by their distinctly different and more typical chelipeds, including the depth of the carpus face being less than two thirds that of its length and by not having the merus extending posterodistally under the carpus to near the margin of the propodus (see Figs. 9 G −H; and 9E, respectively). Like that of Pseudonototanais, the male cheliped of Ogleus has the carpus expanded and subquadrate (depth being about equal to length) with the merus extending underneath to or very near to the proximal margin of the propodus, and the depth of the carpal face becoming greatest distally (see Figs. 9 D −E). This condition appears to be less derived than that of either Pseudonototanais or Ogleus, and both species of Makassaritanais appear to exhibit characters closer to a probable Leptochelia -like progenitor. Although the female of Ogleus generally fits the diagnosis for Makassaritanais angustus, there are some differences, including the shape of the spines on the maxillular endite: subacute on Ogleus and short and blunt on Makassaritanais as defined here. Whether this latter character is generic or specific awaits the discovery of additional species. The width of the basis on last three pairs of pereopods has also been used as generic character. Although it can be useful, it is qualitative condition and subject to the artefacts of examination such as the effects of coverslip pressure or using or not using mounting media during microscopic examination. Notwithstanding the apparently highly derived condition of the male chelipeds, based on the morphology of the females, the genera Ogleus and Makassaritanais appear to be moreclosely related to Leptochelia than to Pseudonototanais and Heterotanais.