Dalhousia McIntosh, 1885

Salazar-Vallejo, Sergio I., 2020, Revision of Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 (Annelida, Errantia, Hesionidae), Zootaxa 4739 (1), pp. 1-114 : 20-21

Dalhousia McIntosh, 1885 reinstated

Dalhousia McIntosh, 1885: 186 .

Type species: Dalhousia atlantica McIntosh, 1885 , by monotypy.

Diagnosis: Hesioninae with two lateral antennae, and one median antenna on dorsal prostomial surface. Palps biarticulate, palpophores large, massive, palpostyles smaller, blunt. Eyes dark, black, brown or reddish, anterior ones larger than posterior ones, sometimes approaching each other in lateral view. Nuchal organs U-shaped. Peristomial dorsolateral and ventrolateral tubercles low, barely projected. Pharynx with upper jaw double, lower jaw transverse plate. Parapodia sesquiramous along chaetigers 1–3, biramous thereafter. Notochaetae from chaetiger 4, subdistally denticulate, delicate, sometimes abundant, usually very long, reaching neurochaetal tips. Neurochaetae compound falcigers, blades bidentate, guards approaching subdistal tooth.

Etymology. McIntosh (1885: 186, footnote 2) indicated that the genus group name was named ‘after the Earl of Dalhousie, K.T.’ It was Fox Maule-Ramsay, 11 th Earl of Dalhousie (22 Apr. 1801 – 6 Jul. 1874), who under Queen Victoria was the Secretary of State for War (1855–1858) ( Fryde et al. 1941). ‘K.T.’ stands for Knight of the Order of the Thistle, a Scotish order of chivalry.

Gender. Feminine. Indicated by the declination of the nominative, and after the combination with the specific epithet, atlantica , used in its feminine acception to emphasize that the type specimen was found in the Atlantic Ocean.

Remarks. von Marenzeller (1904: 308), Chamberlin (1919: 190), Horst (1921: 80), and Pleijel (1998: 110) regarded Dalhousia as a junior synonym of Leocrates . It is herein regarded as distinct on the bases of the above diagnosis. It can be separated from other genera in the tribe by following the key above.

Roule (1896b: 454) rejected the independent status of Dalhousia McIntosh, 1885 because the morphological characters seemed insufficient, especially regarding the presence of the so-called frontal tubercle. However, McIntosh (1885: 187) included in the diagnosis the lack of median antenna. Further, Roule (1896: 454) regarded Dalhousia as a junior synonym of Fallacia de Quatrefages, 1866 probably because McIntosh (1885: 188) wrongly indicated that the pharynx was unarmed, but Fallacia is a junior synonym of Hesione Savigny in Lamarck, 1818 , as indicated elsewhere ( Salazar-Vallejo 2018). Roule (1906: 51) modified his perspective by clarifying that Dalhousia was proposed because it lacks median antenna, and pharyngeal jaws, and he regarded it as a junior synonym of Tyrrhena Claparède, 1868 based upon a damaged specimen and concluded that ‘Ce genre, avec son unique espèce, doit probablement disparaitre de la nomenclature.’ [This genus, with its only species, should probably disappear from nomenclature].

This conclusion was probably taken too literally, including by McIntosh himself, because he referred to Roule as the author for the species in his subsequent publications ( McIntosh 1901: 227, 1908: 130). However, provided that both names refer to the same biological species, Dalhousia atlantica McIntosh, 1885 has priority over Tyrrhena atlantica Roule 1896 .

On the other hand, there are some differences worth mentioning based on the original descriptions. For example, McIntosh (1885:187) indicated that eyes were reddish-brown, whereas Roule (1906: 54) reported them as purple and, in the same publication, he included a figure to show some features. This difference, however, might depend on the time spent in the ethanol before the study of specimens by these authors. Then, these differences were the high variation of the relative size of eyes ( Roule 1906, Pl. 5, Fig. 37 ), their fusion, pigmentation of nuchal organs, and insertion of the median antenna: between anterior eyes in two cases, central in one (two if figure 36 is included), and between posterior eyes in the other. Regretfully, despite McIntosh (1885: 187) indicated the eyes were placed in a pigmented prostomial area, this pigmentation was apparently not taken into account by Roule (1906) for clarifying the relative size of eyes.

Further, as indicated in the above key to Hesioninae genera, Dalhousia McIntosh, 1885 is very similar to Paradalhousia n. gen. by having palps biarticulate, jaws in the pharynx, their nuchal organs as two U-shaped lobes, and parapodia are sesquiramous anteriorly and biramous posteriorly. They differ in some features of the pharynx armature and in neurochaetal pigmentation. In Dalhousia the upper jaw is double, T-shaped, and the ventral one is a transverse plate, but there are no marginal denticles, and neurochaetae are often brownish, whereas in Paradalhousia upper and lower jaws are single, fang-shaped, with a marginal circle of denticles, and neurochaetae are pale.

Figures

FIGURE 37. Leocrates reishi n. sp. A. Paratype (LACM 10884), anterior region, dorsal view. B. Same, anterior end, dorsal view, MGS. C. Same, chaetiger 12, right parapodium, anterior view, MGS. D. Additional specimen (LACM 10142), anterior region, dorsal view. E. Same, anterior end, dorsal view, MGS. F. Same, chaetiger 11, right parapodium, anterior view. Scale bars: A: 0.8 mm, B, F: 0.4 mm, C: 0.3 mm, D: 1.4 mm, E: 0.5 mm.