Collettea Lang 1973

Collettea Lang, 1973

Diagnosis. See Larsen (2011).

Remarks. The genus currently comprises 23 species including the one described here, and excludes the three provisional species, “ Collettea sp. A, sp. B, and sp. C”, in Błażewicz-Paszkowycz & Larsen (2005). It is easily recognized by the long cylindrical pleotelson, and females that lack pleopods. However, the genus as currently composed is probably not monophyletic, as certain species (e.g. C. minima and C. lilliputa) have different mandibular molar shapes, longer uropods, and different cheliped forms (especially the fixed finger dentition). Previous keys (Larsen 2000; Błażewicz-Paszkowycz & Larsen 2005) have used the “pleon size relative to pereon size” as an important character, but we feel it may be misleading because in the new species described here, the pleon (defined as including the pleotelson) of the holotype is as long as the pereon, but one of the paratypes has a pleon that is shorter than the pereon. Measurement of pereon and pleon lengths is compromised by the problems of specimen curvature and degree of relaxation/contraction. It is safely done only with straight specimens (as in Fig. 1) or combined measurements of the individual segments. Non-variable features such as cephalothorax and pleotelson lengths are better characters in this regard. Care must also be given to the presence of mancae in the material; in the manca-II stage of Collettea, pereonite-6 is hardly bigger than one of the pleonites and is easy to overlook this and believe one is measuring the pleon.

A few other problems that became apparent when examining Collettea species from the BIOICE material (a large-scale benthic investigation of Iceland waters) were the assessments of the fusion line of antenna article-4 and the number of ventral setae on the cheliped fixed finger - these characters are used to distinguish C. cylindrata (G.O. Sars, 1882) and C. wilsoni Larsen, 1999, for instance. Some specimens lack the fusion line, some have them, and some specimens have a ‘hint’ of a line (Bird, pers. obs.). A more useful character might be the length of antenna article-4. The number of ventral setae on the cheliped fixed finger can also be difficult to observe as they may lie along the lower margin of the propodus and in species such as C. cylindrata where there are two setae, the proximal seta is much smaller and easily hidden.

The inner setal comb of the cheliped palm might prove to be a valuable systematic/phylogenetic character, regarding the number, length, and location of the setae; unfortunately, this has not been described or illustrated for several species.

The genus is cosmopolitan, found in all oceans, from the shelf (ca. 50 m; although mainly in high latitudes), down to abyssal depths but is primarily a deep-water taxon.

Type species. Strongylura cylindrata G.O. Sars, 1882. This is recorded throughout the temperate and arctic North Atlantic and Mediterranean Sea (type locality: Norway). There are dubious records in the North Pacific and Corsica (Larsen 2000).

Other species. Collettea alicjae Błażewicz-Paszkowycz & Larsen, 2005, Antarctica (southern Pacific and Weddell Sea); C. antarctica (Vanhöffen, 1914), Antarctica; C. arnaudi (Shiino, 1978), Antarctica (type locality: Heard Island); C. aspera Wi, Suh & Kim, 2015, eastern Central Pacific; C. cylindratoides Larsen, 2000, Southeast Australia (type locality) and Antarctica; C. elongata Larsen, 2002, Gulf of Mexico; C. eminula Wi, Suh & Kim, 2015, eastern Central Pacific; C. humbolti Larsen, 2000, Antarctica (type locality: Crozet Island); C. larviformis (Kudinova-Pasternak, 1973), Aleutian Trench; C. lilliputa Błażewicz-Paszkowycz & Larsen, 2005, Antarctica, Weddell Sea; C. longipedia Kudinova-Pasternak, 1986, southern Indian Ocean; C. longipleona Błażewicz- Paszkowycz & Larsen, 2005, Antarctica, Weddell Sea; C. longisetosa Larsen, 2011, Central Pacific Manganese Nodule Province; C. minima (Hansen, 1913), Davis Strait, south of Iceland, Greenland, dubious records in the Pacific (Larsen, 2000); C. pegmata Bamber, 2000, Angola (South Africa); C. prominentia Wi et al., 2015, eastern Central Pacific; C. rotundicauda Kudinova-Pasternak, 1983, Iberian Plateau, off Portugal; C. subtilis Kudinova- Pasternak, 1981, Central North Pacific Plateau; C. vermiformis (Lang, 1971), western Mediterranean Sea; C. wilsoni Larsen, 1999, Georges Bank (Northwest Atlantic); C. sp. A sensu Larsen, 2005, Gulf of Mexico.