Lucayalana Bruce & Brix

Bruce, Niel L., Brix, Saskia, Balfour, Nicholas, Kihara, Terue C., Weigand, Alexander M., Mehterian, Sevag & Iliffe, Thomas M., 2017, A new genus for Cirolanatroglexuma Botosaneanu & Iliffe, 1997, an anchialine cave dwelling cirolanid isopod (Crustacea, Isopoda, Cirolanidae) from the Bahamas, Subterranean Biology 21, pp. 57-92 : 62-65

Lucayalana Bruce & Brix gen. n.

Diagnosis

(female). Head without rostral point. Frontal lamina short, narrow, less than 7% width of labrum, not extending to anterior margin of head; clypeus ventrally flat, not blade-like, not projecting. Pleonite 3 extending posteriorly to posterior of pleonite 5, laterally overlapping pleonites 4 and 5; ventrally broad, forming a strong ventrally directed blade; pleonite 5 as wide as pleotelson anterior margin; pleonites all visible in dorsal view. Pereopods 1-7 ambulatory, slender; dactylus short, less than half length of propodus. Pereopods 1-3 with ischium superior distal margins weakly produced, sparsely setose; merus superior distal margin weakly produced, not overriding propodus; pereopods 1-3 merus inferior margin RS not molariform; pereopods 5-7 basis without long PMS, ischium and merus distally without long setae. Vasa deferentia opening flush on sternite. Pleopod 1 rami sub-similar in width, exopod about ⅔ width exopod, peduncle wider than long. Uropodal rami lamellar, subequal in size, with marginal robust and plumose setae.

Description.

Head approximately 65% as wide as pereonite 1, anterior margin sub-truncate, rostrum absent. Body surfaces unornamented; pereonite 1 about 1.7 times as long as pereonite 2 in dorsal view. Pleon unornamented, about 16% BL, with 5 visible unfused segments, pleonite 1 partly visible in dorsal view; pleonite 2 posterolateral margin weakly produced; those of pleonite 3 extending to posterior of pleonite 5. Pleotelson without longitudinal carinae, ridges or without tubercles; posterior margin with PMS and RS.

Antennula peduncle articles 1 and 2 not fused; peduncular article 2 at right angles to article 1; articles 1 and 2 short, combined length about length of article 3; articles 2 and 3 collinear flagellum 1.4x 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 about twice as long as peduncle.

Frontal lamina short, ventrally flat, lanceolate, not extending to anterior margin of antennal peduncle, posteriorly abutting clypeus. Clypeus ventral surface not projecting relative to frontal lamina. Mandible incisors wide, right incisor tricuspidate; spine row with 4-5 RS. Maxillule mesial lobe with 3 CP 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; endite with 2 coupling hooks.

Pereopods 1-7 dactylus with elongate secondary unguis present. Pereopod 1 dactylus shorter than palm; simple RS opposing dactylus. 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; inferodistal angles of ischium.

Pleopod 1 rami lamellar; endopod about 0.6 as wide as exopod, 2.4 times as long as wide. Pleopod 2 appendix masculina longer than endopod. Pleopods 1-5 with PMS present on all exopods and endopods of pleopods 1-4; endopod of pleopod 5 with small proximomesial lobe. Uropod peduncle mesial margin strongly produced; exopod lateral margin not excised.

Male.

To date only one male specimen (described herein) has been collected. Appendix masculina inserted basally, slender; penial processes flat, quadrate, widely separate lobes.

Type species.

Cirolana troglexuma Botosaneanu & Iliffe, 1997; by monotypy and original designation.

Remarks.

Lucayalana gen. n. presents a suite of characters little derived from free-living cirolanid genera such as Cirolana , reflected by the original placing of Cirolana troglexuma in that genus ( Botosaneanu and Iliffe 1997). The pleon, mouthparts, pereopods and pleopods are relatively unmodified and these characters differ to that seen in many of the subterranean or stygial genera. Typical of stygian cirolanids, the genus lacks eyes, the antennular and antennal flagellum are relatively elongate and the pereopods are somewhat slender. Characters that exclude the species from Cirolana are the short and narrow frontal lamina (vs ventrally flat, pentagonal or quadrate and relatively wide, and extending between antennular bases to the anterior margin of head in Cirolana ), antennula peduncle articles 1 and 2 being at approximately right angles (co-linear in Cirolana ), with article 3 being slightly longer (1.1) than the combined lengths of articles 1 and 2 (shorter in Cirolana ); and the lack of tubercular robust setae on the inferior margin of the merus of pereopods 1-3 (present in Cirolana ). The shape of the anterior margin of the head is unusual in being subtruncate, although this does vary within genera. Species of Cirolana with a rounded anterior margin to the head that lacks a rostral point all belong to the ‘tuberculate’ group of species (see Bruce 1986; Bruce 1995), characterized by the presence of dorsal tubercles on the pereonites, pleon and pleotelson and also with a characteristic discontinuous pattern or robust setae on the uropodal exopod lateral margin.

The difference in frontal lamina shape and size between Lucayalana and Cirolana is substantial. In Cirolana the frontal lamina is pentagonal, with five straight margins, as is seen in the type species Cirolana cranchii Leach, 1818 (see Bruce and Ellis 1983) and species Cirolana ' parva - group’ (see Bruce and Bowman 1982, Bruce 2004), or quadrate with two more-or-less straight and parallel lateral margins and a rounded or truncate anterior margin that may or may not project (e.g. Bruce 1995, Bruce and Brandt 2006). In most species of Cirolana the frontal lamina extends anteriorly past the antennula bases (see previous citations), and ranges in proportion from 1.5 to 3.0 as long as posterior width. In Lucayalana the frontal lamina is short, lacks the broad flat ventral surface and does not extend anteriorly beyond the antennula and has two weakly convex lateral margins that form an acute or narrowly rounded point. The frontal lamina Cirolana can be considered broad–that is the posterior width is approximately 0.4 (40%) the width of the clypeus; in Lucayalana the posterior width is less than 10% (c. 0.07) the width of the clypeus.

Pleon morphology is generally consistent within cirolanid genera with regard to a characters such as fusion, extent of the pleonite posterolateral margins, expansion of posterolateral margins and also relative size of the pleon (as a percentage of total body length) and the number of visible somites. Bowman (1975, fig. 9) summarised and illustrated nine types of pleonal arrangement from full fusion of all pleonites and pleotelson to all pleonites unfused. The pleon type of Lucayalana does not conform to any of these and is similar to the pleon morphology shown by species of the Cirolana " parva -group" (see Bruce 2004), and also Antrolana Bowman, 1964, where pleonites 3 and 4 both extend posteriorly to or beyond or the anterior margin of the pleotelson, with pleonite 3 laterally overlapping pleonites 4 and 5; pleonites 4 and 5 are not narrower than the anterior margin of the pleon. A similar pleon morphology is also shown by genera such as Aatolana Bruce, 1993 and Plakolana Bruce, 1993 and also the unrelated genus Dolicholana Bruce, 1986, but in that case the posterolateral margins of pleonite 3 are expanded. Lucayalana differs from the genera mentioned in that the ventral part of pleonite 3 is expanded and forms a strongly developed and ventrally directed blade, a character lacking in Cirolana ; furthermore species of Cirolana typically have a short pleon (c. 10-12% of total body length) with pleonite1 largely or wholly concealed by pereonite 7 in dorsal view; in Lucayalana pleonite 1 is dorsally largely visible and consequently the pleon is proportionally longer (16% body length).

The most similar genus is the monotypic Antrolana , known only from freshwater caves in Virginia and West Virginia, USA. Antrolana differs in having antennula peduncular articles co-linear, and article 2 notable longer than in the new genus; pleonite 3 posterolateral margins that do not extend posteriorly beyond pleonite 4 (vs extending to anterior margin of pleotelson), the endopods of pleopods 3-5 are significantly smaller than exopod (vs rami subsimilar). There are other differences between the two genera though we would be reluctant to attach generic significance to them at this point–these include shorter pereopodal dactylus, lack of penial processes, and in Lucayalana a subtruncate anterior margin of the head. The molecular delineation based on COI likewise demonstrates that our species of Lucayalana and Antrolana lira are genetically distinct.

There are three other genera that are superficially similar to Lucayalana , but all can be separated by one or more distinct and easily observed characters. The genus Haptolana Bowman, 1966 (worldwide, and see Bruce 2008) has haptorial pereopods and an anteriorly wide frontal lamina; Speocirolana Bolívar y Pieltain, 1950 ( Texas–Mexico region) has pleonites 4 and 5 distinctly narrower than the pleotelson anterior margin and also has haptorial pereopods. Molecular data available for two species of Speocirolana , show that Lucayalana is distinct. Sphaeromides Dollfus, 1897 (France, Bulgaria and former Yugoslavia) has an elongate frontal lamina that is widest distally and anterior pereopods with haptorial dactylus; and pleopod 1 endopod is elongate, 3.5 times as long as wide ( Racovitza 1912).

The monotypic Exumalana Botosaneanu & Iliffe, 2003 (also Bahamas) superficially appears distinct from Lucayalana gen. n., with a far wider body shape, and wide, broadly rounded pleotelson. The appendages, notably antennae, antennulae, mouthparts and pereopods do not markedly differ from free-living genera similar to Cirolana or Lucayalana gen. n. In contrast Exumalana has a long, wide and anteriorly rounded frontal lamina (vs short anteriorly acute in Lucayalana ), the anterior margin of the head is smoothly rounded with a rostral point (vs truncate, no rostral point), and the uropodal peduncle is broad and flat, with rounded rami the exopod of which is less than half the length of peduncle and about 0.6 length of endopod (vs rami longer than peduncle, distally acute).

Etymology.

The name is derived from the Lucayan peoples, the original inhabitants of the Bahamas.