Aphantolana, MOORE & BRUSCA, 2003

MOORE, WENDY & BRUSCA, RICHARD C., 2003, A monograph on the isopod genus Colopisthus (Crustacea: Isopoda: Cirolanidae) with the description of a new genus, Journal of Natural History 37 (11), pp. 1329-1399 : 1378-1382

Aphantolana new genus

(figures 35, 36) Type species. Metacirolana costaricensis Brusca and Iverson, 1985: 36–37 , figure 11D; Bruce,

1986: 222; Brusca, Wetzer and France, 1995: 72–74, figures 60, 63, 64; Espinosa-Perez

and Hendrickx, 1997: 175–185; type material deposited at USNM .

Diagnosis. Small, body length 3–4 mm. Pereon four to five times pleon length.

Body length 2.0–2.2 times greatest width; pereonite 1 longest. Cephalon without interocular depression. Antenna 1 short; peduncle four-articulate, distal article minute; flagellum three-articulate or four-articulate. Antennae 2 short, extended to posterior margin of pereonite 1; peduncle five-articulate, proximal article minute (not easily dissected, visible with SEM); 8–12 flagellar articles. Maxilliped with five-articulate palp, endite extended barely to palp article 3, with one or two coupling setae and three large circumplumose setae. Clypeus triangular, anterior margin broadly rounded, projecting antero-ventrally; set at an approximate 45° angle to frontal lamina. P-1 propodal palm with three large complex setae and two or three connate spines. P-1 to P-7 dactylus with thin, acute accessory seta and a secondary unguis. Coxal plates become progressively larger posteriorly; coxae of pereonite 7 largest and extended well beyond pleonite 3 and often beyond anterior margin of pleotelson. Pleon with five distinct pleonites; without epimeres. Appendix masculina extended to, but not beyond, distal margin of pleopodal exopod, flask-like (narrows abruptly distally), articulating sub-basally on endopod. Pleopods with PMS present on all rami except the endopod of P1-5; exopods of Pl-3 to Pl-5 with transverse suture; endopods never as wide as exopods. Uropodal peduncle with two robust ventral setae arising from mediodistal margin; endopod dorsal surface with two clusters of long palmate setae, one distal and one proximo-lateral; exopod not reaching pleotelson apex. Pleotelson tapering abruptly posteriorly, with three dorsal longitudinal carinae; apex narrowly rounded with fine slender setae and two stout setae.

Description

Sexual dimorphism pronounced. Body length 2.0–2.2 times greatest width. Pereon four to five times pleon length.

Head. Cephalon without interocular depression, without tubercles. Eyes round, well developed, ommatidia arranged in rows. Frontal margin of cephalon not medially concave, with small rostral process separating first antennae. Frontal lamina not fused to rostrum, without ventral projection, anterior end expanded, anterior margin rounded, posterior end stemmed; posterior margin abutting clypeus. Clypeus triangular, anterior margin broadly rounded, projects antero-ventrally; set at an approximate 45° angle to frontal lamina.

Antennae. Antennae 1 short, reaching just beyond lateral margin of cephalon; peduncle four-articulate; 1 and 2 subquadrate; article 3 longer than wide; article 4 minute, with setation; flagellum three-articulate or four-articulate, the first of which is elongate (length at least twice width), the remaining being short (width greater than or equal to length), all with aesthetascs, usually with slender setae, terminal article often with one uniplumose or biplumose seta. Antennae 2 peduncular article 1 minute (generally not visible except with SEM), article 4 longer than 3, article 5 longer than 4; 8–12 flagellar articles, all with slender setae.

Maxilliped. Endite well developed reaching third palp article, with one or two coupling setae and three large lateral circumplumose setae. Palp article 1 (proximal article) subquadrate; article 2 subtriangular; article 3 largest longer than wide; article 4 wider than long; article 5 subquadrate.

Maxillae. Maxilla 1 with medial and lateral lobes distinct, gnathal surface of lateral lobe with five to seven circumserrate setae and two or three stout setae; inner lobe with three stout circumplumose setae and one or two slender setae. Maxilla 2 with apical setae on all three lobes; gnathal lobe with one large circumplumose seta and three to five stout biplumose setae and/or slender setae.

Mandible. Incisor broad, with three large teeth and a small medial accessory tooth. Molar process with 16–18 small acute spines on anterior margin, dorsal surface smooth, without setae; spine row well developed, with 8–14 large flexible spines without intermediate, slender setae; without a lacinia mobilis. Mandibular palp three-articulate, article 2 longest with uniserrate, biserrate and slender setae; distal article well developed, 1.5 times longer than wide, with six or seven biserrate setae on lateral margin.

Pereon. Smooth, without ornamentation. Pereonite 1 longest.

Coxae. Coxae 2–7 or 3–7 visible dorsally; coxae become progressively larger posteriorly; coxae 2–7 with oblique ridge; posterolateral angles of coxae 7 extend beyond anterior margin of pleotelson.

Pereopods. P-1 to P-7 dactylus often with thin, acute accessory seta and a secondary unguis lying alongside primary unguis, one to four slender setae on superior margin; basis with weak anterior ridge.

Pereopods 1–3. Haptorial, propodus ovate. P-1 merus superior-distal angle not produced. P-1 broader than P-2 and P-3. P-1 to P-3 with unique, complex pattern of setae and spines as follows: merus inferior margin with three stout molariform setae, inferior distal angle with one or two stout setae; carpus with one or two connate spines, propodus inferior margin with two connate spines and three large complex setae.

Pereopods 4–7. Long, ambulatory. P-4 to P-7 without connate spines or molariform setae; distal angles of ischium, merus and carpus with one to four robust setae. P-5 to P-7 with basis-propodus articles not flattened.

Pleon. Five free pleonites; without epimeres.

Penes. Penes simple, well developed, free (not basally fused), rounded (not flattened).

Pleopods. Without digitate respiratory branchiae or accessory lamellae. Peduncles of all pleopods wider than long; Pl-1 to Pl-4 with three or four coupling setae on medial margin. Pl-1 exopod and endopod elongate, not operculate to Pl-2 to Pl-5. Exopods approximately 1.5 times wider than endopods; endopod and exopods subequal length on Pl-1, endopod increasingly shorter than exopod on Pl-2 to Pl-5. Pl-1 to Pl-4 endopods and exopods with PMS, absent on endopod of Pl-5; endopods with PMS restricted to distal margins; exopods with PMS on distal and lateral margins. Exopods of Pl-3 to Pl-5 with transverse suture.

Uropod. Uropodal endopod reaches pleotelson apex, exopods much shorter. Peduncle with two robust setae arising from ventral surface; distolateral angle not produced; disto-medial angle produced, subacute, with one large, apical, circumplumose seta. Endopod margins with biplumose setae; medial margin with three large robust setae; lateral margin with one robust seta. Exopod medial margin with biplumose setae and two robust setae; lateral margin with two robust setae.

Pleotelson. With one dorso-medial and two dorso-lateral longitudinal carinae; apex narrowly round with slender setae and two stout setae.

Remarks

Aphantolana species occur in the intertidal zone with algae and/or coral rubble. One of the species, Aphantolana sphaeromiformis , has been reported from the Caribbean, Indian Ocean and western Pacific. We agree with Müller and Salvat (1993) that this broad distribution is suspect and requires confirmation. Brusca et al. (1995) did not find this species in the Eastern Tropical Pacific, and we doubt that it has a circumtropical range, as has been suggested by some authors (Menzies and Glynn, 1968; Bruce, 1981). Aphantolana species are characterized by various combinations of the following features: (1) pereonite 1 longer than others; (2) antennae 2 short, extended only to the posterior margin of pereonite 1; (3) pereopods 1–3 propodal palm with complex setae and connate spines; (4) pereopods 1–7 dactyli with thin accessory setae; (5) pleonite lateral margins covered by the seventh coxal plate (at least in females); (6) pleotelson tapering abruptly, apex narrowly rounded; (7) appendix masculina flask-like and articulating sub-basally; (8) clypeus projecting antero-ventrally (rather than ventrally, as in Metacirolana sensu stricto); (9) antenna 1 reduced, with no more than four flagellar articles; (10) pleotelson with three longitudinal dorsal carinae; (11) carpus of P-1 inferior-distal angle with complex seta; (12) carpus of P-2 inferior-distal angle forms notched lobe. The latter two characters are synapomorphies of the genus. In addition, in Aphantolana and Colopisthus species the seventh coxal plates are the largest and they cover the lateral margins of the pleon. In comparison, Metacirolana have coxal plates 2–7 either subequal in size, or coxae 6 are the largest and may cover a portion of the pleon (as seen in M. spinosa , M. convexissima , M. nana and M. mbudya ).

Etymology

The genus name is derived from the Greek word, aphantos, meaning unseen, invisible or secret, in reference to it being hidden inside the genus Metacirolana for over 50 years.

In 1931 Nierstrasz proposed the genus Paracirolana to include only Cirolana sphaeromiformis Hansen, 1980 . In the same paper, Nierstrasz proposed the genus Metacirolana to include two species Cirolana japonica Hansen and Cirolana hanseni Bonnier. However , in both cases Nierstrasz did not designate a type species for the genus, nor did he provide a description or definition that stated characters purported to differentiate the taxa. Thus both names are invalid in accordance with the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature, 2000) rules (see Articles 13.1 and 13.3). However, Kussakin (1979) designated Cirolana japonica as the type species of the genus Metacirolana , and in doing so he became the official author of the genus.