Flagitopisa philippensis ( Chilton, 1920 )

Sawicki, Thomas R., Holsinger, John R. & Sket, Boris, 2005, Redescription Of The Subterranean Amphipod Crustacean Flagitopisa Philippensis (Hadzioidea: Melitidae), With Notes On Its Unique Morphology And Clarification Of The Taxonomic Status Of Psammogammarus Fluviatilis, Raffles Bulletin of Zoology 53 (1), pp. 59-68 : 59-66

Flagitopisa philippensis ( Chilton, 1920)

( Figs. 1-5 )

Niphargus philippensis Chilton, 1920: 515-521 , Pls. 1-3. Flagitopisa philippensis (Chilton) - G. Karaman, 1984: 50. Psammogammarus philippensis (Chilton) - Stock, 1991: 231, 233. Eriopisa sp.- Sket, 1995, 1997 (in part: specimens from Bohol only).

Material examined. – 20 specimens (males & females) ( USNM acc. 364310), well at Tigaon, Camarines Sur Province, Luzon Island , coll. T. M. Iliffe, 4 Apr.1985 ; 6 specimens (males and females) ( USNM acc. 364310), well, Pinet Ocampo, coll. T. M. Iliffe, 4 Apr.1985 . 100 + specimens (males, females and juveniles) from Bohol Island as follows: Maitom Cave in Behind-the-Clouds , Batuan, coll. B. Sket, Feb.1995 ; Quilas Cave in Nueva Vida Norte, Batuan , coll. B. Sket, Feb.1995 ; pump wells in Tejero , coll. B. Sket, Feb.1995 ; open well, in Batuan , coll. B. Sket, Feb.1995 ; pump well in Bungamar , coll. B. Sket, Feb.1995 ; spring below C. Serapia, Ginjuyuran , coll. B. Sket, Feb.1995 ; spring below cave Serapia , coll. B. Sket, Feb.1995 ; spring-cave Anislag, Valencia , coll. B. Sket, Feb.1995 ; spring Badyang, Valencia , coll. B. Sket, Feb.1995 ; spring Badyang in Omhon, Velencia , coll. B. Sket, Feb.1995 ; spring 1, Roxas Park in Roxas, Garcia-Hernandez , coll. B. Sket, Feb.1995 ; spring 2, Roxas Park , coll. B. Sket, Feb.1995 ; cave Inambokan Boho inVilla Aurora, Antequera , coll. B. Sket, Feb.1995 .

The material examined during the present study includes specimens from the National Museum of Natural History of the Smithsonian Institution ( USNM), numerous specimens collected by B. Sket and deposited in the J. R. Holsinger research collection, and paratypes on loan from Amsterdam University. Largest males are 7.0 mm in length; largest females are 6.5 mm .

Diagnosis. – Flagitopisa philippensis is clearly distinguished from all other hadzioid amphipods except F. fluviatilis (see below) by presence of a pair of conspicuous subovate gills attached to ventral surface of the first pleonite.

Description of female. – Antenna 1 ca. 1.4 times longer than body and 3.2 times longer than antenna 2; primary flagellum with up to 44 segments, accessory flagellum 2 segmented (tiny second segment not shown in Fig. 1A ). Antenna 2: flagellum with up to 7 segments. Mandible: right mandible molar well developed, with molar seta, lacinia mobilis 3 dentate; incisor 6 dentate, with 8 serrate accessory spines and 4 small setae; left molar prominent, with molar seta, lacinia mobilis 6 dentate, incisor 7 dentate; palp segment 3 with 4- 5 D setae and 4 E setae. Lower lip with inner lobes. Maxilla 1: inner plate with up to 15 apical plumose setae; outer plate with 9 pectinate spines; palps 2-segmented, second segment bearing 8 spines and 2 long setae apically. Maxilla 2: inner plate bearing dorsal oblique row of up to 20 setae, inner and apical margins bearing numerous setae. Maxilliped: inner plate narrow, bearing 2 spines along inner apical margin and 8-9 spines along apical margin; outer plate expanded with numerous long setae along inner and apical margins; palp 4- segmented, segment 2 with numerous long setae along inner margin, segment 3 longer than wide, weakly pubescent distally.

Gnathopod 1: propodus ca. 72% length of carpus, palm transverse bearing 7-8 long setae and up to 6 small setae medially and 8 spines, 4 of which are bifurcate at the defining angle; dactyl subequal in length to palm; carpus elongate, posterior margin with numerous long setae; merus expanded distally, pubescent, with up to 10 setae along distoposterior margin; basis with 9 long setae along posterior margin; coxa deeper than broad with 8 marginal setae. Gnathopod 2: propodus elongate and expanded, ca. 1.7 times longer than carpus, palm oblique with 5 long setae and 6 short setae and 2 stout spines medially, defining angle with 2 spines and 2 long setae; propodus posterior margin bearing numerous setae; carpus weakly subtriangular, posterior margin with 5 sets of setae; basis with 4 sets of long setae on posterior margin and few shorter setae on anterior margin; coxa only slightly deeper than broad with 10 marginal setae. Pereopod 3: subequal in length to 4, coxa about as deep as broad with 10 marginal setae; basis expanded with 7 long setae on posterior margin. Pereopod 4: coxa posterior margin not excavate, slightly broader than deep with 8 marginal setae; basis expanded with 8 long setae on posterior margin. Pereopod 5 ca. 44% length of body; basis weakly expanded, distoposterior lobe not developed; dactyl ca. 16% length of propodus. Pereopod 6 ca. 71% length of body; basis posterior margin expanded relative to pereopod 5, distoposterior lobe well developed; dactyl ca. 16% length of propodus. Pereopod 7 ca. 75% length of body; posterior margin of basis expanded greatly, distoposterior lobe well developed, its width about 50% the length of the basis; dactyl ca. 22% length of propodus. Coxal gills on pereopods 2-6, subovate, with distinct peduncles; brood plates subequal in length to gills, narrow, with small lateral and distal setae.

Pleonite 1 with pair of weakly stalked, subovate coxal-like gills attached to ventral surface, just anterior to pleopod 1. Distoposterior margin of pleonal plate 1 rounded, with 6 small spines; distoposterior margins of. pleonal plates 2 and 3 less rounded, both posterior and ventral margins with many small spines. Pleopods normal, each bearing 2 coupling spines. Uropod 1: outer ramus ca. 89% length of inner, bearing 5 apical and 4 lateral spines; inner ramus ca. 79% length of peduncle with 5 apical and 4 lateral spines; peduncle with 13 spines, 1 of which is basofacial. Uropod 2: outer ramus ca. 72% length of inner ramus, bearing 3 apical and 4 lateral spines; inner ramus slightly longer than peduncle, with 6 apical and 3 lateral spines; peduncle with up to 4 spines. Uropod 3: ca. 48% length of body; inner ramus small, scalelike, with small apical seta; peduncle long, ca. 40% length of segment 1 of outer ramus; outer ramus 2-segmented, first segment armed with numerous clusters of spines, second segment ca. 48% length of segment 1, with 7 long, thin setae apically and numerous lateral spines. Telson short, cleft to base, wider than long, each half bearing 3 lateral and 2 apical spines (the second apical spine being much smaller).

Male. – Differing only slightly from the female as follows: palm of propodus of gnathopod 2 with additional spines and setae. Propodus of gnathopod 2 in mature males may be nearly twice as long as carpus. (period) Basis of pereopod 7 may be narrower, its width only only 65% of length. Uropod 3 may be 60 % as long as body length, with peduncle up to 60 % length of segment 1 of outer ramus.

Type-locality. – A well at Los Baños, Laguna Province, on the south shore of Laguna de Bay, 25 km SW of Santa Cruz and 54 km SE of Manila .

Distribution and Ecology. – Until recent years, Flagitopisa philippensis was known only from its type locality. In April of 1985, Thomas M. Iliffe collected the species from two new, separate locations, both being wells on Luzon Island in Camarines Sur Province. In February of 1995, one of us (BS) made numerous collections of this species from wells and springs on the island of Bohol in the Philippines, marking a significant range extension for F. philippensis . Subsequent to collections from the above mentioned localities in 1995 (see Material Examined), new localities were established in 1999 in the Antequera region (cave Tubang in Celing; Bongcawi Cave in Villa Aurora, Camantong Cave in Quinapon-an; Kanador Cave in Canla-as) and near Jagna (Kabulihan Cave in Odiong). This species appears to be present throughout that part of Bohol Island, which was biospeleologically investigated and includes the area within the triangle formed by Jagna – Sagbayan – Antequera. It appears to be the only amphipod of this territory and is replaced by one species of Hadzia and two of Tegano in anchialine caves of tiny Panglao Island just 1 km off the southwestern corner of Bohol Island ( Sawicki et al., 2004, 2005) and probably in some coastal localities of Bohol itself. Flagitopisa was found in caves, wells, and some springs, and it occupies subterranean waters in karst voids but apparently also inhabits fresh interstitial water in coarse sands close to the shore. Its most common cohabitants are shrimps of the genus Caridina (Atyidae) and quite often also crabs Sundathelphusa spp. ( Parathelphusidae ). Both of these crustacean groups are represented in Bohol by troglomorphic and non-troglomorphic species ( Sket, 1995, 1997; Ng & Sket, 1996). Given the presently known disjunct distributional pattern of F. philippensis ( Fig. 6 ), it is probable that this species inhabits other, less investigated, parts of the Philippine archipelago, especially in areas between Manila in Luzon and Bohol.

Figures

Fig. 1. Flagitopisa philippensis, Spring 1, Roxas Park, Bohol Island, Philippines. Male (5.0 mm): A, whole animal. Male (7.0 mm): B, lower lip; D, left mandible incisor and lacinia mobilis; E, right mandible. Female (6.0 mm): C, maxilla 1.

Fig. 2. Flagitopisa philippensis, Spring 1, Roxas Park, Bohol Island, Philippines. Male (7.0 mm): A, gnathopod 1; B, enlarged distal end of propodus and dactyl of gnathopod 1; C, gnathopod 2; D, enlarged distal end of propodus and dactyl of gnathopod 2.

Fig. 3. Flagitopisa philippensis, Spring 1. Roxas Park, Bohol Island, Philippines. Male (7.0 mm): A, pereopod 3; C, pereopod 4; E, maxilla 2; F, pleopod 1 (coupling spines enlarged); G, maxilliped. Female (6.0 mm):B, pereopod 3 coxal plate with brood plate and gill; D, pereopod 5.

Fig. 4. Flagitopisa philippensis, Spring 1, Roxas Park, Bohol Island, Philippines. Male (7.0 mm): A, pereopod 6; B, pereopod 7. Female (6.0 mm): C, Telson.

Fig. 5. Flagitopisa philippensis, Spring 1, Roxas Park, Bohol Island, Philippines. Male (7.0 mm): A, uropod 1; B, uropod 2; F, pleonal plate 1 with gill attached anterior to pleopod 1; G, pleonal plates 2 and 3. Female (6.0 mm): C, uropod 3; D, carpus and propodus of gnathopod 2; Spring 2, Roxas Park, Bohol Island, Philippines. Second Female (6.0 mm): E, pleonal gill drawn from opposite perspective.

Fig. 6. Distribution of Flagitopisa in the Philippine archipelago. Solid circles indicate known localities as follows: 1a) Flagitopisa philippensis—Type-locality, Luzon Island, near Los Baños, on the southern shore of Laguna de Bay; 1b) Luzon Island, in the Camarines Sur Province, approximately 240 km SE of the type locality; 1c) the island of Bohol, approximately 550 km SSE of the type locality; 2) Flagitopisa fluviatilis—Luzon Island, Laguna Province, Pagsanjan Falls.