Studies On The Tetraclitidae Cirripedia Thoracica A New Tetraclitellian From India

Abstract

Tetraclitella contains eight species, including T. karandei n. sp. from Mad'h Island, India, all of which are restricted largely to the Indo-West Pacific faunal province. Two groups may be recognized in this genus on the basis of opercular morphology. One species in each of these groups has radii that are elevated well above the surface of the parietes. In T. danvini the elevated radii serve to strengthen the shell in the absence of sutural ridges and denticulae; in T. karandei they probably create water turbulence and thus enhance the fishing capabilities of the cirral net. Tetraclitella comprises eight, relatively small, patelliform, balanomorph barnacles that occupy habitats low in the intertidal zone. They are confined largely to the Indo-West Pacific faunal province, contrary to the statement by Utinomi (1970: 349) that they are "mostly circumtropical." All of the species occur predominantly on continental islands but there are a few scattered mainland records. Exceptions to this distribution pattern are T. purpurascens, which ranges from Australia to India, and T. divisa which is the only species that occurs circumtropically (Ross, 1968: 14). The barnacle fauna of India and adjacent areas is relatively well known through the work of Annandale, Nilsson-Cantell, Karande (1966) and several contemporary Indian workers. Therefore, it is surprising to note the presence of a new tetraclitellan from Mad'h Island on the Bombay coast of India (Fig. 1). This new species is similar in many ways to the widely occurring T. purpurascens, and records for that species should be reevaluated in the light of the present discovery. Dr. A. A. Karande, who collected the specimens reported on here, informed me that it occurs on the under surface of rocks, low in the intertidal zone, where it normally remains moist during periods of low tide. The shells commonly are covered with a dense mat of brownish-green, finely particulate, organic matter. The associated animals include the ubiquitous Planaxis sulcatus Born and a species of Acmaea. The ecological conditions under which this species lives and the few animals with which it is associated do not differ appreciably from those of other species of Tetraclitella. Family Tetraclitidae Gruvel, 1903 Genus Tetraclitella Hiro, 1939 Definition. —Shell generally less than 20 mmin rostro-carinal diameter, patelliform, ribbed; compartments discrete; parietes with 2 or more rows of tubes; radii broad, flush with or raised above parietal surface, summits horizontal, tubiferous, lacking teeth or denticles on articular surface; alae non-tubiferous; basis membranous, calcareous peripherally or wholly calcareous; scutum transversely elongated or higher than wide, commonly ornamented externally, lacking crests for depresser muscles; mandible with 5 teeth and spine-like lower angle; maxilla I with 6-8 major spines below subapical notch. SANDIEGOSOC. NAT. HIST., TRANS. 16 (8): 215-224, 21 MAY1971 216 SANDIEGOSOCIETY OFNATURALHISTORY VOL. 16 Figure 1 . Map showing position of Mad'h Island relative to other islands along the Bombay coast of India. 1971 ROSS: STUDIES ONTHETETRACLITIDAE 217 Type species. —Lepas purpurascens Wood (1815: 55), Recent, Australia, by original designation of Hiro ( 1 939: 273). Remarks. —Hiro (1939: 273) established Tetraclitella as a subgenus of Tetraclita. Recently, in reevaluating the tetraclitids I raised the subfamily to familial status (Ross, 1968: 6), and accordingly the subgenera of Tetraclita were raised to genera to better retlect relationships within the family (Ross, 1969: 237; Ross, 1970: 3). Utinomi (1970: 349) independently also accorded Tetraclitella generic rank. Species referable to Tetraclitella include: T. purpurascens (Wood, 1815: 55), T. costata (Darwin, 1854: 339), T. chinensis (Nilsson-Cantell, 1921: 359), T. divisa (NilssonCantell, 1921: 362), T. darwini (Pilsbry, 1928: 314), T. multicostata (Nilsson-Cantell, 1930: 2) and T. pilsbryi (Utinomi, 1962: 234). Tetraclita squamosa depressa (Kolosvary, 1941: 42) from southern Australia, Tetraclita purpurascens darwini {Kolosvary, 1942: 140) from Port Jackson, New South Wales, Australia, and Tetraclita radiata wagneri (Kolosvary, in Kolosvary and Wagner, 1941: 11) from Tasmania, on the basis of morphology and biogeography, are apparently conspecific with T. purpurascens purpurascens. KEYJOTHESPECIESOFTETRACLITELLA 1. Radii elevated above surface of parietes 2 1 . Radii flush with or sunken below surface of parietes 3 2. Scutum higher than wide; intermediate segments of cirrus VI with 4 pairs of setae (Japan, Formosa) T. darwini 2. Scutum wider than high; intermediate segments of cirrus VI with 3 pairs of setae (India) T. karandei 3. Scutum higher than wide 4 3. Scutum wider than high 5 4. Scutum with a row of small longitudinal pits; intermediate segments of cirrus VI with 4 pairs of setae; basis calcareous (Lesser Sunda Islands, Sulu and Philippine Archipelagos) T. costata 4. Scutum with 5 rows of longitudinal pits; intermediate segments of cirrus VI with 3 pairs of setae; basis membranous (Japan) T. pilsbryi 5. Tergal spur essentially confluent with scutal margin 6 5. Tergal spur well separated from scutal margin (intermediate segments of cirrus VI with 3 pairs of setae; circumtropical) T. divisa 6. Parietal plates without hollows 7 6. Parietal plates pierced by hollows (intermediate segments or cirrus VI with 4, rarely 3 pairs of setae; southern China, Formosa, Japan) T. chinensis 1. Shell with 14 or fewer primary longitudinal ribs; cuticle persistent (West Irian, New Guinea) T. multicostata 1 . Shell with 20 or more primary longitudinal ribs; cuticle not persistent (intermediate segments of cirrus VI with 2 pairs of setae; New Zealand, Tasmania, Australia, Malay Archipelago, India) . . T. purpurascens Tetraclitella karandei n. sp. Diagnosis. —Radii transversely ridged, the apical 3-4 ridges extending like fingers out and over adjoining plate; scutum transversely elongated, externally ornamented with prominent nodes where longitudinal ridges cross growth lines; intermediate articles of posterior cirri armed with 3 pairs of setae. 218 SAN DIEGOSOCIETY OFNATURALHISTORY VOL.16 Description. —Shell white or grayish white, patelliform, ovate in outline, covered with persistent, hirsute, chitinous cuticle; parietes ornamented with prominent growth ridges, and high, primary, longitudinal ribs intercalated with lower secondary and tertiary ribs; ribs square or T-shaped in section, extending from orifice to or beyond basal edge of shell, occasionally bifurcate basally (Fig. 2a, b); orifice diamond-shaped; radii broad, horizontally ridged from base to apex, the ridges becoming progressively higher, produced and free from the surface (Fig. 2a); articular margin and finger like projections tubiferous, the apertural margins of the tubes being crenate; on the adjoining plate a narrow, longitudinal ridge occurs on parietal surface where the radius butts against the plate (Fig. 2b); alae broad, summits horizontal and crenate; sheath less than '/2 height of wall, basal margin not depending; basis calcareous peripherally. Scutum wider than high; external surface deeply sulcate (Fig. 2e); where the growth ridges are crossed by longitudinal ridges prominent nodes are formed thus rendering a scabrous appearance; articular ridge straight, about 2/3 length of tergal margin; adductor ridge low, not undercut, apically fused with articular ridge, terminating basally at basioccludent angle; adductor muscle depression ovate, shallow, borders poorly delimited; depression for lateral depressor muscle shallow, poorly defined; depression for rostral depressor muscle lacking; apical portion of plate with weak ridges (Fig. 2d). Tergum higher than wide; external longitudinal furrow open, broad, shallow, extending to base of spur; spur evenly rounded basally, confluent with scutul margin, width about '/2 that of basal margin (Fig. 2g); articular ridge inclined; articular furrow wide and shallow; 6-7 crests for depressor muscle, low, short, inclined; apical portion of valve ridged or roughened (Fig. 20Measurements of the holotype are as follows (in mm): rostro-carinal diameter 10.1; height 3.5; rostro-carinal diameter of orifice 3.6; height of scutum 1.5; width of scutum 2.1; height of tergum 1.5; width of tergum 1.0. The mean rostro-carinal diameter of five paratypes is 13.5 mmand the height is 3.8 mm. Labrum with shallow, broad, medial depression; crest thick, heavily chitinized,armed with short, fine bristles but rarely with teeth (Fig. 3a). Palps long, broad, distal end broadly rounded; superior margin straight, basal margin convex; proximal setae on superior margin short, stout, coarsely bipectinate; distal setae on margin long, slender, finely bipinnate; basal portion of lateral surface covered with ctenae. Mandible with 5 unequally spaced teeth; teeth 2 and 3 commonly with 1-2 subsidiary cusps; tooth 4 with 3-5 subsidiary cusps; comb between tooth 5 and inferior angle containing 8-12 teeth; inferior angle commonly with 1 long, slender and 1 short, stout tooth (Fig. 4). Maxilla I with 2 long, stout and 1-2 shorter spines above sub-apical notch; 2-3 short, slender spines in notch; 6-8 stout spines medially; 8-12 short, slender spines in basal cluster (Fig. 3c). Maxilla II bilobate; setae along apical margin long; bipinnate, setae becoming progressively shorter toward the notch; setae on basal lobe coarse, bipectinate. Posterior ramus of cirrus I about 3/5 length of anterior ramus; intermediate articles of both rami broader than high; segments of anterior ramus normal, but those of posterior ramus protuberant; distal articles of both rami clothed with finely bipinnate setae (Fig. 3g). Rami of cirrus II essentially equal in length, and slightly longer than posterior ramus of cirrus I; medial segments of both rami protuberant; distal two segments of both rami armed with bipectinate setae, proximal segments with bipinnate setae (Fig. 3h). Ra