Cassidinidea andamanensis, Anil & Bruce & Samson & Jayaraj, 2024

Anil, Pathan, Bruce, Niel L., Samson, Rokkarukala & Jayaraj, Kadeparambil Arjunan, 2024, Cassidinidea andamanensis sp. nov., a new species of intertidal Sphaeromatidae (Crustacea: Isopoda) from the Andaman Islands, northern Indian Ocean, Zootaxa 5397 (4), pp. 578-588 : 580-587

Cassidinidea andamanensis sp. nov.

Figs 2–5

Material examined (all South Andaman, Andaman Islands)

Holotype. 1♁ (3.0 mm), stn. Chidiyatapu, 11°29’55’’N; 092°42’50’’E, intertidal sand, coll. Pathan Anil, 16 th January 2019 (Reg. no. BAKRZRL 2706).

Paratypes. 3♁ (2.5, 2.8, 3.0 mm), 2 ♀♀ (3.0, 3.2 mm), same data as holotype (Reg. no. BAKRZRL 2707); 2♁♁ (2.3, 2.9 mm), 1♀ (3.1 mm), stn. Wandoor, intertidal sand, coll. Pathan Anil, 15 th January 2019 (Reg. no. BAKRZRL 2708); 2♁♁(2.6, 3.0 mm), stn. Corbyns Cove, intertidal sand, coll. Pathan Anil, 15 th January 2019 (Reg. no. BAKRZRL 2709); 1♁ (2.8 mm), stn. Manjeri, intertidal sand, coll. Pathan Anil, 27 th January 2019; 1♁ (3.0 mm), 4♀♀ (2.9, 3.0, 3.2, 3.2 mm), stn. Kodiyaghat, intertidal mudflat with green algae, coll. Pathan Anil, 1 st February 2019 (Reg. no. BAKRZRL 2710) .

Description: Body oval, smooth, margins fringed with small setae; 2.0 times as long as greatest width, widest at pereonite 5. Head distal part slightly embraced by pereonite 1; pereonites 1−7 smooth, pereonite 1 longer than pereonite 2. Pleonite 2 slightly shorter than pereonite 7. Pleotelson as wide as pleonite 2, 1.8 times as wide as long, dorsally smooth with convex sub-truncate apex, posterior margin subtruncate, weakly convex with small setae.

Antennula not extending to posterior of pereonite 1; peduncle article 1, 2.2 times as long as article 2, dorsal distal margin with 4 simple short setae, superior proximal margin with 2 simple short setae, medial margin with 3 long simple setae, many small fine setae, distal margin with 2 plumose setae, 5 simple short setae and inferior distal margin with 2 plumose setae, 2 simple short setae and many short fine setae; peduncle article 2 dorsal margin with 3 simple short setae, superior medial margin with 2 simple short setae, 1 plumose seta, distal margin with 2 plumose setae, 4 simple short setae and inferior margin with 3 simple short setae, many small fine setae; peduncle article 3, 1.5 times longer than article 2, dorsal medial margin with 1 simple short seta, superior medial margin with 3 short simple setae, many small fine setae, distal margin with 1 plumose seta, 3 simple short setae and inferior margin with 3 simple short setae, many small fine setae and 1 plumose seta; flagellum with 8 articles, articles 4−8 each bearing an aesthetasc.

Antenna extending to posterior of pereonite1, peduncle article 1 superior margin with 9 fine setae; article 2 dorsal medial margin with 1 simple short seta, superior margin with 2 short setae, many fine short setae and inferior margin with 2 short simple setae, 1 plumose seta; article 3 superior distal margin with 1 plumose seta, 2 short simple setae and inferior distal margin with 2 simple short setae; articles 4 and 5 sub-equal in length; article 4 superior medial margin with 2 simple short setae, many short fine setae, distal margin with 1 plumose seta, 1 simple short seta and inferior margin with 3 simple short setae; article 5 superior medial margin with 1 simple short seta, many fine setae, distal margin with 2 short simple setae, 1 plumose seta and inferior margin with 6 simple short setae; flagellum shorter than peduncle, with 9 articles.

Epistome anterior margin convex, bearing some marginal simple long setae interspersed among smaller fine setae; lateral margins concave.

Maxillula lateral endite with 10 simple and serrated RS; mesial endite with 4 long comb setae and 2 simple setae.

Maxilla lateral and middle endites each with 4 curved pectinate RS; mesial endite with 6 long finely plumose and long comb RS.

Left mandible palp articles 2 with 5 biserrate setae, article 3 with 4 biserrate setae.

Maxilliped endite lateral margin sinuate, mesial margin with 1 coupling hook, distal margin with 8 long circumplumose and 3 simple RS; palp articles 2−5 both superior and inferior distal angles with long setae.

Pereopod 1 basis 2.8 times as long as greatest width, superior margin with 3 plumose setae and inferior margin with 2 simple setae; ischium 3.2 times as long as greatest width, superior margin with 3 simple setae and inferior margin with 3 simple setae; merus 0.7 times as long as ischium, superior margin with 2 long simple RS, 1 short simple seta and inferior margin with 3 simple long setae; carpus sub-triangular, inferior margin with 3 simple RS; propodus 3.0 times as long as wide, superior margin with 1 long palmate seta, 2 short simple setae and inferior medial margin with 1 simple RS, 3 simple short setae, distal margin with 2 biserrate RS, 1 uniserrate RS; dactylus with an acute secondary unguis, superior margin with 1 simple seta and inferior margin with 2 long simple setae.

Pereopod 2 basis 3.0 times as long as greatest width, superior margin with 1 plumose seta, 4 simple short setae, superior dorsal medial margin with 1 short seta and inferior margin with 4 simple setae, inferior dorsal medial margin with 1 short seta; ischium 3.4 times as long as greatest width, superior margin with 2 simple setae and inferior margin with 4 simple setae; merus 0.9 times as long as ischium, superior margin with 1 simple seta, 2 simple RS and inferior margin with 2 uniserrated RS and 1 simple RS; carpus superior margin with 2 biserrate RS and inferior margin with 2 simple setae; propodus 3.2 times as long as wide, superior margin with 1 plumose seta, 3 simple setae and inferior margin with 2 biserrate RS, 1 simple seta; dactylus with an acute secondary unguis, superior margin with 1 simple seta and inferior margin with 2 long simple setae.

Pereopod 3 basis superior margin with 2 plumose setae, 4 simple setae and inferior margin with 3 simple setae; ischium superior margin with 3 simple setae and inferior margin with 5 simple setae; merus superior margin with 2 comb RS and inferior margin with 5 simple setae; carpus superior margin with 4 biserrate RS and inferior margin with 1 seta; propodus superior margin with 1 plumose seta, 4 simple setae and inferior margin with 4 simple setae; dactylus with an acute secondary unguis, superior margin with 3 simple setae and inferior margin with 2 simple long setae.

Pereopod 4 basis superior margin with 3 plumose setae, 4 simple setae and inferior margin with 5 simple setae; ischium superior margin with 4 simple setae and inferior margin with 6 setae; merus superior margin with 2 comb RS, 1 simple seta and inferior margin with 5 simple setae; carpus superior margin with 4 biserrate RS, 1 short simple seta and inferior margin with 4 simple setae; propodus superior margin with 2 plumose setae, 3 simple setae and inferior margin with 7 simple setae; dactylus with an acute secondary unguis, superior margin with 3 simple setae and inferior margin with 2 long simple setae.

Pereopod 5 basis superior margin with 3 plumose setae, 4 simple setae, superior dorsal medial margin with 1 short simple seta and inferior margin with 5 simple setae; ischium superior margin with 4 simple setae and inferior margin with 6 simple setae; merus superior margin with 2 comb RS, 1 simple seta and inferior margin with 3 simple setae; carpus superior margin with 4 biserrate RS and inferior margin with 3 simple setae; propodus superior margin with 1 plumose seta, 3 simple setae and inferior margin with 4 simple setae; dactylus with an acute secondary unguis, superior margin with 3 simple setae and inferior margin with 2 simple long setae.

Pereopod 6 basis 3.0 times as long as greatest width, superior margin with 2 plumose setae, 5 simple setae and inferior margin with 1 plumose seta, 5 simple setae; ischium 3.4 times as long as greatest width, superior margin with 4 simple setae and inferior margin with 4 simple setae; merus 0.9 times as long as ischium, superior margin with 2 comb RS, 1 short simple seta and inferior margin with 5 simple setae; carpus superior margin with 3 biserrated RS, 1 uniserrated RS, 1 short simple seta and inferior margin with 5 simple setae; propodus 3.6 times as long as wide, superior margin with 1 plumose seta, 4 simple setae and inferior margin with 5 simple long setae; dactylus with an acute secondary unguis, superior margin with 3 setae and inferior margin with 2 long setae.

Pereopod 7 basis 3.2 times as long as greatest width, superior margin with 2 plumose setae, 4 simple setae and inferior margin with 5 simple setae; ischium 3.6 times as long as greatest width, superior margin with 4 simple setae and inferior margin with 10 simple setae; merus superior margin with 1 comb RS, 2 simple setae and inferior margin with 7 simple setae; carpus superior margin with group of biserrate RS, 3 short simple setae and inferior margin with 6 simple setae; propodus 3.6 times as long as width, superior margin with 2 plumose setae, 4 simple setae and inferior margin with 8 simple setae; dactylus with an acute secondary unguis, superior margin with 3 simple setae and inferior margin with 2 simple long setae.

Penial process subtriangular, 1.17 times as long as basal width.

Pleopod 1 exopod 1.2 times as long as wide, lateral margin weakly convex, distally narrowly rounded with weakly oblique medial margin, mesial margin weakly convex, with PMS from distal one-fourth, with 16 PMS; endopod 1.8 times as long as wide, lateral margin weakly convex, distally narrowly rounded with 8 PMS; peduncle 0.4 times as wide as long, sympod mesial margin with 3 coupling hooks, distolateral corner with short simple fine setae.

Pleopod 2 endopod and exopod with 12 and 15 PMS respectively, endopod slightly longer than exopod; sympod mesial margin with 3 coupling hooks; appendix masculina 1.7 times as long as proximal width, 2.5 times as long as endopod, apically narrowly rounded, bearing minute short setae almost throughout length.

Pleopod 3 endopod and exopod with 7 and 18 PMS respectively, endopod slightly shorter than exopod, subtriangular; exopod with weak transverse suture.

Pleopod 4 without marginal setae; both rami subequal in length, exopod wider than endopod, with weak transverse suture.

Pleopod 5 without marginal setae; exopod with two scale patches, scales with 7−14 spinules of sub-equal length; endopod entirely covered with transverse folds.

Uropod extending to distal margin of pleotelson; endopod 3.5 times length of exopod; distally rounded, exopod and endopod lateral margins fringed with long slender setae interspersed among smaller fine setae.

Female: Body wider than male, about 1.9 times as long as wide.

Size: Adult males (n=10) 2.3−3.0 mm (mean 2.7 mm); females (n=7) 2.9−3.2 mm (mean 3.0 mm).

Remarks: Cassidinidea andamanensis sp. nov. can be separated from other species of the genus by the prominently convex epistome anterior margin, pleotelson with a smooth dorsal surface, posterior margin subtruncate and weakly convex with small setae and the appendix masculina distal margin being narrowly rounded.

Cassidinidea andamanensis differ from C. clarkae Schotte & Kensley, 2005 from the Seychelles, in having the epistome lateral margins concave (vs sub-parallel in C. clarkae ), epistome lacking incurving extensions posteriorly (vs incurving extensions posteriorly), pleotelson dorsal surface smooth (vs four very weak longitudinal carinae, not tuberculate), pleotelson posterior margin sinuate with small setae (vs smooth and without setae), pereonite 7 and pleon lacking scattered tubercles (vs pereonite 7 and pleon with few scattered tubercles), pereopod 1, propodus inferodistal angle with two prominent biserrate setae, one pectinate seta (vs two prominent biserrate setae), appendix masculina twice as long as endopod (vs extending beyond endopod by one-third total length). Cassidinidea andamanensis sp. nov; differs from C. clarkae in having a slightly more elongate body (2.0 times as long as greatest width vs 1.8).

Cassidinidea andamanensis sp. nov. differs from C. extenda ( Joshi & Bal, 1962) from Bombay in having pleotelson with a sub-truncate apex (2.2 times width of anterior margin of the pleotelson), (vs narrowly truncate or possibly narrowly rounded (1.1 times width of anterior margin of the pleotelson in C. extenda ), pleotelson dorsal surface smooth, unornamented (vs with two submedian longitudinal ridges), uropodal endopod distally broadly rounded (vs distally narrow with a straight mesial margin and curved lateral margin), and each pereonite lacking a submedian pair of tubercles along the mid-dorsal region (vs present).

Cassidinidea andamanensis sp. nov. may be separated from another Indian Ocean species, C. quadricarinata Pillai, 1954 from Thiruvananthapuram, by the pleotelson dorsal surface being smooth (vs dorsum with four distinct longitudinal rows of tubercles in C. quadricarinata ), pereopod 1, propodus inferodistal angle with two prominent biserrate setae, one pectinate seta (vs one large biserrate seta on the propodus of pereopod 1).

Cassidinidea andamanensis sp. nov. differ from C. monodi ( Barnard, 1951) from the Indian Ocean coast of South Africa from the Bashee River, Eastern Cape to Khosi Bay, Kwa-Zulu Natal, in the pleotelson dorsal surface being smooth (vs four low, rounded keels on the pleotelson in C. monodi ), apex of pleotelson truncate (vs bluntly rounded apex).

Cassidinidea andamanensis sp. nov. is somewhat similar to Cassidinidea ovalis ( Say, 1818) , known only from eastern United States ( Khalaji-Pirbalouty & Bruce 2021), and shares characters such as the lack of dorsal ornamentation. Cassidinidea andamanensis sp. nov. differs from Cassidinidea ovalis in having a convex epistome anterior margin (vs transversely straight in Cassidinidea ovalis ), pleotelson lacking weak median elevation dorsally (vs bearing a single, weak median elevation dorsally).

Distribution: Known only from the type locality, South Andaman, Andaman Islands.

Etymology: Cassidinidea andamanensis sp. nov. is named for the type locality.

Figures

FIGURE 2. Cassidinidea andamanensis sp. nov., holotype male (3.0 mm, Reg. no. BAKRZRL 2706). A, dorsal view; B, lateral view; C, frontal lamina; D, pleotelson apex; E, antennula; F, antenna.

FIGURE 3. Cassidinidea andamanensis sp. nov., holotype male (3.0 mm, Reg. no. BAKRZRL 2706). A, maxilliped; B, maxillule; C, mandible; D, maxilla; E, penial process.

FIGURE 4. Cassidinidea andamanensis sp. nov., holotype male (3.0 mm, Reg. no. BAKRZRL 2706). A–G, pereopods 1–7 respectively.

FIGURE 5. Cassidinidea andamanensis sp. nov., holotype male (3.0 mm, Reg. no. BAKRZRL 2706). A–E, pleopods 1–5 respectively; F, uropods.