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

Cassidinidea andamanensis sp. nov.

Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 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.