Atyopsis spinipes ( Newport, 1847 ), 1983

Kunjulakshmi, Kozhikkaparambil, Santos, Maclean Antony & Prakash, Sanjeevi, 2025, Rediscovery of the genus Atyopsis Chace, 1983 (Decapoda: Atyidae) in mainland India following a 72 - year gap, Zootaxa 5722 (4), pp. 570-582 : 573-578

Atyopsis spinipes ( Newport, 1847)

( Fig. 3 A, B )

Material examined. Karnataka specimens (Icr-1027): 4 females with CL (carapace length) ranging from 17 mm to 17.5 mm and TL (Total length) 47 mm to 51 mm collected from Mulki—Pavanje estuary in Dakshina Kannada district , Karnataka, India ( 13° 04’ 35.1” N 74° 46’ 46.5” E), 12 Dec 2024. Coll. M. A. Santos. The specimens are deposited in the National Zoological Collection ( NZC) at Southern Regional Centre ( SRC), Zoological Survey of India ( ZSI), Chennai

Odisha specimen (Icr-1028): 1 immature male with CL = 11 mm; TL = 24 mm collected from Kuakhai river , a Mahanadi distributary near Bhubaneswar city in Khordha district , Odisha, India ( 20° 21’ 23.5” N 85° 52’ 43.6” E), 18 Nov 2023. Coll. Abhisek Mishra. The specimens are deposited in the National Zoological Collection ( NZC) at Southern Regional Centre ( SRC), Zoological Survey of India ( ZSI), Chennai .

Comparative material: Atyopsis moluccensis with CL = 15 mm (Voucher/Reg. No. 3344/10], freshwater stream near Saddle Hill, South Andaman (Coll. J. Wood-Mason) deposited at Crustacea Section, Zoological Survey of India, Kolkata, India.

Description: Rostrum ( Fig. 4 A ) abruptly terminates in a comparatively broad apex, armed ventrally with 2–6 discrete teeth, almost reaching the middle of the second antennular peduncle. Carapace ( Fig. 4 B ) scabrous with minute spines; antennal spine well developed, situated below the orbit. Eyes well developed; cornea broader than stalk. Hepatic spine absent; branchiostegal spine sharp, situated on anterior margin of cephalon, pointed forward.

Abdomen segments rough, textured, first to third pleura broadly rounded; fourth subtriangular,fifth subrectangular and sixth pleuron with a distal blunt edge at the posterodistal margin.

Antennular peduncle ( Fig. 4 C ) three segmented. The second and basal segment of the antennular peduncle is subequal in length. Second segment is 1.46 times as long as the terminal segment.

Scaphocerite ( Fig. 4 D ) large, rectangular, 2.6 times as long as the width, lateral margin straight, sharply pointed in disto‐lateral end.

Telson ( Fig. 4 E ) conical and slender with 5 to 6 pairs of dorsal spines, posterior tip with 3 to 5 pairs of long plumose setae presents in between the spines. Telson terminated with a conical spine at the apices, close to 17 to 19 spines on the dieresis of the lateral branch of the uropod.

Endopod of first pleopod ( Fig. 5 F ) of the males is 1.7 times as long as wide. The endopods has no appendix interna and no cincinulli. In females ( Fig. 5 G ), endopods are abundant with plumose setae along the margins. The endopod appears as an extension projecting anteromedially, and terminates in a subtle, elongated hook-like structure. The endopod of the second pleopod of the female ( Fig. 5 H ) extends up to approximately 1.69 times the length of the appendix interna.

First pereiopod ( Fig. 5 I ) smooth, slender and elongated in form. Chelae monomorphic (without palm). Fingers tipped with brushes of long setae adapted for filter feeding. Carpus is triangular and noticeably shorter than merus and ischium.

Second pereiopod ( Fig. 5 J ) slightly longer than the first pereiopod, smooth, slender and elongated in form. Chelae monomorphic (without palm). Fingers tipped with brushes of long setae adapted for filter feeding. Carpus is triangular and noticeably shorter than merus and ischium. Merus 1.03 to 1.1 times longer than ischium.

Third pereiopod ( Fig. 5 K ) stout, covered with numerous minute spines. The merus bears 1 to 4 prominent spines. Merus 3 to 3.62 times longer than ischium; 1.5 to 2.5 times longer than carpus; 1.3 to 2.1 times longer than propodus. The dactyl of the third pereiopod bears 4 to 6 flexor spines.

Fourth pereiopod ( Fig. 5 L ) stout, covered with numerous minute spines. Merus is 2.3 to 3.2 times longer than ischium; 2.1 to 3.6 times longer than carpus; 1.7 to 2.4 times longer than propodus. The merus bears 3 to 4 prominent spines. The dactyl of the fourth pereiopod bears 4 to 5 flexor spines.

Fifth pereiopod ( Fig. 5 M ) propodus 1.42 times longer than carpus; 1.2 times longer than merus; 2.5 times longer than ischium. Merus bears 2 meral spines. The dactyl of the fifth pereiopod bears numerous spinules along the flexor margin.

Variation: Ventral rostral teeth in the five examined specimens (n=5): two specimens with 2 teeth, one specimen with 3 teeth, one specimen with 4 teeth, and one specimen with 5 teeth.

Live colouration: A broad pale streak in the dorsal midline extending from the tip of the rostrum to the end of the telson. The carapace was marked with 6 longitudinal stripes outlined with dark pigment. The front part of the abdomen had about four similar stripes that merged into two stripes on the fifth segment. The three posterior pairs of pereiopods are almost translucent with pale white coloured. The proximal end of the dactyl is brownish black ( Fig. 3 A, B ).

Habitat: Mulki—Pavanje estuary ( Fig. 2A, B ) The collection area is subjected to tidal influence due to its close proximity to the Arabian Sea. The estuary’s topography is predominantly sandy substrate, with its banks lined by mangroves, scattered driftwood and leaf litter, creating an ideal ecosystem for aquatic life. During monsoons, this area becomes almost inaccessible due to strong currents and high water levels. Conversely during summers, the water level drastically reduces, creating isolated pools along the margins which are particularly evident during low tide periods.

Kuakhai River ( Fig. 2 C, D ) The collection area is a freshwater environment that remains free from the influence of brackish water year-round. The topography of the collection site is characterized by strong currents with sandy gravel substrate and marginal vegetation.

Distribution. Greater Sunda Islands, Japan (Ryukyu), Taiwan, Indonesia, Micronesia, Samoa ( Cai et al, 2007) and Philippines Islands ( De Grave and Fransen, 2011), Sri Lanka (De Silva 1983), Andaman Islands ( Costa 1984). Now confirmed from mainland India.

Remarks. The major morphological differences distinguishing Atyopsis moluccensis and Atyopsis spinipes are in the shape and armature of the rostrum. A. moluccensis possesses a rostrum that gradually tapers to a slender apex with 7–16 (commonly 10–14) indistinct ventral serrations, and the endopod of the male first pleopod is less than 1.5 times as long as its maximum width. In contrast, A. spinipes exhibits a rostrum that narrows rather abruptly to a somewhat broad apex with 2–6 discrete ventral teeth. The species identification of A. spinipes was further supported by molecular phylogenetic analysis of 16S rRNA markers ( Fig. 6 ).

Molecular identification. BLASTn analysis revealed that the 16S rRNA gene sequence of the specimen was 96.15%—97.18% similar to A. spinipes (with GenBank accession No. EF489996 , DQ681282 , KP725501 , KP725500 , OR417093, PP455325, PP455323, PP455322, PP455324, PP455326). The phylogenetic analysis based on an ML tree constructed using a single mitochondrial gene fragment (16S rRNA—489 nucleotide sites) resulted in a tree topology that A. spinipes from the present study (PX369075 & PX369076) is closely related to the same species previously reported in the East Timor, Vanuatu, Samoa and Solomon Islands ( Page et al., 2008; Aznar-Cormano et al., 2015; Page et al., 2007). Out of 489 sites, 92 were parsimony informative sites. In the ML tree, A. spinipes from India formed a separate sub-clade, sister to A. spinipes from other biogeographical locations ( East Timor, Vanuatu, Samoa and Solomon Islands). Atyopsis moluccensis was found to form a separate clade along with Atyopsis sp. ( EU868634 , KF023110 ). Hence, these two sequences are identified to be of Atyopsis moluccensis . As expected, outgroups Australatya and Atyoida formed separate clade sister to the genus Atyopsis ( Fig. 6 ).

Additionally, the calculated pairwise genetic distance of 16S rRNA gene fragment using the Kimura-2 parameter revealed that the genetic distance of 2.2% to 3.3% was calculated between A. spinipes of the present study and the existing sequences of A. spinipes in the NCBI GenBank from Indonesia, Solomon Islands, Samoa, East Timor and Micronesia. While A. spinipes showed around 6.1% to 7.1% genetic distance with A. moluccensis . Further, the genetic distance between A. spinipes and members of the other closely related genera such as Atyoida and Australatya was more than 11% ( Table 2).

Figures

FIGURE 2. (A, B) Habitat of Atyopsis spinipes in Mulki—Pavanje estuary of Dakshina Kannada district in Karnataka. (C, D) Habitat of Atyopsis spinipes in Kuakhai river of Khordha district in Odisha. (Image courtesy: A & B: Rakesh Kote; C & D: Abhisek Mishra.)

FIGURE 3. Live colouration of Atyopsis spinipes. (A) Odisha specimen; (B) Karnataka specimen. (Image courtesy—A:Abhisek Mishra; B: Maclean Antony Santos).

FIGURE 4. Atyopsis spinipes (Icr-1027). Female specimen, TL 47 mm, CL 17 mm. A, anterior part of carapace, eyestalks and frontal appendages, lateral; B, same as in A, dorsal; C, antennal peduncle, dorsal; D, scapocerite, ventral; E, telson, dorsal. (Scale bar: A, B, E = 2.0 mm; C, D = 1.0 mm).

FIGURE 5. Atyopsis spinipes (Icr-1027). Female specimen, TL 47 mm, CL 17 mm. F,1st pleopod of male (TL 24 mm, CL 11 mm), anterior; G, 1st pleopod of female, anterior; H, 2nd pleopod of female, anterior; I, 1st pereiopod, mesial; J, 2nd pereiopod, mesial; K, L, M, 3rd, 4th, 5th pereiopod, mesial. (Scale bar: F, G–I, K–M = 1 mm; J = 2 mm)

FIGURE 6. Molecular phylogeny (ML) of Atyopsis spinipes and allied species based on the mitochondrial 16S rRNA marker. Numbers above or below the branches represent the bootstrap values obtained from ML analysis.