Introduction

The family Labridae is one of the most specious marine ichthyofaunal group with valid 668 species belonging to 76 valid genera, of this 45 species were described in last decade (Fricke et al. 2023). The fishes of the family Labridae are prominently known and collected for ornamental trade in all around the world waters (Randall 1986). The genus Cirrhilabrus Temminck and Schlegel (1845) comprises of tiny, bright-coloured and planktivorous labrid fish group, also commonly called fairy wrasses, which mostly dwell in the rubble slopes of tropical coral reefs of the Indo-Pacific Ocean (Tea et al. 2018). This is the second speciose genus of the family Labridae after Halichoeres with 64 valid species (Fricke et al. 2023). Extensive usage of scuba gear in the past few years resulted in the description of many new species and also the distributional status of the various species of this group around the world (Allen and Hammer 2016, 2017; Tea and Gill 2017; Tea et al. 2018, 2019, 2020, 2021). Even though 64 valid species exist, Cirrhilabrus exquisitus Smith 1957 was the only species documented from the Indian waters (Mohapatra et al. 2020). The Ruby longfin fairy wrasse, Cirrhilabrus rubeus Victor 2016 was originally described based on three specimens collected from the Sri Lankan waters and Maldives.

The genus Paracheilinus are small-sized (~ 70 mm standard length) labrid group of fishes and commonly called ‘flasher wrasses’ owing to the eye-catching display pattern of males during courting and are mostly inhabiting rubble bottoms or algal beds of outer reef slopes at the depth of 5–70 m and widely distributed along the Indo-Pacific Ocean (Allen et al. 2016). The genus Paracheilinus is currently comprised of 20 valid species (Allen et al. 2016; Fricke et al. 2023). Among them, only 5 species are distributed along the Indian Ocean and the Red Sea viz., Paracheilinus attenuatus Randall 1999 (distribution: Western Indian Ocean: Seychelles and Kenya), Paracheilinus hemitaeniatus Randall and Harmelin-Vivien 1977 (Southwestern Indian Ocean: KwaZulu-Natal (South Africa) to Southwestern Madagascar), Paracheilinus mccoskeri Randall and Harmelin-Vivien 1977 (Indian Ocean: East Africa, Persian Gulf and the Comoro Islands, Maldives to the Andaman Sea and Pulau Weh, western Indonesia), Paracheilinus octotaenia Fourmanoir 1955 (Red Sea, Northwestern Indian Ocean: Gulf of Aden, Socotra), Paracheilinus piscilineatus (Cornic 1987) (Southwestern Indian Ocean: Mauritius [Mascarenes endemic]) (Fricke et al. 2023). Along the Indian coastal waters, hitherto no species of the genus Paracheilinus was documented to date (Ramakrishna et al. 2010; Joshi et al. 2016; Jayakumar et al. 2016; Rajan and Mishra 2018; Mohapatra et al. 2020; Rajan et al. 2021).

In this study, we have presented the new distributional record of Cirrhilabrus rubeus and Paracheilinus mccoskeri from the Indian waters with morphology, meristic, and phylogenetic discussion.

Materials and methods

Five wrasse specimens were collected during the samplings at the Kasuwari Island (8° 52’ 13.58’’ N; 78° 13’ 11.71’’ E), Gulf of Mannar, Bay of Bengal, Indian coast, using a scoop net at low tide. Specimens were photographed in freshly dead condition. The collected specimens were identified following Randall and Harmelin-Vivien (1977), Allen et al. (2016) and Victor (2016). For the meristic and morphometric documentation, Randall and Masuda (1991) and Allen et al. (2016) were adopted, using a digital Vernier calliper to the nearest 0.1 mm and values are given in Tables 1 and 2 as percentages of the standard length (SL). Further the specimens were preserved in 10% formaldehyde for taxonomy studies and deposited in the National Fish Repository Museum of the ICAR-National Bureau of Fish Genetic Resources, Lucknow India, for future references. .

Table 1 Morphometric measurements of Cirrhilabrus rubeus as percentages of the standard length collected from the Gulf of Mannar, Bay of Bengal
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Table 2 Proportional measurements of Paracheilinus mccoskeri collected from the Gulf of Mannar, Bay of Bengal, expressed as a percentage of the standard length
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Molecular Analysis

Part of the right-side pectoral fin was taken after sedation and subsequently preserved in 99.9% ethanol for molecular analysis and this has been done before preserving the specimen in formalin. The DNA was extracted following the Origin Marine DNA Kit Premium protocol (Kerala, India) and partial mitochondrial cytochrome oxidase subunit 1 (COI) was amplified using Ward et al. (2005). PCR amplification and analysis were performed following Kodeeswaran et al. (2022). Newly generated sequences were edited aiding BioEdit version 5.0.9 (Hall 1999) and deposited in GenBank (OM802842–OM802843 and ON016082). The evolutionary tree was reconstructed using the Kimura 2-parameter distribution model and 1000 bootstrap replicates using MEGA X software (Kumar et al. 2018).

Results

Cirrhilabrus rubeus Victor 2016.

Ruby Longfin Fairy Wrasse

Materials Examined

NBFGR/LABCRUB.1, 1 specimen, 49.6 mm SL, Gulf of Mannar (8° 52’ 13.58’’ N; 78° 13’ 11.71’’ E), East coast of India, Bay of Bengal at 5–6 m depth. Coll. on 17 December 2021, coll. by Mohan.

Description

Dorsal rays XI, 9; anal rays III, 9, pelvic rays 5; pectoral rays 15; caudal rays 15 and segmented; pored lateral-line scale 16 + 7 (+ 1 over caudal-fin base); scales beneath dorsal-fin origin to lateral line 2; 3 median pre-dorsal scales; 5 scales in a row on cheek beneath eye; gill rakers 13. Moderately elongate body, depth 3.8 in SL; body relatively compressed, width 2.1 in body depth; dorsal view of head fairly straight, slightly convex on nape; head length (HL) 4.5 in SL; pointed and short snout, length 3.0 in HL; eye orbit 3.1 in HL; interorbital width 3.1 in HL; least depth at caudal peduncle 2.0 in HL. Mouth tiny and oblique; 3 canine teeth pairs on each side of the anterior upper jaw, longer and laterally recurved at posterior portion. Cycloid scales, head scaled, snout, lips, interorbital space, ventral and posterior edge of preopercle scaleless; a row of large scales beneath the eye on the cheek; dorsal- and anal- fin base with a row of large, elongated scales; 3 scales at caudal-fin base. Dorsal fin origin above the second lateral-line scales; first two dorsal-fin spines comparably longer than following spines, with greatly elongated filamentous membrane; first dorsal-fin spine 3.0 in HL; ultimate dorsal-fin spine 2.0 in HL; first filamentous dorsal-fin membrane 5.3 in SL; second filamentous dorsal-fin membrane 5.6 in SL; longest dorsal-fin soft ray 1.6 in HL; anal-fin origin beneath the penultimate dorsal-fin spine; first anal-spine 3.9 in HL; second anal-spine 3.4 in HL; third anal-fin 3.1 in HL; anal fin longest soft ray 1.5 in HL; rounded caudal fin, 1.0 in HL; pectoral-fin length 1.3 in HL; pelvic-fin origin below the dorsal base of pectoral fin, fairly elongated and reaching well before the anal fin, its length 4.9 in SL.

Colouration of freshly dead specimen

Head and body brilliant red to reddish-orange, posterior body darker red and anterior body red-orange. Notably, black stripe present below the orbit passes throw the mid-pectoral-fin base; pectoral fin clear with a reddish tinge; pelvic fin dark red; dorsal fin base bright red, yellowish-orange distally; anal fin reddish; caudal fin red-orange with reddish base (Fig. 1).

Fig. 1
figure 1

Cirrhilabrus rubeus (49.6 mm SL; NBFGR/LABCRUB.1) collected from the Gulf of Mannar, Bay of Bengal

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Colouration of formalin preserved specimen

Body colour turned tan, dorsal, anal and pectoral fin mostly translucent; reflective pigmentation marking persist as dark markings on dorsal- and anal-fin rays; pelvic fin completely dusky.

Molecular analysis

In the present study, the intra-specific genetic divergence value with 0% was exhibited between the present samples and the specimens from Sri Lanka and Maldives. Cirrhilabrus rubeus forms a monophyletic clade with Cirrhilabrus rubriventralis by a genetic distance of 2.8% followed by 2.9% with Cirrhilabrus naokoae and Cirrhilabrus joanallenae, 3.1% with Cirrhilabrus hygroxerus and 3.2% in Cirrhilabrus africanus (Fig. 2).

Fig. 2
figure 2

Phylogenetic position of Cirrhilabrus rubeus based on the maximum likelihood analysis

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Distribution

Indian Ocean: Sri Lanka and Maldives; present study, first record from Indian waters.

Paracheilinus mccoskeri Randall and Harmelin-Vivien 1977.

McCosker’s Flasher

Materials Examined

NBFGR/LABPMCC.1–4, 4 specimens, 47.9–56.3 mm SL, Gulf of Mannar (8° 52’ 13.58’’ N; 78° 13’ 11.71’’ E), East coast of India, Bay of Bengal at 5–6 m depth. Coll. on 17 December 2021, coll. by Mohan.

Description

Dorsal fin IX, 11; anal fin III, 9; pectoral rays 14 including upmost rudimentary ray; pelvic fin I, 5; principle caudal rays 13; lateral-line scales 16–17 + 9; 2 scales beneath dorsal-fin origin to lateral-line; 6 scales above anal-fin origin to lateral-line; 16 circumpeduncular scales; gill rakers 13–14; vertebrae 25.

Body depth 3.8–4.2 in SL; body width 1.7–2.0 in body depth; head length (HL) 3.5–3.7 in SL; snout length 3.4–3.7 in HL; eye diameter 3.9–4.2 in HL; interorbital width 3.0–3.7 in HL; least caudal-peduncle depth 2.2–2.9 in HL; caudal-peduncle length 1.3–1.5 in HL; pelvic fin, 1.5–2.0 in HL. Mouth smaller, terminal; maxillary almost reaching the anterior eye edge, only lower edge of premaxillary visible, when mouth closed. Canine teeth three pairs, located anteriorly at upper jaw, median two pairs projected forward and laterally curved downwards; third pair larger projecting outwards and posteriorly curved downwards. Gill rakers short, smaller nostril, posterior nostril positioned before the upper eye margin, short tubular anterior nostril located beneath the anterior edge of posterior nostril.

Head with comparatively large scales; chin, interorbital space and snout region scale-less; a couple of scale rows on cheek present in between preopercular margin and eye orbit; single row of large pointed scales on dorsal-fin base; moderate row of scales on anal-fin base; very larger scale covers half the caudal-fin base; pelvic fin scale-less, two mid-ventral scales before the pelvic-fin origin. 11 prominent pores around the eye orbit, 2 pores at upper interorbital space, 2 pores on each side of the upper snout, front of the nape with 3 pores in a curvilinear line, single pore at the upper end of preopercular margin, mandibular pores 4 in a series running to lower preopercular series.

Slightly rounded caudal fin; dorsal fin origin above second or third lateral-line scale, somewhat at level of pectoral-fin base; first dorsal-fin spine 9.7–11.4 in HL; size increasing posteriorly; last dorsal spine 1.6–2.0 in HL; prolonged first dorsal ray 2.3–2.7 in SL. Anal fin origin, below the base of first dorsal ray, first anal spine fairly long 2.6–3.6 in HL; third anal spine 1.8–2.8 in HL; longest anal-fin soft ray seventh or eighth, 1.0–1.2 in HL; pectoral fin moderately short, reaches the anterior to anus, 1.2–1.3 in HL. Pelvic fin short, origin at the level of pectoral-fin ventral base.

Colouration of freshly dead specimen

Body reddish with series of reddish-orange stripes or bands on body and head, a short band from snout to the middle eye, a band running below the eye orbit and continues up to opercular lower edge, another band commencing at posterior-dorsal margin of eye and lasts to short distance at upper body. Three reddish-orange with blue tinge coloured stripes or bands on body, uppermost stripe commences at posterior half of body and continues up to caudal peduncle base, middle stripe short, passes just above the pectoral-fin base and reaches up to the level of anal rays, lowermost stripe from posterior-ventral margin of pectoral-fin base and continues up to lower caudal peduncle base; dorsal fin bright orange anteriorly, thin stripe runs across the middle with consolidating dark orange spot with bluish margin, dorsal-fin soft ray base with brilliant orange spots in variable length-ranges; anal fin prominent red with pale orange at base; caudal fin yellowish-brown with dark reddish band at the base with thin blue margin, extremity of caudal fin with a thin reddish band; pectoral translucent; pelvic fin mild yellow with striking reddish on outer portion; eye reddish with dark pupil (Fig. 3).

Fig. 3
figure 3

Fresh colouration of McCosker’s flasher Paracheilinus mccoskeri (56.3 mm SL; NBFGR/ LABPMCC.4) collected from the Gulf of Mannar, Bay of Bengal

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Colouration of formalin preserved specimen

Body turns pale to brownish, caudal-fin base and posterior caudal peduncle darker; reddish-orange stripes or bands turns dark brown; dorsal-fin base pale darker with clear distal margins, translucent spots on dorsal-fin soft rays; pectoral and pelvic translucent; anal fin faint milky white; eye turned tan with dark pupil (Fig. 4).

Fig. 4
figure 4

Formalin preserved colouration of McCosker’s flasher Paracheilinus mccoskeri (56.3 mm SL; NBFGR/ LABPMCC.4) collected from the Gulf of Mannar, Bay of Bengal

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Molecular analysis

The genetic divergence value of mitochondrial COI region between P. carpenteri and P. mccoskeri was 5.6%, whereas the value between P. mccoskeri and P. flavianalis was 5.4% and 5.8% genetic distance was perceived between P. rubricaudalis and P. mccoskeri. The maximum likelihood tree (Fig. 5) reveals that P. mccoskeri forms a distinct separate clade with a maximum bootstrap value of 100 than the other congener in the mccoskeri species-complex group, which may be due to P. mccoskeri being the only species distributed in the Indian Ocean, whereas the other three species are habitat along the Pacific Ocean.

Fig. 5
figure 5

Phylogenetic position of Paracheilinus mccoskeri based on the maximum likelihood analysis

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Distribution

Indian Ocean: Kenya, Comoro Islands, Persian Gulf (Jana Island and Saudi Arabia), Oman (Randall 1995), Chagos Archipelago (Winterbottom and Anderson 1997), Maldives (Randall and Anderson 1993), Andaman Sea and Sumatra, westernmost document at Pulau Weh, Indonesia (Allen et al. 2016) and the present documentation from the Gulf of Mannar, east coast of India.

Discussion

Meristic and morphological analysis were indistinct diagnosing characters for the species of genus Cirrhilabrus, though dorsal, caudal and pelvic fins shapes often play a vital role in distinguishing this species. The most useful diagnostic character was the terminal phase (TP) male colour pattern which was more escalated during spawning and courtship that happens daily around 1–2 h before the sunset (Allen and Hammer 2016). Molecular confirmation, using mitochondrial COI gene plays an energetic role in species demarcation among these species in sub-adult or juvenile stages, which does not express the TP colour pattern and that the DNA does not change with maturity stages or sex. The specimen examined in the present study does not show the colour pattern and showed the deviation in morphometric characters as described in the type specimens, it may be due the examination of the juvenile specimen in the present study which does not show TP colour pattern or geographic distribution (Randall 1986) or also may be due to examination of very limited numbers of type specimens, but the genetic analysis confirmed that the species exhibit 0% genetic diverge from type specimens from Sri Lanka and the Maldives, which was fitted with the threshold value of 2% (Ward et al. 2009).

Cirrhilabrus exquisitus was the only species of this genus recorded from Indian waters, i.e. only from Lakshadweep (Rajan et al. 2021; Sandra et al. 2022) and there was no other species in this genus documented from coastal waters of India, including Lakshadweep (Mohapatra et al. 2020) and Andaman and Nicobar Islands (Rajan and Mishra 2018). The present study forms the first documentation of Cirrhilabrus rubeus from the Gulf of Mannar, east coast of India, assured the addition of one more ichthyofauna from Indian waters.

Like other labrid species, flasher wrasses also exhibit protogynous sex reversal, males and females show different colour patterns during ontogeny. Hence, the colour pattern of the terminal-phase male is used as a diagnostic character to distinguish this species group (Allen et al. 2016). Several other diagnostic characteristics include dorsal fin shape, specifically the presence and absence of elongated filamentous dorsal-fin rays; caudal fin shape, etc. The species of the genus Paracheilinus can be divided into 4 groups. Among them, P. mccoskeri is the only Indian Ocean species of the mccoskeri group, which shares similar rounded caudal fin and elongated dorsal-fin rays (Allen et al. 2016) with the closely related three species from the Pacific Ocean viz. Paracheilinus carpenteri Randall and Lubbock 1981 distributed in Western Pacific: Philippines and the South China Sea; Paracheilinus flavianalis Kuiter and Allen 1999 from Indonesia and North-western Australian waters and Paracheilinus rubricaudalis Randall and Allen 2003 from Papua New Guinea, Vanuatu, and Fiji waters. Paracheilinus mccoskeri differs from P. carpenter, having a single mid-anterior stripe in the body (vs. double in P. carpenteri, see Fig. 21 in Allen et al. 2016); it differs from P. flavianalis with reddish anal fin (vs. yellow in P. flavianalis); differs from P. rubricaudalis with the presence of bluish-red spots on dorsal-fin soft ray (vs. absence of blue spots on dorsal-fin rays; in P. rubricaudalis) (Allen et al. 2016).

In the past few years, numerous studies engaged in the documentation, diversity and distributional status of various labrid species from the Gulf of Mannar as well as from the several parts of Indian waters which resulted in the documentation of several new distributional records and diversity and distribution patterns of labrid fishes in Indian waters (Prakash and Kumar 2016; Pradhan et al. 2019; Mohanty et al. 2021; Jayakumar et al. 2020; Kodeeswaran et al. 2022). Nonetheless, there is no material evidence for the documentation of the species belonging to the genus Paracheilinus from Indian waters including Lakshadweep Archipelago and Andaman & Nicobar Islands (Rajan and Mishra 2018; Mohapatra et al. 2020; Rajan et al. 2021). The present report of Paracheilinus mccoskeri from the Gulf of Mannar forms the first documentation of the genus Paracheilinus from Indian waters as well as extended distributional range of P. mccoskeri by about 800 km from its nearest reported location in south-west direction, i.e. Maldives, Indian Ocean.