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First record of Thysanozoon brocchii (Platyhelminthes: Polycladida) from Indian waters

Marine Biodiversity Records201710:21

https://doi.org/10.1186/s41200-017-0123-0

Received: 15 April 2016

Accepted: 6 February 2017

Published: 28 July 2017

Abstract

This work reports the occurrence of Thysanozoon brocchii from the rocky intertidal coast of Ratnagiri and Dwarka, the West Coast of India, for the first time. Two morphotypes were found, the first morph has a buff brownish papillate dorsal surface, with few specimens having white spots. The second morph has light coloured papillae which form a distinct cross marking along the dorsal surface. The species possesses double male copulatory apparatus with seminal vesicle, prostatic vesicle and sclerotized stylet. This cosmopolitan species has previously been recorded from Italy and Mediterranean, Japan, South and West Africa, Florida, New Zealand, Brazil, and United Kingdom. Synonymized species and older descriptions have been compared to examine similarities and dissimilarities. Considering the existence of varied colour morphs of this species, a detailed comparative analysis of morphological characters, reproductive histology and molecular framework is recommended.

Keywords

PseudocerotidaeColour patternsIntraspecific variationsReproductive anatomyCosmopolitanMaharashtraGujarat

Introduction

Polyclad flatworms are free living members of the phylum Platyhelminthes. These coral reef and rocky shore inhabitants are more diverse in the tropical environment (Prudhoe, 1985). Cryptic behavior, apparent specificity with food preference, aposematic colouration and mimicry with opisthobranch molluscs and fishes (Ang & Newman 1998; Newman & Canon, 2005) make them potentially significant in intertidal or reef ecology.

Members of the family Pseudocerotidae are peculiar for their brilliant colour patterns. However, colour variation is commonly seen forming species complex in their systematics. Perhaps such complexities arising in the taxonomy of these worms can be resolved by careful observations of external as well as reproductive anatomical features. Newman and Canon (1995) described three species of the genus Pseudoceros from the Indo-Pacific region showing remarkable similarity within external appearance. They, too, emphasized the significance of precise documentation of colour and patterns. Litvaitis, et al. (2010) tested the coloration pattern of Pseudoceros bicolor complex against molecular evidence and emerging complexities in the taxonomy of the same.

Grube (1840) described the genus Thysanozoon considering the papillate dorsal surface, unlike the rest of the Cotylean genera. Type species of the genus was Thysanozoon diesingii, which has later been synonymized for T. brocchii. This genus includes about 23 species worldwide (Tyler, 2013). Laidlaw (1902) reported Thysanozoon plehni from the Laccadive Island of India. However, this species has been reviewed and assigned to Acanthozoon plehni. After a gap of about a century, Apte and Pitale (2011) mentioned a member of this genus from Kavaratti, Lakshadweep Island, India. Later, Sreeraj and Raghunathan (2013) reported Thysanozoon nigropapilosum from South Andaman.

The present study reports Thysanozoon brocchii for the first time from the Indian shoreline. Apart from external morphology and reproductive anatomy, the study encompassed the review of characteristic features of some of the synonyms and a few previous descriptions, and their comparisons with the two different morphs presented herein.

Materials and methods

Collection was carried out during the daytime low tide by handpicking the worm using a paint brush, within the littoral area of Ratnagiri (Mandvi 16.98758° N 73.27486° E), Maharashtra state and Dwarka (22.240323° N 68.957424° E), Gujarat state, West Coast of India (Fig. 1). Presence of heterogeneous habitat is a common characteristic of both these shores, and pebbles, cobbles and rock pools of various sizes and depths are found at various zones. Luxuriant growth of algae and patches of coral-rubble were observed during surveys.
Fig. 1

Geographical distribution of Thysanozoon brocchii from Ratnagiri and Dwarka, West Coast of India. Courtesy: Google earth

Photographs were taken in the wild as well as ex situ to record true colour and pattern. Animals were then fixed in 10% frozen buffered formalin and later stored in 70% ethanol for long term preservation (Quiroga et al., 2004). Studies on key anatomical features were carried out using a Stereo Microscope (Leica EZ4 D). The systematic classification system established by Faubel (1984) was followed. Longitudinal serial sections of the reproductive system (6 μm) were obtained by specimen (Pclad-0044) embedding in paraplast and staining with hematoxilin and eosine. Remaining specimens are deposited in collections of the Bombay Natural History Society.

SYSTEMATICS.

Order POLYCLADIDA Lang, 1884

Suborder COTYLEA Lang, 1884

Family Pseudocerotidae Lang, 1884

Genus Thysanozoon Grube, 1840

Thysanozoon brocchii Risso, 1818

Material examined

Two specimens (11.49 mm × 8.32 mm and 11.30 mm × 8 mm, preserved) found under rock pebble at Mandavi, Ratnagiri, 9 May 2012 (BNHS_Pclad-0044) as 18 histological slides.

One specimen (10.2 mm × 8.5 mm preserved) found under rock pebble within algae at Dwarka, Gujarat, 12 December 2012 (BNHS_Pclad-0080).

Diagnosis

Brown-buff to cream dorsal surface with yellowish brown to dark brown papillae cover, margin with pinkish tint; ends with white dotted line. Papillae from median longitudinal line are lighter thus distinct, transverse line of light coloured papillae about 1/3rd posterior to longitudinal length also present in single specimen (Pclad-0080); double male reproductive structures; elongated vagina.

Description

The first morph (BNHS-Pclad-0044) is broadly oval, oblong body and found slightly raised medially. Dorsal surface covered with papillae which are aggregated in median region, diminish in size, and become scarce towards margin and found absent a little above the margin. Papillae are approximately cylindrical (0.3 mm–0.4 mm), knob-like or even tapering in the same specimen.

Dorsal surface, ground colour is buff-brown-creamish with black median longitudinal stripe. Yellowish reticulation of intestinal branches observed prominently towards margin. Pinkish tint found towards periphery, and a dotted white line on the rim. Papillae are buff-brown to dark brown having grayish outline and some possess white spots around the tip. Papillae present over median longitudinal stripe are mostly distinct, tapering, and lack brown pigments. These papillae are creamish or whitish, possess white dots and run antero-posteriorly. Pseudotentacles are held erect; they are ear-like, creamish brown and with white tip. On the inner margin of each pseudotentacle, a fine black line that runs towards the median stripe can be observed. Cerebral eyespots (30–34) arranged in horseshoe-shaped cluster (size 0.27 mm), present within the colourless area just posterior to the pseudotentacles (Fig. 2c). Pseudotentacular eyes are found distributed as four clusters dorsally and two clusters ventrally. Dorsal cluster bears about 40–45 eyespots whereas ventral cluster bears about 50–60 eyespots.
Fig. 2

Thysanozoon brocchii Risso, 1818: a (1st morph) under pebble within the rock pool (b) 2nd morph (c) anterior end with cerebral eyespots (ce), pseudotentacular eyespots (pe); (d) ventral surface showing pharynx (ph), Mouth (mo) male gonopore (mp), female gonopore (fp), sucker (su); (e) Sagittal section of male reproductive system with male antrum (ma), prostatic vesicle (pv), stylet (st); (f) female reproductive structure with vagina (vg), cement pouch (cp), cement gland (cg), Intestine (it); (g) ventral testes and dorsal papillae

Another morph (BNHS-Pclad-0080) has creamish dorsal surface and yellowish reticulation noticed especially towards margin (Fig. 2b). Dotted white line delineates the margin. Brown coloured papillae are cylindrical, pointed, with white spots around the tip. Papillae present over median longitudinal and transverse line are creamish, possess white spots and form a cross-like marking. Black-brown pigments of the median stripe can be seen over anterior region and on the pseudotentacles.

The two morphs described above are similar in terms papillae arrangement, median lighter papillae and margin colouration. The papillae shape in second morph is cylindrical and white dots present over each papillae are more numerous than the first morph. Ground colour is creamish and papillae colour is darker and colour tone is more even in second morph as in the first one. Considering the distinctive colour pattern of second morph the single specimen has been kept intact and not been sectioned for histology.

Semi-transparent whitish ventral surface, with a mouth, opening medially within pharynx and about 3.01 mm distant from anterior margin (Fig. 2d). Pharynx is in the form of 4–5 simple and shallow folds and about 4.68 mm long. Two male gonopores are present immediately behind the pharynx, on either side of the median line and about 1.24 mm distant from each other. Medially placed, female gonopore is present 0.71 mm posterior to the male gonopore followed by sucker (0.46 mm from fp).

Double male copulatory system with numerous testes (0.02 mm to 0.04 mm in length) arranged in 2–3 rows located ventrally. Seminal vesicle (0.14 mm × 0.064 mm) is muscular, slightly oval, bent and pointed at its anterior end (Fig. 2e). Vas deference arranged laterally, visible through ventral side and runs posteriorly. Small and oval prostatic vesicle (0.0435 mm × 0.0342 mm) found ventral to the seminal vesicle. Penis with stylet found further down to the seminal vesicle, probably contracted or bent during fixation, as it is visible only in the form of a rounded structure (Fig. 2e). Male atrium is shallow (0.045 mm).

Female reproductive system consists of ovaries which are found scattered dorsally. Female antrum is narrow, with minute lateral invagination for cement pouches. Vagina elongated backward (0.2 mm) and cement glands are seen spread around vagina (Fig. 2f).

Taxonomic remarks

In taxonomic study of pseudocerotidae, the genus Thysanozoon is difficult, probably due to the unavailability of enough details in the older literature. Body colour pattern, papillae shape, their colour and distribution are important features in the taxonomic study of this genus (Brusa et al., 2009). The specimens (BNHS_Pclad-0044 and 0080) somewhat fit with the original description of Risso, 1818 and specimens described later (Palombi, 1928; Pearse, 1938; Marcus and Marcus, 1968; Brusa et al., 2009 and Bahia et al., 2012, 2014) from different parts of the world.

About twenty species described earlier have later been synonymized for T. brocchii (Faubel, 1984). Table 1 gives the review of the characters noted from these synonyms.
Table 1

Review of the characters from synonymized taxa of Thysanozoon brocchii

Synonymized taxa

Body form

Colour -pattern

Eye spots/arrangement

Habitat/Locality

Remarks

Tergipes dicquemare Risso, 1818

oblong, flattened,

Dorsal: covered with many sessile papillae serving as respiratory organ, tentacles earlike,

Ventral: greyish

Dorsal

White- yellowish Intestinal canal - white –reddish

-

Under stone

Nice sea, France

-

Planaria tuberculata Delle chiaje, 1828

compressed, ovate, wide

Dorsal: papillate; absent towards margin, longitudinal median line present

Dorsal

Papillae: few with white dots, median line white colour

Margin: white band even on pseudotentacles

-

Algae dweller

Naples, Italy

Not identical to Planaria brocchii described by

Risso 1818, although has certain similar characters in body colouration

Thysanozoon tuberculatum Delle Chiaje, 1828

Elliptical

Dorsal: long tentacles, median papillae with conical tip

Dorsal: Blackish

Papillae: median with white tip and bluish at the base

-

Found among algae

-

Planaria verrucosa Delle chiaje, 1829

Dorsal: papillate; more on back and smaller towards margin

Dorsal

Margin: milky white and black

-

Naples, Italy

differs from P. tuberculata being small, colourful

margin without papillae and papillae bears white dots at the tip

Stylochus papillosus Diesing, 1836

½ - 1-1/2 in.

narrows ovate flattened

Tentacles: filament like, medially raised (keel on the middle)

Papillae: numerous papillae present on the keel area

Dorsal: light yellow or reddish-brown keel: white

Indefinite number on the disc shape bright spot

Adriatic Sea

-

Thysanozoon diesingii Grube, 1840

flat, leaf like

Dorsal: covered with papillae (pedicels)

Dorsal: longitudinal bright yellowish line

Margin: white with purple dash lines

Eye spots 31–28

Palermo-Italy

east coast of Ceylon (Sri-Lanka) Indian Ocean

compared with Mediterranean P. brochii and P. tuberculata

and mentioned the similarity with P. brochii except for the

absence of papillae opening

Planaria dicquemari Delle Chiaje, 1841

Papillae: larger in the middle and smaller towards margin

Dorsal: Yellow, blackish speckled

Margin: whitish

In two groups at the base of the tentacles

 

differs from P. tuberculata (Delle Chiaje, 1828)

in terms of size, papillae and colour

Thysanozoon diequemaris (Delle Chiaje, 1841) Diesing, 1850

Elliptical,

Papillae: long, conical, tentacles somewhat sickle shape

Dorsal: Body greyish

Papillae: yellowish white

Ventral: Grey

-

In stones- Mediterranean Sea

-

Eolidiceros brochii

Quatrafages, 1845

regularly elliptical, slightly curved in the middle

Tentacles: triangular, Papillae

(appendages): fusiform, longer and bigger and smaller towards edges

Size: 18 mm

Dorsal: light yellowish brown, edges are transparent and bluish

Upper side of the head region is white; tinted with greenish, sides are light brown

Papillae: reddish-brown but tip is yellowish white; blackish purple dots all over the surface

Numerous

CE: 20–25

TE: group of 5–6 eyespots between the tentacles

In Fucus

Naples

May be similar to Planaria tuberculate (Delle Chiaje, 1828)

Eolidiceros panormis Quatrefage, 1845

elliptical, triangular head and straight large tentacles

Dorsal: papillate (cylindrical appendages)

Size: 6 mm × 3 mm

Dorsal: mid region yellow-greenish speckled with brown, head region white, anterior end with purple and brown pigments, transverse pale yellow band present 1/3 posterior of the body

Papillae: similar colour like body but less numerous than E. brocchii

Margin: brown speckled and purple dashes

Dorsal: 3 large eyespots

surrounded by smaller ones;

one is posterior and two are at the base of the pseudotentacles

Ventral: arranged between and at the base of the pseudotentacles

on rock

Palermo, Italy

Compared with E. brocchii for eyespots, body shape, colour pattern and arrangement of dorsal papillae

Thysanozoon fockei Diesing, 1850

Sub elliptical

Dorsal: papillated

Papillae: yellow-purple papillae

-

Tergesti, Italy

-

Planeolis panormus, Stimpson 1857

Papillae: scattered over the body; head larger and with large tentacles

-

ocelli on the tentacles at the base of the tentacles and between the tentacles

-

information about genus is given but refers to Eolidiceros panormus Quatrefage, 1845 for the species description

Thysanozoon sp. (Eolidiceros quatrefages) Moseley, 1877

Size: when expanded 10 cm × 6 cm

Dorsal: dark purple, tubercles with white tip

-

Zamboangan, Philippines

 

Thysanozoon brochii var. cruciatum Laidlaw, 1906

Size: 8–16 mm

Dorsal: yellow-dark gray, narrow longitudinal white stripe and 1/3 posterior transverse band present

-

under rock

Porto Praya,

Cape Verde Island

-

Thysanozoon lagidium Marcus, 1949

Dorsal: papillate

Size: 13x7mm

Dorsal: Grayish brown-purplish

Papillae: darker, few with white tip light coloured papillae forming longitudinal stripe and medial transverse stripe present

-

Brazil

-

Thysazonoon cf. lagidium Quiroga et al. 2004

Based on image presented in the paper

-

Dorsal

Papillae: black- brown

midline papillae whitish; whitish papillae forming cross are present around 1/3rd of body length

 

Coloumbia; Brazil

-

Tergipes dicquemare, Planaria dicquemari and Thysanozoon dicquemaris although very poorly described, seems to be similar in terms of dorsal and ventral colour pattern. Planaria tuberculata, Planaria verrucosa are similar in terms of colour and pattern. Eolidiceros panormis and Thysanozoon diesingii are nearly identical due to possession of yellow and purple pigment on dorsal surface as well as the purple dash lines on the margin. The colour pattern of Eolidiceros brochii is slightly different from the other species due to possession of reddish-brown papillae and purple dots all over the dorsal surface. Four of the synonyms viz. E. panormis, T. diesingii, T. lagidium and T. fockei are found possessing purple pigmentation on dorsal surface. Transverse bands of lighter papillae forming a cross were observed within E. panormis, T. brochii var. cruciatum and T. lagidium. The remarks section of Table 1 elaborates the comments from the authors about the resemblance of their respective specimens, either with T. brocchii or previously described allied species. Diesing (1850) reports about Thysanozoon tuberculatum and synonymizes three previously known species viz. Planaria tuberculata, Thysanozoon dicquemaris and Planaria dicquemari. Planaria brocchi and Eolidiceros brocchi are synonymised for the species Thysanozoon brocchii and Eolidiceros panormus for Thysanozoon panormus respectively. Further, Diesing (1862) while separately mentioning the genus Thysanozoon, synonymizes species which are described earlier under the varied genera viz. Planariae spec. by Delle Chiaje, Stylochi spec. by Diesing Eolidiceri spec. by Quatrefages.

Table 2 gives an account of characters mentioned from some of the older descriptions of Thysanozoon brocchii. The descriptions by Quatrefage (1845) and Lang (1884) are unvarying and collected from type locality of the concerned species. Material obtained from Japan (Yeri and Kaburaki, 1916; Kato, 1944) was found resembling the above two descriptions, especially in terms of possessing purple pigment and papillae colour pattern. Palombi (1928) differs with Lang (1884), Quatrefage (1845), Yeri & Kaburaki (1916), and Marcus and Marcus (1968) due to having exclusive brown dorsal pigment and ventral eyespot arrangements. Meanwhile, Pearse (1938) recorded the three morphs (pigmentation- brown, purple and intermediate) of the species from Crooked Island. Marcus and Marcus (1968) elaborated the reason for presence of broader female antrum in Marcus (1949) material of T. lagidium. They also discussed the external and internal anatomical, intraspecific variations within this species and finally merged T. lagidium with T. brocchii. Faubel (1984) while reviewing the polyclad systematics followed the same criteria. However, Prudhoe (1985) considered T. lagidium as a separate species. Two recent findings (Brusa et al., 2009 & Bahia et al., 2012, 2014) from Argentina and Brazil respectively show absence of purple pigments mentioned in most of the older records. Current specimens (First morph) found intermediate of all the older descriptions, but shows approximate resemblance with Bahia et al., 2012, 2014 in terms of colour-pattern and eyespots arrangement. Second morph shows close similarity with Pearse (1938) (brown morph) Quiroga et al., 2004 and Brusa et al., 2009.
Table 2

Review of the characters noted from older literature of Thysanozoon brocchii

Author

Body form

Colour -Pattern

Eye spots/arrangement

Habitat/Locality

Remark

Tergipes brocchii Risso, 1818

Oval, oblong, tubercles on the dorsal surface; tentacles ear shaped

Dorsal: violet brown;

Papillae: white dots at the end of the tubercles

Ventral: transparent

small, black

Under stones

Nice sea, France and Naples, Italy

Original description

Quatrefages, 1845

Elliptical, raised medially

Papillae: dense in the middle surface and scarce towards margin longitudinal mid-line papillae are fusiform and longer; small tubers towards margin

Size: 16 mm × 8-9 mm

Dorsal: yellowish-brown reddish; purple pigments

Papillae: brown reddish with yellowish white tip

Margin: dark brown ends with white line

Cerebral area is colourless triangular portion between pseudotentacles

CE: two groups 20–25; 5–6

PE: 5–6 smaller eyes near the edges of the pseudotentacles Ventral- 5-6 eyes placed on each tentacle; line of 7–8 large eyespots

Naples, Italy

-

Diesing, 1850

Elongated plane

Papillae: fusiform

Tentacles- thick and tuberculate

Dorsal: yellowish

Margin: white-blue

Papillae: red-brown to black -blue

Beneath, above and at the base of the tentacles

In rocks

Nice Sea; Toulouse

-

Lang, 1884

Compressed, broadly oval, oblong

Dorsal: papillate (tubers or tubes)

Papillae: bulgy at the base and tapers further; small and sparse in the longitudinal and transverse midline

Pseudotentacles: Bead shaped, sharp

Dorsal: dark brown-violet with white margin; lighter than the papillae

Papillae: whitish spots on the darker papillae, lighter in transverse and longitudinal bands, pore at the tip might be the intestinal diverticulum leading outside

Pseudotentacles: Whitish grey or dark brown-black with light colour spots

Cerebral area is lighter and clearly demarcated within pseudotentacular area

Ventral: dirty gray-blue-brownish or yellowish

CE: Horseshoe shape

PE: two roundish groups each on either side of mid-line

shallow water in

association with ascidian and sabellids,

Naples and coast of Posilipo, Italy

wide variations observed within same individuals for various characters (papillae shape, number, colour and size vary greatly),

Eolidiceros panormus is young specimen of T. brochii; sexual maturation occurs at different size

Yeri and Kaburaki, 1916

Broadly Oval, frilled margin

Size: 35 mm × 21 mm

Papillae: slender-conical, all over the dorsal surface, longer in the mid region; smaller and sparse towards the margin

Dorsal: purplish gray or yellowish purple, yellowish-whitish; longitudinal median stripe

Papillae: dark gray with purple tint, base colourless, few with whitish tip

Some specimens with whitish papillae forming transverse line

Ventral: Lighter and comparatively darker at the margin

CE: two clusters above the brain in colourless area

PE: numerous

Misaki and Matsuwa, Japan

Internal anatomy same as Mediterranean specimens,

intestinal branches extending in to the papillae

Palombi, 1928

Flatten with free wavy margin

Dorsal: surface chestnut brown except for the marginal area, space between the pseudotentacles lighter

CE: two clusters placed centrally within colourless area

PE: irregular arrangement

ventral: present within each pseudotentacles

two groups of eye clusters, further adjoining row of eyes run along the anterior margin

Suez Canal

Specimen observed matches Lang’s description of T. brochii.

T. dissingii Grube, 1840 can be considered as T. brochii

Pearse, 1938

Dorsal: Papillate

Size: 28-33 × 8-12 mm

Dorsal: cream with light yellow reticulum, black pigmentation, median longitudinal dark stripe with light line through it, anterior tentacular region blackish with unpigmented cerebral patch containing eyespots

Papillae: light brown

Papillae: purplish-brown become light brown towards margin, some with white spots and dark tips and forms ‘T’

Margin: brown-purple redial bands

-

Eel grass, Crooked Island, near Florida

Three colour morphs were collected, immature specimens

Palombi, 1939

-

-

-

Shelley beach (East London) South Africa

compare with Palombi, 1938 and Kato’s Japanese specimen and mentioned cosmopolitan distribution

Kato, 1944

Size: 50–60 mm

Dorsal: Brown colour

Papillae: brown with whitish yellow especially at median line and spread otherwise

Margin: bluish

-

Misaki, Susaki near Simoda, Sugasima, Sima, Seto- Japan

gives cross section of male reproductive system and papillae showing intestinal branch

Hyman, 1952

-

Dorsal: purplish maroon

Papillae: brown some with white spots

Margin: white spots

-

Under stones county causeway/Biscayne Bay; Florida

immature specimen thus not sectioned for reproductive histology however, intestinal branches going to papillae is observed uncertainty about the identification

Marcus & Marcus, 1968

Dorsal: Papillate, scares towards margin

Size: 15 mm × 5 mm and 24 mm × 16 mm

Dorsal: papillae are darker and become lighter towards the margin, white spots on the papillae

-

Algae and mangroves from Piscadera bay, Curacao and Florida

Broader cement pouches resulting in complex female antrum can be considered as usual intraspecific variation thus T. lagidium can be merged with T. brocchii.

Review of Lang,1884; Marcus, 1949 and Pearse, 1938 and Hyman, 1952 descriptions were made

Vera et al. 2008

elongated

Dorsal: darker to light brown ground colour, mid-dorsal longitudinal line and perpendicular white line forming cross

-

Canary Islands (Eastern Atlantic Ocean)

active swimmer

compared with Quiroga et al. 2004 Thysanozoon cf. lagidum from Colombia

Brusa et al. 2009

Oval, papillate, slightly undulated margins

Papillae:

Mid-line papillae are longer and decreases towards the periphery

Pseudotentacles: pointed ear like

Size: 25 mm × 15 mm

Dorsal: yellowish brown,

margin with discontinuous black line

Pseudotentacles: dark brown with white tip

CE: Horseshoe shape

PE: four dorsal and two ventral clusters

Puerto Pirámides and Puerto Madryn, Argentina

Followed the Marcus and Marcus, 1968 and considered the T. lagidium as synonym of T. brocchii

Bulnes et al. 2011

Oval

Pseudotentacles: enlarged distally and no pigmentation

Papillae: big bulky conical, longer and dense around dorsal bulge; declines towards margin (length and number); no papillae on the margin

Size: 26 mm × 15 mm

Dorsal: overall light brown but yellowish brown in the central became transparent towards margin; round black spots over the surface especially towards margin

CE: two separated triangular clusters

\TE: numerous single row dorsally

Ventral: scattered

In mussel and ascidians community Mar del Plata harbour, Argentina

Hypothesised papillae on surface for gas exchange and digestion as also mentioned by Prodhoe.

Bahia et al., 2012

Oval, elongated

Size: 12-17 mm × 10-14 mm

Papillae: dorsal surface with smaller towards the margin

Pseudotentacles: ear like

Dorsal: Whitish with dark brown to yellow brown pigmentation median longitudinal whitish line, some specimens with transverse line also forming cross

Some papillae with white spot

Ventral: white

CE- Horseshoe shape, 30–50 eyespots

PE- four dorsal(20–25) and two ventral clusters (65–70)

rocky and reef-flat areas Santa Rita and Búzios, Brazil

Differ in eye spots arrangement with Palombi, 1928;

Considered the presence of complex female antrum as intraspecific variation;

Emphasis on the revision of species considering the varied colour pattern and its cosmopolitan occurrence

Noreña et al. 2014

oval, oblong

Papillae: acorn-like

Colour photo reference is also available

 

Atlantic coast of the Iberian Peninsula

 

Bahia et al. 2014

Papillae: size decrease towards margin

Size: 25 × 19 mm to 7 × 6 mm

Dorsal: brown to yellowish brown with longitudinal median line cream coloured, cream transversal line, some papillae with white spots

-

Praia das Conchas, Cabo Frio, Brazil

-

Overall, compilation and comparison certainly represents the combinations of colour patterns exist between the T. brocchii species complex (Table 3). Perhaps these combinations are accountable for the current taxonomic confusion. Nonetheless, several currently synonymized species have also been synonymized previously and their progress (from genera - Tergipes, Eolidiceros or Planeolis) towards the genus Thysanozoon (after 1840) is clearly evident as one approaches from Risso (1818) to Marcus and Marcus (1968). But, several older descriptions are not even and do not cover all the criteria which can be commonly used to compare species within the complex. Faubel (1984) while revising polyclad systematics includes twenty such species as synonyms of T. brocchii. Prudhoe (1985) proposed the T. lagidium as different species based on the transfer line forming ‘T’ shape colour pattern of papillae. However, with reference to the information presented in the Table1 few more species exist with similar character and not found stated by Prodhoe (1985). Thus, for a time being T. lagidium should be consider as the synonym for T. brocchii as mentioned by Faubel (1984).
Table 3

Colour variation on each part of the colour pattern observed in the literature cited

Major colour and pattern combinations observed

Dorsal ground colour

whitish; cream; light yellow; brown; light brown; grey; dark gray; blackish; dark purple; chestnut brown; white-yellowish; yellowish brown; yellow-greenish; yellowish-brown-reddish; yellowish purple, reddish-brown; grayish-brown-purple; violet-brown; purplish gray; purplish maroon;

Ground colour-pattern

 Speckled

Black; brown

 Pigments

Purple; brown; dark brown to yellow brown

 Reticulation

light yellow

 Median stripe

dark

 Round spots

black

 Papillae colour

whitish; dark gray; yellowish-white; yellow-purple, reddish-brown; black-brown; brown reddish; black-blue; purplish-brown, brown; Bluish base

Papillae colour - pattern

 Dots

White; blackish purple

 Tip

White; yellowish white

 Base

colourless

 Tints

purple

Margin Colour

white; Milky white to black; white-purple; white-blue; bluish; dark brown; brown-purple; transparent

Margin colour-pattern

 Band

White; radial

 Dash

purple

 Speckled

brown

 Spots

white

 Line

discontinuous black

Currently, this species is known from Naples, Italy (type locality), other parts of the Mediterranean, Algeria, Suez Canal (Palombi, 1928), South and West Africa, Florida, Brazil, Argentina, Borneo, Japan, Vietnam, New Zealand (Prudhoe, 1989) and with this report, extend to the Indian Coast.

Discussion

Comparative examinations clearly indicate and support the fact of existence of variable colour morphs of this species. Certainly, usual intraspecific variation and two or more species sharing similar colour patterns are two contended facts that exist, particularly in the pseudocerotid polyclads. Thus, the allocation of all presently noted morphs for T. brocchii is only convincing when external colour patterns, characters of reproductive anatomy and molecular framework reveal the similarity. In this context, revision of this species is urgently required. Perhaps fresh collection of specimens from the similar or adjacent places of previously described region can contribute to resolve mystery of colour patterns. Cladistical analysis using external characters and molecular data techniques are beneficial. Bulnes et al., 2011 raised important query about the cosmopolitan distribution and temperature as limiting factor in polyclad species distribution. Thus, ecological data inferring the habitat and food preference should be encouraged.

Declarations

Acknowledgments

The authors are grateful to Dr. Marcela Bolaños for providing valuable guidance and required literature. Special thanks to Ms. Juliana Bahia from the Zoologische Staatssammlung, München, Germany for sharing some of the references and to Ashok Bhagat for expertly providing histological sections. We greatly appreciate Dr.Vishal Bhave for collection and Mr. Rajendra Pawar, Mr. Vishwas Shinde and Mr. Rajesh Parmar for assistance during fieldwork and collection.

Authors’ contributions

RP first collected, identified and reported species. RP drafted the manuscript. DA guided and provided funds required for the study and carried out final editing of the manuscript. Both authors read and approved the final manuscript.

Competing interests

The authors declare that they have no competing interests.

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Authors’ Affiliations

(1)
Bombay Natural History Society

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