Systematics

Family Teredinidae Rafinesque, 1815 Tamilokus Shipway, Distel & Rosenberg, gen. nov. urn:lsid:zoobank.org:act:61B916B1-54D1-418D-B1A3-342162C261C2

Type species: Tamilokus mabinia sp. nov.

Type material: Holotype PMS-3916Y; paratypes PMS-3899P, PMS-3915X, PMS-3943P, PMS-3949Y, PMS-4037Y, and PMS-4051L. Smallest to largest specimens measured 6.2 cm–15.4 cm in total body length. The holotype is currently held at the Academy of Natural Sciences of Philadelphia (ANSP) and will be deposited in the National Museum of the Philippines in Manila pending completion of an ongoing reorganization. Paratypes are deposited at ANSP, at the Marine Science Institute of the University of the Philippines (MSI) and at the Ocean Genome Legacy Center of New England Biolabs, Northeastern University (OGL). For catalog numbers assigned by holding institutions see Table 1.

Type locality: Balayan Bay, off Mabini, Batangas Province, Philippines (coordinates 13.758°N, 120.925°E).

Comparative Material: The following material was examined: Teredora malleolus (Turton, 1822) MCZ-350541 (3 specimens); Teredora princesae (Sivickis, 1928) MCZ-232090 (5 specimens); Uperotus clava (Gmelin, 1791) MCZ-238009 (3 specimens); and, Uperotus panamensis (Bartsch, 1922) MCZ-357824 (4 specimens).

Diagnosis: pallets triangular-shaped with an ovate, flattened stalk, prominent cephalic hood and cephalic crest, crystalline style extends beyond posterior adductor muscle, caecum U-shaped doubling back upon itself, siphons with distinct pin-striped pigmentation with incurrent siphon featuring three rows of papillae

Etymology: Tamilokus (masculine), in recognition of the common name for shipworm in the Philippines, ‘tamilok’.

Habitat: Marine, wood-borer.

Description: Pallets very small in relation to body length (Fig. 2A), formed of a broad, flattened, translucent and ovate stalk, with a solid, white calcareous blade (Fig. 4A); cephalic hood prominent, extending to cover the posterior slope of the shell valves (Figs. 2A, 3A–3C & 5A, 5C); “cephalic collar”, formed from protruding folds of the mantle, extending along the ventral surface from the base of the foot to a point slightly posterior to the posterior margin of the shell valves (Figs. 2A–2B, 3A, 3D–3E, 5A–5B); large crystalline style and style sac originating within the cephalic collar and extending beyond the posterior adductor muscle into the posteriorly located stomach (Figs. 5A–5E); large globular stomach (Figs. 2B & 5A, 5E–5F) located posteriorly in relation to posterior adductor muscle and valve pedal gape, composed of three lobes, with muscular opening into caecum (Figs. 5A, 5F); large digestive glands (Figs. 2A–2C & Fig. 5A, 5C–5E); caecum (Figs. 2A–2C & 5A, 5D–5I) large, elongate, U-shaped, doubling back upon itself anteriorly towards the right (Figs. 2B & 5D–5I), lacking a typhlosole (Figs. 5D–5I); intestine unusually broad and voluminous (Fig. 2B), especially where it passes ventral to the caecum (Figs. 5G–5I), containing short ovoid faecal pellets packed in multiple rows across its width (Fig. 2B); intestine extends anteriorly, looping over crystalline style sac (Figs. 5C–5E), then doubles back posteriorly, looping under the caecum before extending anteriorly on the dorsal surface of the caecum, finally looping under the posterior adductor muscle before extending a short distance posteriorly and opening into the anal canal; anal canal is open and does not retain faeces; gonad located centrally (Figs. 5A, 5I–5K), beginning posterior to the caecum and ending at the heart; heart located medially (Figs. 5J–5K); gill extends from the siphons anteriorly to the posterior tip of the gonads (Figs. 5A, 5K–5L); prominently flared mantle collar around siphons and pallets (Figs. 2B, 3A & 5A).

Remarks: Tamilokus gen. nov may be easily differentiated from all other genera within the family Teredinidae based on pallet morphology. The simple triangular cup-shaped pallet and thick ovate stalk of Tamilokus may be distinguished from the pallets of: Bankia Gray 1842, Nausitora Wright 1864, Nototeredo Bartsch 1923, and Spathoteredo Moll 1928 by the lack of segmentation; from Lyrodus Gould 1870, Teredo Linnaeus 1758, Zachsia Bulatoff & Rjabtschikoff 1933, and Nivanteredo Velásquez & Shipway, 2018 by the absence of a periostracum and presence of a broad ovate stalk; from Teredothyra Bartsch 1921 by the presence of a single undivided cup; from Dicyathifer Iredale 1932 and Kuphus Guettard 1770 by the absence of a medial ridge; from Bactronophorus Tapparone Canefri 1877 by the absence of a dagger-like extension; from Neoteredo Bartsch 1920, Psiloteredo Bartsch 1922, Teredora Bartsch 1921 and Uperotus Guettard 1770 by the cup-rather than paddle-shaped blades, and from the latter three genera by the lack a distinct thumb-nail like depression bearing concentric or radiating ridges.

Additionally, Tamilokus may be easily distinguished from Bactronophorus Tapparone Canefri 1877, Dicyathifer Iredale 1932, Neoteredo Bartsch 1920 and Teredothyra Bartsch 1921 by the absence of a muscular sphincter at the posterior end of the anal canal; from Lyrodus Gould 1870, Teredo Linnaeus 1758 and Zachsia Bulatoff & Rjabtschikoff 1933 by the absence of brood pouches on the gill; from Neoteredo Bartsch 1920 by the absence of dorsal lappets; and from Kuphus Guettard 1770 by the presence of a caecum and the absence of a strong muscular collar surrounding the valves.

Tamilokus is similar to Teredora Bartsch 1921 and Uperotus Guettard 1770 in that it possesses a U-shaped caecum that, after passing posteriorly from the stomach, doubles back upon itself towards the right and extends anteriorly, terminating near its origin on the right side of the stomach (Turner, 1966). However, Tamilokus can be easily distinguished from these genera based on pallet morphology (as previously described). Additionally, the gills of Teredora and Uperotus extend the entire length of the animal from the base of the siphons to the mouth, whereas those of Tamilokus terminate near the posterior end of the caecum; the labial palps in both Teredora and Uperotus are large and free, but are very small and attached in Tamilokus; the crystalline style in both Teredora and Uperotus is located anteriorly to the posterior adductor muscle, but extends from the base of the foot well beyond the posterior margin of the adductor muscle in Tamilokus; the stomach of both Teredora and Uperotus is located anterior to posterior adductor muscle, whereas the stomach of Tamilokus is located posterior to the posterior adductor muscle; the heart of both Teredora and Uperotus is positioned anteriorly, but is medially positioned in Tamilokus; the siphons of Teredora and Uperotus are united along their entire length, but are separate in Tamilokus; the incurrent siphons of both Teredora and Uperotus feature a single primary row of papillae, whereas the incurrent siphon of Tamilokus has an additional secondary row that includes compound branched papillae; and, the cephalic hood in both Teredora and Uperotus is inconspicuous, whereas the cephalic hood in Tamilokus is prominent and covers the posterior slope of the shell valves. Finally, Tamilokus may be recognized by the presence of the cephalic collar which is unique to this genus. Taxonomic characters differentiating Tamilokus from Teredora and Uperotus are summarized in Table 2.

Taxonomic character Tamilokus Teredora Uperotus Labial palps Reduced/absent Free Large and free Crystalline style Extends from base of foot beyond posterior adductor muscle Located anterior to posterior adductor muscle Located anterior to posterior adductor muscle Stomach Globular, located posterior to posterior adductor muscle Globular, located anterior to posterior adductor muscle Globular, located anterior to posterior adductor muscle Caecum Doubles back upon itself, to the right Doubles back upon itself, to the right Doubles back upon itself, to the right Caecal typhlosole Absent Rudimentary Absent Heart Median position Located anteriorly Located anteriorly Gills Located posteriorly, extending to posterior caecum Extend from base of siphons to mouth Extend from base of siphons to mouth Siphons Separated along entire length, pink pinstriped pigmentation United to the tip United to the tip Incurrent siphon papillae Primary row numerous small papillae, secondary row compound papillae Incurrent siphon numerous large papillae Incurrent siphon numerous small papillae Excurrent siphon papillae Numerous small papillae – Excurrent siphon two large papillae on dorsal surface Cephalic hood Prominent, covers valve posterior slope Inconspicuous, does not cover valve posterior slope Inconspicuous, does not cover valve posterior slope Cephalic collar Present Absent Absent Flared mantle collar Present Absent Absent Pallets Triangular, cup-shaped, non-segmented, ovate flattened stalk Paddle shaped, non-segmented, ‘thumbnail’ depression Paddle shaped, non-segmented, ‘thumbnail’ depression, radiating ribs DOI: 10.7717/peerj.6256/table-2

Tamilokus mabiniaShipway & Distel,sp. nov. urn:lsid:zoobank.org:act:88D193B6-9062-48C2-AC9D-EC6F858B3C05

Etymology: Mabinia (noun in apposition), in honour of Apolinario Mabini, a Philippine national hero, and pertaining to the type location of the specimens from Mabini, Batangas, Philippines.

Description: All characteristics of the genus, plus; dorsal anterior slope of shell valves highly elongated (Fig. 4B); incurrent and excurrent siphons ringed with papillae (Fig. 3F); incurrent siphon features outer ring of long papillae, and inner ring of shorter compound or branched papillae (Fig. 3G); siphon tips are ringed with pink to brownish red pigment that extends posteriorly in narrow closely spaced parallel stripes (Figs. 2A–2C & 3A).

Definition: Pallets elongate, composed of an unsegmented blade built upon a central stalk (Fig. 4A); blade triangular, single concave U-shaped cup on distal margin with slightly more pronounced curvature on outer face; periostracum absent; mantle collar flared, extending approximately half the length of the pallet; stalk and blade approximately equal in length; stalk translucent, ovate and flattened in both sagittal and transverse section; blade calcareous and white.