Anoplodactylus monotrema Stock, 1979

Lucena, Rudá Amorim & Christoffersen, Martin Lindsey, 2018, Anoplodactylus (Pycnogonida: Phoxichilidiidae) from Brazil, new records and two new species, Turkish Journal of Zoology 42 (4), pp. 372-388 : 378-380

Anoplodactylus monotrema Stock, 1979 ( Figures 2a– 2g )

Halosoma robustum : Marcus, 1940: 68-71, figures 8a– 8c ( Dohrn, 1881).

Anoplodactylus robustum : Stock, 1955: 237, figures 12b and 12c.

Anoplodactylus monotrema : Stock, 1979: 15-18, figures 4 and 5; Müller and Krapp, 2009: 105-107, figure 56.

Material examined: Alagoas: ( UFPB.PYC–127) 1 ♂, Galés de Maragogi, intertidal, 14 Jun. 2014, coll. R. A. Lucena, J. Prata and J.P. de Araújo; ( UFPB.PYC–129) 1 ♀, Praia de Peroba , intertidal, 13 Jun. 2014, coll. R. A. Lucena, J. Prata and J.P. de Araújo .

Diagnosis: Trunk robust. Trunk segments 3 and 4 fused. Lateral processes separated by one-fourth of their diameter, with a dorsal seta. Proboscis very robust, cylindrical. Cheliphores moderately robust. Chela with curved fingers having 3 teeth. Oviger with 5 articles. Tube of cement gland oval and long, placed at end of first fourth of femur. Propodus slightly curved, heel with 2 robust spines and 2 smaller subventral spines. Sole with 6 small spines, curved towards distal region, and bordered by 5 short setae on both sides. Main claw robust. Auxiliary claws strongly reduced.

Distribution: Brazil (São Paulo, off Espírito Santo, Alagoas), Colombia; Curaçao, Aruba, Bonaire, Caribbean coast of Panama, Virgin Islands, Jamaica, Bahamas, Mexico, USA (Florida), Galapagos ( Stock, 1992; Müller, 1993; Müller and Krapp, 2009).

Depth: Up to 41 m deep.

Remarks: A. monotrema belongs to a group of species of Halosoma Cole, 1904 (later synonymized with Anoplodactylus ) that have 5 articles on the oviger instead of 6, as is more common in Anoplodactylus , known as the A. robustus group ( Dohrn, 1881) ( Stock, 1979; Child, 1982a). A. robustus , A. virescens (Hodge, 1864) , and a few other species, together with A. monotrema , are characterized for being small, stout, with contiguous lateral processes, and short articles on appendages ( Child, 1982a).

We may differentiate the three main species of the group by the absence of teeth on the fingers in A. robustus and A. virescens , segmentation completely absent in the trunk of A. robustus (absent only in the segments 3 and 4 in the remaining species), 3–6 pores in the cement gland in A. robustus and A. virescens (only one in A. monotrema ). The abdomen surpasses the lateral process 4 in A. virescens (in A. monotrema it reaches the margin of the process) and coxa 1 has dorso-distal tubercles in A. robustus (smooth in A. monotrema ) ( Stock, 1979; Child, 1979, 1982b; Müller and Krapp, 2009).

In the material examined here, all the characters are equal to the original description ( Figures 2a–2f ) but the pore of the cement gland is longer ( Figure 2f ) than that described by Stock (1979) and Müller and Krapp (2009). Besides, the auxiliary claws are ornamented by teeth ( Figure 2g ), a character not observed in other species of the genus. Both characters differ from the original description by Stock (1979) for specimens representing the first record in Brazil (see Stock, 1992).

The female observed herein has the proboscis somewhat longer and more robust, the abdomen is more erect, and the lateral processes are more widely separated in the female, as also described for the female by Stock (1992). Segmentation is complete in our material, as in the description of A. monotrema . More specimens have to be examined in order to determine if the reduced auxiliary claws observed in the material from Alagoas is a useful character for the characterization of this species. Here we record this species for the first time in the northeastern State of Alagoas.

Figures

Figure 2. Anoplodactylus monotrema Stock, 1979 (UFPB.PYC–127). Adult male. Habitus:a, dorsal view (scale bar:1 mm); b, lateral view (scale bar: 1 mm); c, proboscis ventral view (scale bar: 0.05 mm); d, chela (scale bar: 0.1 mm); e, oviger (scale bar: 0.25 mm; detail of e: 0.05 mm); f, leg 3 (scale bar: 0.25 mm; detail of f, 0.05 mm); g, propodus (scale bar: 0.05 mm; detail of g, 0.025 mm).