Caprella moradi Momtazi & Sari & Darvish 2020, sp. nov.

Caprella moradi sp. nov.

(Figures 1–6)

Types. Holotype: male 6.59 mm. Mouthparts completely dissected and mounted on one slide (Djod village; coordinates: N 25˚28ʹ 7ʺ, E 59˚ 28ʹ 20ʺ; intertidal zone), ( ZUTC Amph. 2425). Allotype, adult female 4.69 mm. Mouthparts completely dissected and mounted on one slide (same data as holotype), ( ZUTC Amph. 2426).

Paratypes (same data as holotype): 10 males (ZUTC Amph. 2427) December 2010; 41 males (ZUTC Amph. 2428), May 2011; 24 females (ZUTC Amph. 2429), December 2010; 90 females (ZUTC Amph. 2430), May 2011.

Comparative material loan. Caprella danilevskii Czerwinski, 1968; three males and seven females (AM P61184) and one male (MV J24131).

Description. Based on holotype, male.

Head. Lateral view (Fig. 1 Lv) Body length 6.59 mm. Head 0.55 mm, and pereonite1 0.31 mm; head and pereonite 1 fused and showing a suture demarking its boundary; body with numerous fine setae between head and pereonite 1, arranged in four rows on dorsal body surface (Fig. 1 Dv and Fig. 5G); eye large, distinctive; pereonite 2, 1.24 mm longest, following pereonites becoming shorter progressively, insertion second gnathopod in middle; pereonite 3, 1.23 mm; pereonite 4, 1.13 mm; pereonite 5, 0.86 mm; pereonite 6, 0.60 mm, with postero-lateral projection; pereonite 7, 0.55 mm; abdomen 0.12 mm.

Antenna 1 (Fig. 1 A1), about 0.46 × body length; peduncular article 1, 0.79 × second article, article 2 longest, 1.46 × article 3; flagellum with 11 articles, subequal to peduncle, proximal article with 3 articles. Antenna 2 (Fig. 1 A 2), slender, 1.14 × peduncle of first antenna, third and forth articles with long setae, flagellum biarticulate with motor setae (Fig. 5 I).

Mouthparts (Fig. 2), Upper lip (Fig. 2 U.L) notched, wider than long, with small setae on anterior surface. Lower lip (Fig. 2 L. L) well developed, finely setose on inner and outer lobes. Mandible (Fig. 2 LMd); left incisor with 4 teeth, lacinia mobilis with five teeth and three accessory setae; some fine setae between accessory setae and molar; molar well developed, truncate; palp absent. Right mandible (Fig. 2 RMd); incisor with 5 teeth and lacinia mobilis with two anteriorly serrated plates, two accessory setae; with some fine setae between accessory setae and molar; molar well developed; palp absent. Maxilla 1 (Fig. 2 Mx1), outer plate with seven stout apical tooth-like setae, distal margin of outer plate truncate with fine setae, palp biarticulate; article 2, with 4 triangular projections at distal margin and armed with five robust, two simple and 10 facial setae, inner margin with fine setae. Maxilla 2 (Fig. 2 Mx2), inner plate with 14 apical setae, one medial plumose seta and some fine setae along inner margin; outer plate with 12 long apical setae and one shorter seta. Maxilliped (Fig. 2 Mxp), inner plate subrectangular and reach to first article of maxillipedal palp, with two stout tooth, six plumose setae and one subapical stout seta; outer plate reach to second article of maxilliped palp, with three stout setae and some setae; palp four articulated; article 1 with three setae; article 2 longest with 12 setae, article 3 with some setae on inner and outer margins, article 4 (dactylus) falcate, distally bifid, inner margin moderately serrated, with one proximal seta on outer margin.

Pereon. Gnathopod 1 (Fig. 1 G1), basis longer than wide, shorter than propodus, border than ischium; merus and carpus combined, in posterior margin setose; propodus subpyriform, longer than wide with anteriorly submarginal setae, palm slightly convex and dentate, with 1 pair of proximal robust setae; dactylus curved, inner margin serrated, fine setae in outer and inner margins, bifid distally. Gnathopod 2 (Fig. 1G 2), with a triangular projection at the insertion (Fig. 3 Gb2 and Fig. 5 H), basis 0.48× the length of pereonite 2 and 0.6 × the length of propodus, with dorsal carina provided with one fine seta; ischium and basis width equal; merus and carpus combined, merus with three distal setae; propodus enlarged, about 2.5 × width, with fine setae along anterior and posterior margins, palm about 0.4 × propodus length, proximal part of palm with one poison teeth and two spine-like setae followed by fine setae in three rows and distal triangle projection with some setae; dactylus short, not reaching to end of palm, medially swollen.

Gill 3 (Fig. 1 Lv), length 0.46 × pereonite 3, oval, with some fine setae, about 1.3 × gill 4. Gill 4 (Fig. 1 3 Lv), length 0.38 × pereonite 4, oval, with some fine setae, smaller than gill 3.

Pereopods 3 and 4 absent. Pereopod 5 (Fig. 3 P 5), well developed; ischium with dorsal carina; carpus with two pectinate setae intermixed with 5–7 cuticular teeth; propodus longer than carpus without grasping spines but with some pectinate setae, dactylus falcate, inner margin serrated, several fine setae along inner and outer margins. Pereopod 6 (Fig. 3 P 6), similar to pereopod 5 but slightly longer. Pereopod 7 (Fig. 3 P 7), length about 2 × pereopod 5, basis lacking dorsal carina, propodus without robust seta.

Pleon. Abdomen (Fig. 3 Abv, Abd and Fig. 5 A-C), with one pair of hooked-like appendages, a pair of lateral lobes and a dorsal lobe. Penis median. Appendages (Fig. 5 C) with four medial setae and several rows of robust setae distally. Dorsal lobe medially cleft, with some proximal setae under appendages. Lateral lobes, thin and shorter than dorsal lobe, armed with a group of setae proximally and four apical setae. Telson (Fig. 3 Abd and Fig. 5 A), semicircular, with two plumose setae distally.

Female. Body length (Fig. 4 Lv), 4.69 mm. Head length 0.48 mm and pereonite 1 0.1 mm; head and pereonite 1 fused, with a markedly concaved suture between head and pereonite 1; eye large, distinctive; body with numerous fine setae in four rows on dorsal body surface (Fig. 4 Dv); pereonite 2, 0.75 mm; pereonite 3, 0.92 mm; pereonite 4, 0.83 mm; pereonite 5, 0.63 mm; pereonite 6, 0.51 mm; pereonite 7, 0.42 mm; abdomen 0.05 mm.

Antenna 1 (Fig. 4 Lv), 0.45 × body length; peduncular article 1 slightly longer than 3rd article; article 2 longest, 1.36 × article 1; flagellum with seven articles. Antenna 2 (Fig. 4 Lv), slender, 1.3 × peduncle of 1st article, 2nd and 3rd articles with long plumose setae; flagellum with two articles.

Mouthparts, similar to males. Gnathopod 1 (Fig. 4 G 1), without sexual dimorphism. Gnathopod 2 (Fig. 4 G 2) basis length equal to 2 × width; merus and carpus combined; propodus enlarged, about 2.5 × width, with few fine setae along anterior and posterior margins, palm concave, proximal part of palm with one poison teeth, some robust and fine seta along palm; dactylus short, not reaching to end of palm, medially swollen.

Gill 3 (Fig. 4 Lv), subequal to gill 4, oval. Oostegite 3 (Fig. 4 Os3), length 1.0× the width, setose along entire margin. Gill 4 (Fig. 4 Lv), subequal to gill 3, oval. Oostegite 4 (Fig. 4 Os4), length 0.84× the width with seven setae on anterior margin. Pereopods 5–7 similar to male.

Abdomen (Fig. 4 Ab and Fig. 5 D), with one pair of small palp-like appendages armed with one distal seta.

Variations. Number of stout seta on outer plate of maxilliped is variable from 2–3. Stout setae on second article of first maxilla is recorded as between 4–6. Some material have long second pereonite, basis and propodus of second male gnathopod and first antenna. These elongated forms are illustrated in Figure 6. These material resembled elongated forms of Caprella danilevskii from Tasmania (Guerra-García and Takeuchi, 2004) but material of the present study are prominently discriminated by setose body. Female individuals found to have two types of genital pore including material with few (Fig. 5 E) and several setae (Fig. 5 F).

Etymology. This species named after the late ruler of the Djod village Mr. Morad Salari who generously helped the University of Tehran biodiversity survey team for many years.

Remarks. The new species, Caprella moradi, is the only intertidal member of genus Caprella in the Gulf of Oman (Maghsoudlou et al., 2019). Caprella danilevskii (Czerniavski, 1868) shows the most similarity to C. moradi based on shared characters including; lacking grasping spines in pereonite 5–7, one pair of hooked abdominal appendages in male, short dactylus in second gnathopod. However, C. moradi could be differentiated from C. danilevskii based on smooth body surface covered with fine setae in four rows, curved anterior surface of propodus in second male gnathopod, unequal setose gills, flagellum of first antenna longer than peduncle and equal to the peduncle of the second antenna.

The anterior surface of propodus was straight in all records of C. danilevskii except in material from Japan studied by Arimoto (1976). But Czerniavski (1868) in description of C. danilevskii mentioned anterior surface of second gnathopod is straight. The flagellum of the first antenna is shorter than the peduncle of the second antenna, and it is equal to the peduncle of first antenna. In the report of C. danilevskii from Bermuda by Stebbing (1888) and also Barnard (1916) from Cape Town, presence of body setae was reported but without stating their regular arrangement as seen in C. moradi. Barnard (1937) recorded C. danilevskii from the south coast of Arabia but with no information on setation. Diagnostic characters of C. moradi, especially fine setae along body surface, are visible under light microscope but for more details, electron microscopic micrographs are provided.

The Black Sea is the type locality of Caprella danilevskii Czerniavski (1868). The life history of this species was carefully studied by Takeuchi & Hirano (1991, 1992). They mentioned that there is no planktonic larva in life cycle of this species or rafting behavior. In the studies of Guerra-Garcia and Takeuchi (2004) and Guerra-Garcia (2004), the presence of C. danilevskii was extended to Australia and Tasmania. However, there were several records of C. danilevskii from geographically distanced localities including; the Atlantic Ocean (McCain, 1968), the Mediterranean Sea (Krapp-Schickel, 1993) and the Indian Ocean (Mayer, 1890). In another study, Guerra-Garcia et al. (2006) mentioned that collected material of Colombia resembled type specimens of C. danilevskii. All of these materials were assigned to C. danilevskii which make its taxonomic status ambiguous; therefore there is a need for a thorough study of world material assigned to C. danilevskii. It seems, emphasis on lacking grasping spines abdominal appendages and short dactylus led to neglect of other characters.