Benthesicymus tanneri Faxon, 1893

Hendrickx, Michel E. & Papiol, Vanesa, 2015, Distribution of Benthesicymustanneri Faxon, 1893 (Dendrobranchiata, Benthesicymidae) off the west coast of Mexico and notes on its morphology, ZooKeys 473, pp. 119-136 : 121-130

Taxon classification Animalia Decapoda Benthesicymidae

Benthesicymus tanneri Faxon, 1893 Figures 2, 3, 4, 5, 6

Material examined.

Specimens of Benthesicymus tanneri were collected in 44 of the 228 stations visited during the survey (Figure 1).

TALUD III. Material reported by Hendrickx (2001). Additional material. St. 14A (24°38'48"N; 108°26'54"W), Aug 19, 1991, 1M (CL 32.5 mm), AD, 1016-1020 (EMU-4418); St. 14B (24°39'12"N; 108°37'48"W), Aug. 19, 1991, 1F (CL 31.9 mm), AD, 1188-1208 m (EMU-2609); St. 17 (24°33'0"N; 108°50'54"W), Aug 19, 1991, 1M (CL 22.1 mm), AD, 770 m (EMU-4417); St. 24A (25°45'12"N; 109°46'48"W), Aug 24, 1991, 2M (CL 29.0-30.8 mm), AD, 1027-1060 m (EMU-100).

TALUD IV. Material reported by Hendrickx (2001).

TALUD V, St. 5 (22°0'57"N; 106°40'0"W), Dec 13, 2000, 1F (CL 36.3 mm), BS, 1515-1620 m (EMU-5540-A); St. 6 (22°N; 106°48'5"W), Dec 13, 2000, 1F (CL 41.1 mm), BS, 1950-2010 m (EMU-5540-B); St. 19 (23°17'30"N; 107°29'51"W), Dec 15, 2000, 1M (CL 31.1 mm), 3F (CL 29.1-36 mm), BS, 1180-1200 m (EMU-5523-A); St. 26 (24°15'18"N; 108°24'6"W), Dec 16, 2000, 2M (CL 29-30.7 mm), 2F (CL 32-34.2 mm), BS, 1280-1310 m (EMU-5523-B).

TALUD VI, St. 12 (23°18'36"N; 107°26'56"W), Mar 14, 2001, 1M (CL 32.5 mm), 1F (CL 34.8 mm), BS, 1050-1160 m (EMU-5539-A); St. 19 (24°16'24"N; 108°24'18"W), Mar 15, 2001, 1F (CL 50.4 mm), BS, 1160-1200 m (EMU-5539-B); St. 26 (24°56'18"N; 109°6'42"W), Mar 16, 2001, 1M (CL 33.4 mm), 1F (CL 25.2 mm), BS, 1190-1270 m (EMU-5997-A); St. 27 (25°1'12"N; 109°11'36"W), Mar 16, 2001, 1F (CL 32.3 mm), BS, 1580-1600 m (EMU-5539-C); St. 34 (25°43'50"N; 109°53'59"W), Mar 17, 2001, 1M (CL 31.9 mm), 2F (CL 3025-33.6 mm), BS, 1240-1270 m (EMU-5997-B), and 7M (CL 31.4-34.8 mm), 12F (CL 30.5-42.5 mm), and 3 unsexed specimens (14.5-21.4 mm).

TALUD VII, St. 4 (22°3'18"N; 106°34'42"W), Jun 5, 2001, 1F (CL 37.8 mm), BS, 1190 m (EMU-5541); St. 19 (24°16'12"N; 108°23'42"W), Jun 7, 2001, 1M (CL 11.2 mm) and 1F (CL 34.7 mm), BS, 1160-1180 m (EMU-6004-A); St. 33B (26°6'30"N; 110°6'42"W), Jun 9, 2001, 1F (CL 23.0 mm), BS, 1260-1300 m (EMU-6004-B).

TALUD VIII, St. 10 (24°58'12"N; 110°16'6"W), Apr 17, 2005, 1M (CL 30.4 mm), and 1F (CL 11.2 mm), BS, 1500 m (EMU-8143); St. 3 (24°32'36"N; 109°30'30"W), Apr 16, 2005, 2M (CL 31.9-34.7 mm), 3F (CL 29.2-35.7 mm), BS, 1100 m (EMU-8147).

TALUD IX, St. 20B (25°58'7"N; 110°40'4"W), Nov 14, 2005, 2F (CL 33.7-36.2 mm), BS, 1229-1343 m (EMU-8236).

TALUD X, St. 10 (27°50'5"N; 112°10'7"W), Feb 10, 2007, 1F (CL 32.3 mm), BS, 1399-1422 m (EMU-8030); St. 18 (27°9'6"N; 111°46'54"W), Feb 12, 2007, 1F (CL 31.3 mm), BS, 1526 m (EMU-8118); St. 30 (26°36'50"N; 110°21'10"W), Feb 15, 2007, 1M (CL 29.9 mm), BS, 1203-1213 m (EMU-8203).

TALUD XII, St. 5 (16°58'28"N; 100°55'20"W), Mar 28, 2008, 1F (CL 53.3 mm), BS, 1925-1977 m (EMU-8872); St. 9 (17°10'15"N; 101°37'23"W), Mar 28, 2008, 6F (CL 30.1-35.3 mm), BS, 1392-1420 m (EMU-8874); St. 10 (17°11'18"N; 101°28'30"W), Mar 29, 2008, 3F (CL 21.1-38.7 mm), BS, 1180-1299 m (EMU-10500); St. 13 (17°45'16"N; 102°0'29"W), Mar 30, 2008, 1F (CL 30 mm), BS, 1198 m (EMU-8904); St. 28 (18°50'19"N; 104°34'14"W), Apr 2, 2008, 1F (CL, 38.1 mm), BS, 1101-1106 m (EMU-10499); St. 29 (19°19'37"N; 105°26'20"W), Apr 2, 2008, 1F (CL 44.7 mm), BS, 1609-1643 m (EMU-8873).

TALUD XV, St. 1 (23°18'40"N; 111°19'37"W), Aug 4, 2012, 1F (CL 40.2 mm), BS, 750-850 m (EMU-10435); same station, 5M (CL 17.9-29.1 mm) and 7F (CL 25.3-41.1 mm), BS, 750-850 m (EMU-10434); St. 2 (23°12'2"N; 111°20'50"W), Aug 4, 2012, 4M (CL 32-33.9 mm), 5F (CL 23.2-40.6 mm) and 1Juv. (CL 12.4 mm), BS, 1118-1150 m (EMU-10436); St. 3 (23°9'N; 111°20'W), Aug 4, 2012, 1F (CL 36.4 mm), BS, 1395-1465 m (EMU-10433); St. 5C (23°16'42"N; 110°54'55"W), Aug 5, 2012, 8M (CL 20.5-35.5 mm), BS, 980-1036 m (EMU-10496-A); same station 25F (CL 20.3-40.5 mm), 1M (CL 13.4 mm), BS, 980-1036 m (EMU-10496-B); St. 5F (22°58'15"N; 110°40'17"W), Aug 5, 2012, 1F (CL 39.3 mm), BS, 1035-1108 m (EMU-10432); St. 8 (24°25'48"N; 112°38'6"W), Jul 30, 2012, 1M (CL 29.8 mm), 3F (CL 23.2-41.1 mm), BS, 1212-1235 m (EMU-10431); St. 24 (27°5'42"N; 114°35'30"W), Aug 1, 2012, 2F (CL 25-32.6 mm), BS, 772-786 m (EMU-10430).

TALUD XVI-B, St. 3 (28°42'36"N; 115°50'42"W), May 23, 2014, 2F (CL 30.1-31.0 mm), BS, 1350-1365 m (EMU-10623) St. 6 (29°08'9"N; 115°33'25"W), May 24, 2014, 10M (CL 16.4-29.9 mm) and 9F (CL 16.7-29.5 mm), BS, 1004-1102 m (EMU-10498); St. 8 (29°23'28"N; 115°45'W), May 31, 2014, 1M (CL 35.4 mm), 1F (CL 27 mm), BS, 1416-1480 m (EMU-10438); St. 16 (29°51'N; 116°9'W), May 29, 2014, 4F (CL 23.2-37.2 mm), BS, 1425-1360 m (EMU-10441); St. 23 (30°56'N; 116°40'33"W), May 27, 2014, 1M (CL 33.3 mm), 2F (CL 30.1-32.7 mm), BS, 1296-1340 m (EMU-10439); St. 26 (31°46'3"N; 116°58'12"W), May 26, 2014, 1F (CL 31.4 mm), BS, 982-989 m (EMU-10437); St. 27 (31°42'21"N; 117°13'W), May 27, 2014, BS, 1394-1397 m, 1F (CL 34.7 mm) (EMU-10440) and 1 F (CL 30.5 mm) (EMU-10497).

Size and sex.

With 187 specimens available (61 males, CL 11.2-35.5 mm; 122 females, CL 16.7-53.3 mm; 3 unsexed; and 1 juvenile, CL 12.4) (M:F = 1:2), the collection of Benthesicymus tanneri from off western Mexico came from 44 stations and is the largest available to date for this species (Figure 1). The largest specimens measured 103 mm (male; TALUD XV, St. 5C) and 116 mm (female; TALUD XII, St. 5) total length, the latter constituting the largest specimen collected to date. The size of individuals differed across sexes (Mann-Whitney U test, U=2058.00, p<0.001) with females growing larger than males (Figure 2).

Geographic and bathymetric distributions.

The syntype series, collected by the “Albatross”, contained 56 males and 78 females (134 specimens) from 22 lots captured over a wide latitudinal range (1°3'S to 27°34'N), and included material from 4 stations in Mexico: off Acapulco and Islas Tres Marías, and in the vicinity of Guaymas (Figure 1). We are not aware of further material collected off western Mexico.

According to Wicksten (1989), Retamal and Jara (2002) and Wicksten and Hendrickx (2003), Benthesicymus tanneri is known from San Diego, California, USA, to Chile. The material currently examined slightly increases the distributional range of Benthesicymus tanneri within the Gulf of California to the north, and indicates that Benthesicymus tanneri occurs all along the west coast of the Baja California Peninsula where it had not been reported previously (Figure 1). In the Mexican Pacific it is a widely distributed and frequently captured species.

The material examined herein was collected between 750 and 2010 m depth with bottom sampling gear. One specimen (TALUD III, St. 17) was collected with a mid-water trawl hauled from surface to 770 m depth, in a locality where total depth was 1560 m. All species of Benthesicymus occur in deep water and the general depth range for Benthesicymus tanneri is 606-2422 m (Table 1) ( Wicksten 1989).

Of the 15 recognized species of Benthesicymus (Table 1), currently known distributions indicate that three are widespread ( Benthesicymus altus , Benthesicymus bartletti , Benthesicymus investigatoris ), one occurs in both the Atlantic and part of the Pacific ( Benthesicymus brasiliensis ), one is distributed in the Indo-Pacific ( Benthesicymus urinator ), three are restricted to the Indian Ocean (or part of it) ( Benthesicymus armatus , Benthesicymus seymouri , Benthesicymus tirmiziae ), five occur in the Pacific Ocean ( Benthesicymus crenatus , Benthesicymus howensis , Benthesicymus strabus , Benthesicymus laciniatus , Benthesicymus tanneri ; the latter two only known from the eastern Pacific), and two are restricted to the Atlantic Ocean ( Benthesicymus iridescens , Benthesicymus cereus ).

On the presence of the hepatic spine in Benthesicymus tanneri .

In their identification key of Group II, Kikuchi and Nemoto (1991) indicated that Benthesicymus tanneri possesses a hepatic spine, a character that separates this species from the other four species of their Group II. Guzmán and Wicksten (2000) emphasize that the presence of a hepatic spine was not mentioned in some of the previous literature referring to Benthesicymus tanneri (i.e., Méndez 1981, Wicksten and Hendrickx 1992, Retamal and Soto 1993). Incidentally, the figure provided by Méndez (1981: fig. 62) does not show the presence of an hepatic spine but its reproduction in Hendrickx (1995) does (p. 437), which is an error due to the illustration process in the editorial office. In his preliminary description of Benthesicymus tanneri , Faxon (1893) indicated that " Benthesicymus moratus , Smith [S.-I. Smith, 1886, now recognized as a junior synonym of Benthesicymus brasiliensis Spence Bate, 1881], another allied species [of Benthesicymus tanneri ], differs in having a distinct hepatic spine", from which it could be concluded that the type material of Benthesicymus tanneri examined by Faxon (1893) lacks this spine. Re-description by Faxon (1895: 205) repeats essentially the same statement as in 1893, and his lateral illustration of the carapace (Plate H 1a) does not indicate the presence of a hepatic spine, although the lower extension of the cervical carina could easily be confused with a strong spine. Besides, this drawing does not include the presence of the pterygostomial spine either, which is definitively present in Benthesicymus tanneri (see Burkenroad 1936: 52). Revision by Dr. Rafael Lemaitre of part of the material used by Faxon (1893, 1895) in his syntypic series and deposited at the National Museum of Natural History, Washington, DC (USNM 21214; syntypes from the Gulf of California, Mexico) confirms the fact that there is no trace of a hepatic spine on the specimens examined. Another revision by Adam Baldinger of one of the syntypes of Benthesicymus tanneri (MCZ-4662) deposited at the Museum of Comparative Zoology at Harvard also clearly indicates the absence of a hepatic spine (Figure 3A). An illustration of a large specimen of Benthesicymus tanneri collected during this survey is also provided for comparison (Figure 3B). References to this spine in earlier literature ( Kikuchi and Nemoto 1991, Hendrickx 1995, Dall 2001) are therefore in error. Consequently, the groups definition presented by Kikuchi and Nemoto (1991) have to be altered because all species of Group II as defined by these authors in their key lack the hepatic spine which is otherwise present in seven of the ten species of their Group I. Moreover, the identification key proposed by Dall (2001) should be partly modified.

Reproductive organs.

While studying fine morphology of Benthesicymus carinatus (now included in Altelatipes ), Tavares (2009) noted the lack of basic information related with the description and development of the reproductive organs of Benthesicymus s.l. The male petasma of Benthesicymus tanneri was illustrated by Faxon (1895) and by Hendrickx and Estrada-Navarrete (1996). Material examined collected in station 6 of the TALUD XVI-B cruise includes small and medium-size males with immature petasma (Figure 4 A–D). The smallest male with visible petasma was 11.2 mm CL, in which a small bud without any elaborated structure could be seen. A slightly larger male (CL 16.4 mm) had a similar petasma (Figure 4D). However, another young male from station 19 of TALUD VII cruise with CL 11.2 mm (i.e., smaller than the male of Figure 4D) presented a relatively larger petasma (Figure 4E). The crescent-shape lateral process, which is typical of Benthesicymus tanneri , is not yet developed in males of CL 17.5 mm (Figure 4C). In a male of CL 29.9 mm the two sections (left and right) of the petasma are well developed (Figure 4B) but not yet united medially.

The fully developed petasma (Figure 5 A–D) of Benthesicymus tanneri (CL ≥ 35 mm) is clearly distinct from known petasma of mature males of nine species of the genus in the presence of the lateral crescent-shape process. In Benthesicymus altus , Benthesicymus brasiliensis , Benthesicymus crenatus (the type species of the genus), Benthesicymus investigatoris Alcok & Anderson, 1899, Benthesicymus iridescens Spence Bate, 1881, Benthesicymus laciniatus , Benthesicymus seymouri Tirmizi, 1960, Benthesicymus strabus Burkenroad, 1936, and Benthesicymus urinator Burkenroad, 1936, the petasma lacks the lateral crescent-shape process (see A. Milne Edwards and Bouvier 1909, Burkenroad 1936, Crosnier 1978, 1985, Hendrickx 1996, Kikuchi and Nemoto 1991) (see below for the case of Benthesicymus bartletti S.I. Smith, 1882). It should be noted that figure 1, page 28, of Burkenroad (1936) is labeled " Benthesicymus laciniatus Rathbun", which is most certainly an error, and this illustration likely belongs to Benthesicymus crenatus , as indicated earlier in the text by the author. Burkenroad (1936: fig. 35) also provided an illustration of the petasma of Benthesicymus cereus Burkenroad, 1936, probably a juvenile. This figure lacks a lateral crescent-shape process but, as in the case of Benthesicymus tanneri (see Figures 3, 4), this process may appear later during the growth of the species. Of the remaining three species of Benthesicymus , a crescent-like process has been described only in Benthesicymus tirmiziae Crosnier, 1978 (but see below). The petasma of Benthesicymus howensis Dall, 2001, remains undescribed as the species (originally described as a new subspecies of Benthesicymus urinator ) is known only from the two females of the type material. We were not able to locate an illustration of the petasma of Benthesicymus armatus MacGilchrist, 1905. Another question remains open as far as illustrations of petasma in literature are concerned. Peréz-Farfante and Kensley (1997: fig. 27) provided an illustration of both the petasma and the thelycum of a species which certainly belongs to Benthesicymus ; however, the figure caption is the same as the one inserted in figure 25 of the same monograph (i.e. for Bentheogennema intermedia (Spence Bate, 1888)) and it was therefore difficult to assess to which species of the genus this figure actually belongs to. A search by Rose Gulledge, Museum specialist at the US National History Museum, Smithsonian Institution crustacean department, Maryland, USA, was successful in finding the original plates prepared by the illustrator of Peréz-Farfante and Kensley (1997). Pencil markings and notes on the plates indicate that the petasma and thelycum of figure 27 belong to Benthesicymus bartletti , and that "species in book is wrong [...] must say Benthesicymus bartletti ". Consequently, Benthesicymus bartletti represents a third species featuring a crescent-shaped lateral process on the petasma, as Benthesicymus tanneri and Benthesicymus tirmiziae do.

The female thelycum of Benthesicymus tanneri was roughly illustrated by Faxon (1895, plate H-1b) and is illustrated herein (Figure 4F). A small tuft of setae is clearly observed arising from each minute pit of the thelycum middle plate (sternite XIII). Of the two groups of species considered by Burkenroad (1936) in his synopsis of Benthesicymus , Group I possesses a "thelycum without well-defined receptacles between the twelfth and the thirteenth sternites, the scutes of the twelfth and thirteenth sternites being simple and unexpanded". Group II posseses "well-defined cavities between the twelfth and the thirteenth sternites, the scutes of the thirteenth sternites being broadly expanded to overlap the sternal surface proper". Based on these criteria Benthesicymus tanneri belongs to Group II, with the scutes of sternite XIII broadly expanded (Figure 4F).

Color.

The color of fresh specimens was described by Faxon (1895: 207) and a color drawing (Plate H-1) was added to his contribution (reproduced here as Figure 6A). All specimens collected during the TALUD survey presented the typical "deep red" color (Figure 6B) described by Faxon (1895). The large patch of bright blue color on the back of the abdominal somites 2-4 mentioned by Faxon (op. cit.) and also observed by Moscoso (2012) actually corresponds to the gonads of mature specimens that extend backward from the thoracic area (pers. observ.).

Fishery resource.

Although it reaches a size (i.e., over 115 mm total length) comparable with other species of Dendrobranchiata used as food, Benthesicymus tanneri is not currently subject to any commercial exploitation. It has been considered a potential fisheries resource for the area (see Hendrickx 1995) to a large extent because it occurs together with other species of established potential for deep-water fisheries (e.g., Heterocarpus affinis Faxon, 1893, Haliporoides diomedeae Faxon, 1893) ( Barriga et al. 2009). Since 2004, the Peru fishery program has included Benthesicymus tanneri in a short list of sub-exploited deep-water shrimps subject to "exploratory fishing" in Peruvian waters ( Ministerio de la Producción 2004). In the specific case of the western central Pacific, Chan (1998) reported the presence of six species of Benthesicymus in this area, but none was considered of importance to fishery, even as a potential resource, probably because this genus has nowhere been reported to be abundant. The 15 species of Benthesicymus known to date are from mid-sized (from ca 70-80 mm TL) to large (ca 200 mm TL) (Table 1) but are all from deep-water, thus rending any exploitation attempt very complex.