Acetes maratayama Bochini, Costa & Mantelatto 2024, sp. nov.

Acetes maratayama Bochini, Costa & Mantelatto sp. nov.

Figs 1, 2, 3, 4

Type material.

Holotype: Brazil: • ♂ (cl 2.94 mm); CCDB 7957; São Paulo, Cananéia, Mar Pequeno; (24 ° 59 ' 55 " S, 47 ° 53 ' 49 " W); 5–10 m deep; colls. Costa, R. C. et al.; 17 April 2011. Paratypes: • 4 ♂ s and 4 ♀ s (cl 2.70 – 3.93 mm); CCDB 7958 (photo available, one dissected specimen); same data as holotype • 1 ♂ and 1 ♀ (cl 2.9 and 4.04 mm, respectively); MOUFPE 22042; same data as holotype • 1 ♂ and 1 ♀ (cl 3.04 and 3.93 mm, respectively); MZUSP 45904; same data as holotype • 2 ♂ s and 2 ♀ s (cl 4.01 – 5.19 mm); CCDB 7959; Brazil, Rio de Janeiro, Macaé; (22 ° 22 ' 13.65 " S, 41 ° 39 ' 9.42 " W); colls. Davanso, T. M. et al.; 01 September 2013 • 2 ♂ s and 2 ♀ s (cl 3.25 – 5.34 mm); MNRJ 31168; Brazil, Rio de Janeiro, Macaé; (22 ° 22 ' 13.65 " S, 41 ° 39 ' 9.42 " W); colls. Davanso, T. M. et al.; 01 September 2013 • 1 ♂ and 1 ♀ (cl 4.20 and 5.53 mm, respectively); DZ / UFRGS 7089; Brazil, Rio de Janeiro, Macaé; (22 ° 22 ' 13.65 " S, 41 ° 39 ' 9.42 " W); colls. Davanso, T. M. et al.; 01 September 2013.

Additional material.

•> 30 ind. (not measured); CCDB 3251; same data as holotype •> 50 ind. (not measured); CCDB 7624; Brazil, Rio de Janeiro, Macaé; (22 ° 22 ' 13.65 " S, 41 ° 39 ' 9.42 " W); colls. Davanso, T. M. et al.; 01 September 2013.

Comparative material.

Acetes a. americanus: • 7 ind.; CCDB 6320; Brazil, Rio Grande do Norte, Baía Formosa; (06 ° 21 ' 11.6 " S, 35 ° 00 ' 1.9 " W); colls. Lopes, M., Carvalho-Batista, A.; 25 April 2014 • 2 ♀ s (cl 3.6 and 5.1 mm); MZUSP 21210; Brazil, Alagoas, Maceió; 27 / 06 / 1989 •> 15 ind.; CCLC 258; Brazil, Espírito Santo, Anchieta, col. Braga, A. C. A.; 01 January 2014 • 10 ind.; CCDB 7626; Brazil, Rio de Janeiro, Macaé; (22 ° 22 ' 13.65 " S, 41 ° 39 ' 9.42 " W); colls. Davanso, T. M. et al.; 01 September 2013 •> 10 ind.; CCLC 253; Brazil, São Paulo, Ubatuba, col. Costa, R. C.; 02 October 2014 • 10 ind.; CCDB 4939; Brazil, São Paulo, São Vicente, col. Castilho, A. L.; 03 September 2012 • 2 ♀ s (cl 5.10 and 4.80 mm); CCLC 257; Brazil, Santa Catarina, Penha, coll. Davanso, T. M.; 24 June 2014.

Acetes a. carolinae: • 2 ♂ s and 3 ♀ s; ULLZ 3274; United States, Gulf of Mexico, Louisiana; coll. Forman, W. W.; 31 October 1972.

Diagnosis.

Rostrum acuminate, acute; median ridge with strong posterior tooth. Carapace smooth on surface, except for post-orbital and hepatic spine. Hepatic spine present in males, external part petasma not exceeding base of capitellum; inferior antennular flagellum with 10 articles. Concavity of anterior margin of genital sternite in females forming very deep arch.

Description.

Male. The rostrum (Fig. 1 A, B) is acuminate, acute; the median ridge has a strong posterior tooth. There is a small supraorbital spine on each side above the eyes, near the face. The hepatic spine is present (Fig. 1 A). Quite large eyes do not exceed the posterior margin of the first antennular article (Fig. 1 A, C). Antennule with long peduncle; very elongated third article, which is approximately three times longer than the inner margin of the second article, similar to the size of the first article (Fig. 1 D); the first article in females is twice the length of the third article and approximately 4.5 × longer than the second article; the inner distal lateral margin of the first article presents simple setae in the anterior half (Fig. 1 G); males with inferior antennular flagellum have 10 articles; there is no clasping organ; males’ thickened proximal 3 - article portion occupies less than half of the flagellum; third article has 6 obtuse spinules similar to fingers, and 1 procurved and robust projection (Fig. 1 E, F); article 8 has a projection similar to a lobe in the inner lateral part of the article’s distal region (Fig. 1 E). Antennal scale extending to the middle of the second antennular peduncle article with small spine on the anterior external portion (Fig. 1 A, H).

Mandible with biarticulated palp; first article of the palp 3 × longer than the second article (Fig. 2 A); first maxilla without palp (Fig. 2 B); second maxilla with one single undivided lobe (Fig. 2 C); first maxilliped without palp (Fig. 2 D); second maxilliped with 5 articles (Fig. 2 E); third maxilliped exceeding half of the antennal scale, without reaching the distal margin of the antennal scale (Fig. 2 F).

The first 3 pairs of pereiopods are elongated and have a small chela (Fig. 3 A – C). Fourth and fifth pereiopods were completely absent, except for a pair of protuberances (genital thighs) in males. The sixth segment of the pleon is longer than the others (Fig. 1 A). Slender pleopods, the hind ones, are a little stockier. First pair with one single branch, with sexual appendages in males (Fig. 3 D) - the remainder has two appendages (Fig. 3 E – H). Pleopods with a row of spines on the basal articles of the endopods and exopods. PL 2 with 5 spines on the outer margin of the endopod basal joint and 5 spines on the inner margin of the exopod basal joint (Fig. 3 E); PL 3 with 12 spines on the outer margin of the endopod and with 5 ones on the outer margin of the exopod (Fig. 3 F); PL 4 with 7 spines on the external margin of the endopod (Fig. 3 G) and PL 5 with 8 spines on the external margin of the endopod (Fig. 3 H). Telson shorter than the anterior segment, long triangularly truncated at the tip (Fig. 3 I). Uropods significantly longer than the telson, external branch much longer than the internal one, with a thin tooth on the external edge closer to the tip (Fig. 3 I). The uropod exopod is 4.5 times longer than it is wide; a small spine on the outer margin in the 1 / 3 rd portion separates the ciliated portion from the non-ciliated portion (Fig. 3 I). Telson apex is truncated; lateral margins are often curved inwards and form two short teeth between which the slightly convex posterior margin is found; there are 4 bristles between the terminal teeth, the two median ones are larger than the outer teeth, and two equal-sized bristles are external to the terminal teeth (Fig. 3 J).

Males. Acetes maratayama sp. nov. is very similar to the other two described Atlantic species (A. a. americanus and A. a. carolinae), except for its different petasma and female genital sternite. Petasma pars externa in A. maratayama sp. nov. does not reach the base of the capitulum (Fig. 4 B); the pars externa extends above the base of the capitulum in A. a. carolinae (Fig. 4 C). On the other hand, it extends far beyond the capitulum base and reaches the middle portion of it in A. americanus (Fig. 4 A). Pars externa insertion in A. maratayama sp. nov. is located in the middle section of the pars media (Fig. 4 B, black arrow), similar to A. a. carolinae (Fig. 4 C, black arrow). However, pars externa insertion in A. americanus is located close to the capitulum base (Fig. 4 A, black arrow).

Female. The concave anterior margin of the genital sternite forms a very deep arch (Fig. 4 E, red arrow) in comparison to A. americanus (Fig. 4 D, red arrow), which has a shallow-arched concavity. The free sublateral projections by the margin’s sides are enclosed and taper to a defined point, besides being slightly curved. Acetes a. carolinae shape is similar to that of A. maratayama sp. nov.; however, the concavity of the genital sternite is not as deep, and the arch region is straight (Fig. 4 F, red arrow). The thigh of the third pair of pereopods of A. maratayama sp. nov. accounts for most of the inner margin convex and presents a small indentation (Fig. 4 E, black arrow). No tooth was found in its distal end. However, a large, oblong, acute process projects downwards the lower side of each thigh, close to the inner margin, and far forward and somewhat outward. Acetes a. americanus did not have an indentation (Fig. 4 D, black arrow) and A. a. carolinae had a small projection (Fig. 4 F, black arrow).

Habitat.

The species was collected by trawling in shallow waters in depths between 5 and 30 m. The bottom sediment type at the locality comprises medium and fine sand and has a salinity close to 26–28 ppt. It is considered the mesohaline area of the estuary (see Garcia et al. 2018 for environmental characterization of the Cananéia region’s bottom area).

Coloration in life.

Translucent like other species.

Type locality.

Brazil, São Paulo, Cananéia (24 ° 59 ' 55 " S, 47 ° 53 ' 49 " W).

Distribution.

Brazil, São Paulo, Cananéia (24 ° 59 ' 55 " S, 47 ° 53 ' 49 " W) and Rio de Janeiro, Macaé (22 ° 22 ' 13.65 " S, 41 ° 39 ' 9.42 " W).

Etymology.

The new species is named after the type locality, Cananéia, southern São Paulo state, Brazil. Maratayama is the old name of Cananéia recorded in the navigation log of the expedition from Portugal that arrived in the region in 1531. From the Tupi-Guarani language, Maratayama means a place where the land meets the sea or land of the sea (Mara = sea and Tayama = land).

Genetic sequences.

The previous genetic characterization and generated sequences obtained by Simões et al. [2023 – as “ Acetes americanus (Brazil 2) ” - https://peerj.com/articles/14751/#supplemental-information] are updated and should be referred to as Acetes maratayama sp. nov. The data, i. e., gene marker, geographic region, voucher catalogue collection and sequence accession number (GenBank), are: 16 S Ribosomal RNA (16 S) — Macaé / RJ: CCLC 0261 (OP 035684 to OP 035686), CCLC 0267 (OP 035697); Cananéia / SP: CCLC 0262 (OP 035687), CCDB 3251 (OP 035688, OP 035698 to OP 035700); cytochrome c oxidase subunit I (COI) — Macaé / RJ: CCLC 0255 (OP 060472), CCLC 0261 (OP 060504 to OP 060507), CCLC 0267 (OP 060521 to OP 060523); Cananéia / SP: CCLC 0262 (OP 060508), CCDB 3251 (OP 060509, OP 060524 to OP 060528). Some of these sequences were herein used to prepare the phylogenetic tree (Suppl. material 1).

Genetic distance.

16 SrRNA gene: Intraspecific distances ranged from 0 % (A. americanus, A. maratayama sp. nov. and A. carolinae) to 0.21 % (A. paraguayensis) (Table 1). Interspecific distances between congeneric species ranged from 1.49 to 8.53 % (Table 1). Regarding A. maratayama sp. nov., the smallest genetic distance observed was 0.85 % with A. carolinae, 1.49 % with A. americanus and the highest was 8.53 % with A. paraguayensis (Table 1).

COI gene: Intraspecific distances ranged from 0 to 0.19 % (A. americanus and A. carolinae), from 0 to 0.38 (A. maratayama sp. nov.), and from 0.57 % (A. paraguayensis) (Table 2). Interspecific distances between congeneric species ranged from 4.78 to 19.89 % (Table 2). Regarding A. maratayama sp. nov., the smallest genetic distance observed was with A. americanus (6.12–6.50 %), followed by A. carolinae (7.65–8.63 %), and the largest was with A. paraguayensis (19.50–19.89 %) (Table 2).

Phylogenetic analyses.

The phylogenetic tree based on concatenated data (16 S rRNA and COI) generated a similar topology found by Simões et al. (2023), with high support values. Two distinct clades were observed, one formed by A. americanus and A. carolinae and the sister clade formed by A. maratayama sp. nov. (Fig. 5)

Remarks.

Acetes maratayama sp. nov. is closely related to A. americanus and A. a. carolinae, and it presents small morphological differences, mainly in reproductive structures. Furthermore, A. maratayama sp. nov. has 10 articles in the antennular flagellum, whereas A. a. carolinae has 9 articles, A. binghami Burkenroad, 1934 a has 7 articles and A. intermedius Omori, 1975 has 13–14 articles. Acetes maratayama sp. nov. is easily distinguishable from A. binghami, since the rostrum in this species does not have denticles behind the terminal tip, whereas the rostrum in A. paraguayensis has a strong tooth. There is a rudimentary denticle or hair minus one angular bend between this tooth and the end of the rostrum. The first article of the palp is 3 times longer than the second article. It is 5 times longer in A. binghami. The first article of the palp in A. intermedius is 2 times longer than the second article.

Historically, Burkenroad (1934 b) recognized four A. americanus subspecies: A. americanus carolinae (type locality: Beaufort Inlet, North Carolina, USA), A. a. louisianensis (type locality: Louisiana coast, from the Mississippi River West to Timbalier Island, Gulf of Mexico, USA), A. a. limonensis (type locality: Sweetwater River mouth, Limon Bay, Panama) and A. a. americanus (type locality: mouth of Tocantins River). However, A. a. louisianensis was synonymized with A. a. carolinae and A. a. limonensis was synonymized with A. a. americanus (DecaNet 2024). Holthuis (1948) states that subspecies A. a. louisianensis presents intermediate characteristics of other subspecies in this genus. They are not considered valid clinal variants. Burkenroad (1934 b – Penaeidae from Louisiana, p. 132) states that:

“ Although I do not consider the differences here pointed out sufficiently certain or significant to require taxonomic recognition, if direct comparisons prove this to be desirable, I would suggest for Material from Louisiana with the subspecific name Acetes carolinae louisianensis. ”.

This author also added important notes to Hansen’s (1919) description of A. carolinae (pp. 130–132).

Thus, several records show the geographic disjunction between the Gulf of Mexico and Panama and the well-documented vicariance processes in this region, which point out speciation between these regions and Western United States Atlantic (Coates and Obando 1996; Allmon 2001; Harrison 2004; Mantelatto et al. 2023). We are still not fully convinced that A. a. louisianensis is synonymous with A. a. carolinae. Therefore, more robust morphological analyses associated with molecular analyses must be carried out to help better understand these entities.

Individuals from the Western Atlantic (North Carolina - NC) were not included in the molecular analyses carried out by Simões et al. (2023), since they focused on species distributed within Brazil. It means that doubts about A. a. carolinae remain unresolved. Unfortunately, we did not have the opportunity to morphologically analyze the specimens (Fig. 6) identified as the cotype of A. a. carolinae, from USNM (74550). There is only one sequence (histone 3 gene) of A. a. carolinae from the North Carolina locality deposited in GenBank (KX 216649) compared to our newly generated sequences of nuclear gene, histone 3 (H 3), for individuals from Louisiana and Mississippi regions (ULLZ 14545 – Genbank PP 816024, PP 816025, PP 816026). However, this gene’s DNA fragment (very conserved region) is not informative enough to identify congeneric species. Simões et al. (2023) recovered the lineage identified as “ A. americanus (USA) ”, which is formed by individuals from Louisiana and Mississippi, USA. Thus, doubts are raised about the likely validity / resurrection of subspecies A. a. louisianensis, which is strongly supported by the type locality being in the Gulf of Mexico. Further molecular analyses using other genes are necessary to elucidate the taxonomic status of Acetes species located in the Gulf of Mexico region and in North Carolina, named A. a. carolinae.

It is also important to recall that Hansen (1919) described Acetes brasiliensis (p. 45–46, figs 1–7) collected from the Amazon River estuary. He mentioned the similarity to A. americanus, as described by Ortmann (1893), for collections from the mouth of Tocantins River, Brazil (Foz do rio Pará), which is very close to Amazon River. Despite a general description and undetailed figures, he emphasized that A. brasiliensis presented two features (length of third joint of the antennule and exopod of the uropod) making it impossible to refer A. brasiliensis to the species established by Ortmann. Burkenroad (1934 b, p. 130), stated that:

“ The characters by which Hansen has distinguished A. brasiliensis from A. americanus seem of very uncertain importance. The differences in length of the ciliated part of the external margin of the exopod of the uropod, as those in other characters not mentioned by Hansen, are perhaps attributable to the obvious inaccuracy of Ortmann’s figure. That Ortmann failed to notice the elongation of the third segment of the antennular peduncle of the male of his species is no more astonishing than that Kishinouye failed to do so for A. japonicus, as Kemp has shown to be the fact. ”.

We had access (by photos) to the material (one male and one female – Fig. 7) used by Hansen to describe A. brasiliensis, due to the great help from Dr Jørgen Olesen (curator). They are deposited at the Natural History Museum of Denmark - University of Copenhagen (NHMD 83728). We agree with Burkenroad’s assertion and suggestion that A. brasiliensis is more likely synonymous with A. americanus after carefully analyzing the main characters.